Actual source code: snes.c

  1: #include <petsc/private/snesimpl.h>
  2: #include <petscdmshell.h>
  3: #include <petscdraw.h>
  4: #include <petscds.h>
  5: #include <petscdmadaptor.h>
  6: #include <petscconvest.h>

  8: PetscBool         SNESRegisterAllCalled = PETSC_FALSE;
  9: PetscFunctionList SNESList              = NULL;

 11: /* Logging support */
 12: PetscClassId  SNES_CLASSID, DMSNES_CLASSID;
 13: PetscLogEvent SNES_Solve, SNES_SetUp, SNES_FunctionEval, SNES_JacobianEval, SNES_NGSEval, SNES_NGSFuncEval, SNES_NPCSolve, SNES_ObjectiveEval;

 15: /*@
 16:   SNESSetErrorIfNotConverged - Causes `SNESSolve()` to generate an error immediately if the solver has not converged.

 18:   Logically Collective

 20:   Input Parameters:
 21: + snes - iterative context obtained from `SNESCreate()`
 22: - flg  - `PETSC_TRUE` indicates you want the error generated

 24:   Options Database Key:
 25: . -snes_error_if_not_converged <true,false> - cause an immediate error condition and stop the program if the solver does not converge

 27:   Level: intermediate

 29:   Note:
 30:   Normally PETSc continues if a solver fails to converge, you can call `SNESGetConvergedReason()` after a `SNESSolve()`
 31:   to determine if it has converged. Otherwise the solution may be inaccurate or wrong

 33: .seealso: [](ch_snes), `SNES`, `SNESGetErrorIfNotConverged()`, `KSPGetErrorIfNotConverged()`, `KSPSetErrorIfNotConverged()`
 34: @*/
 35: PetscErrorCode SNESSetErrorIfNotConverged(SNES snes, PetscBool flg)
 36: {
 37:   PetscFunctionBegin;
 40:   snes->errorifnotconverged = flg;
 41:   PetscFunctionReturn(PETSC_SUCCESS);
 42: }

 44: /*@
 45:   SNESGetErrorIfNotConverged - Indicates if `SNESSolve()` will generate an error if the solver does not converge?

 47:   Not Collective

 49:   Input Parameter:
 50: . snes - iterative context obtained from `SNESCreate()`

 52:   Output Parameter:
 53: . flag - `PETSC_TRUE` if it will generate an error, else `PETSC_FALSE`

 55:   Level: intermediate

 57: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetErrorIfNotConverged()`, `KSPGetErrorIfNotConverged()`, `KSPSetErrorIfNotConverged()`
 58: @*/
 59: PetscErrorCode SNESGetErrorIfNotConverged(SNES snes, PetscBool *flag)
 60: {
 61:   PetscFunctionBegin;
 63:   PetscAssertPointer(flag, 2);
 64:   *flag = snes->errorifnotconverged;
 65:   PetscFunctionReturn(PETSC_SUCCESS);
 66: }

 68: /*@
 69:   SNESSetAlwaysComputesFinalResidual - tells the `SNES` to always compute the residual (nonlinear function value) at the final solution

 71:   Logically Collective

 73:   Input Parameters:
 74: + snes - the shell `SNES`
 75: - flg  - `PETSC_TRUE` to always compute the residual

 77:   Level: advanced

 79:   Note:
 80:   Some solvers (such as smoothers in a `SNESFAS`) do not need the residual computed at the final solution so skip computing it
 81:   to save time.

 83: .seealso: [](ch_snes), `SNES`, `SNESFAS`, `SNESSolve()`, `SNESGetAlwaysComputesFinalResidual()`
 84: @*/
 85: PetscErrorCode SNESSetAlwaysComputesFinalResidual(SNES snes, PetscBool flg)
 86: {
 87:   PetscFunctionBegin;
 89:   snes->alwayscomputesfinalresidual = flg;
 90:   PetscFunctionReturn(PETSC_SUCCESS);
 91: }

 93: /*@
 94:   SNESGetAlwaysComputesFinalResidual - checks if the `SNES` always computes the residual at the final solution

 96:   Logically Collective

 98:   Input Parameter:
 99: . snes - the `SNES` context

101:   Output Parameter:
102: . flg - `PETSC_TRUE` if the residual is computed

104:   Level: advanced

106: .seealso: [](ch_snes), `SNES`, `SNESFAS`, `SNESSolve()`, `SNESSetAlwaysComputesFinalResidual()`
107: @*/
108: PetscErrorCode SNESGetAlwaysComputesFinalResidual(SNES snes, PetscBool *flg)
109: {
110:   PetscFunctionBegin;
112:   *flg = snes->alwayscomputesfinalresidual;
113:   PetscFunctionReturn(PETSC_SUCCESS);
114: }

116: /*@
117:   SNESSetFunctionDomainError - tells `SNES` that the input vector, a proposed new solution, to your function you provided to `SNESSetFunction()` is not
118:   in the functions domain. For example, a step with negative pressure.

120:   Logically Collective

122:   Input Parameter:
123: . snes - the `SNES` context

125:   Level: advanced

127:   Notes:
128:   If this is called the `SNESSolve()` stops iterating and returns with a `SNESConvergedReason` of `SNES_DIVERGED_FUNCTION_DOMAIN`

130:   You should always call `SNESGetConvergedReason()` after each `SNESSolve()` and verify if the iteration converged (positive result) or diverged (negative result).

132:   You can direct `SNES` to avoid certain steps by using `SNESVISetVariableBounds()`, `SNESVISetComputeVariableBounds()` or
133:   `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`

135: .seealso: [](ch_snes), `SNESCreate()`, `SNESSetFunction()`, `SNESFunction`, `SNESSetJacobianDomainError()`, `SNESVISetVariableBounds()`,
136:           `SNESVISetComputeVariableBounds()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESConvergedReason`, `SNESGetConvergedReason()`
137: @*/
138: PetscErrorCode SNESSetFunctionDomainError(SNES snes)
139: {
140:   PetscFunctionBegin;
142:   PetscCheck(!snes->errorifnotconverged, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "User code indicates input vector is not in the function domain");
143:   snes->domainerror = PETSC_TRUE;
144:   PetscFunctionReturn(PETSC_SUCCESS);
145: }

147: /*@
148:   SNESSetJacobianDomainError - tells `SNES` that the function you provided to `SNESSetJacobian()` at the proposed step. For example there is a negative element transformation.

150:   Logically Collective

152:   Input Parameter:
153: . snes - the `SNES` context

155:   Level: advanced

157:   Notes:
158:   If this is called the `SNESSolve()` stops iterating and returns with a `SNESConvergedReason` of `SNES_DIVERGED_FUNCTION_DOMAIN`

160:   You should always call `SNESGetConvergedReason()` after each `SNESSolve()` and verify if the iteration converged (positive result) or diverged (negative result).

162:   You can direct `SNES` to avoid certain steps by using `SNESVISetVariableBounds()`, `SNESVISetComputeVariableBounds()` or
163:   `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`

165: .seealso: [](ch_snes), `SNESCreate()`, `SNESSetFunction()`, `SNESFunction()`, `SNESSetFunctionDomainError()`, `SNESVISetVariableBounds()`,
166:           `SNESVISetComputeVariableBounds()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESConvergedReason`, `SNESGetConvergedReason()`
167: @*/
168: PetscErrorCode SNESSetJacobianDomainError(SNES snes)
169: {
170:   PetscFunctionBegin;
172:   PetscCheck(!snes->errorifnotconverged, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "User code indicates computeJacobian does not make sense");
173:   snes->jacobiandomainerror = PETSC_TRUE;
174:   PetscFunctionReturn(PETSC_SUCCESS);
175: }

177: /*@
178:   SNESSetCheckJacobianDomainError - tells `SNESSolve()` whether to check if the user called `SNESSetJacobianDomainError()` Jacobian domain error after
179:   each Jacobian evaluation. By default, it checks for the Jacobian domain error in the debug mode, and does not check it in the optimized mode.

181:   Logically Collective

183:   Input Parameters:
184: + snes - the `SNES` context
185: - flg  - indicates if or not to check Jacobian domain error after each Jacobian evaluation

187:   Level: advanced

189:   Note:
190:   Checks require one extra parallel synchronization for each Jacobian evaluation

192: .seealso: [](ch_snes), `SNES`, `SNESConvergedReason`, `SNESCreate()`, `SNESSetFunction()`, `SNESFunction()`, `SNESSetFunctionDomainError()`, `SNESGetCheckJacobianDomainError()`
193: @*/
194: PetscErrorCode SNESSetCheckJacobianDomainError(SNES snes, PetscBool flg)
195: {
196:   PetscFunctionBegin;
198:   snes->checkjacdomainerror = flg;
199:   PetscFunctionReturn(PETSC_SUCCESS);
200: }

202: /*@
203:   SNESGetCheckJacobianDomainError - Get an indicator whether or not `SNES` is checking Jacobian domain errors after each Jacobian evaluation.

205:   Logically Collective

207:   Input Parameter:
208: . snes - the `SNES` context

210:   Output Parameter:
211: . flg - `PETSC_FALSE` indicates that it is not checking Jacobian domain errors after each Jacobian evaluation

213:   Level: advanced

215: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESSetFunction()`, `SNESFunction()`, `SNESSetFunctionDomainError()`, `SNESSetCheckJacobianDomainError()`
216: @*/
217: PetscErrorCode SNESGetCheckJacobianDomainError(SNES snes, PetscBool *flg)
218: {
219:   PetscFunctionBegin;
221:   PetscAssertPointer(flg, 2);
222:   *flg = snes->checkjacdomainerror;
223:   PetscFunctionReturn(PETSC_SUCCESS);
224: }

226: /*@
227:   SNESGetFunctionDomainError - Gets the status of the domain error after a call to `SNESComputeFunction()`

229:   Logically Collective

231:   Input Parameter:
232: . snes - the `SNES` context

234:   Output Parameter:
235: . domainerror - Set to `PETSC_TRUE` if there's a domain error; `PETSC_FALSE` otherwise.

237:   Level: developer

239: .seealso: [](ch_snes), `SNES`, `SNESSetFunctionDomainError()`, `SNESComputeFunction()`
240: @*/
241: PetscErrorCode SNESGetFunctionDomainError(SNES snes, PetscBool *domainerror)
242: {
243:   PetscFunctionBegin;
245:   PetscAssertPointer(domainerror, 2);
246:   *domainerror = snes->domainerror;
247:   PetscFunctionReturn(PETSC_SUCCESS);
248: }

250: /*@
251:   SNESGetJacobianDomainError - Gets the status of the Jacobian domain error after a call to `SNESComputeJacobian()`

253:   Logically Collective

255:   Input Parameter:
256: . snes - the `SNES` context

258:   Output Parameter:
259: . domainerror - Set to `PETSC_TRUE` if there's a Jacobian domain error; `PETSC_FALSE` otherwise.

261:   Level: advanced

263: .seealso: [](ch_snes), `SNES`, `SNESSetFunctionDomainError()`, `SNESComputeFunction()`, `SNESGetFunctionDomainError()`
264: @*/
265: PetscErrorCode SNESGetJacobianDomainError(SNES snes, PetscBool *domainerror)
266: {
267:   PetscFunctionBegin;
269:   PetscAssertPointer(domainerror, 2);
270:   *domainerror = snes->jacobiandomainerror;
271:   PetscFunctionReturn(PETSC_SUCCESS);
272: }

274: /*@C
275:   SNESLoad - Loads a `SNES` that has been stored in `PETSCVIEWERBINARY` with `SNESView()`.

277:   Collective

279:   Input Parameters:
280: + snes   - the newly loaded `SNES`, this needs to have been created with `SNESCreate()` or
281:            some related function before a call to `SNESLoad()`.
282: - viewer - binary file viewer, obtained from `PetscViewerBinaryOpen()`

284:   Level: intermediate

286:   Note:
287:   The `SNESType` is determined by the data in the file, any type set into the `SNES` before this call is ignored.

289: .seealso: [](ch_snes), `SNES`, `PetscViewer`, `SNESCreate()`, `SNESType`, `PetscViewerBinaryOpen()`, `SNESView()`, `MatLoad()`, `VecLoad()`
290: @*/
291: PetscErrorCode SNESLoad(SNES snes, PetscViewer viewer)
292: {
293:   PetscBool isbinary;
294:   PetscInt  classid;
295:   char      type[256];
296:   KSP       ksp;
297:   DM        dm;
298:   DMSNES    dmsnes;

300:   PetscFunctionBegin;
303:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERBINARY, &isbinary));
304:   PetscCheck(isbinary, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Invalid viewer; open viewer with PetscViewerBinaryOpen()");

306:   PetscCall(PetscViewerBinaryRead(viewer, &classid, 1, NULL, PETSC_INT));
307:   PetscCheck(classid == SNES_FILE_CLASSID, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONG, "Not SNES next in file");
308:   PetscCall(PetscViewerBinaryRead(viewer, type, 256, NULL, PETSC_CHAR));
309:   PetscCall(SNESSetType(snes, type));
310:   PetscTryTypeMethod(snes, load, viewer);
311:   PetscCall(SNESGetDM(snes, &dm));
312:   PetscCall(DMGetDMSNES(dm, &dmsnes));
313:   PetscCall(DMSNESLoad(dmsnes, viewer));
314:   PetscCall(SNESGetKSP(snes, &ksp));
315:   PetscCall(KSPLoad(ksp, viewer));
316:   PetscFunctionReturn(PETSC_SUCCESS);
317: }

319: #include <petscdraw.h>
320: #if defined(PETSC_HAVE_SAWS)
321: #include <petscviewersaws.h>
322: #endif

324: /*@C
325:   SNESViewFromOptions - View a `SNES` based on values in the options database

327:   Collective

329:   Input Parameters:
330: + A    - the `SNES` context
331: . obj  - Optional object that provides the options prefix for the checks
332: - name - command line option

334:   Level: intermediate

336: .seealso: [](ch_snes), `SNES`, `SNESView`, `PetscObjectViewFromOptions()`, `SNESCreate()`
337: @*/
338: PetscErrorCode SNESViewFromOptions(SNES A, PetscObject obj, const char name[])
339: {
340:   PetscFunctionBegin;
342:   PetscCall(PetscObjectViewFromOptions((PetscObject)A, obj, name));
343:   PetscFunctionReturn(PETSC_SUCCESS);
344: }

346: PETSC_EXTERN PetscErrorCode SNESComputeJacobian_DMDA(SNES, Vec, Mat, Mat, void *);

348: /*@C
349:   SNESView - Prints or visualizes the `SNES` data structure.

351:   Collective

353:   Input Parameters:
354: + snes   - the `SNES` context
355: - viewer - the `PetscViewer`

357:   Options Database Key:
358: . -snes_view - Calls `SNESView()` at end of `SNESSolve()`

360:   Level: beginner

362:   Notes:
363:   The available visualization contexts include
364: +     `PETSC_VIEWER_STDOUT_SELF` - standard output (default)
365: -     `PETSC_VIEWER_STDOUT_WORLD` - synchronized standard
366:   output where only the first processor opens
367:   the file.  All other processors send their
368:   data to the first processor to print.

370:   The available formats include
371: +     `PETSC_VIEWER_DEFAULT` - standard output (default)
372: -     `PETSC_VIEWER_ASCII_INFO_DETAIL` - more verbose output for `SNESNASM`

374:   The user can open an alternative visualization context with
375:   `PetscViewerASCIIOpen()` - output to a specified file.

377:   In the debugger you can do "call `SNESView`(snes,0)" to display the `SNES` solver. (The same holds for any PETSc object viewer).

379: .seealso: [](ch_snes), `SNES`, `SNESLoad()`, `SNESCreate()`, `PetscViewerASCIIOpen()`
380: @*/
381: PetscErrorCode SNESView(SNES snes, PetscViewer viewer)
382: {
383:   SNESKSPEW     *kctx;
384:   KSP            ksp;
385:   SNESLineSearch linesearch;
386:   PetscBool      iascii, isstring, isbinary, isdraw;
387:   DMSNES         dmsnes;
388: #if defined(PETSC_HAVE_SAWS)
389:   PetscBool issaws;
390: #endif

392:   PetscFunctionBegin;
394:   if (!viewer) PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &viewer));
396:   PetscCheckSameComm(snes, 1, viewer, 2);

398:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii));
399:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERSTRING, &isstring));
400:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERBINARY, &isbinary));
401:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERDRAW, &isdraw));
402: #if defined(PETSC_HAVE_SAWS)
403:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERSAWS, &issaws));
404: #endif
405:   if (iascii) {
406:     SNESNormSchedule normschedule;
407:     DM               dm;
408:     PetscErrorCode (*cJ)(SNES, Vec, Mat, Mat, void *);
409:     void       *ctx;
410:     const char *pre = "";

412:     PetscCall(PetscObjectPrintClassNamePrefixType((PetscObject)snes, viewer));
413:     if (!snes->setupcalled) PetscCall(PetscViewerASCIIPrintf(viewer, "  SNES has not been set up so information may be incomplete\n"));
414:     if (snes->ops->view) {
415:       PetscCall(PetscViewerASCIIPushTab(viewer));
416:       PetscUseTypeMethod(snes, view, viewer);
417:       PetscCall(PetscViewerASCIIPopTab(viewer));
418:     }
419:     PetscCall(PetscViewerASCIIPrintf(viewer, "  maximum iterations=%" PetscInt_FMT ", maximum function evaluations=%" PetscInt_FMT "\n", snes->max_its, snes->max_funcs));
420:     PetscCall(PetscViewerASCIIPrintf(viewer, "  tolerances: relative=%g, absolute=%g, solution=%g\n", (double)snes->rtol, (double)snes->abstol, (double)snes->stol));
421:     if (snes->usesksp) PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of linear solver iterations=%" PetscInt_FMT "\n", snes->linear_its));
422:     PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of function evaluations=%" PetscInt_FMT "\n", snes->nfuncs));
423:     PetscCall(SNESGetNormSchedule(snes, &normschedule));
424:     if (normschedule > 0) PetscCall(PetscViewerASCIIPrintf(viewer, "  norm schedule %s\n", SNESNormSchedules[normschedule]));
425:     if (snes->gridsequence) PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of grid sequence refinements=%" PetscInt_FMT "\n", snes->gridsequence));
426:     if (snes->ksp_ewconv) {
427:       kctx = (SNESKSPEW *)snes->kspconvctx;
428:       if (kctx) {
429:         PetscCall(PetscViewerASCIIPrintf(viewer, "  Eisenstat-Walker computation of KSP relative tolerance (version %" PetscInt_FMT ")\n", kctx->version));
430:         PetscCall(PetscViewerASCIIPrintf(viewer, "    rtol_0=%g, rtol_max=%g, threshold=%g\n", (double)kctx->rtol_0, (double)kctx->rtol_max, (double)kctx->threshold));
431:         PetscCall(PetscViewerASCIIPrintf(viewer, "    gamma=%g, alpha=%g, alpha2=%g\n", (double)kctx->gamma, (double)kctx->alpha, (double)kctx->alpha2));
432:       }
433:     }
434:     if (snes->lagpreconditioner == -1) {
435:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Preconditioned is never rebuilt\n"));
436:     } else if (snes->lagpreconditioner > 1) {
437:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Preconditioned is rebuilt every %" PetscInt_FMT " new Jacobians\n", snes->lagpreconditioner));
438:     }
439:     if (snes->lagjacobian == -1) {
440:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is never rebuilt\n"));
441:     } else if (snes->lagjacobian > 1) {
442:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is rebuilt every %" PetscInt_FMT " SNES iterations\n", snes->lagjacobian));
443:     }
444:     PetscCall(SNESGetDM(snes, &dm));
445:     PetscCall(DMSNESGetJacobian(dm, &cJ, &ctx));
446:     if (snes->mf_operator) {
447:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is applied matrix-free with differencing\n"));
448:       pre = "Preconditioning ";
449:     }
450:     if (cJ == SNESComputeJacobianDefault) {
451:       PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using finite differences one column at a time\n", pre));
452:     } else if (cJ == SNESComputeJacobianDefaultColor) {
453:       PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using finite differences with coloring\n", pre));
454:       /* it slightly breaks data encapsulation for access the DMDA information directly */
455:     } else if (cJ == SNESComputeJacobian_DMDA) {
456:       MatFDColoring fdcoloring;
457:       PetscCall(PetscObjectQuery((PetscObject)dm, "DMDASNES_FDCOLORING", (PetscObject *)&fdcoloring));
458:       if (fdcoloring) {
459:         PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using colored finite differences on a DMDA\n", pre));
460:       } else {
461:         PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using a DMDA local Jacobian\n", pre));
462:       }
463:     } else if (snes->mf && !snes->mf_operator) {
464:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is applied matrix-free with differencing, no explicit Jacobian\n"));
465:     }
466:   } else if (isstring) {
467:     const char *type;
468:     PetscCall(SNESGetType(snes, &type));
469:     PetscCall(PetscViewerStringSPrintf(viewer, " SNESType: %-7.7s", type));
470:     PetscTryTypeMethod(snes, view, viewer);
471:   } else if (isbinary) {
472:     PetscInt    classid = SNES_FILE_CLASSID;
473:     MPI_Comm    comm;
474:     PetscMPIInt rank;
475:     char        type[256];

477:     PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
478:     PetscCallMPI(MPI_Comm_rank(comm, &rank));
479:     if (rank == 0) {
480:       PetscCall(PetscViewerBinaryWrite(viewer, &classid, 1, PETSC_INT));
481:       PetscCall(PetscStrncpy(type, ((PetscObject)snes)->type_name, sizeof(type)));
482:       PetscCall(PetscViewerBinaryWrite(viewer, type, sizeof(type), PETSC_CHAR));
483:     }
484:     PetscTryTypeMethod(snes, view, viewer);
485:   } else if (isdraw) {
486:     PetscDraw draw;
487:     char      str[36];
488:     PetscReal x, y, bottom, h;

490:     PetscCall(PetscViewerDrawGetDraw(viewer, 0, &draw));
491:     PetscCall(PetscDrawGetCurrentPoint(draw, &x, &y));
492:     PetscCall(PetscStrncpy(str, "SNES: ", sizeof(str)));
493:     PetscCall(PetscStrlcat(str, ((PetscObject)snes)->type_name, sizeof(str)));
494:     PetscCall(PetscDrawStringBoxed(draw, x, y, PETSC_DRAW_BLUE, PETSC_DRAW_BLACK, str, NULL, &h));
495:     bottom = y - h;
496:     PetscCall(PetscDrawPushCurrentPoint(draw, x, bottom));
497:     PetscTryTypeMethod(snes, view, viewer);
498: #if defined(PETSC_HAVE_SAWS)
499:   } else if (issaws) {
500:     PetscMPIInt rank;
501:     const char *name;

503:     PetscCall(PetscObjectGetName((PetscObject)snes, &name));
504:     PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
505:     if (!((PetscObject)snes)->amsmem && rank == 0) {
506:       char dir[1024];

508:       PetscCall(PetscObjectViewSAWs((PetscObject)snes, viewer));
509:       PetscCall(PetscSNPrintf(dir, 1024, "/PETSc/Objects/%s/its", name));
510:       PetscCallSAWs(SAWs_Register, (dir, &snes->iter, 1, SAWs_READ, SAWs_INT));
511:       if (!snes->conv_hist) PetscCall(SNESSetConvergenceHistory(snes, NULL, NULL, PETSC_DECIDE, PETSC_TRUE));
512:       PetscCall(PetscSNPrintf(dir, 1024, "/PETSc/Objects/%s/conv_hist", name));
513:       PetscCallSAWs(SAWs_Register, (dir, snes->conv_hist, 10, SAWs_READ, SAWs_DOUBLE));
514:     }
515: #endif
516:   }
517:   if (snes->linesearch) {
518:     PetscCall(SNESGetLineSearch(snes, &linesearch));
519:     PetscCall(PetscViewerASCIIPushTab(viewer));
520:     PetscCall(SNESLineSearchView(linesearch, viewer));
521:     PetscCall(PetscViewerASCIIPopTab(viewer));
522:   }
523:   if (snes->npc && snes->usesnpc) {
524:     PetscCall(PetscViewerASCIIPushTab(viewer));
525:     PetscCall(SNESView(snes->npc, viewer));
526:     PetscCall(PetscViewerASCIIPopTab(viewer));
527:   }
528:   PetscCall(PetscViewerASCIIPushTab(viewer));
529:   PetscCall(DMGetDMSNES(snes->dm, &dmsnes));
530:   PetscCall(DMSNESView(dmsnes, viewer));
531:   PetscCall(PetscViewerASCIIPopTab(viewer));
532:   if (snes->usesksp) {
533:     PetscCall(SNESGetKSP(snes, &ksp));
534:     PetscCall(PetscViewerASCIIPushTab(viewer));
535:     PetscCall(KSPView(ksp, viewer));
536:     PetscCall(PetscViewerASCIIPopTab(viewer));
537:   }
538:   if (isdraw) {
539:     PetscDraw draw;
540:     PetscCall(PetscViewerDrawGetDraw(viewer, 0, &draw));
541:     PetscCall(PetscDrawPopCurrentPoint(draw));
542:   }
543:   PetscFunctionReturn(PETSC_SUCCESS);
544: }

546: /*
547:   We retain a list of functions that also take SNES command
548:   line options. These are called at the end SNESSetFromOptions()
549: */
550: #define MAXSETFROMOPTIONS 5
551: static PetscInt numberofsetfromoptions;
552: static PetscErrorCode (*othersetfromoptions[MAXSETFROMOPTIONS])(SNES);

554: /*@C
555:   SNESAddOptionsChecker - Adds an additional function to check for `SNES` options.

557:   Not Collective

559:   Input Parameter:
560: . snescheck - function that checks for options

562:   Calling sequence of `snescheck`:
563: . snes - the `SNES` object for which it is checking options

565:   Level: developer

567: .seealso: [](ch_snes), `SNES`, `SNESSetFromOptions()`
568: @*/
569: PetscErrorCode SNESAddOptionsChecker(PetscErrorCode (*snescheck)(SNES snes))
570: {
571:   PetscFunctionBegin;
572:   PetscCheck(numberofsetfromoptions < MAXSETFROMOPTIONS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many options checkers, only %d allowed", MAXSETFROMOPTIONS);
573:   othersetfromoptions[numberofsetfromoptions++] = snescheck;
574:   PetscFunctionReturn(PETSC_SUCCESS);
575: }

577: static PetscErrorCode SNESSetUpMatrixFree_Private(SNES snes, PetscBool hasOperator, PetscInt version)
578: {
579:   Mat          J;
580:   MatNullSpace nullsp;

582:   PetscFunctionBegin;

585:   if (!snes->vec_func && (snes->jacobian || snes->jacobian_pre)) {
586:     Mat A = snes->jacobian, B = snes->jacobian_pre;
587:     PetscCall(MatCreateVecs(A ? A : B, NULL, &snes->vec_func));
588:   }

590:   PetscCheck(version == 1 || version == 2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "matrix-free operator routines, only version 1 and 2");
591:   if (version == 1) {
592:     PetscCall(MatCreateSNESMF(snes, &J));
593:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
594:     PetscCall(MatSetFromOptions(J));
595:     /* TODO: the version 2 code should be merged into the MatCreateSNESMF() and MatCreateMFFD() infrastructure and then removed */
596:   } else /* if (version == 2) */ {
597:     PetscCheck(snes->vec_func, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "SNESSetFunction() must be called first");
598: #if !defined(PETSC_USE_COMPLEX) && !defined(PETSC_USE_REAL_SINGLE) && !defined(PETSC_USE_REAL___FLOAT128) && !defined(PETSC_USE_REAL___FP16)
599:     PetscCall(MatCreateSNESMFMore(snes, snes->vec_func, &J));
600: #else
601:     SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "matrix-free operator routines (version 2)");
602: #endif
603:   }

605:   /* attach any user provided null space that was on Amat to the newly created matrix-free matrix */
606:   if (snes->jacobian) {
607:     PetscCall(MatGetNullSpace(snes->jacobian, &nullsp));
608:     if (nullsp) PetscCall(MatSetNullSpace(J, nullsp));
609:   }

611:   PetscCall(PetscInfo(snes, "Setting default matrix-free operator routines (version %" PetscInt_FMT ")\n", version));
612:   if (hasOperator) {
613:     /* This version replaces the user provided Jacobian matrix with a
614:        matrix-free version but still employs the user-provided preconditioner matrix. */
615:     PetscCall(SNESSetJacobian(snes, J, NULL, NULL, NULL));
616:   } else {
617:     /* This version replaces both the user-provided Jacobian and the user-
618:      provided preconditioner Jacobian with the default matrix-free version. */
619:     if (snes->npcside == PC_LEFT && snes->npc) {
620:       if (!snes->jacobian) PetscCall(SNESSetJacobian(snes, J, NULL, NULL, NULL));
621:     } else {
622:       KSP       ksp;
623:       PC        pc;
624:       PetscBool match;

626:       PetscCall(SNESSetJacobian(snes, J, J, MatMFFDComputeJacobian, NULL));
627:       /* Force no preconditioner */
628:       PetscCall(SNESGetKSP(snes, &ksp));
629:       PetscCall(KSPGetPC(ksp, &pc));
630:       PetscCall(PetscObjectTypeCompareAny((PetscObject)pc, &match, PCSHELL, PCH2OPUS, ""));
631:       if (!match) {
632:         PetscCall(PetscInfo(snes, "Setting default matrix-free preconditioner routines\nThat is no preconditioner is being used\n"));
633:         PetscCall(PCSetType(pc, PCNONE));
634:       }
635:     }
636:   }
637:   PetscCall(MatDestroy(&J));
638:   PetscFunctionReturn(PETSC_SUCCESS);
639: }

641: static PetscErrorCode DMRestrictHook_SNESVecSol(DM dmfine, Mat Restrict, Vec Rscale, Mat Inject, DM dmcoarse, void *ctx)
642: {
643:   SNES snes = (SNES)ctx;
644:   Vec  Xfine, Xfine_named = NULL, Xcoarse;

646:   PetscFunctionBegin;
647:   if (PetscLogPrintInfo) {
648:     PetscInt finelevel, coarselevel, fineclevel, coarseclevel;
649:     PetscCall(DMGetRefineLevel(dmfine, &finelevel));
650:     PetscCall(DMGetCoarsenLevel(dmfine, &fineclevel));
651:     PetscCall(DMGetRefineLevel(dmcoarse, &coarselevel));
652:     PetscCall(DMGetCoarsenLevel(dmcoarse, &coarseclevel));
653:     PetscCall(PetscInfo(dmfine, "Restricting SNES solution vector from level %" PetscInt_FMT "-%" PetscInt_FMT " to level %" PetscInt_FMT "-%" PetscInt_FMT "\n", finelevel, fineclevel, coarselevel, coarseclevel));
654:   }
655:   if (dmfine == snes->dm) Xfine = snes->vec_sol;
656:   else {
657:     PetscCall(DMGetNamedGlobalVector(dmfine, "SNESVecSol", &Xfine_named));
658:     Xfine = Xfine_named;
659:   }
660:   PetscCall(DMGetNamedGlobalVector(dmcoarse, "SNESVecSol", &Xcoarse));
661:   if (Inject) {
662:     PetscCall(MatRestrict(Inject, Xfine, Xcoarse));
663:   } else {
664:     PetscCall(MatRestrict(Restrict, Xfine, Xcoarse));
665:     PetscCall(VecPointwiseMult(Xcoarse, Xcoarse, Rscale));
666:   }
667:   PetscCall(DMRestoreNamedGlobalVector(dmcoarse, "SNESVecSol", &Xcoarse));
668:   if (Xfine_named) PetscCall(DMRestoreNamedGlobalVector(dmfine, "SNESVecSol", &Xfine_named));
669:   PetscFunctionReturn(PETSC_SUCCESS);
670: }

672: static PetscErrorCode DMCoarsenHook_SNESVecSol(DM dm, DM dmc, void *ctx)
673: {
674:   PetscFunctionBegin;
675:   PetscCall(DMCoarsenHookAdd(dmc, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, ctx));
676:   PetscFunctionReturn(PETSC_SUCCESS);
677: }

679: /* This may be called to rediscretize the operator on levels of linear multigrid. The DM shuffle is so the user can
680:  * safely call SNESGetDM() in their residual evaluation routine. */
681: static PetscErrorCode KSPComputeOperators_SNES(KSP ksp, Mat A, Mat B, void *ctx)
682: {
683:   SNES  snes = (SNES)ctx;
684:   Vec   X, Xnamed = NULL;
685:   DM    dmsave;
686:   void *ctxsave;
687:   PetscErrorCode (*jac)(SNES, Vec, Mat, Mat, void *) = NULL;

689:   PetscFunctionBegin;
690:   dmsave = snes->dm;
691:   PetscCall(KSPGetDM(ksp, &snes->dm));
692:   if (dmsave == snes->dm) X = snes->vec_sol; /* We are on the finest level */
693:   else { /* We are on a coarser level, this vec was initialized using a DM restrict hook */ PetscCall(DMGetNamedGlobalVector(snes->dm, "SNESVecSol", &Xnamed));
694:     X = Xnamed;
695:     PetscCall(SNESGetJacobian(snes, NULL, NULL, &jac, &ctxsave));
696:     /* If the DM's don't match up, the MatFDColoring context needed for the jacobian won't match up either -- fixit. */
697:     if (jac == SNESComputeJacobianDefaultColor) PetscCall(SNESSetJacobian(snes, NULL, NULL, SNESComputeJacobianDefaultColor, NULL));
698:   }
699:   /* Make sure KSP DM has the Jacobian computation routine */
700:   {
701:     DMSNES sdm;

703:     PetscCall(DMGetDMSNES(snes->dm, &sdm));
704:     if (!sdm->ops->computejacobian) PetscCall(DMCopyDMSNES(dmsave, snes->dm));
705:   }
706:   /* Compute the operators */
707:   PetscCall(SNESComputeJacobian(snes, X, A, B));
708:   /* Put the previous context back */
709:   if (snes->dm != dmsave && jac == SNESComputeJacobianDefaultColor) PetscCall(SNESSetJacobian(snes, NULL, NULL, jac, ctxsave));

711:   if (Xnamed) PetscCall(DMRestoreNamedGlobalVector(snes->dm, "SNESVecSol", &Xnamed));
712:   snes->dm = dmsave;
713:   PetscFunctionReturn(PETSC_SUCCESS);
714: }

716: /*@
717:   SNESSetUpMatrices - ensures that matrices are available for `SNES` Newton-like methods, this is called by `SNESSetUp_XXX()`

719:   Collective

721:   Input Parameter:
722: . snes - `SNES` object to configure

724:   Level: developer

726:   Note:
727:   If the matrices do not yet exist it attempts to create them based on options previously set for the `SNES` such as `-snes_mf`

729: .seealso: [](ch_snes), `SNES`, `SNESSetUp()`
730: @*/
731: PetscErrorCode SNESSetUpMatrices(SNES snes)
732: {
733:   DM     dm;
734:   DMSNES sdm;

736:   PetscFunctionBegin;
737:   PetscCall(SNESGetDM(snes, &dm));
738:   PetscCall(DMGetDMSNES(dm, &sdm));
739:   if (!snes->jacobian && snes->mf) {
740:     Mat   J;
741:     void *functx;
742:     PetscCall(MatCreateSNESMF(snes, &J));
743:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
744:     PetscCall(MatSetFromOptions(J));
745:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
746:     PetscCall(SNESSetJacobian(snes, J, J, NULL, NULL));
747:     PetscCall(MatDestroy(&J));
748:   } else if (snes->mf_operator && !snes->jacobian_pre && !snes->jacobian) {
749:     Mat J, B;
750:     PetscCall(MatCreateSNESMF(snes, &J));
751:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
752:     PetscCall(MatSetFromOptions(J));
753:     PetscCall(DMCreateMatrix(snes->dm, &B));
754:     /* sdm->computejacobian was already set to reach here */
755:     PetscCall(SNESSetJacobian(snes, J, B, NULL, NULL));
756:     PetscCall(MatDestroy(&J));
757:     PetscCall(MatDestroy(&B));
758:   } else if (!snes->jacobian_pre) {
759:     PetscDS   prob;
760:     Mat       J, B;
761:     PetscBool hasPrec = PETSC_FALSE;

763:     J = snes->jacobian;
764:     PetscCall(DMGetDS(dm, &prob));
765:     if (prob) PetscCall(PetscDSHasJacobianPreconditioner(prob, &hasPrec));
766:     if (J) PetscCall(PetscObjectReference((PetscObject)J));
767:     else if (hasPrec) PetscCall(DMCreateMatrix(snes->dm, &J));
768:     PetscCall(DMCreateMatrix(snes->dm, &B));
769:     PetscCall(SNESSetJacobian(snes, J ? J : B, B, NULL, NULL));
770:     PetscCall(MatDestroy(&J));
771:     PetscCall(MatDestroy(&B));
772:   }
773:   {
774:     KSP ksp;
775:     PetscCall(SNESGetKSP(snes, &ksp));
776:     PetscCall(KSPSetComputeOperators(ksp, KSPComputeOperators_SNES, snes));
777:     PetscCall(DMCoarsenHookAdd(snes->dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, snes));
778:   }
779:   PetscFunctionReturn(PETSC_SUCCESS);
780: }

782: static PetscErrorCode SNESMonitorPauseFinal_Internal(SNES snes)
783: {
784:   PetscInt i;

786:   PetscFunctionBegin;
787:   if (!snes->pauseFinal) PetscFunctionReturn(PETSC_SUCCESS);
788:   for (i = 0; i < snes->numbermonitors; ++i) {
789:     PetscViewerAndFormat *vf = (PetscViewerAndFormat *)snes->monitorcontext[i];
790:     PetscDraw             draw;
791:     PetscReal             lpause;

793:     if (!vf) continue;
794:     if (vf->lg) {
795:       if (!PetscCheckPointer(vf->lg, PETSC_OBJECT)) continue;
796:       if (((PetscObject)vf->lg)->classid != PETSC_DRAWLG_CLASSID) continue;
797:       PetscCall(PetscDrawLGGetDraw(vf->lg, &draw));
798:       PetscCall(PetscDrawGetPause(draw, &lpause));
799:       PetscCall(PetscDrawSetPause(draw, -1.0));
800:       PetscCall(PetscDrawPause(draw));
801:       PetscCall(PetscDrawSetPause(draw, lpause));
802:     } else {
803:       PetscBool isdraw;

805:       if (!PetscCheckPointer(vf->viewer, PETSC_OBJECT)) continue;
806:       if (((PetscObject)vf->viewer)->classid != PETSC_VIEWER_CLASSID) continue;
807:       PetscCall(PetscObjectTypeCompare((PetscObject)vf->viewer, PETSCVIEWERDRAW, &isdraw));
808:       if (!isdraw) continue;
809:       PetscCall(PetscViewerDrawGetDraw(vf->viewer, 0, &draw));
810:       PetscCall(PetscDrawGetPause(draw, &lpause));
811:       PetscCall(PetscDrawSetPause(draw, -1.0));
812:       PetscCall(PetscDrawPause(draw));
813:       PetscCall(PetscDrawSetPause(draw, lpause));
814:     }
815:   }
816:   PetscFunctionReturn(PETSC_SUCCESS);
817: }

819: /*@C
820:   SNESMonitorSetFromOptions - Sets a monitor function and viewer appropriate for the type indicated by the user

822:   Collective

824:   Input Parameters:
825: + snes         - `SNES` object you wish to monitor
826: . name         - the monitor type one is seeking
827: . help         - message indicating what monitoring is done
828: . manual       - manual page for the monitor
829: . monitor      - the monitor function
830: - monitorsetup - a function that is called once ONLY if the user selected this monitor that may set additional features of the `SNES` or `PetscViewer` objects

832:   Calling sequence of `monitor`:
833: + snes - the nonlinear solver context
834: . it   - the current iteration
835: . r    - the current function norm
836: - vf   - a `PetscViewerAndFormat` struct that contains the `PetscViewer` and `PetscViewerFormat` to use

838:   Calling sequence of `monitorsetup`:
839: + snes - the nonlinear solver context
840: - vf   - a `PetscViewerAndFormat` struct that contains the `PetscViewer` and `PetscViewerFormat` to use

842:   Options Database Key:
843: . -name - trigger the use of this monitor in `SNESSetFromOptions()`

845:   Level: advanced

847: .seealso: [](ch_snes), `PetscOptionsGetViewer()`, `PetscOptionsGetReal()`, `PetscOptionsHasName()`, `PetscOptionsGetString()`,
848:           `PetscOptionsGetIntArray()`, `PetscOptionsGetRealArray()`, `PetscOptionsBool()`
849:           `PetscOptionsInt()`, `PetscOptionsString()`, `PetscOptionsReal()`,
850:           `PetscOptionsName()`, `PetscOptionsBegin()`, `PetscOptionsEnd()`, `PetscOptionsHeadBegin()`,
851:           `PetscOptionsStringArray()`, `PetscOptionsRealArray()`, `PetscOptionsScalar()`,
852:           `PetscOptionsBoolGroupBegin()`, `PetscOptionsBoolGroup()`, `PetscOptionsBoolGroupEnd()`,
853:           `PetscOptionsFList()`, `PetscOptionsEList()`
854: @*/
855: PetscErrorCode SNESMonitorSetFromOptions(SNES snes, const char name[], const char help[], const char manual[], PetscErrorCode (*monitor)(SNES snes, PetscInt it, PetscReal r, PetscViewerAndFormat *vf), PetscErrorCode (*monitorsetup)(SNES snes, PetscViewerAndFormat *vf))
856: {
857:   PetscViewer       viewer;
858:   PetscViewerFormat format;
859:   PetscBool         flg;

861:   PetscFunctionBegin;
862:   PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, name, &viewer, &format, &flg));
863:   if (flg) {
864:     PetscViewerAndFormat *vf;
865:     PetscCall(PetscViewerAndFormatCreate(viewer, format, &vf));
866:     PetscCall(PetscObjectDereference((PetscObject)viewer));
867:     if (monitorsetup) PetscCall((*monitorsetup)(snes, vf));
868:     PetscCall(SNESMonitorSet(snes, (PetscErrorCode(*)(SNES, PetscInt, PetscReal, void *))monitor, vf, (PetscErrorCode(*)(void **))PetscViewerAndFormatDestroy));
869:   }
870:   PetscFunctionReturn(PETSC_SUCCESS);
871: }

873: PetscErrorCode SNESEWSetFromOptions_Private(SNESKSPEW *kctx, PetscBool print_api, MPI_Comm comm, const char *prefix)
874: {
875:   const char *api = print_api ? "SNESKSPSetParametersEW" : NULL;

877:   PetscFunctionBegin;
878:   PetscOptionsBegin(comm, prefix, "Eisenstat and Walker type forcing options", "KSP");
879:   PetscCall(PetscOptionsInt("-ksp_ew_version", "Version 1, 2 or 3", api, kctx->version, &kctx->version, NULL));
880:   PetscCall(PetscOptionsReal("-ksp_ew_rtol0", "0 <= rtol0 < 1", api, kctx->rtol_0, &kctx->rtol_0, NULL));
881:   kctx->rtol_max = PetscMax(kctx->rtol_0, kctx->rtol_max);
882:   PetscCall(PetscOptionsReal("-ksp_ew_rtolmax", "0 <= rtolmax < 1", api, kctx->rtol_max, &kctx->rtol_max, NULL));
883:   PetscCall(PetscOptionsReal("-ksp_ew_gamma", "0 <= gamma <= 1", api, kctx->gamma, &kctx->gamma, NULL));
884:   PetscCall(PetscOptionsReal("-ksp_ew_alpha", "1 < alpha <= 2", api, kctx->alpha, &kctx->alpha, NULL));
885:   PetscCall(PetscOptionsReal("-ksp_ew_alpha2", "alpha2", NULL, kctx->alpha2, &kctx->alpha2, NULL));
886:   PetscCall(PetscOptionsReal("-ksp_ew_threshold", "0 < threshold < 1", api, kctx->threshold, &kctx->threshold, NULL));
887:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p1", "p1", NULL, kctx->v4_p1, &kctx->v4_p1, NULL));
888:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p2", "p2", NULL, kctx->v4_p2, &kctx->v4_p2, NULL));
889:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p3", "p3", NULL, kctx->v4_p3, &kctx->v4_p3, NULL));
890:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m1", "Scaling when rk-1 in [p2,p3)", NULL, kctx->v4_m1, &kctx->v4_m1, NULL));
891:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m2", "Scaling when rk-1 in [p3,+infty)", NULL, kctx->v4_m2, &kctx->v4_m2, NULL));
892:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m3", "Threshold for successive rtol (0.1 in Eq.7)", NULL, kctx->v4_m3, &kctx->v4_m3, NULL));
893:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m4", "Adaptation scaling (0.5 in Eq.7)", NULL, kctx->v4_m4, &kctx->v4_m4, NULL));
894:   PetscOptionsEnd();
895:   PetscFunctionReturn(PETSC_SUCCESS);
896: }

898: /*@
899:   SNESSetFromOptions - Sets various `SNES` and `KSP` parameters from user options.

901:   Collective

903:   Input Parameter:
904: . snes - the `SNES` context

906:   Options Database Keys:
907: + -snes_type <type>                                                            - newtonls, newtontr, ngmres, ncg, nrichardson, qn, vi, fas, `SNESType` for complete list
908: . -snes_stol <stol>                                                            - convergence tolerance in terms of the norm of the change in the solution between steps
909: . -snes_atol <abstol>                                                          - absolute tolerance of residual norm
910: . -snes_rtol <rtol>                                                            - relative decrease in tolerance norm from initial
911: . -snes_divergence_tolerance <divtol>                                          - if the residual goes above divtol*rnorm0, exit with divergence
912: . -snes_force_iteration <force>                                                - force `SNESSolve()` to take at least one iteration
913: . -snes_max_it <max_it>                                                        - maximum number of iterations
914: . -snes_max_funcs <max_funcs>                                                  - maximum number of function evaluations
915: . -snes_max_fail <max_fail>                                                    - maximum number of line search failures allowed before stopping, default is none
916: . -snes_max_linear_solve_fail                                                  - number of linear solver failures before SNESSolve() stops
917: . -snes_lag_preconditioner <lag>                                               - how often preconditioner is rebuilt (use -1 to never rebuild)
918: . -snes_lag_preconditioner_persists <true,false>                               - retains the -snes_lag_preconditioner information across multiple SNESSolve()
919: . -snes_lag_jacobian <lag>                                                     - how often Jacobian is rebuilt (use -1 to never rebuild)
920: . -snes_lag_jacobian_persists <true,false>                                     - retains the -snes_lag_jacobian information across multiple SNESSolve()
921: . -snes_tr_tol <trtol>                                                         - trust region tolerance
922: . -snes_convergence_test <default,skip,correct_pressure>                       - convergence test in nonlinear solver. default `SNESConvergedDefault()`. skip `SNESConvergedSkip()` means continue iterating until max_it or some other criterion is reached, saving expense of convergence test. correct_pressure `SNESConvergedCorrectPressure()` has special handling of a pressure null space.
923: . -snes_monitor [ascii][:filename][:viewer format]                             - prints residual norm at each iteration. if no filename given prints to stdout
924: . -snes_monitor_solution [ascii binary draw][:filename][:viewer format]        - plots solution at each iteration
925: . -snes_monitor_residual [ascii binary draw][:filename][:viewer format]        - plots residual (not its norm) at each iteration
926: . -snes_monitor_solution_update [ascii binary draw][:filename][:viewer format] - plots update to solution at each iteration
927: . -snes_monitor_lg_residualnorm                                                - plots residual norm at each iteration
928: . -snes_monitor_lg_range                                                       - plots residual norm at each iteration
929: . -snes_monitor_pause_final                                                    - Pauses all monitor drawing after the solver ends
930: . -snes_fd                                                                     - use finite differences to compute Jacobian; very slow, only for testing
931: . -snes_fd_color                                                               - use finite differences with coloring to compute Jacobian
932: . -snes_mf_ksp_monitor                                                         - if using matrix-free multiply then print h at each `KSP` iteration
933: . -snes_converged_reason                                                       - print the reason for convergence/divergence after each solve
934: . -npc_snes_type <type>                                                        - the `SNES` type to use as a nonlinear preconditioner
935: . -snes_test_jacobian <optional threshold>                                     - compare the user provided Jacobian with one computed via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
936: - -snes_test_jacobian_view                                                     - display the user provided Jacobian, the finite difference Jacobian and the difference between them to help users detect the location of errors in the user provided Jacobian.

938:   Options Database Keys for Eisenstat-Walker method:
939: + -snes_ksp_ew                       - use Eisenstat-Walker method for determining linear system convergence
940: . -snes_ksp_ew_version ver           - version of  Eisenstat-Walker method
941: . -snes_ksp_ew_rtol0 <rtol0>         - Sets rtol0
942: . -snes_ksp_ew_rtolmax <rtolmax>     - Sets rtolmax
943: . -snes_ksp_ew_gamma <gamma>         - Sets gamma
944: . -snes_ksp_ew_alpha <alpha>         - Sets alpha
945: . -snes_ksp_ew_alpha2 <alpha2>       - Sets alpha2
946: - -snes_ksp_ew_threshold <threshold> - Sets threshold

948:   Level: beginner

950:   Notes:
951:   To see all options, run your program with the -help option or consult the users manual

953:   `SNES` supports three approaches for computing (approximate) Jacobians: user provided via `SNESSetJacobian()`, matrix-free using `MatCreateSNESMF()`,
954:   and computing explicitly with
955:   finite differences and coloring using `MatFDColoring`. It is also possible to use automatic differentiation and the `MatFDColoring` object.

957: .seealso: [](ch_snes), `SNESType`, `SNESSetOptionsPrefix()`, `SNESResetFromOptions()`, `SNES`, `SNESCreate()`, `MatCreateSNESMF()`, `MatFDColoring`
958: @*/
959: PetscErrorCode SNESSetFromOptions(SNES snes)
960: {
961:   PetscBool   flg, pcset, persist, set;
962:   PetscInt    i, indx, lag, grids;
963:   const char *deft        = SNESNEWTONLS;
964:   const char *convtests[] = {"default", "skip", "correct_pressure"};
965:   SNESKSPEW  *kctx        = NULL;
966:   char        type[256], monfilename[PETSC_MAX_PATH_LEN], ewprefix[256];
967:   PCSide      pcside;
968:   const char *optionsprefix;

970:   PetscFunctionBegin;
972:   PetscCall(SNESRegisterAll());
973:   PetscObjectOptionsBegin((PetscObject)snes);
974:   if (((PetscObject)snes)->type_name) deft = ((PetscObject)snes)->type_name;
975:   PetscCall(PetscOptionsFList("-snes_type", "Nonlinear solver method", "SNESSetType", SNESList, deft, type, 256, &flg));
976:   if (flg) {
977:     PetscCall(SNESSetType(snes, type));
978:   } else if (!((PetscObject)snes)->type_name) {
979:     PetscCall(SNESSetType(snes, deft));
980:   }
981:   PetscCall(PetscOptionsReal("-snes_stol", "Stop if step length less than", "SNESSetTolerances", snes->stol, &snes->stol, NULL));
982:   PetscCall(PetscOptionsReal("-snes_atol", "Stop if function norm less than", "SNESSetTolerances", snes->abstol, &snes->abstol, NULL));

984:   PetscCall(PetscOptionsReal("-snes_rtol", "Stop if decrease in function norm less than", "SNESSetTolerances", snes->rtol, &snes->rtol, NULL));
985:   PetscCall(PetscOptionsReal("-snes_divergence_tolerance", "Stop if residual norm increases by this factor", "SNESSetDivergenceTolerance", snes->divtol, &snes->divtol, NULL));
986:   PetscCall(PetscOptionsInt("-snes_max_it", "Maximum iterations", "SNESSetTolerances", snes->max_its, &snes->max_its, NULL));
987:   PetscCall(PetscOptionsInt("-snes_max_funcs", "Maximum function evaluations", "SNESSetTolerances", snes->max_funcs, &snes->max_funcs, NULL));
988:   PetscCall(PetscOptionsInt("-snes_max_fail", "Maximum nonlinear step failures", "SNESSetMaxNonlinearStepFailures", snes->maxFailures, &snes->maxFailures, NULL));
989:   PetscCall(PetscOptionsInt("-snes_max_linear_solve_fail", "Maximum failures in linear solves allowed", "SNESSetMaxLinearSolveFailures", snes->maxLinearSolveFailures, &snes->maxLinearSolveFailures, NULL));
990:   PetscCall(PetscOptionsBool("-snes_error_if_not_converged", "Generate error if solver does not converge", "SNESSetErrorIfNotConverged", snes->errorifnotconverged, &snes->errorifnotconverged, NULL));
991:   PetscCall(PetscOptionsBool("-snes_force_iteration", "Force SNESSolve() to take at least one iteration", "SNESSetForceIteration", snes->forceiteration, &snes->forceiteration, NULL));
992:   PetscCall(PetscOptionsBool("-snes_check_jacobian_domain_error", "Check Jacobian domain error after Jacobian evaluation", "SNESCheckJacobianDomainError", snes->checkjacdomainerror, &snes->checkjacdomainerror, NULL));

994:   PetscCall(PetscOptionsInt("-snes_lag_preconditioner", "How often to rebuild preconditioner", "SNESSetLagPreconditioner", snes->lagpreconditioner, &lag, &flg));
995:   if (flg) {
996:     PetscCheck(lag != -1, PetscObjectComm((PetscObject)snes), PETSC_ERR_USER, "Cannot set the lag to -1 from the command line since the preconditioner must be built as least once, perhaps you mean -2");
997:     PetscCall(SNESSetLagPreconditioner(snes, lag));
998:   }
999:   PetscCall(PetscOptionsBool("-snes_lag_preconditioner_persists", "Preconditioner lagging through multiple SNES solves", "SNESSetLagPreconditionerPersists", snes->lagjac_persist, &persist, &flg));
1000:   if (flg) PetscCall(SNESSetLagPreconditionerPersists(snes, persist));
1001:   PetscCall(PetscOptionsInt("-snes_lag_jacobian", "How often to rebuild Jacobian", "SNESSetLagJacobian", snes->lagjacobian, &lag, &flg));
1002:   if (flg) {
1003:     PetscCheck(lag != -1, PetscObjectComm((PetscObject)snes), PETSC_ERR_USER, "Cannot set the lag to -1 from the command line since the Jacobian must be built as least once, perhaps you mean -2");
1004:     PetscCall(SNESSetLagJacobian(snes, lag));
1005:   }
1006:   PetscCall(PetscOptionsBool("-snes_lag_jacobian_persists", "Jacobian lagging through multiple SNES solves", "SNESSetLagJacobianPersists", snes->lagjac_persist, &persist, &flg));
1007:   if (flg) PetscCall(SNESSetLagJacobianPersists(snes, persist));

1009:   PetscCall(PetscOptionsInt("-snes_grid_sequence", "Use grid sequencing to generate initial guess", "SNESSetGridSequence", snes->gridsequence, &grids, &flg));
1010:   if (flg) PetscCall(SNESSetGridSequence(snes, grids));

1012:   PetscCall(PetscOptionsEList("-snes_convergence_test", "Convergence test", "SNESSetConvergenceTest", convtests, PETSC_STATIC_ARRAY_LENGTH(convtests), "default", &indx, &flg));
1013:   if (flg) {
1014:     switch (indx) {
1015:     case 0:
1016:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedDefault, NULL, NULL));
1017:       break;
1018:     case 1:
1019:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedSkip, NULL, NULL));
1020:       break;
1021:     case 2:
1022:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedCorrectPressure, NULL, NULL));
1023:       break;
1024:     }
1025:   }

1027:   PetscCall(PetscOptionsEList("-snes_norm_schedule", "SNES Norm schedule", "SNESSetNormSchedule", SNESNormSchedules, 5, "function", &indx, &flg));
1028:   if (flg) PetscCall(SNESSetNormSchedule(snes, (SNESNormSchedule)indx));

1030:   PetscCall(PetscOptionsEList("-snes_function_type", "SNES Norm schedule", "SNESSetFunctionType", SNESFunctionTypes, 2, "unpreconditioned", &indx, &flg));
1031:   if (flg) PetscCall(SNESSetFunctionType(snes, (SNESFunctionType)indx));

1033:   kctx = (SNESKSPEW *)snes->kspconvctx;

1035:   PetscCall(PetscOptionsBool("-snes_ksp_ew", "Use Eisentat-Walker linear system convergence test", "SNESKSPSetUseEW", snes->ksp_ewconv, &snes->ksp_ewconv, NULL));

1037:   PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
1038:   PetscCall(PetscSNPrintf(ewprefix, sizeof(ewprefix), "%s%s", optionsprefix ? optionsprefix : "", "snes_"));
1039:   PetscCall(SNESEWSetFromOptions_Private(kctx, PETSC_TRUE, PetscObjectComm((PetscObject)snes), ewprefix));

1041:   flg = PETSC_FALSE;
1042:   PetscCall(PetscOptionsBool("-snes_monitor_cancel", "Remove all monitors", "SNESMonitorCancel", flg, &flg, &set));
1043:   if (set && flg) PetscCall(SNESMonitorCancel(snes));

1045:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor", "Monitor norm of function", "SNESMonitorDefault", SNESMonitorDefault, SNESMonitorDefaultSetUp));
1046:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_short", "Monitor norm of function with fewer digits", "SNESMonitorDefaultShort", SNESMonitorDefaultShort, NULL));
1047:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_range", "Monitor range of elements of function", "SNESMonitorRange", SNESMonitorRange, NULL));

1049:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_ratio", "Monitor ratios of the norm of function for consecutive steps", "SNESMonitorRatio", SNESMonitorRatio, SNESMonitorRatioSetUp));
1050:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_field", "Monitor norm of function (split into fields)", "SNESMonitorDefaultField", SNESMonitorDefaultField, NULL));
1051:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_solution", "View solution at each iteration", "SNESMonitorSolution", SNESMonitorSolution, NULL));
1052:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_solution_update", "View correction at each iteration", "SNESMonitorSolutionUpdate", SNESMonitorSolutionUpdate, NULL));
1053:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_residual", "View residual at each iteration", "SNESMonitorResidual", SNESMonitorResidual, NULL));
1054:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_jacupdate_spectrum", "Print the change in the spectrum of the Jacobian", "SNESMonitorJacUpdateSpectrum", SNESMonitorJacUpdateSpectrum, NULL));
1055:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_fields", "Monitor norm of function per field", "SNESMonitorSet", SNESMonitorFields, NULL));
1056:   PetscCall(PetscOptionsBool("-snes_monitor_pause_final", "Pauses all draw monitors at the final iterate", "SNESMonitorPauseFinal_Internal", PETSC_FALSE, &snes->pauseFinal, NULL));

1058:   PetscCall(PetscOptionsString("-snes_monitor_python", "Use Python function", "SNESMonitorSet", NULL, monfilename, sizeof(monfilename), &flg));
1059:   if (flg) PetscCall(PetscPythonMonitorSet((PetscObject)snes, monfilename));

1061:   flg = PETSC_FALSE;
1062:   PetscCall(PetscOptionsBool("-snes_monitor_lg_range", "Plot function range at each iteration", "SNESMonitorLGRange", flg, &flg, NULL));
1063:   if (flg) {
1064:     PetscViewer ctx;

1066:     PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, NULL, PETSC_DECIDE, PETSC_DECIDE, 400, 300, &ctx));
1067:     PetscCall(SNESMonitorSet(snes, SNESMonitorLGRange, ctx, (PetscErrorCode(*)(void **))PetscViewerDestroy));
1068:   }

1070:   flg = PETSC_FALSE;
1071:   PetscCall(PetscOptionsBool("-snes_converged_reason_view_cancel", "Remove all converged reason viewers", "SNESConvergedReasonViewCancel", flg, &flg, &set));
1072:   if (set && flg) PetscCall(SNESConvergedReasonViewCancel(snes));

1074:   flg = PETSC_FALSE;
1075:   PetscCall(PetscOptionsBool("-snes_fd", "Use finite differences (slow) to compute Jacobian", "SNESComputeJacobianDefault", flg, &flg, NULL));
1076:   if (flg) {
1077:     void *functx;
1078:     DM    dm;
1079:     PetscCall(SNESGetDM(snes, &dm));
1080:     PetscCall(DMSNESUnsetJacobianContext_Internal(dm));
1081:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
1082:     PetscCall(SNESSetJacobian(snes, snes->jacobian, snes->jacobian_pre, SNESComputeJacobianDefault, functx));
1083:     PetscCall(PetscInfo(snes, "Setting default finite difference Jacobian matrix\n"));
1084:   }

1086:   flg = PETSC_FALSE;
1087:   PetscCall(PetscOptionsBool("-snes_fd_function", "Use finite differences (slow) to compute function from user objective", "SNESObjectiveComputeFunctionDefaultFD", flg, &flg, NULL));
1088:   if (flg) PetscCall(SNESSetFunction(snes, NULL, SNESObjectiveComputeFunctionDefaultFD, NULL));

1090:   flg = PETSC_FALSE;
1091:   PetscCall(PetscOptionsBool("-snes_fd_color", "Use finite differences with coloring to compute Jacobian", "SNESComputeJacobianDefaultColor", flg, &flg, NULL));
1092:   if (flg) {
1093:     DM dm;
1094:     PetscCall(SNESGetDM(snes, &dm));
1095:     PetscCall(DMSNESUnsetJacobianContext_Internal(dm));
1096:     PetscCall(SNESSetJacobian(snes, snes->jacobian, snes->jacobian_pre, SNESComputeJacobianDefaultColor, NULL));
1097:     PetscCall(PetscInfo(snes, "Setting default finite difference coloring Jacobian matrix\n"));
1098:   }

1100:   flg = PETSC_FALSE;
1101:   PetscCall(PetscOptionsBool("-snes_mf_operator", "Use a Matrix-Free Jacobian with user-provided preconditioner matrix", "SNESSetUseMatrixFree", PETSC_FALSE, &snes->mf_operator, &flg));
1102:   if (flg && snes->mf_operator) {
1103:     snes->mf_operator = PETSC_TRUE;
1104:     snes->mf          = PETSC_TRUE;
1105:   }
1106:   flg = PETSC_FALSE;
1107:   PetscCall(PetscOptionsBool("-snes_mf", "Use a Matrix-Free Jacobian with no preconditioner matrix", "SNESSetUseMatrixFree", PETSC_FALSE, &snes->mf, &flg));
1108:   if (!flg && snes->mf_operator) snes->mf = PETSC_TRUE;
1109:   PetscCall(PetscOptionsInt("-snes_mf_version", "Matrix-Free routines version 1 or 2", "None", snes->mf_version, &snes->mf_version, NULL));

1111:   flg = PETSC_FALSE;
1112:   PetscCall(SNESGetNPCSide(snes, &pcside));
1113:   PetscCall(PetscOptionsEnum("-snes_npc_side", "SNES nonlinear preconditioner side", "SNESSetNPCSide", PCSides, (PetscEnum)pcside, (PetscEnum *)&pcside, &flg));
1114:   if (flg) PetscCall(SNESSetNPCSide(snes, pcside));

1116: #if defined(PETSC_HAVE_SAWS)
1117:   /*
1118:     Publish convergence information using SAWs
1119:   */
1120:   flg = PETSC_FALSE;
1121:   PetscCall(PetscOptionsBool("-snes_monitor_saws", "Publish SNES progress using SAWs", "SNESMonitorSet", flg, &flg, NULL));
1122:   if (flg) {
1123:     void *ctx;
1124:     PetscCall(SNESMonitorSAWsCreate(snes, &ctx));
1125:     PetscCall(SNESMonitorSet(snes, SNESMonitorSAWs, ctx, SNESMonitorSAWsDestroy));
1126:   }
1127: #endif
1128: #if defined(PETSC_HAVE_SAWS)
1129:   {
1130:     PetscBool set;
1131:     flg = PETSC_FALSE;
1132:     PetscCall(PetscOptionsBool("-snes_saws_block", "Block for SAWs at end of SNESSolve", "PetscObjectSAWsBlock", ((PetscObject)snes)->amspublishblock, &flg, &set));
1133:     if (set) PetscCall(PetscObjectSAWsSetBlock((PetscObject)snes, flg));
1134:   }
1135: #endif

1137:   for (i = 0; i < numberofsetfromoptions; i++) PetscCall((*othersetfromoptions[i])(snes));

1139:   PetscTryTypeMethod(snes, setfromoptions, PetscOptionsObject);

1141:   /* process any options handlers added with PetscObjectAddOptionsHandler() */
1142:   PetscCall(PetscObjectProcessOptionsHandlers((PetscObject)snes, PetscOptionsObject));
1143:   PetscOptionsEnd();

1145:   if (snes->linesearch) {
1146:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
1147:     PetscCall(SNESLineSearchSetFromOptions(snes->linesearch));
1148:   }

1150:   if (snes->usesksp) {
1151:     if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
1152:     PetscCall(KSPSetOperators(snes->ksp, snes->jacobian, snes->jacobian_pre));
1153:     PetscCall(KSPSetFromOptions(snes->ksp));
1154:   }

1156:   /* if user has set the SNES NPC type via options database, create it. */
1157:   PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
1158:   PetscCall(PetscOptionsHasName(((PetscObject)snes)->options, optionsprefix, "-npc_snes_type", &pcset));
1159:   if (pcset && (!snes->npc)) PetscCall(SNESGetNPC(snes, &snes->npc));
1160:   if (snes->npc) PetscCall(SNESSetFromOptions(snes->npc));
1161:   snes->setfromoptionscalled++;
1162:   PetscFunctionReturn(PETSC_SUCCESS);
1163: }

1165: /*@
1166:   SNESResetFromOptions - Sets various `SNES` and `KSP` parameters from user options ONLY if the `SNESSetFromOptions()` was previously called

1168:   Collective

1170:   Input Parameter:
1171: . snes - the `SNES` context

1173:   Level: advanced

1175: .seealso: [](ch_snes), `SNES`, `SNESSetFromOptions()`, `SNESSetOptionsPrefix()`
1176: @*/
1177: PetscErrorCode SNESResetFromOptions(SNES snes)
1178: {
1179:   PetscFunctionBegin;
1180:   if (snes->setfromoptionscalled) PetscCall(SNESSetFromOptions(snes));
1181:   PetscFunctionReturn(PETSC_SUCCESS);
1182: }

1184: /*@C
1185:   SNESSetComputeApplicationContext - Sets an optional function to compute a user-defined context for
1186:   the nonlinear solvers.

1188:   Logically Collective; No Fortran Support

1190:   Input Parameters:
1191: + snes    - the `SNES` context
1192: . compute - function to compute the context
1193: - destroy - function to destroy the context

1195:   Calling sequence of `compute`:
1196: + snes - the `SNES` context
1197: - ctx  - context to be computed

1199:   Calling sequence of `destroy`:
1200: . ctx - context to be computed by `compute()`

1202:   Level: intermediate

1204:   Note:
1205:   This routine is useful if you are performing grid sequencing or using `SNESFAS` and need the appropriate context generated for each level.

1207:   Use `SNESSetApplicationContext()` to see the context immediately

1209: .seealso: [](ch_snes), `SNESGetApplicationContext()`, `SNESSetApplicationContext()`
1210: @*/
1211: PetscErrorCode SNESSetComputeApplicationContext(SNES snes, PetscErrorCode (*compute)(SNES snes, void **ctx), PetscErrorCode (*destroy)(void **ctx))
1212: {
1213:   PetscFunctionBegin;
1215:   snes->ops->usercompute = compute;
1216:   snes->ops->userdestroy = destroy;
1217:   PetscFunctionReturn(PETSC_SUCCESS);
1218: }

1220: /*@
1221:   SNESSetApplicationContext - Sets the optional user-defined context for the nonlinear solvers.

1223:   Logically Collective

1225:   Input Parameters:
1226: + snes - the `SNES` context
1227: - usrP - optional user context

1229:   Level: intermediate

1231:   Notes:
1232:   Users can provide a context when constructing the `SNES` options and then access it inside their function, Jacobian, or other evaluation function
1233:   with `SNESGetApplicationContext()`

1235:   To provide a function that computes the context for you use `SNESSetComputeApplicationContext()`

1237:   Fortran Note:
1238:   You must write a Fortran interface definition for this
1239:   function that tells Fortran the Fortran derived data type that you are passing in as the `usrP` argument.

1241: .seealso: [](ch_snes), `SNES`, `SNESSetComputeApplicationContext()`, `SNESGetApplicationContext()`
1242: @*/
1243: PetscErrorCode SNESSetApplicationContext(SNES snes, void *usrP)
1244: {
1245:   KSP ksp;

1247:   PetscFunctionBegin;
1249:   PetscCall(SNESGetKSP(snes, &ksp));
1250:   PetscCall(KSPSetApplicationContext(ksp, usrP));
1251:   snes->user = usrP;
1252:   PetscFunctionReturn(PETSC_SUCCESS);
1253: }

1255: /*@
1256:   SNESGetApplicationContext - Gets the user-defined context for the
1257:   nonlinear solvers set with `SNESGetApplicationContext()` or `SNESSetComputeApplicationContext()`

1259:   Not Collective

1261:   Input Parameter:
1262: . snes - `SNES` context

1264:   Output Parameter:
1265: . usrP - user context

1267:   Level: intermediate

1269:   Fortran Note:
1270:   You must write a Fortran interface definition for this
1271:   function that tells Fortran the Fortran derived data type that you are passing in as the `usrP` argument.

1273: .seealso: [](ch_snes), `SNESSetApplicationContext()`, `SNESSetComputeApplicationContext()`
1274: @*/
1275: PetscErrorCode SNESGetApplicationContext(SNES snes, void *usrP)
1276: {
1277:   PetscFunctionBegin;
1279:   *(void **)usrP = snes->user;
1280:   PetscFunctionReturn(PETSC_SUCCESS);
1281: }

1283: /*@
1284:   SNESSetUseMatrixFree - indicates that `SNES` should use matrix-free finite difference matrix-vector products to apply the Jacobian.

1286:   Logically Collective

1288:   Input Parameters:
1289: + snes        - `SNES` context
1290: . mf_operator - use matrix-free only for the Amat used by `SNESSetJacobian()`, this means the user provided Pmat will continue to be used
1291: - mf          - use matrix-free for both the Amat and Pmat used by `SNESSetJacobian()`, both the Amat and Pmat set in `SNESSetJacobian()` will be ignored. With
1292:    this option no matrix-element based preconditioners can be used in the linear solve since the matrix won't be explicitly available

1294:   Options Database Keys:
1295: + -snes_mf_operator - use matrix-free only for the mat operator
1296: . -snes_mf          - use matrix-free for both the mat and pmat operator
1297: . -snes_fd_color    - compute the Jacobian via coloring and finite differences.
1298: - -snes_fd          - compute the Jacobian via finite differences (slow)

1300:   Level: intermediate

1302:   Note:
1303:   `SNES` supports three approaches for computing (approximate) Jacobians: user provided via `SNESSetJacobian()`, matrix-free using `MatCreateSNESMF()`,
1304:   and computing explicitly with
1305:   finite differences and coloring using `MatFDColoring`. It is also possible to use automatic differentiation and the `MatFDColoring` object.

1307: .seealso: [](ch_snes), `SNES`, `SNESGetUseMatrixFree()`, `MatCreateSNESMF()`, `SNESComputeJacobianDefaultColor()`, `MatFDColoring`
1308: @*/
1309: PetscErrorCode SNESSetUseMatrixFree(SNES snes, PetscBool mf_operator, PetscBool mf)
1310: {
1311:   PetscFunctionBegin;
1315:   snes->mf          = mf_operator ? PETSC_TRUE : mf;
1316:   snes->mf_operator = mf_operator;
1317:   PetscFunctionReturn(PETSC_SUCCESS);
1318: }

1320: /*@
1321:   SNESGetUseMatrixFree - indicates if the `SNES` uses matrix-free finite difference matrix vector products to apply the Jacobian.

1323:   Not Collective, but the resulting flags will be the same on all MPI processes

1325:   Input Parameter:
1326: . snes - `SNES` context

1328:   Output Parameters:
1329: + mf_operator - use matrix-free only for the Amat used by `SNESSetJacobian()`, this means the user provided Pmat will continue to be used
1330: - mf          - use matrix-free for both the Amat and Pmat used by `SNESSetJacobian()`, both the Amat and Pmat set in `SNESSetJacobian()` will be ignored

1332:   Level: intermediate

1334: .seealso: [](ch_snes), `SNES`, `SNESSetUseMatrixFree()`, `MatCreateSNESMF()`
1335: @*/
1336: PetscErrorCode SNESGetUseMatrixFree(SNES snes, PetscBool *mf_operator, PetscBool *mf)
1337: {
1338:   PetscFunctionBegin;
1340:   if (mf) *mf = snes->mf;
1341:   if (mf_operator) *mf_operator = snes->mf_operator;
1342:   PetscFunctionReturn(PETSC_SUCCESS);
1343: }

1345: /*@
1346:   SNESGetIterationNumber - Gets the number of nonlinear iterations completed in the current or most recent `SNESSolve()`

1348:   Not Collective

1350:   Input Parameter:
1351: . snes - `SNES` context

1353:   Output Parameter:
1354: . iter - iteration number

1356:   Level: intermediate

1358:   Notes:
1359:   For example, during the computation of iteration 2 this would return 1.

1361:   This is useful for using lagged Jacobians (where one does not recompute the
1362:   Jacobian at each `SNES` iteration). For example, the code
1363: .vb
1364:       ierr = SNESGetIterationNumber(snes,&it);
1365:       if (!(it % 2)) {
1366:         [compute Jacobian here]
1367:       }
1368: .ve
1369:   can be used in your function that computes the Jacobian to cause the Jacobian to be
1370:   recomputed every second `SNES` iteration. See also `SNESSetLagJacobian()`

1372:   After the `SNES` solve is complete this will return the number of nonlinear iterations used.

1374: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetLagJacobian()`, `SNESGetLinearSolveIterations()`, `SNESSetMonitor()`
1375: @*/
1376: PetscErrorCode SNESGetIterationNumber(SNES snes, PetscInt *iter)
1377: {
1378:   PetscFunctionBegin;
1380:   PetscAssertPointer(iter, 2);
1381:   *iter = snes->iter;
1382:   PetscFunctionReturn(PETSC_SUCCESS);
1383: }

1385: /*@
1386:   SNESSetIterationNumber - Sets the current iteration number.

1388:   Not Collective

1390:   Input Parameters:
1391: + snes - `SNES` context
1392: - iter - iteration number

1394:   Level: developer

1396:   Note:
1397:   This should only be called inside a `SNES` nonlinear solver.

1399: .seealso: [](ch_snes), `SNESGetLinearSolveIterations()`
1400: @*/
1401: PetscErrorCode SNESSetIterationNumber(SNES snes, PetscInt iter)
1402: {
1403:   PetscFunctionBegin;
1405:   PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
1406:   snes->iter = iter;
1407:   PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
1408:   PetscFunctionReturn(PETSC_SUCCESS);
1409: }

1411: /*@
1412:   SNESGetNonlinearStepFailures - Gets the number of unsuccessful steps
1413:   attempted by the nonlinear solver in the current or most recent `SNESSolve()` .

1415:   Not Collective

1417:   Input Parameter:
1418: . snes - `SNES` context

1420:   Output Parameter:
1421: . nfails - number of unsuccessful steps attempted

1423:   Level: intermediate

1425:   Note:
1426:   This counter is reset to zero for each successive call to `SNESSolve()`.

1428: .seealso: [](ch_snes), `SNES`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1429:           `SNESSetMaxNonlinearStepFailures()`, `SNESGetMaxNonlinearStepFailures()`
1430: @*/
1431: PetscErrorCode SNESGetNonlinearStepFailures(SNES snes, PetscInt *nfails)
1432: {
1433:   PetscFunctionBegin;
1435:   PetscAssertPointer(nfails, 2);
1436:   *nfails = snes->numFailures;
1437:   PetscFunctionReturn(PETSC_SUCCESS);
1438: }

1440: /*@
1441:   SNESSetMaxNonlinearStepFailures - Sets the maximum number of unsuccessful steps
1442:   attempted by the nonlinear solver before it gives up and returns unconverged or generates an error

1444:   Not Collective

1446:   Input Parameters:
1447: + snes     - `SNES` context
1448: - maxFails - maximum of unsuccessful steps

1450:   Options Database Key:
1451: . -snes_max_fail <n> - maximum number of unsuccessful steps allowed

1453:   Level: intermediate

1455:   Developer Note:
1456:   The options database key is wrong for this function name

1458: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1459:           `SNESGetMaxNonlinearStepFailures()`, `SNESGetNonlinearStepFailures()`
1460: @*/
1461: PetscErrorCode SNESSetMaxNonlinearStepFailures(SNES snes, PetscInt maxFails)
1462: {
1463:   PetscFunctionBegin;
1465:   snes->maxFailures = maxFails;
1466:   PetscFunctionReturn(PETSC_SUCCESS);
1467: }

1469: /*@
1470:   SNESGetMaxNonlinearStepFailures - Gets the maximum number of unsuccessful steps
1471:   attempted by the nonlinear solver before it gives up and returns unconverged or generates an error

1473:   Not Collective

1475:   Input Parameter:
1476: . snes - `SNES` context

1478:   Output Parameter:
1479: . maxFails - maximum of unsuccessful steps

1481:   Level: intermediate

1483: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1484:           `SNESSetMaxNonlinearStepFailures()`, `SNESGetNonlinearStepFailures()`
1485: @*/
1486: PetscErrorCode SNESGetMaxNonlinearStepFailures(SNES snes, PetscInt *maxFails)
1487: {
1488:   PetscFunctionBegin;
1490:   PetscAssertPointer(maxFails, 2);
1491:   *maxFails = snes->maxFailures;
1492:   PetscFunctionReturn(PETSC_SUCCESS);
1493: }

1495: /*@
1496:   SNESGetNumberFunctionEvals - Gets the number of user provided function evaluations
1497:   done by the `SNES` object in the current or most recent `SNESSolve()`

1499:   Not Collective

1501:   Input Parameter:
1502: . snes - `SNES` context

1504:   Output Parameter:
1505: . nfuncs - number of evaluations

1507:   Level: intermediate

1509:   Note:
1510:   Reset every time `SNESSolve()` is called unless `SNESSetCountersReset()` is used.

1512: .seealso: [](ch_snes), `SNES`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`, `SNESSetCountersReset()`
1513: @*/
1514: PetscErrorCode SNESGetNumberFunctionEvals(SNES snes, PetscInt *nfuncs)
1515: {
1516:   PetscFunctionBegin;
1518:   PetscAssertPointer(nfuncs, 2);
1519:   *nfuncs = snes->nfuncs;
1520:   PetscFunctionReturn(PETSC_SUCCESS);
1521: }

1523: /*@
1524:   SNESGetLinearSolveFailures - Gets the number of failed (non-converged)
1525:   linear solvers in the current or most recent `SNESSolve()`

1527:   Not Collective

1529:   Input Parameter:
1530: . snes - `SNES` context

1532:   Output Parameter:
1533: . nfails - number of failed solves

1535:   Options Database Key:
1536: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

1538:   Level: intermediate

1540:   Note:
1541:   This counter is reset to zero for each successive call to `SNESSolve()`.

1543: .seealso: [](ch_snes), `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`
1544: @*/
1545: PetscErrorCode SNESGetLinearSolveFailures(SNES snes, PetscInt *nfails)
1546: {
1547:   PetscFunctionBegin;
1549:   PetscAssertPointer(nfails, 2);
1550:   *nfails = snes->numLinearSolveFailures;
1551:   PetscFunctionReturn(PETSC_SUCCESS);
1552: }

1554: /*@
1555:   SNESSetMaxLinearSolveFailures - the number of failed linear solve attempts
1556:   allowed before `SNES` returns with a diverged reason of `SNES_DIVERGED_LINEAR_SOLVE`

1558:   Logically Collective

1560:   Input Parameters:
1561: + snes     - `SNES` context
1562: - maxFails - maximum allowed linear solve failures

1564:   Options Database Key:
1565: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

1567:   Level: intermediate

1569:   Note:
1570:   By default this is 0; that is `SNES` returns on the first failed linear solve

1572:   Developer Note:
1573:   The options database key is wrong for this function name

1575: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetLinearSolveFailures()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`
1576: @*/
1577: PetscErrorCode SNESSetMaxLinearSolveFailures(SNES snes, PetscInt maxFails)
1578: {
1579:   PetscFunctionBegin;
1582:   snes->maxLinearSolveFailures = maxFails;
1583:   PetscFunctionReturn(PETSC_SUCCESS);
1584: }

1586: /*@
1587:   SNESGetMaxLinearSolveFailures - gets the maximum number of linear solve failures that
1588:   are allowed before `SNES` returns as unsuccessful

1590:   Not Collective

1592:   Input Parameter:
1593: . snes - `SNES` context

1595:   Output Parameter:
1596: . maxFails - maximum of unsuccessful solves allowed

1598:   Level: intermediate

1600:   Note:
1601:   By default this is 1; that is `SNES` returns on the first failed linear solve

1603: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`,
1604: @*/
1605: PetscErrorCode SNESGetMaxLinearSolveFailures(SNES snes, PetscInt *maxFails)
1606: {
1607:   PetscFunctionBegin;
1609:   PetscAssertPointer(maxFails, 2);
1610:   *maxFails = snes->maxLinearSolveFailures;
1611:   PetscFunctionReturn(PETSC_SUCCESS);
1612: }

1614: /*@
1615:   SNESGetLinearSolveIterations - Gets the total number of linear iterations
1616:   used by the nonlinear solver in the most recent `SNESSolve()`

1618:   Not Collective

1620:   Input Parameter:
1621: . snes - `SNES` context

1623:   Output Parameter:
1624: . lits - number of linear iterations

1626:   Level: intermediate

1628:   Notes:
1629:   This counter is reset to zero for each successive call to `SNESSolve()` unless `SNESSetCountersReset()` is used.

1631:   If the linear solver fails inside the `SNESSolve()` the iterations for that call to the linear solver are not included. If you wish to count them
1632:   then call `KSPGetIterationNumber()` after the failed solve.

1634: .seealso: [](ch_snes), `SNES`, `SNESGetIterationNumber()`, `SNESGetLinearSolveFailures()`, `SNESGetMaxLinearSolveFailures()`, `SNESSetCountersReset()`
1635: @*/
1636: PetscErrorCode SNESGetLinearSolveIterations(SNES snes, PetscInt *lits)
1637: {
1638:   PetscFunctionBegin;
1640:   PetscAssertPointer(lits, 2);
1641:   *lits = snes->linear_its;
1642:   PetscFunctionReturn(PETSC_SUCCESS);
1643: }

1645: /*@
1646:   SNESSetCountersReset - Sets whether or not the counters for linear iterations and function evaluations
1647:   are reset every time `SNESSolve()` is called.

1649:   Logically Collective

1651:   Input Parameters:
1652: + snes  - `SNES` context
1653: - reset - whether to reset the counters or not, defaults to `PETSC_TRUE`

1655:   Level: developer

1657: .seealso: [](ch_snes), `SNESGetNumberFunctionEvals()`, `SNESGetLinearSolveIterations()`, `SNESGetNPC()`
1658: @*/
1659: PetscErrorCode SNESSetCountersReset(SNES snes, PetscBool reset)
1660: {
1661:   PetscFunctionBegin;
1664:   snes->counters_reset = reset;
1665:   PetscFunctionReturn(PETSC_SUCCESS);
1666: }

1668: /*@
1669:   SNESSetKSP - Sets a `KSP` context for the `SNES` object to use

1671:   Not Collective, but the `SNES` and `KSP` objects must live on the same `MPI_Comm`

1673:   Input Parameters:
1674: + snes - the `SNES` context
1675: - ksp  - the `KSP` context

1677:   Level: developer

1679:   Notes:
1680:   The `SNES` object already has its `KSP` object, you can obtain with `SNESGetKSP()`
1681:   so this routine is rarely needed.

1683:   The `KSP` object that is already in the `SNES` object has its reference count
1684:   decreased by one when this is called.

1686: .seealso: [](ch_snes), `SNES`, `KSP`, `KSPGetPC()`, `SNESCreate()`, `KSPCreate()`
1687: @*/
1688: PetscErrorCode SNESSetKSP(SNES snes, KSP ksp)
1689: {
1690:   PetscFunctionBegin;
1693:   PetscCheckSameComm(snes, 1, ksp, 2);
1694:   PetscCall(PetscObjectReference((PetscObject)ksp));
1695:   if (snes->ksp) PetscCall(PetscObjectDereference((PetscObject)snes->ksp));
1696:   snes->ksp = ksp;
1697:   PetscFunctionReturn(PETSC_SUCCESS);
1698: }

1700: /*@
1701:   SNESCreate - Creates a nonlinear solver context used to manage a set of nonlinear solves

1703:   Collective

1705:   Input Parameter:
1706: . comm - MPI communicator

1708:   Output Parameter:
1709: . outsnes - the new `SNES` context

1711:   Options Database Keys:
1712: + -snes_mf          - Activates default matrix-free Jacobian-vector products, and no preconditioning matrix
1713: . -snes_mf_operator - Activates default matrix-free Jacobian-vector products, and a user-provided preconditioning matrix
1714:                as set by `SNESSetJacobian()`
1715: . -snes_fd_coloring - uses a relative fast computation of the Jacobian using finite differences and a graph coloring
1716: - -snes_fd          - Uses (slow!) finite differences to compute Jacobian

1718:   Level: beginner

1720:   Developer Notes:
1721:   `SNES` always creates a `KSP` object even though many `SNES` methods do not use it. This is
1722:   unfortunate and should be fixed at some point. The flag snes->usesksp indicates if the
1723:   particular method does use `KSP` and regulates if the information about the `KSP` is printed
1724:   in `SNESView()`.

1726:   `TSSetFromOptions()` does call `SNESSetFromOptions()` which can lead to users being confused
1727:   by help messages about meaningless `SNES` options.

1729:   `SNES` always creates the snes->kspconvctx even though it is used by only one type. This should be fixed.

1731: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESDestroy()`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`
1732: @*/
1733: PetscErrorCode SNESCreate(MPI_Comm comm, SNES *outsnes)
1734: {
1735:   SNES       snes;
1736:   SNESKSPEW *kctx;

1738:   PetscFunctionBegin;
1739:   PetscAssertPointer(outsnes, 2);
1740:   *outsnes = NULL;
1741:   PetscCall(SNESInitializePackage());

1743:   PetscCall(PetscHeaderCreate(snes, SNES_CLASSID, "SNES", "Nonlinear solver", "SNES", comm, SNESDestroy, SNESView));

1745:   snes->ops->converged       = SNESConvergedDefault;
1746:   snes->usesksp              = PETSC_TRUE;
1747:   snes->tolerancesset        = PETSC_FALSE;
1748:   snes->max_its              = 50;
1749:   snes->max_funcs            = 10000;
1750:   snes->norm                 = 0.0;
1751:   snes->xnorm                = 0.0;
1752:   snes->ynorm                = 0.0;
1753:   snes->normschedule         = SNES_NORM_ALWAYS;
1754:   snes->functype             = SNES_FUNCTION_DEFAULT;
1755:   snes->rtol                 = PetscDefined(USE_REAL_SINGLE) ? 1.e-5 : 1.e-8;
1756:   snes->ttol                 = 0.0;
1757:   snes->abstol               = PetscDefined(USE_REAL_SINGLE) ? 1.e-25 : 1.e-50;
1758:   snes->stol                 = PetscDefined(USE_REAL_SINGLE) ? 1.e-5 : 1.e-8;
1759:   snes->deltatol             = PetscDefined(USE_REAL_SINGLE) ? 1.e-6 : 1.e-12;
1760:   snes->divtol               = 1.e4;
1761:   snes->rnorm0               = 0;
1762:   snes->nfuncs               = 0;
1763:   snes->numFailures          = 0;
1764:   snes->maxFailures          = 1;
1765:   snes->linear_its           = 0;
1766:   snes->lagjacobian          = 1;
1767:   snes->jac_iter             = 0;
1768:   snes->lagjac_persist       = PETSC_FALSE;
1769:   snes->lagpreconditioner    = 1;
1770:   snes->pre_iter             = 0;
1771:   snes->lagpre_persist       = PETSC_FALSE;
1772:   snes->numbermonitors       = 0;
1773:   snes->numberreasonviews    = 0;
1774:   snes->data                 = NULL;
1775:   snes->setupcalled          = PETSC_FALSE;
1776:   snes->ksp_ewconv           = PETSC_FALSE;
1777:   snes->nwork                = 0;
1778:   snes->work                 = NULL;
1779:   snes->nvwork               = 0;
1780:   snes->vwork                = NULL;
1781:   snes->conv_hist_len        = 0;
1782:   snes->conv_hist_max        = 0;
1783:   snes->conv_hist            = NULL;
1784:   snes->conv_hist_its        = NULL;
1785:   snes->conv_hist_reset      = PETSC_TRUE;
1786:   snes->counters_reset       = PETSC_TRUE;
1787:   snes->vec_func_init_set    = PETSC_FALSE;
1788:   snes->reason               = SNES_CONVERGED_ITERATING;
1789:   snes->npcside              = PC_RIGHT;
1790:   snes->setfromoptionscalled = 0;

1792:   snes->mf          = PETSC_FALSE;
1793:   snes->mf_operator = PETSC_FALSE;
1794:   snes->mf_version  = 1;

1796:   snes->numLinearSolveFailures = 0;
1797:   snes->maxLinearSolveFailures = 1;

1799:   snes->vizerotolerance     = 1.e-8;
1800:   snes->checkjacdomainerror = PetscDefined(USE_DEBUG) ? PETSC_TRUE : PETSC_FALSE;

1802:   /* Set this to true if the implementation of SNESSolve_XXX does compute the residual at the final solution. */
1803:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

1805:   /* Create context to compute Eisenstat-Walker relative tolerance for KSP */
1806:   PetscCall(PetscNew(&kctx));

1808:   snes->kspconvctx  = (void *)kctx;
1809:   kctx->version     = 2;
1810:   kctx->rtol_0      = 0.3; /* Eisenstat and Walker suggest rtol_0=.5, but
1811:                              this was too large for some test cases */
1812:   kctx->rtol_last   = 0.0;
1813:   kctx->rtol_max    = 0.9;
1814:   kctx->gamma       = 1.0;
1815:   kctx->alpha       = 0.5 * (1.0 + PetscSqrtReal(5.0));
1816:   kctx->alpha2      = kctx->alpha;
1817:   kctx->threshold   = 0.1;
1818:   kctx->lresid_last = 0.0;
1819:   kctx->norm_last   = 0.0;

1821:   kctx->rk_last     = 0.0;
1822:   kctx->rk_last_2   = 0.0;
1823:   kctx->rtol_last_2 = 0.0;
1824:   kctx->v4_p1       = 0.1;
1825:   kctx->v4_p2       = 0.4;
1826:   kctx->v4_p3       = 0.7;
1827:   kctx->v4_m1       = 0.8;
1828:   kctx->v4_m2       = 0.5;
1829:   kctx->v4_m3       = 0.1;
1830:   kctx->v4_m4       = 0.5;

1832:   *outsnes = snes;
1833:   PetscFunctionReturn(PETSC_SUCCESS);
1834: }

1836: /*MC
1837:     SNESFunction - Functional form used to convey the nonlinear function to `SNES` in `SNESSetFunction()`

1839:      Synopsis:
1840:      #include "petscsnes.h"
1841:      PetscErrorCode SNESFunction(SNES snes,Vec x,Vec f,void *ctx);

1843:      Collective

1845:      Input Parameters:
1846: +     snes - the `SNES` context
1847: .     x    - state at which to evaluate residual
1848: -     ctx     - optional user-defined function context, passed in with `SNESSetFunction()`

1850:      Output Parameter:
1851: .     f  - vector to put residual (function value)

1853:    Level: intermediate

1855: .seealso: [](ch_snes), `SNESSetFunction()`, `SNESGetFunction()`
1856: M*/

1858: /*@C
1859:   SNESSetFunction - Sets the function evaluation routine and function
1860:   vector for use by the `SNES` routines in solving systems of nonlinear
1861:   equations.

1863:   Logically Collective

1865:   Input Parameters:
1866: + snes - the `SNES` context
1867: . r    - vector to store function values, may be `NULL`
1868: . f    - function evaluation routine;  for calling sequence see `SNESFunction`
1869: - ctx  - [optional] user-defined context for private data for the
1870:          function evaluation routine (may be `NULL`)

1872:   Level: beginner

1874: .seealso: [](ch_snes), `SNES`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESSetPicard()`, `SNESFunction`
1875: @*/
1876: PetscErrorCode SNESSetFunction(SNES snes, Vec r, PetscErrorCode (*f)(SNES, Vec, Vec, void *), void *ctx)
1877: {
1878:   DM dm;

1880:   PetscFunctionBegin;
1882:   if (r) {
1884:     PetscCheckSameComm(snes, 1, r, 2);
1885:     PetscCall(PetscObjectReference((PetscObject)r));
1886:     PetscCall(VecDestroy(&snes->vec_func));
1887:     snes->vec_func = r;
1888:   }
1889:   PetscCall(SNESGetDM(snes, &dm));
1890:   PetscCall(DMSNESSetFunction(dm, f, ctx));
1891:   if (f == SNESPicardComputeFunction) PetscCall(DMSNESSetMFFunction(dm, SNESPicardComputeMFFunction, ctx));
1892:   PetscFunctionReturn(PETSC_SUCCESS);
1893: }

1895: /*@C
1896:   SNESSetInitialFunction - Set an already computed function evaluation at the initial guess to be reused by `SNESSolve()`.

1898:   Logically Collective

1900:   Input Parameters:
1901: + snes - the `SNES` context
1902: - f    - vector to store function value

1904:   Level: developer

1906:   Notes:
1907:   This should not be modified during the solution procedure.

1909:   This is used extensively in the `SNESFAS` hierarchy and in nonlinear preconditioning.

1911: .seealso: [](ch_snes), `SNES`, `SNESFAS`, `SNESSetFunction()`, `SNESComputeFunction()`, `SNESSetInitialFunctionNorm()`
1912: @*/
1913: PetscErrorCode SNESSetInitialFunction(SNES snes, Vec f)
1914: {
1915:   Vec vec_func;

1917:   PetscFunctionBegin;
1920:   PetscCheckSameComm(snes, 1, f, 2);
1921:   if (snes->npcside == PC_LEFT && snes->functype == SNES_FUNCTION_PRECONDITIONED) {
1922:     snes->vec_func_init_set = PETSC_FALSE;
1923:     PetscFunctionReturn(PETSC_SUCCESS);
1924:   }
1925:   PetscCall(SNESGetFunction(snes, &vec_func, NULL, NULL));
1926:   PetscCall(VecCopy(f, vec_func));

1928:   snes->vec_func_init_set = PETSC_TRUE;
1929:   PetscFunctionReturn(PETSC_SUCCESS);
1930: }

1932: /*@
1933:   SNESSetNormSchedule - Sets the `SNESNormSchedule` used in convergence and monitoring
1934:   of the `SNES` method, when norms are computed in the solving process

1936:   Logically Collective

1938:   Input Parameters:
1939: + snes         - the `SNES` context
1940: - normschedule - the frequency of norm computation

1942:   Options Database Key:
1943: . -snes_norm_schedule <none, always, initialonly, finalonly, initialfinalonly> - set the schedule

1945:   Level: advanced

1947:   Notes:
1948:   Only certain `SNES` methods support certain `SNESNormSchedules`.  Most require evaluation
1949:   of the nonlinear function and the taking of its norm at every iteration to
1950:   even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
1951:   `SNESNGS` and the like do not require the norm of the function to be computed, and therefore
1952:   may either be monitored for convergence or not.  As these are often used as nonlinear
1953:   preconditioners, monitoring the norm of their error is not a useful enterprise within
1954:   their solution.

1956: .seealso: [](ch_snes), `SNESNormSchedule`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`
1957: @*/
1958: PetscErrorCode SNESSetNormSchedule(SNES snes, SNESNormSchedule normschedule)
1959: {
1960:   PetscFunctionBegin;
1962:   snes->normschedule = normschedule;
1963:   PetscFunctionReturn(PETSC_SUCCESS);
1964: }

1966: /*@
1967:   SNESGetNormSchedule - Gets the `SNESNormSchedule` used in convergence and monitoring
1968:   of the `SNES` method.

1970:   Logically Collective

1972:   Input Parameters:
1973: + snes         - the `SNES` context
1974: - normschedule - the type of the norm used

1976:   Level: advanced

1978: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
1979: @*/
1980: PetscErrorCode SNESGetNormSchedule(SNES snes, SNESNormSchedule *normschedule)
1981: {
1982:   PetscFunctionBegin;
1984:   *normschedule = snes->normschedule;
1985:   PetscFunctionReturn(PETSC_SUCCESS);
1986: }

1988: /*@
1989:   SNESSetFunctionNorm - Sets the last computed residual norm.

1991:   Logically Collective

1993:   Input Parameters:
1994: + snes - the `SNES` context
1995: - norm - the value of the norm

1997:   Level: developer

1999: .seealso: [](ch_snes), `SNES`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2000: @*/
2001: PetscErrorCode SNESSetFunctionNorm(SNES snes, PetscReal norm)
2002: {
2003:   PetscFunctionBegin;
2005:   snes->norm = norm;
2006:   PetscFunctionReturn(PETSC_SUCCESS);
2007: }

2009: /*@
2010:   SNESGetFunctionNorm - Gets the last computed norm of the residual

2012:   Not Collective

2014:   Input Parameter:
2015: . snes - the `SNES` context

2017:   Output Parameter:
2018: . norm - the last computed residual norm

2020:   Level: developer

2022: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2023: @*/
2024: PetscErrorCode SNESGetFunctionNorm(SNES snes, PetscReal *norm)
2025: {
2026:   PetscFunctionBegin;
2028:   PetscAssertPointer(norm, 2);
2029:   *norm = snes->norm;
2030:   PetscFunctionReturn(PETSC_SUCCESS);
2031: }

2033: /*@
2034:   SNESGetUpdateNorm - Gets the last computed norm of the solution update

2036:   Not Collective

2038:   Input Parameter:
2039: . snes - the `SNES` context

2041:   Output Parameter:
2042: . ynorm - the last computed update norm

2044:   Level: developer

2046:   Note:
2047:   The new solution is the current solution plus the update, so this norm is an indication of the size of the update

2049: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `SNESGetFunctionNorm()`
2050: @*/
2051: PetscErrorCode SNESGetUpdateNorm(SNES snes, PetscReal *ynorm)
2052: {
2053:   PetscFunctionBegin;
2055:   PetscAssertPointer(ynorm, 2);
2056:   *ynorm = snes->ynorm;
2057:   PetscFunctionReturn(PETSC_SUCCESS);
2058: }

2060: /*@
2061:   SNESGetSolutionNorm - Gets the last computed norm of the solution

2063:   Not Collective

2065:   Input Parameter:
2066: . snes - the `SNES` context

2068:   Output Parameter:
2069: . xnorm - the last computed solution norm

2071:   Level: developer

2073: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `SNESGetFunctionNorm()`, `SNESGetUpdateNorm()`
2074: @*/
2075: PetscErrorCode SNESGetSolutionNorm(SNES snes, PetscReal *xnorm)
2076: {
2077:   PetscFunctionBegin;
2079:   PetscAssertPointer(xnorm, 2);
2080:   *xnorm = snes->xnorm;
2081:   PetscFunctionReturn(PETSC_SUCCESS);
2082: }

2084: /*@C
2085:   SNESSetFunctionType - Sets the `SNESFunctionType`
2086:   of the `SNES` method.

2088:   Logically Collective

2090:   Input Parameters:
2091: + snes - the `SNES` context
2092: - type - the function type

2094:   Level: developer

2096:   Values of the function type\:
2097: +  `SNES_FUNCTION_DEFAULT` - the default for the given `SNESType`
2098: .  `SNES_FUNCTION_UNPRECONDITIONED` - an unpreconditioned function evaluation (this is the function provided with `SNESSetFunction()`
2099: -  `SNES_FUNCTION_PRECONDITIONED` - a transformation of the function provided with `SNESSetFunction()`

2101:   Note:
2102:   Different `SNESType`s use this value in different ways

2104: .seealso: [](ch_snes), `SNES`, `SNESFunctionType`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2105: @*/
2106: PetscErrorCode SNESSetFunctionType(SNES snes, SNESFunctionType type)
2107: {
2108:   PetscFunctionBegin;
2110:   snes->functype = type;
2111:   PetscFunctionReturn(PETSC_SUCCESS);
2112: }

2114: /*@C
2115:   SNESGetFunctionType - Gets the `SNESFunctionType` used in convergence and monitoring set with `SNESSetFunctionType()`
2116:   of the SNES method.

2118:   Logically Collective

2120:   Input Parameters:
2121: + snes - the `SNES` context
2122: - type - the type of the function evaluation, see `SNESSetFunctionType()`

2124:   Level: advanced

2126: .seealso: [](ch_snes), `SNESSetFunctionType()`, `SNESFunctionType`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2127: @*/
2128: PetscErrorCode SNESGetFunctionType(SNES snes, SNESFunctionType *type)
2129: {
2130:   PetscFunctionBegin;
2132:   *type = snes->functype;
2133:   PetscFunctionReturn(PETSC_SUCCESS);
2134: }

2136: /*@C
2137:   SNESSetNGS - Sets the user nonlinear Gauss-Seidel routine for
2138:   use with composed nonlinear solvers.

2140:   Input Parameters:
2141: + snes - the `SNES` context
2142: . f    - function evaluation routine to apply Gauss-Seidel
2143: - ctx  - [optional] user-defined context for private data for the
2144:             smoother evaluation routine (may be `NULL`)

2146:   Calling sequence of `f`:
2147: + snes - the `SNES` context
2148: . X    - the current solution
2149: . B    - the right hand side vector (which may be `NULL`)
2150: - ctx  - a user provided context

2152:   Level: intermediate

2154:   Note:
2155:   The `SNESNGS` routines are used by the composed nonlinear solver to generate
2156:   a problem appropriate update to the solution, particularly `SNESFAS`.

2158: .seealso: [](ch_snes), `SNESGetNGS()`, `SNESNCG`, `SNESGetFunction()`, `SNESComputeNGS()`
2159: @*/
2160: PetscErrorCode SNESSetNGS(SNES snes, PetscErrorCode (*f)(SNES snes, Vec X, Vec B, void *ctx), void *ctx)
2161: {
2162:   DM dm;

2164:   PetscFunctionBegin;
2166:   PetscCall(SNESGetDM(snes, &dm));
2167:   PetscCall(DMSNESSetNGS(dm, f, ctx));
2168:   PetscFunctionReturn(PETSC_SUCCESS);
2169: }

2171: /*
2172:      This is used for -snes_mf_operator; it uses a duplicate of snes->jacobian_pre because snes->jacobian_pre cannot be
2173:    changed during the KSPSolve()
2174: */
2175: PetscErrorCode SNESPicardComputeMFFunction(SNES snes, Vec x, Vec f, void *ctx)
2176: {
2177:   DM     dm;
2178:   DMSNES sdm;

2180:   PetscFunctionBegin;
2181:   PetscCall(SNESGetDM(snes, &dm));
2182:   PetscCall(DMGetDMSNES(dm, &sdm));
2183:   /*  A(x)*x - b(x) */
2184:   if (sdm->ops->computepfunction) {
2185:     PetscCallBack("SNES Picard callback function", (*sdm->ops->computepfunction)(snes, x, f, sdm->pctx));
2186:     PetscCall(VecScale(f, -1.0));
2187:     /* Cannot share nonzero pattern because of the possible use of SNESComputeJacobianDefault() */
2188:     if (!snes->picard) PetscCall(MatDuplicate(snes->jacobian_pre, MAT_DO_NOT_COPY_VALUES, &snes->picard));
2189:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->picard, snes->picard, sdm->pctx));
2190:     PetscCall(MatMultAdd(snes->picard, x, f, f));
2191:   } else {
2192:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->picard, snes->picard, sdm->pctx));
2193:     PetscCall(MatMult(snes->picard, x, f));
2194:   }
2195:   PetscFunctionReturn(PETSC_SUCCESS);
2196: }

2198: PetscErrorCode SNESPicardComputeFunction(SNES snes, Vec x, Vec f, void *ctx)
2199: {
2200:   DM     dm;
2201:   DMSNES sdm;

2203:   PetscFunctionBegin;
2204:   PetscCall(SNESGetDM(snes, &dm));
2205:   PetscCall(DMGetDMSNES(dm, &sdm));
2206:   /*  A(x)*x - b(x) */
2207:   if (sdm->ops->computepfunction) {
2208:     PetscCallBack("SNES Picard callback function", (*sdm->ops->computepfunction)(snes, x, f, sdm->pctx));
2209:     PetscCall(VecScale(f, -1.0));
2210:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->jacobian, snes->jacobian_pre, sdm->pctx));
2211:     PetscCall(MatMultAdd(snes->jacobian_pre, x, f, f));
2212:   } else {
2213:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->jacobian, snes->jacobian_pre, sdm->pctx));
2214:     PetscCall(MatMult(snes->jacobian_pre, x, f));
2215:   }
2216:   PetscFunctionReturn(PETSC_SUCCESS);
2217: }

2219: PetscErrorCode SNESPicardComputeJacobian(SNES snes, Vec x1, Mat J, Mat B, void *ctx)
2220: {
2221:   PetscFunctionBegin;
2222:   /* the jacobian matrix should be pre-filled in SNESPicardComputeFunction */
2223:   /* must assembly if matrix-free to get the last SNES solution */
2224:   PetscCall(MatAssemblyBegin(J, MAT_FINAL_ASSEMBLY));
2225:   PetscCall(MatAssemblyEnd(J, MAT_FINAL_ASSEMBLY));
2226:   PetscFunctionReturn(PETSC_SUCCESS);
2227: }

2229: /*@C
2230:   SNESSetPicard - Use `SNES` to solve the system A(x) x = bp(x) + b via a Picard type iteration (Picard linearization)

2232:   Logically Collective

2234:   Input Parameters:
2235: + snes - the `SNES` context
2236: . r    - vector to store function values, may be `NULL`
2237: . bp   - function evaluation routine, may be `NULL`, for the calling sequence see `SNESJacobianFunction`
2238: . Amat - matrix with which A(x) x - bp(x) - b is to be computed
2239: . Pmat - matrix from which preconditioner is computed (usually the same as `Amat`)
2240: . J    - function to compute matrix values, for the calling sequence see `SNESJacobianFunction`
2241: - ctx  - [optional] user-defined context for private data for the function evaluation routine (may be `NULL`)

2243:   Level: intermediate

2245:   Notes:
2246:   It is often better to provide the nonlinear function F() and some approximation to its Jacobian directly and use
2247:   an approximate Newton solver. This interface is provided to allow porting/testing a previous Picard based code in PETSc before converting it to approximate Newton.

2249:   One can call `SNESSetPicard()` or `SNESSetFunction()` (and possibly `SNESSetJacobian()`) but cannot call both

2251:   Solves the equation A(x) x = bp(x) - b via the defect correction algorithm A(x^{n}) (x^{n+1} - x^{n}) = bp(x^{n}) + b - A(x^{n})x^{n}.
2252:   When an exact solver is used this corresponds to the "classic" Picard A(x^{n}) x^{n+1} = bp(x^{n}) + b iteration.

2254:   Run with `-snes_mf_operator` to solve the system with Newton's method using A(x^{n}) to construct the preconditioner.

2256:   We implement the defect correction form of the Picard iteration because it converges much more generally when inexact linear solvers are used then
2257:   the direct Picard iteration A(x^n) x^{n+1} = bp(x^n) + b

2259:   There is some controversity over the definition of a Picard iteration for nonlinear systems but almost everyone agrees that it involves a linear solve and some
2260:   believe it is the iteration  A(x^{n}) x^{n+1} = b(x^{n}) hence we use the name Picard. If anyone has an authoritative  reference that defines the Picard iteration
2261:   different please contact us at petsc-dev@mcs.anl.gov and we'll have an entirely new argument :-).

2263:   When used with `-snes_mf_operator` this will run matrix-free Newton's method where the matrix-vector product is of the true Jacobian of A(x)x - bp(x) -b and
2264:   A(x^{n}) is used to build the preconditioner

2266:   When used with `-snes_fd` this will compute the true Jacobian (very slowly one column at at time) and thus represent Newton's method.

2268:   When used with `-snes_fd_coloring` this will compute the Jacobian via coloring and thus represent a faster implementation of Newton's method. But the
2269:   the nonzero structure of the Jacobian is, in general larger than that of the Picard matrix A so you must provide in A the needed nonzero structure for the correct
2270:   coloring. When using `DMDA` this may mean creating the matrix A with `DMCreateMatrix()` using a wider stencil than strictly needed for A or with a `DMDA_STENCIL_BOX`.
2271:   See the comment in src/snes/tutorials/ex15.c.

2273: .seealso: [](ch_snes), `SNES`, `SNESGetFunction()`, `SNESSetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESGetPicard()`, `SNESLineSearchPreCheckPicard()`, `SNESJacobianFunction`
2274: @*/
2275: PetscErrorCode SNESSetPicard(SNES snes, Vec r, PetscErrorCode (*bp)(SNES, Vec, Vec, void *), Mat Amat, Mat Pmat, PetscErrorCode (*J)(SNES, Vec, Mat, Mat, void *), void *ctx)
2276: {
2277:   DM dm;

2279:   PetscFunctionBegin;
2281:   PetscCall(SNESGetDM(snes, &dm));
2282:   PetscCall(DMSNESSetPicard(dm, bp, J, ctx));
2283:   PetscCall(DMSNESSetMFFunction(dm, SNESPicardComputeMFFunction, ctx));
2284:   PetscCall(SNESSetFunction(snes, r, SNESPicardComputeFunction, ctx));
2285:   PetscCall(SNESSetJacobian(snes, Amat, Pmat, SNESPicardComputeJacobian, ctx));
2286:   PetscFunctionReturn(PETSC_SUCCESS);
2287: }

2289: /*@C
2290:   SNESGetPicard - Returns the context for the Picard iteration

2292:   Not Collective, but `Vec` is parallel if `SNES` is parallel. Collective if `Vec` is requested, but has not been created yet.

2294:   Input Parameter:
2295: . snes - the `SNES` context

2297:   Output Parameters:
2298: + r    - the function (or `NULL`)
2299: . f    - the function (or `NULL`);  for calling sequence see `SNESFunction`
2300: . Amat - the matrix used to defined the operation A(x) x - b(x) (or `NULL`)
2301: . Pmat - the matrix from which the preconditioner will be constructed (or `NULL`)
2302: . J    - the function for matrix evaluation (or `NULL`);  for calling sequence see `SNESJacobianFunction`
2303: - ctx  - the function context (or `NULL`)

2305:   Level: advanced

2307: .seealso: [](ch_snes), `SNESSetFunction()`, `SNESSetPicard()`, `SNESGetFunction()`, `SNESGetJacobian()`, `SNESGetDM()`, `SNESFunction`, `SNESJacobianFunction`
2308: @*/
2309: PetscErrorCode SNESGetPicard(SNES snes, Vec *r, PetscErrorCode (**f)(SNES, Vec, Vec, void *), Mat *Amat, Mat *Pmat, PetscErrorCode (**J)(SNES, Vec, Mat, Mat, void *), void **ctx)
2310: {
2311:   DM dm;

2313:   PetscFunctionBegin;
2315:   PetscCall(SNESGetFunction(snes, r, NULL, NULL));
2316:   PetscCall(SNESGetJacobian(snes, Amat, Pmat, NULL, NULL));
2317:   PetscCall(SNESGetDM(snes, &dm));
2318:   PetscCall(DMSNESGetPicard(dm, f, J, ctx));
2319:   PetscFunctionReturn(PETSC_SUCCESS);
2320: }

2322: /*@C
2323:   SNESSetComputeInitialGuess - Sets a routine used to compute an initial guess for the nonlinear problem

2325:   Logically Collective

2327:   Input Parameters:
2328: + snes - the `SNES` context
2329: . func - function evaluation routine
2330: - ctx  - [optional] user-defined context for private data for the
2331:          function evaluation routine (may be `NULL`)

2333:   Calling sequence of `func`:
2334: + snes - the `SNES` solver
2335: . x    - vector to put initial guess
2336: - ctx  - optional user-defined function context

2338:   Level: intermediate

2340: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`
2341: @*/
2342: PetscErrorCode SNESSetComputeInitialGuess(SNES snes, PetscErrorCode (*func)(SNES snes, Vec x, void *ctx), void *ctx)
2343: {
2344:   PetscFunctionBegin;
2346:   if (func) snes->ops->computeinitialguess = func;
2347:   if (ctx) snes->initialguessP = ctx;
2348:   PetscFunctionReturn(PETSC_SUCCESS);
2349: }

2351: /*@C
2352:   SNESGetRhs - Gets the vector for solving F(x) = `rhs`. If `rhs` is not set
2353:   it assumes a zero right hand side.

2355:   Logically Collective

2357:   Input Parameter:
2358: . snes - the `SNES` context

2360:   Output Parameter:
2361: . rhs - the right hand side vector or `NULL` if there is no right-hand side vector

2363:   Level: intermediate

2365: .seealso: [](ch_snes), `SNES`, `SNESGetSolution()`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESSetFunction()`
2366: @*/
2367: PetscErrorCode SNESGetRhs(SNES snes, Vec *rhs)
2368: {
2369:   PetscFunctionBegin;
2371:   PetscAssertPointer(rhs, 2);
2372:   *rhs = snes->vec_rhs;
2373:   PetscFunctionReturn(PETSC_SUCCESS);
2374: }

2376: /*@
2377:   SNESComputeFunction - Calls the function that has been set with `SNESSetFunction()`.

2379:   Collective

2381:   Input Parameters:
2382: + snes - the `SNES` context
2383: - x    - input vector

2385:   Output Parameter:
2386: . y - function vector, as set by `SNESSetFunction()`

2388:   Level: developer

2390:   Note:
2391:   `SNESComputeFunction()` is typically used within nonlinear solvers
2392:   implementations, so users would not generally call this routine themselves.

2394: .seealso: [](ch_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeMFFunction()`
2395: @*/
2396: PetscErrorCode SNESComputeFunction(SNES snes, Vec x, Vec y)
2397: {
2398:   DM     dm;
2399:   DMSNES sdm;

2401:   PetscFunctionBegin;
2405:   PetscCheckSameComm(snes, 1, x, 2);
2406:   PetscCheckSameComm(snes, 1, y, 3);
2407:   PetscCall(VecValidValues_Internal(x, 2, PETSC_TRUE));

2409:   PetscCall(SNESGetDM(snes, &dm));
2410:   PetscCall(DMGetDMSNES(dm, &sdm));
2411:   PetscCheck(sdm->ops->computefunction || snes->vec_rhs, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetFunction() or SNESSetDM() before SNESComputeFunction(), likely called from SNESSolve().");
2412:   if (sdm->ops->computefunction) {
2413:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) PetscCall(PetscLogEventBegin(SNES_FunctionEval, snes, x, y, 0));
2414:     PetscCall(VecLockReadPush(x));
2415:     /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
2416:     snes->domainerror = PETSC_FALSE;
2417:     {
2418:       void *ctx;
2419:       PetscErrorCode (*computefunction)(SNES, Vec, Vec, void *);
2420:       PetscCall(DMSNESGetFunction(dm, &computefunction, &ctx));
2421:       PetscCallBack("SNES callback function", (*computefunction)(snes, x, y, ctx));
2422:     }
2423:     PetscCall(VecLockReadPop(x));
2424:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) PetscCall(PetscLogEventEnd(SNES_FunctionEval, snes, x, y, 0));
2425:   } else /* if (snes->vec_rhs) */ {
2426:     PetscCall(MatMult(snes->jacobian, x, y));
2427:   }
2428:   if (snes->vec_rhs) PetscCall(VecAXPY(y, -1.0, snes->vec_rhs));
2429:   snes->nfuncs++;
2430:   /*
2431:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
2432:      propagate the value to all processes
2433:   */
2434:   if (snes->domainerror) PetscCall(VecSetInf(y));
2435:   PetscFunctionReturn(PETSC_SUCCESS);
2436: }

2438: /*@
2439:   SNESComputeMFFunction - Calls the function that has been set with `SNESSetMFFunction()`.

2441:   Collective

2443:   Input Parameters:
2444: + snes - the `SNES` context
2445: - x    - input vector

2447:   Output Parameter:
2448: . y - function vector, as set by `SNESSetMFFunction()`

2450:   Level: developer

2452:   Notes:
2453:   `SNESComputeMFFunction()` is used within the matrix-vector products called by the matrix created with `MatCreateSNESMF()`
2454:   so users would not generally call this routine themselves.

2456:   Since this function is intended for use with finite differencing it does not subtract the right hand side vector provided with `SNESSolve()`
2457:   while `SNESComputeFunction()` does. As such, this routine cannot be used with  `MatMFFDSetBase()` with a provided F function value even if it applies the
2458:   same function as `SNESComputeFunction()` if a `SNESSolve()` right hand side vector is use because the two functions difference would include this right hand side function.

2460: .seealso: [](ch_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeFunction()`, `MatCreateSNESMF`
2461: @*/
2462: PetscErrorCode SNESComputeMFFunction(SNES snes, Vec x, Vec y)
2463: {
2464:   DM     dm;
2465:   DMSNES sdm;

2467:   PetscFunctionBegin;
2471:   PetscCheckSameComm(snes, 1, x, 2);
2472:   PetscCheckSameComm(snes, 1, y, 3);
2473:   PetscCall(VecValidValues_Internal(x, 2, PETSC_TRUE));

2475:   PetscCall(SNESGetDM(snes, &dm));
2476:   PetscCall(DMGetDMSNES(dm, &sdm));
2477:   PetscCall(PetscLogEventBegin(SNES_FunctionEval, snes, x, y, 0));
2478:   PetscCall(VecLockReadPush(x));
2479:   /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
2480:   snes->domainerror = PETSC_FALSE;
2481:   PetscCallBack("SNES callback function", (*sdm->ops->computemffunction)(snes, x, y, sdm->mffunctionctx));
2482:   PetscCall(VecLockReadPop(x));
2483:   PetscCall(PetscLogEventEnd(SNES_FunctionEval, snes, x, y, 0));
2484:   snes->nfuncs++;
2485:   /*
2486:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
2487:      propagate the value to all processes
2488:   */
2489:   if (snes->domainerror) PetscCall(VecSetInf(y));
2490:   PetscFunctionReturn(PETSC_SUCCESS);
2491: }

2493: /*@
2494:   SNESComputeNGS - Calls the Gauss-Seidel function that has been set with  `SNESSetNGS()`.

2496:   Collective

2498:   Input Parameters:
2499: + snes - the `SNES` context
2500: . x    - input vector
2501: - b    - rhs vector

2503:   Output Parameter:
2504: . x - new solution vector

2506:   Level: developer

2508:   Note:
2509:   `SNESComputeNGS()` is typically used within composed nonlinear solver
2510:   implementations, so most users would not generally call this routine
2511:   themselves.

2513: .seealso: [](ch_snes), `SNESNGS`, `SNESSetNGS()`, `SNESComputeFunction()`
2514: @*/
2515: PetscErrorCode SNESComputeNGS(SNES snes, Vec b, Vec x)
2516: {
2517:   DM     dm;
2518:   DMSNES sdm;

2520:   PetscFunctionBegin;
2524:   PetscCheckSameComm(snes, 1, x, 3);
2525:   if (b) PetscCheckSameComm(snes, 1, b, 2);
2526:   if (b) PetscCall(VecValidValues_Internal(b, 2, PETSC_TRUE));
2527:   PetscCall(PetscLogEventBegin(SNES_NGSEval, snes, x, b, 0));
2528:   PetscCall(SNESGetDM(snes, &dm));
2529:   PetscCall(DMGetDMSNES(dm, &sdm));
2530:   PetscCheck(sdm->ops->computegs, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetNGS() before SNESComputeNGS(), likely called from SNESSolve().");
2531:   if (b) PetscCall(VecLockReadPush(b));
2532:   PetscCallBack("SNES callback NGS", (*sdm->ops->computegs)(snes, x, b, sdm->gsctx));
2533:   if (b) PetscCall(VecLockReadPop(b));
2534:   PetscCall(PetscLogEventEnd(SNES_NGSEval, snes, x, b, 0));
2535:   PetscFunctionReturn(PETSC_SUCCESS);
2536: }

2538: PetscErrorCode SNESTestJacobian(SNES snes)
2539: {
2540:   Mat               A, B, C, D, jacobian;
2541:   Vec               x = snes->vec_sol, f = snes->vec_func;
2542:   PetscReal         nrm, gnorm;
2543:   PetscReal         threshold = 1.e-5;
2544:   MatType           mattype;
2545:   PetscInt          m, n, M, N;
2546:   void             *functx;
2547:   PetscBool         complete_print = PETSC_FALSE, threshold_print = PETSC_FALSE, test = PETSC_FALSE, flg, istranspose;
2548:   PetscViewer       viewer, mviewer;
2549:   MPI_Comm          comm;
2550:   PetscInt          tabs;
2551:   static PetscBool  directionsprinted = PETSC_FALSE;
2552:   PetscViewerFormat format;

2554:   PetscFunctionBegin;
2555:   PetscObjectOptionsBegin((PetscObject)snes);
2556:   PetscCall(PetscOptionsName("-snes_test_jacobian", "Compare hand-coded and finite difference Jacobians", "None", &test));
2557:   PetscCall(PetscOptionsReal("-snes_test_jacobian", "Threshold for element difference between hand-coded and finite difference being meaningful", "None", threshold, &threshold, NULL));
2558:   PetscCall(PetscOptionsDeprecated("-snes_test_jacobian_display", "-snes_test_jacobian_view", "3.13", NULL));
2559:   PetscCall(PetscOptionsViewer("-snes_test_jacobian_view", "View difference between hand-coded and finite difference Jacobians element entries", "None", &mviewer, &format, &complete_print));
2560:   PetscCall(PetscOptionsDeprecated("-snes_test_jacobian_display_threshold", "-snes_test_jacobian", "3.13", "-snes_test_jacobian accepts an optional threshold (since v3.10)"));
2561:   /* Cannot remove the what otherwise would be redundant call to (PetscOptionsReal("-snes_test_jacobian_display_threshold") below because its usage is different than the replacement usage */
2562:   PetscCall(PetscOptionsReal("-snes_test_jacobian_display_threshold", "Display difference between hand-coded and finite difference Jacobians which exceed input threshold", "None", threshold, &threshold, &threshold_print));
2563:   PetscOptionsEnd();
2564:   if (!test) PetscFunctionReturn(PETSC_SUCCESS);

2566:   PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
2567:   PetscCall(PetscViewerASCIIGetStdout(comm, &viewer));
2568:   PetscCall(PetscViewerASCIIGetTab(viewer, &tabs));
2569:   PetscCall(PetscViewerASCIISetTab(viewer, ((PetscObject)snes)->tablevel));
2570:   PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Jacobian -------------\n"));
2571:   if (!complete_print && !directionsprinted) {
2572:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Run with -snes_test_jacobian_view and optionally -snes_test_jacobian <threshold> to show difference\n"));
2573:     PetscCall(PetscViewerASCIIPrintf(viewer, "    of hand-coded and finite difference Jacobian entries greater than <threshold>.\n"));
2574:   }
2575:   if (!directionsprinted) {
2576:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Testing hand-coded Jacobian, if (for double precision runs) ||J - Jfd||_F/||J||_F is\n"));
2577:     PetscCall(PetscViewerASCIIPrintf(viewer, "    O(1.e-8), the hand-coded Jacobian is probably correct.\n"));
2578:     directionsprinted = PETSC_TRUE;
2579:   }
2580:   if (complete_print) PetscCall(PetscViewerPushFormat(mviewer, format));

2582:   PetscCall(PetscObjectTypeCompare((PetscObject)snes->jacobian, MATMFFD, &flg));
2583:   if (!flg) jacobian = snes->jacobian;
2584:   else jacobian = snes->jacobian_pre;

2586:   if (!x) {
2587:     PetscCall(MatCreateVecs(jacobian, &x, NULL));
2588:   } else {
2589:     PetscCall(PetscObjectReference((PetscObject)x));
2590:   }
2591:   if (!f) {
2592:     PetscCall(VecDuplicate(x, &f));
2593:   } else {
2594:     PetscCall(PetscObjectReference((PetscObject)f));
2595:   }
2596:   /* evaluate the function at this point because SNESComputeJacobianDefault() assumes that the function has been evaluated and put into snes->vec_func */
2597:   PetscCall(SNESComputeFunction(snes, x, f));
2598:   PetscCall(VecDestroy(&f));
2599:   PetscCall(PetscObjectTypeCompare((PetscObject)snes, SNESKSPTRANSPOSEONLY, &istranspose));
2600:   while (jacobian) {
2601:     Mat JT = NULL, Jsave = NULL;

2603:     if (istranspose) {
2604:       PetscCall(MatCreateTranspose(jacobian, &JT));
2605:       Jsave    = jacobian;
2606:       jacobian = JT;
2607:     }
2608:     PetscCall(PetscObjectBaseTypeCompareAny((PetscObject)jacobian, &flg, MATSEQAIJ, MATMPIAIJ, MATSEQDENSE, MATMPIDENSE, MATSEQBAIJ, MATMPIBAIJ, MATSEQSBAIJ, MATMPISBAIJ, ""));
2609:     if (flg) {
2610:       A = jacobian;
2611:       PetscCall(PetscObjectReference((PetscObject)A));
2612:     } else {
2613:       PetscCall(MatComputeOperator(jacobian, MATAIJ, &A));
2614:     }

2616:     PetscCall(MatGetType(A, &mattype));
2617:     PetscCall(MatGetSize(A, &M, &N));
2618:     PetscCall(MatGetLocalSize(A, &m, &n));
2619:     PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &B));
2620:     PetscCall(MatSetType(B, mattype));
2621:     PetscCall(MatSetSizes(B, m, n, M, N));
2622:     PetscCall(MatSetBlockSizesFromMats(B, A, A));
2623:     PetscCall(MatSetUp(B));
2624:     PetscCall(MatSetOption(B, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE));

2626:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
2627:     PetscCall(SNESComputeJacobianDefault(snes, x, B, B, functx));

2629:     PetscCall(MatDuplicate(B, MAT_COPY_VALUES, &D));
2630:     PetscCall(MatAYPX(D, -1.0, A, DIFFERENT_NONZERO_PATTERN));
2631:     PetscCall(MatNorm(D, NORM_FROBENIUS, &nrm));
2632:     PetscCall(MatNorm(A, NORM_FROBENIUS, &gnorm));
2633:     PetscCall(MatDestroy(&D));
2634:     if (!gnorm) gnorm = 1; /* just in case */
2635:     PetscCall(PetscViewerASCIIPrintf(viewer, "  ||J - Jfd||_F/||J||_F = %g, ||J - Jfd||_F = %g\n", (double)(nrm / gnorm), (double)nrm));

2637:     if (complete_print) {
2638:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded Jacobian ----------\n"));
2639:       PetscCall(MatView(A, mviewer));
2640:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Finite difference Jacobian ----------\n"));
2641:       PetscCall(MatView(B, mviewer));
2642:     }

2644:     if (threshold_print || complete_print) {
2645:       PetscInt           Istart, Iend, *ccols, bncols, cncols, j, row;
2646:       PetscScalar       *cvals;
2647:       const PetscInt    *bcols;
2648:       const PetscScalar *bvals;

2650:       PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &C));
2651:       PetscCall(MatSetType(C, mattype));
2652:       PetscCall(MatSetSizes(C, m, n, M, N));
2653:       PetscCall(MatSetBlockSizesFromMats(C, A, A));
2654:       PetscCall(MatSetUp(C));
2655:       PetscCall(MatSetOption(C, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE));

2657:       PetscCall(MatAYPX(B, -1.0, A, DIFFERENT_NONZERO_PATTERN));
2658:       PetscCall(MatGetOwnershipRange(B, &Istart, &Iend));

2660:       for (row = Istart; row < Iend; row++) {
2661:         PetscCall(MatGetRow(B, row, &bncols, &bcols, &bvals));
2662:         PetscCall(PetscMalloc2(bncols, &ccols, bncols, &cvals));
2663:         for (j = 0, cncols = 0; j < bncols; j++) {
2664:           if (PetscAbsScalar(bvals[j]) > threshold) {
2665:             ccols[cncols] = bcols[j];
2666:             cvals[cncols] = bvals[j];
2667:             cncols += 1;
2668:           }
2669:         }
2670:         if (cncols) PetscCall(MatSetValues(C, 1, &row, cncols, ccols, cvals, INSERT_VALUES));
2671:         PetscCall(MatRestoreRow(B, row, &bncols, &bcols, &bvals));
2672:         PetscCall(PetscFree2(ccols, cvals));
2673:       }
2674:       PetscCall(MatAssemblyBegin(C, MAT_FINAL_ASSEMBLY));
2675:       PetscCall(MatAssemblyEnd(C, MAT_FINAL_ASSEMBLY));
2676:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded minus finite-difference Jacobian with tolerance %g ----------\n", (double)threshold));
2677:       PetscCall(MatView(C, complete_print ? mviewer : viewer));
2678:       PetscCall(MatDestroy(&C));
2679:     }
2680:     PetscCall(MatDestroy(&A));
2681:     PetscCall(MatDestroy(&B));
2682:     PetscCall(MatDestroy(&JT));
2683:     if (Jsave) jacobian = Jsave;
2684:     if (jacobian != snes->jacobian_pre) {
2685:       jacobian = snes->jacobian_pre;
2686:       PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Jacobian for preconditioner -------------\n"));
2687:     } else jacobian = NULL;
2688:   }
2689:   PetscCall(VecDestroy(&x));
2690:   if (complete_print) PetscCall(PetscViewerPopFormat(mviewer));
2691:   if (mviewer) PetscCall(PetscViewerDestroy(&mviewer));
2692:   PetscCall(PetscViewerASCIISetTab(viewer, tabs));
2693:   PetscFunctionReturn(PETSC_SUCCESS);
2694: }

2696: /*@
2697:   SNESComputeJacobian - Computes the Jacobian matrix that has been set with `SNESSetJacobian()`.

2699:   Collective

2701:   Input Parameters:
2702: + snes - the `SNES` context
2703: - X    - input vector

2705:   Output Parameters:
2706: + A - Jacobian matrix
2707: - B - optional matrix for building the preconditioner, usually the same as `A`

2709:   Options Database Keys:
2710: + -snes_lag_preconditioner <lag>           - how often to rebuild preconditioner
2711: . -snes_lag_jacobian <lag>                 - how often to rebuild Jacobian
2712: . -snes_test_jacobian <optional threshold> - compare the user provided Jacobian with one compute via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
2713: . -snes_test_jacobian_view                 - display the user provided Jacobian, the finite difference Jacobian and the difference between them to help users detect the location of errors in the user provided Jacobian
2714: . -snes_compare_explicit                   - Compare the computed Jacobian to the finite difference Jacobian and output the differences
2715: . -snes_compare_explicit_draw              - Compare the computed Jacobian to the finite difference Jacobian and draw the result
2716: . -snes_compare_explicit_contour           - Compare the computed Jacobian to the finite difference Jacobian and draw a contour plot with the result
2717: . -snes_compare_operator                   - Make the comparison options above use the operator instead of the preconditioning matrix
2718: . -snes_compare_coloring                   - Compute the finite difference Jacobian using coloring and display norms of difference
2719: . -snes_compare_coloring_display           - Compute the finite difference Jacobian using coloring and display verbose differences
2720: . -snes_compare_coloring_threshold         - Display only those matrix entries that differ by more than a given threshold
2721: . -snes_compare_coloring_threshold_atol    - Absolute tolerance for difference in matrix entries to be displayed by `-snes_compare_coloring_threshold`
2722: . -snes_compare_coloring_threshold_rtol    - Relative tolerance for difference in matrix entries to be displayed by `-snes_compare_coloring_threshold`
2723: . -snes_compare_coloring_draw              - Compute the finite difference Jacobian using coloring and draw differences
2724: - -snes_compare_coloring_draw_contour      - Compute the finite difference Jacobian using coloring and show contours of matrices and differences

2726:   Level: developer

2728:   Note:
2729:   Most users should not need to explicitly call this routine, as it
2730:   is used internally within the nonlinear solvers.

2732:   Developer Note:
2733:   This has duplicative ways of checking the accuracy of the user provided Jacobian (see the options above). This is for historical reasons, the routine `SNESTestJacobian()` use to used
2734:   with the `SNESType` of test that has been removed.

2736: .seealso: [](ch_snes), `SNESSetJacobian()`, `KSPSetOperators()`, `MatStructure`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`
2737: @*/
2738: PetscErrorCode SNESComputeJacobian(SNES snes, Vec X, Mat A, Mat B)
2739: {
2740:   PetscBool flag;
2741:   DM        dm;
2742:   DMSNES    sdm;
2743:   KSP       ksp;

2745:   PetscFunctionBegin;
2748:   PetscCheckSameComm(snes, 1, X, 2);
2749:   PetscCall(VecValidValues_Internal(X, 2, PETSC_TRUE));
2750:   PetscCall(SNESGetDM(snes, &dm));
2751:   PetscCall(DMGetDMSNES(dm, &sdm));

2753:   /* make sure that MatAssemblyBegin/End() is called on A matrix if it is matrix-free */
2754:   if (snes->lagjacobian == -2) {
2755:     snes->lagjacobian = -1;

2757:     PetscCall(PetscInfo(snes, "Recomputing Jacobian/preconditioner because lag is -2 (means compute Jacobian, but then never again) \n"));
2758:   } else if (snes->lagjacobian == -1) {
2759:     PetscCall(PetscInfo(snes, "Reusing Jacobian/preconditioner because lag is -1\n"));
2760:     PetscCall(PetscObjectTypeCompare((PetscObject)A, MATMFFD, &flag));
2761:     if (flag) {
2762:       PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2763:       PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2764:     }
2765:     PetscFunctionReturn(PETSC_SUCCESS);
2766:   } else if (snes->lagjacobian > 1 && (snes->iter + snes->jac_iter) % snes->lagjacobian) {
2767:     PetscCall(PetscInfo(snes, "Reusing Jacobian/preconditioner because lag is %" PetscInt_FMT " and SNES iteration is %" PetscInt_FMT "\n", snes->lagjacobian, snes->iter));
2768:     PetscCall(PetscObjectTypeCompare((PetscObject)A, MATMFFD, &flag));
2769:     if (flag) {
2770:       PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2771:       PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2772:     }
2773:     PetscFunctionReturn(PETSC_SUCCESS);
2774:   }
2775:   if (snes->npc && snes->npcside == PC_LEFT) {
2776:     PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2777:     PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2778:     PetscFunctionReturn(PETSC_SUCCESS);
2779:   }

2781:   PetscCall(PetscLogEventBegin(SNES_JacobianEval, snes, X, A, B));
2782:   PetscCall(VecLockReadPush(X));
2783:   {
2784:     void *ctx;
2785:     PetscErrorCode (*J)(SNES, Vec, Mat, Mat, void *);
2786:     PetscCall(DMSNESGetJacobian(dm, &J, &ctx));
2787:     PetscCallBack("SNES callback Jacobian", (*J)(snes, X, A, B, ctx));
2788:   }
2789:   PetscCall(VecLockReadPop(X));
2790:   PetscCall(PetscLogEventEnd(SNES_JacobianEval, snes, X, A, B));

2792:   /* attach latest linearization point to the preconditioning matrix */
2793:   PetscCall(PetscObjectCompose((PetscObject)B, "__SNES_latest_X", (PetscObject)X));

2795:   /* the next line ensures that snes->ksp exists */
2796:   PetscCall(SNESGetKSP(snes, &ksp));
2797:   if (snes->lagpreconditioner == -2) {
2798:     PetscCall(PetscInfo(snes, "Rebuilding preconditioner exactly once since lag is -2\n"));
2799:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_FALSE));
2800:     snes->lagpreconditioner = -1;
2801:   } else if (snes->lagpreconditioner == -1) {
2802:     PetscCall(PetscInfo(snes, "Reusing preconditioner because lag is -1\n"));
2803:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_TRUE));
2804:   } else if (snes->lagpreconditioner > 1 && (snes->iter + snes->pre_iter) % snes->lagpreconditioner) {
2805:     PetscCall(PetscInfo(snes, "Reusing preconditioner because lag is %" PetscInt_FMT " and SNES iteration is %" PetscInt_FMT "\n", snes->lagpreconditioner, snes->iter));
2806:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_TRUE));
2807:   } else {
2808:     PetscCall(PetscInfo(snes, "Rebuilding preconditioner\n"));
2809:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_FALSE));
2810:   }

2812:   PetscCall(SNESTestJacobian(snes));
2813:   /* make sure user returned a correct Jacobian and preconditioner */
2816:   {
2817:     PetscBool flag = PETSC_FALSE, flag_draw = PETSC_FALSE, flag_contour = PETSC_FALSE, flag_operator = PETSC_FALSE;
2818:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit", NULL, NULL, &flag));
2819:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit_draw", NULL, NULL, &flag_draw));
2820:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit_draw_contour", NULL, NULL, &flag_contour));
2821:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_operator", NULL, NULL, &flag_operator));
2822:     if (flag || flag_draw || flag_contour) {
2823:       Mat         Bexp_mine = NULL, Bexp, FDexp;
2824:       PetscViewer vdraw, vstdout;
2825:       PetscBool   flg;
2826:       if (flag_operator) {
2827:         PetscCall(MatComputeOperator(A, MATAIJ, &Bexp_mine));
2828:         Bexp = Bexp_mine;
2829:       } else {
2830:         /* See if the preconditioning matrix can be viewed and added directly */
2831:         PetscCall(PetscObjectBaseTypeCompareAny((PetscObject)B, &flg, MATSEQAIJ, MATMPIAIJ, MATSEQDENSE, MATMPIDENSE, MATSEQBAIJ, MATMPIBAIJ, MATSEQSBAIJ, MATMPIBAIJ, ""));
2832:         if (flg) Bexp = B;
2833:         else {
2834:           /* If the "preconditioning" matrix is itself MATSHELL or some other type without direct support */
2835:           PetscCall(MatComputeOperator(B, MATAIJ, &Bexp_mine));
2836:           Bexp = Bexp_mine;
2837:         }
2838:       }
2839:       PetscCall(MatConvert(Bexp, MATSAME, MAT_INITIAL_MATRIX, &FDexp));
2840:       PetscCall(SNESComputeJacobianDefault(snes, X, FDexp, FDexp, NULL));
2841:       PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &vstdout));
2842:       if (flag_draw || flag_contour) {
2843:         PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, "Explicit Jacobians", PETSC_DECIDE, PETSC_DECIDE, 300, 300, &vdraw));
2844:         if (flag_contour) PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
2845:       } else vdraw = NULL;
2846:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Explicit %s\n", flag_operator ? "Jacobian" : "preconditioning Jacobian"));
2847:       if (flag) PetscCall(MatView(Bexp, vstdout));
2848:       if (vdraw) PetscCall(MatView(Bexp, vdraw));
2849:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Finite difference Jacobian\n"));
2850:       if (flag) PetscCall(MatView(FDexp, vstdout));
2851:       if (vdraw) PetscCall(MatView(FDexp, vdraw));
2852:       PetscCall(MatAYPX(FDexp, -1.0, Bexp, SAME_NONZERO_PATTERN));
2853:       PetscCall(PetscViewerASCIIPrintf(vstdout, "User-provided matrix minus finite difference Jacobian\n"));
2854:       if (flag) PetscCall(MatView(FDexp, vstdout));
2855:       if (vdraw) { /* Always use contour for the difference */
2856:         PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
2857:         PetscCall(MatView(FDexp, vdraw));
2858:         PetscCall(PetscViewerPopFormat(vdraw));
2859:       }
2860:       if (flag_contour) PetscCall(PetscViewerPopFormat(vdraw));
2861:       PetscCall(PetscViewerDestroy(&vdraw));
2862:       PetscCall(MatDestroy(&Bexp_mine));
2863:       PetscCall(MatDestroy(&FDexp));
2864:     }
2865:   }
2866:   {
2867:     PetscBool flag = PETSC_FALSE, flag_display = PETSC_FALSE, flag_draw = PETSC_FALSE, flag_contour = PETSC_FALSE, flag_threshold = PETSC_FALSE;
2868:     PetscReal threshold_atol = PETSC_SQRT_MACHINE_EPSILON, threshold_rtol = 10 * PETSC_SQRT_MACHINE_EPSILON;
2869:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring", NULL, NULL, &flag));
2870:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_display", NULL, NULL, &flag_display));
2871:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_draw", NULL, NULL, &flag_draw));
2872:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_draw_contour", NULL, NULL, &flag_contour));
2873:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold", NULL, NULL, &flag_threshold));
2874:     if (flag_threshold) {
2875:       PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold_rtol", &threshold_rtol, NULL));
2876:       PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold_atol", &threshold_atol, NULL));
2877:     }
2878:     if (flag || flag_display || flag_draw || flag_contour || flag_threshold) {
2879:       Mat           Bfd;
2880:       PetscViewer   vdraw, vstdout;
2881:       MatColoring   coloring;
2882:       ISColoring    iscoloring;
2883:       MatFDColoring matfdcoloring;
2884:       PetscErrorCode (*func)(SNES, Vec, Vec, void *);
2885:       void     *funcctx;
2886:       PetscReal norm1, norm2, normmax;

2888:       PetscCall(MatDuplicate(B, MAT_DO_NOT_COPY_VALUES, &Bfd));
2889:       PetscCall(MatColoringCreate(Bfd, &coloring));
2890:       PetscCall(MatColoringSetType(coloring, MATCOLORINGSL));
2891:       PetscCall(MatColoringSetFromOptions(coloring));
2892:       PetscCall(MatColoringApply(coloring, &iscoloring));
2893:       PetscCall(MatColoringDestroy(&coloring));
2894:       PetscCall(MatFDColoringCreate(Bfd, iscoloring, &matfdcoloring));
2895:       PetscCall(MatFDColoringSetFromOptions(matfdcoloring));
2896:       PetscCall(MatFDColoringSetUp(Bfd, iscoloring, matfdcoloring));
2897:       PetscCall(ISColoringDestroy(&iscoloring));

2899:       /* This method of getting the function is currently unreliable since it doesn't work for DM local functions. */
2900:       PetscCall(SNESGetFunction(snes, NULL, &func, &funcctx));
2901:       PetscCall(MatFDColoringSetFunction(matfdcoloring, (PetscErrorCode(*)(void))func, funcctx));
2902:       PetscCall(PetscObjectSetOptionsPrefix((PetscObject)matfdcoloring, ((PetscObject)snes)->prefix));
2903:       PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)matfdcoloring, "coloring_"));
2904:       PetscCall(MatFDColoringSetFromOptions(matfdcoloring));
2905:       PetscCall(MatFDColoringApply(Bfd, matfdcoloring, X, snes));
2906:       PetscCall(MatFDColoringDestroy(&matfdcoloring));

2908:       PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &vstdout));
2909:       if (flag_draw || flag_contour) {
2910:         PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, "Colored Jacobians", PETSC_DECIDE, PETSC_DECIDE, 300, 300, &vdraw));
2911:         if (flag_contour) PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
2912:       } else vdraw = NULL;
2913:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Explicit preconditioning Jacobian\n"));
2914:       if (flag_display) PetscCall(MatView(B, vstdout));
2915:       if (vdraw) PetscCall(MatView(B, vdraw));
2916:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Colored Finite difference Jacobian\n"));
2917:       if (flag_display) PetscCall(MatView(Bfd, vstdout));
2918:       if (vdraw) PetscCall(MatView(Bfd, vdraw));
2919:       PetscCall(MatAYPX(Bfd, -1.0, B, SAME_NONZERO_PATTERN));
2920:       PetscCall(MatNorm(Bfd, NORM_1, &norm1));
2921:       PetscCall(MatNorm(Bfd, NORM_FROBENIUS, &norm2));
2922:       PetscCall(MatNorm(Bfd, NORM_MAX, &normmax));
2923:       PetscCall(PetscViewerASCIIPrintf(vstdout, "User-provided matrix minus finite difference Jacobian, norm1=%g normFrob=%g normmax=%g\n", (double)norm1, (double)norm2, (double)normmax));
2924:       if (flag_display) PetscCall(MatView(Bfd, vstdout));
2925:       if (vdraw) { /* Always use contour for the difference */
2926:         PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
2927:         PetscCall(MatView(Bfd, vdraw));
2928:         PetscCall(PetscViewerPopFormat(vdraw));
2929:       }
2930:       if (flag_contour) PetscCall(PetscViewerPopFormat(vdraw));

2932:       if (flag_threshold) {
2933:         PetscInt bs, rstart, rend, i;
2934:         PetscCall(MatGetBlockSize(B, &bs));
2935:         PetscCall(MatGetOwnershipRange(B, &rstart, &rend));
2936:         for (i = rstart; i < rend; i++) {
2937:           const PetscScalar *ba, *ca;
2938:           const PetscInt    *bj, *cj;
2939:           PetscInt           bn, cn, j, maxentrycol = -1, maxdiffcol = -1, maxrdiffcol = -1;
2940:           PetscReal          maxentry = 0, maxdiff = 0, maxrdiff = 0;
2941:           PetscCall(MatGetRow(B, i, &bn, &bj, &ba));
2942:           PetscCall(MatGetRow(Bfd, i, &cn, &cj, &ca));
2943:           PetscCheck(bn == cn, ((PetscObject)A)->comm, PETSC_ERR_PLIB, "Unexpected different nonzero pattern in -snes_compare_coloring_threshold");
2944:           for (j = 0; j < bn; j++) {
2945:             PetscReal rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol * PetscAbsScalar(ba[j]));
2946:             if (PetscAbsScalar(ba[j]) > PetscAbs(maxentry)) {
2947:               maxentrycol = bj[j];
2948:               maxentry    = PetscRealPart(ba[j]);
2949:             }
2950:             if (PetscAbsScalar(ca[j]) > PetscAbs(maxdiff)) {
2951:               maxdiffcol = bj[j];
2952:               maxdiff    = PetscRealPart(ca[j]);
2953:             }
2954:             if (rdiff > maxrdiff) {
2955:               maxrdiffcol = bj[j];
2956:               maxrdiff    = rdiff;
2957:             }
2958:           }
2959:           if (maxrdiff > 1) {
2960:             PetscCall(PetscViewerASCIIPrintf(vstdout, "row %" PetscInt_FMT " (maxentry=%g at %" PetscInt_FMT ", maxdiff=%g at %" PetscInt_FMT ", maxrdiff=%g at %" PetscInt_FMT "):", i, (double)maxentry, maxentrycol, (double)maxdiff, maxdiffcol, (double)maxrdiff, maxrdiffcol));
2961:             for (j = 0; j < bn; j++) {
2962:               PetscReal rdiff;
2963:               rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol * PetscAbsScalar(ba[j]));
2964:               if (rdiff > 1) PetscCall(PetscViewerASCIIPrintf(vstdout, " (%" PetscInt_FMT ",%g:%g)", bj[j], (double)PetscRealPart(ba[j]), (double)PetscRealPart(ca[j])));
2965:             }
2966:             PetscCall(PetscViewerASCIIPrintf(vstdout, "\n"));
2967:           }
2968:           PetscCall(MatRestoreRow(B, i, &bn, &bj, &ba));
2969:           PetscCall(MatRestoreRow(Bfd, i, &cn, &cj, &ca));
2970:         }
2971:       }
2972:       PetscCall(PetscViewerDestroy(&vdraw));
2973:       PetscCall(MatDestroy(&Bfd));
2974:     }
2975:   }
2976:   PetscFunctionReturn(PETSC_SUCCESS);
2977: }

2979: /*MC
2980:     SNESJacobianFunction - Functional form used by `SNES` to compute the nonlinear Jacobian of the function to be solved by `SNES`

2982:      Synopsis:
2983:      #include "petscsnes.h"
2984:      PetscErrorCode SNESJacobianFunction(SNES snes,Vec x,Mat Amat,Mat Pmat,void *ctx);

2986:      Collective

2988:     Input Parameters:
2989: +  x - input vector, the Jacobian is to be computed at this value
2990: -  ctx - [optional] user-defined Jacobian context

2992:     Output Parameters:
2993: +  Amat - the matrix that defines the (approximate) Jacobian
2994: -  Pmat - the matrix to be used in constructing the preconditioner, usually the same as `Amat`.

2996:    Level: intermediate

2998: .seealso: [](ch_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESSetJacobian()`, `SNESGetJacobian()`
2999: M*/

3001: /*@C
3002:   SNESSetJacobian - Sets the function to compute Jacobian as well as the
3003:   location to store the matrix.

3005:   Logically Collective

3007:   Input Parameters:
3008: + snes - the `SNES` context
3009: . Amat - the matrix that defines the (approximate) Jacobian
3010: . Pmat - the matrix to be used in constructing the preconditioner, usually the same as `Amat`.
3011: . J    - Jacobian evaluation routine (if `NULL` then `SNES` retains any previously set value), see `SNESJacobianFunction` for details
3012: - ctx  - [optional] user-defined context for private data for the
3013:          Jacobian evaluation routine (may be `NULL`) (if `NULL` then `SNES` retains any previously set value)

3015:   Level: beginner

3017:   Notes:
3018:   If the `Amat` matrix and `Pmat` matrix are different you must call `MatAssemblyBegin()`/`MatAssemblyEnd()` on
3019:   each matrix.

3021:   If you know the operator `Amat` has a null space you can use `MatSetNullSpace()` and `MatSetTransposeNullSpace()` to supply the null
3022:   space to `Amat` and the `KSP` solvers will automatically use that null space as needed during the solution process.

3024:   If using `SNESComputeJacobianDefaultColor()` to assemble a Jacobian, the `ctx` argument
3025:   must be a `MatFDColoring`.

3027:   Other defect-correction schemes can be used by computing a different matrix in place of the Jacobian.  One common
3028:   example is to use the "Picard linearization" which only differentiates through the highest order parts of each term using `SNESSetPicard()`

3030: .seealso: [](ch_snes), `SNES`, `KSPSetOperators()`, `SNESSetFunction()`, `MatMFFDComputeJacobian()`, `SNESComputeJacobianDefaultColor()`, `MatStructure`,
3031:           `SNESSetPicard()`, `SNESJacobianFunction`
3032: @*/
3033: PetscErrorCode SNESSetJacobian(SNES snes, Mat Amat, Mat Pmat, PetscErrorCode (*J)(SNES, Vec, Mat, Mat, void *), void *ctx)
3034: {
3035:   DM dm;

3037:   PetscFunctionBegin;
3041:   if (Amat) PetscCheckSameComm(snes, 1, Amat, 2);
3042:   if (Pmat) PetscCheckSameComm(snes, 1, Pmat, 3);
3043:   PetscCall(SNESGetDM(snes, &dm));
3044:   PetscCall(DMSNESSetJacobian(dm, J, ctx));
3045:   if (Amat) {
3046:     PetscCall(PetscObjectReference((PetscObject)Amat));
3047:     PetscCall(MatDestroy(&snes->jacobian));

3049:     snes->jacobian = Amat;
3050:   }
3051:   if (Pmat) {
3052:     PetscCall(PetscObjectReference((PetscObject)Pmat));
3053:     PetscCall(MatDestroy(&snes->jacobian_pre));

3055:     snes->jacobian_pre = Pmat;
3056:   }
3057:   PetscFunctionReturn(PETSC_SUCCESS);
3058: }

3060: /*@C
3061:   SNESGetJacobian - Returns the Jacobian matrix and optionally the user
3062:   provided context for evaluating the Jacobian.

3064:   Not Collective, but `Mat` object will be parallel if `SNES` is

3066:   Input Parameter:
3067: . snes - the nonlinear solver context

3069:   Output Parameters:
3070: + Amat - location to stash (approximate) Jacobian matrix (or `NULL`)
3071: . Pmat - location to stash matrix used to compute the preconditioner (or `NULL`)
3072: . J    - location to put Jacobian function (or `NULL`), for calling sequence see `SNESJacobianFunction`
3073: - ctx  - location to stash Jacobian ctx (or `NULL`)

3075:   Level: advanced

3077: .seealso: [](ch_snes), `SNES`, `Mat`, `SNESSetJacobian()`, `SNESComputeJacobian()`, `SNESJacobianFunction`, `SNESGetFunction()`
3078: @*/
3079: PetscErrorCode SNESGetJacobian(SNES snes, Mat *Amat, Mat *Pmat, PetscErrorCode (**J)(SNES, Vec, Mat, Mat, void *), void **ctx)
3080: {
3081:   DM dm;

3083:   PetscFunctionBegin;
3085:   if (Amat) *Amat = snes->jacobian;
3086:   if (Pmat) *Pmat = snes->jacobian_pre;
3087:   PetscCall(SNESGetDM(snes, &dm));
3088:   PetscCall(DMSNESGetJacobian(dm, J, ctx));
3089:   PetscFunctionReturn(PETSC_SUCCESS);
3090: }

3092: static PetscErrorCode SNESSetDefaultComputeJacobian(SNES snes)
3093: {
3094:   DM     dm;
3095:   DMSNES sdm;

3097:   PetscFunctionBegin;
3098:   PetscCall(SNESGetDM(snes, &dm));
3099:   PetscCall(DMGetDMSNES(dm, &sdm));
3100:   if (!sdm->ops->computejacobian && snes->jacobian_pre) {
3101:     DM        dm;
3102:     PetscBool isdense, ismf;

3104:     PetscCall(SNESGetDM(snes, &dm));
3105:     PetscCall(PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre, &isdense, MATSEQDENSE, MATMPIDENSE, MATDENSE, NULL));
3106:     PetscCall(PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre, &ismf, MATMFFD, MATSHELL, NULL));
3107:     if (isdense) {
3108:       PetscCall(DMSNESSetJacobian(dm, SNESComputeJacobianDefault, NULL));
3109:     } else if (!ismf) {
3110:       PetscCall(DMSNESSetJacobian(dm, SNESComputeJacobianDefaultColor, NULL));
3111:     }
3112:   }
3113:   PetscFunctionReturn(PETSC_SUCCESS);
3114: }

3116: /*@
3117:   SNESSetUp - Sets up the internal data structures for the later use
3118:   of a nonlinear solver.

3120:   Collective

3122:   Input Parameter:
3123: . snes - the `SNES` context

3125:   Level: advanced

3127:   Note:
3128:   For basic use of the `SNES` solvers the user need not explicitly call
3129:   `SNESSetUp()`, since these actions will automatically occur during
3130:   the call to `SNESSolve()`.  However, if one wishes to control this
3131:   phase separately, `SNESSetUp()` should be called after `SNESCreate()`
3132:   and optional routines of the form SNESSetXXX(), but before `SNESSolve()`.

3134: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESSolve()`, `SNESDestroy()`
3135: @*/
3136: PetscErrorCode SNESSetUp(SNES snes)
3137: {
3138:   DM             dm;
3139:   DMSNES         sdm;
3140:   SNESLineSearch linesearch, pclinesearch;
3141:   void          *lsprectx, *lspostctx;
3142:   PetscBool      mf_operator, mf;
3143:   Vec            f, fpc;
3144:   void          *funcctx;
3145:   void          *jacctx, *appctx;
3146:   Mat            j, jpre;
3147:   PetscErrorCode (*precheck)(SNESLineSearch, Vec, Vec, PetscBool *, void *);
3148:   PetscErrorCode (*postcheck)(SNESLineSearch, Vec, Vec, Vec, PetscBool *, PetscBool *, void *);
3149:   PetscErrorCode (*func)(SNES, Vec, Vec, void *);
3150:   PetscErrorCode (*jac)(SNES, Vec, Mat, Mat, void *);

3152:   PetscFunctionBegin;
3154:   if (snes->setupcalled) PetscFunctionReturn(PETSC_SUCCESS);
3155:   PetscCall(PetscLogEventBegin(SNES_SetUp, snes, 0, 0, 0));

3157:   if (!((PetscObject)snes)->type_name) PetscCall(SNESSetType(snes, SNESNEWTONLS));

3159:   PetscCall(SNESGetFunction(snes, &snes->vec_func, NULL, NULL));

3161:   PetscCall(SNESGetDM(snes, &dm));
3162:   PetscCall(DMGetDMSNES(dm, &sdm));
3163:   PetscCall(SNESSetDefaultComputeJacobian(snes));

3165:   if (!snes->vec_func) PetscCall(DMCreateGlobalVector(dm, &snes->vec_func));

3167:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));

3169:   if (snes->linesearch) {
3170:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
3171:     PetscCall(SNESLineSearchSetFunction(snes->linesearch, SNESComputeFunction));
3172:   }

3174:   PetscCall(SNESGetUseMatrixFree(snes, &mf_operator, &mf));
3175:   if (snes->npc && snes->npcside == PC_LEFT) {
3176:     snes->mf          = PETSC_TRUE;
3177:     snes->mf_operator = PETSC_FALSE;
3178:   }

3180:   if (snes->npc) {
3181:     /* copy the DM over */
3182:     PetscCall(SNESGetDM(snes, &dm));
3183:     PetscCall(SNESSetDM(snes->npc, dm));

3185:     PetscCall(SNESGetFunction(snes, &f, &func, &funcctx));
3186:     PetscCall(VecDuplicate(f, &fpc));
3187:     PetscCall(SNESSetFunction(snes->npc, fpc, func, funcctx));
3188:     PetscCall(SNESGetJacobian(snes, &j, &jpre, &jac, &jacctx));
3189:     PetscCall(SNESSetJacobian(snes->npc, j, jpre, jac, jacctx));
3190:     PetscCall(SNESGetApplicationContext(snes, &appctx));
3191:     PetscCall(SNESSetApplicationContext(snes->npc, appctx));
3192:     PetscCall(SNESSetUseMatrixFree(snes->npc, mf_operator, mf));
3193:     PetscCall(VecDestroy(&fpc));

3195:     /* copy the function pointers over */
3196:     PetscCall(PetscObjectCopyFortranFunctionPointers((PetscObject)snes, (PetscObject)snes->npc));

3198:     /* default to 1 iteration */
3199:     PetscCall(SNESSetTolerances(snes->npc, 0.0, 0.0, 0.0, 1, snes->npc->max_funcs));
3200:     if (snes->npcside == PC_RIGHT) {
3201:       PetscCall(SNESSetNormSchedule(snes->npc, SNES_NORM_FINAL_ONLY));
3202:     } else {
3203:       PetscCall(SNESSetNormSchedule(snes->npc, SNES_NORM_NONE));
3204:     }
3205:     PetscCall(SNESSetFromOptions(snes->npc));

3207:     /* copy the line search context over */
3208:     if (snes->linesearch && snes->npc->linesearch) {
3209:       PetscCall(SNESGetLineSearch(snes, &linesearch));
3210:       PetscCall(SNESGetLineSearch(snes->npc, &pclinesearch));
3211:       PetscCall(SNESLineSearchGetPreCheck(linesearch, &precheck, &lsprectx));
3212:       PetscCall(SNESLineSearchGetPostCheck(linesearch, &postcheck, &lspostctx));
3213:       PetscCall(SNESLineSearchSetPreCheck(pclinesearch, precheck, lsprectx));
3214:       PetscCall(SNESLineSearchSetPostCheck(pclinesearch, postcheck, lspostctx));
3215:       PetscCall(PetscObjectCopyFortranFunctionPointers((PetscObject)linesearch, (PetscObject)pclinesearch));
3216:     }
3217:   }
3218:   if (snes->mf) PetscCall(SNESSetUpMatrixFree_Private(snes, snes->mf_operator, snes->mf_version));
3219:   if (snes->ops->usercompute && !snes->user) PetscCall((*snes->ops->usercompute)(snes, (void **)&snes->user));

3221:   snes->jac_iter = 0;
3222:   snes->pre_iter = 0;

3224:   PetscTryTypeMethod(snes, setup);

3226:   PetscCall(SNESSetDefaultComputeJacobian(snes));

3228:   if (snes->npc && snes->npcside == PC_LEFT) {
3229:     if (snes->functype == SNES_FUNCTION_PRECONDITIONED) {
3230:       if (snes->linesearch) {
3231:         PetscCall(SNESGetLineSearch(snes, &linesearch));
3232:         PetscCall(SNESLineSearchSetFunction(linesearch, SNESComputeFunctionDefaultNPC));
3233:       }
3234:     }
3235:   }
3236:   PetscCall(PetscLogEventEnd(SNES_SetUp, snes, 0, 0, 0));
3237:   snes->setupcalled = PETSC_TRUE;
3238:   PetscFunctionReturn(PETSC_SUCCESS);
3239: }

3241: /*@
3242:   SNESReset - Resets a `SNES` context to the snessetupcalled = 0 state and removes any allocated `Vec`s and `Mat`s

3244:   Collective

3246:   Input Parameter:
3247: . snes - iterative context obtained from `SNESCreate()`

3249:   Level: intermediate

3251:   Notes:
3252:   Call this if you wish to reuse a `SNES` but with different size vectors

3254:   Also calls the application context destroy routine set with `SNESSetComputeApplicationContext()`

3256: .seealso: [](ch_snes), `SNES`, `SNESDestroy()`, `SNESCreate()`, `SNESSetUp()`, `SNESSolve()`
3257: @*/
3258: PetscErrorCode SNESReset(SNES snes)
3259: {
3260:   PetscFunctionBegin;
3262:   if (snes->ops->userdestroy && snes->user) {
3263:     PetscCall((*snes->ops->userdestroy)((void **)&snes->user));
3264:     snes->user = NULL;
3265:   }
3266:   if (snes->npc) PetscCall(SNESReset(snes->npc));

3268:   PetscTryTypeMethod(snes, reset);
3269:   if (snes->ksp) PetscCall(KSPReset(snes->ksp));

3271:   if (snes->linesearch) PetscCall(SNESLineSearchReset(snes->linesearch));

3273:   PetscCall(VecDestroy(&snes->vec_rhs));
3274:   PetscCall(VecDestroy(&snes->vec_sol));
3275:   PetscCall(VecDestroy(&snes->vec_sol_update));
3276:   PetscCall(VecDestroy(&snes->vec_func));
3277:   PetscCall(MatDestroy(&snes->jacobian));
3278:   PetscCall(MatDestroy(&snes->jacobian_pre));
3279:   PetscCall(MatDestroy(&snes->picard));
3280:   PetscCall(VecDestroyVecs(snes->nwork, &snes->work));
3281:   PetscCall(VecDestroyVecs(snes->nvwork, &snes->vwork));

3283:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

3285:   snes->nwork = snes->nvwork = 0;
3286:   snes->setupcalled          = PETSC_FALSE;
3287:   PetscFunctionReturn(PETSC_SUCCESS);
3288: }

3290: /*@
3291:   SNESConvergedReasonViewCancel - Clears all the reason view functions for a `SNES` object provided with `SNESConvergedReasonViewSet()`

3293:   Collective

3295:   Input Parameter:
3296: . snes - iterative context obtained from `SNESCreate()`

3298:   Level: intermediate

3300: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESDestroy()`, `SNESReset()`, `SNESConvergedReasonViewSet()`
3301: @*/
3302: PetscErrorCode SNESConvergedReasonViewCancel(SNES snes)
3303: {
3304:   PetscInt i;

3306:   PetscFunctionBegin;
3308:   for (i = 0; i < snes->numberreasonviews; i++) {
3309:     if (snes->reasonviewdestroy[i]) PetscCall((*snes->reasonviewdestroy[i])(&snes->reasonviewcontext[i]));
3310:   }
3311:   snes->numberreasonviews = 0;
3312:   PetscFunctionReturn(PETSC_SUCCESS);
3313: }

3315: /*@C
3316:   SNESDestroy - Destroys the nonlinear solver context that was created
3317:   with `SNESCreate()`.

3319:   Collective

3321:   Input Parameter:
3322: . snes - the `SNES` context

3324:   Level: beginner

3326: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESSolve()`
3327: @*/
3328: PetscErrorCode SNESDestroy(SNES *snes)
3329: {
3330:   PetscFunctionBegin;
3331:   if (!*snes) PetscFunctionReturn(PETSC_SUCCESS);
3333:   if (--((PetscObject)(*snes))->refct > 0) {
3334:     *snes = NULL;
3335:     PetscFunctionReturn(PETSC_SUCCESS);
3336:   }

3338:   PetscCall(SNESReset((*snes)));
3339:   PetscCall(SNESDestroy(&(*snes)->npc));

3341:   /* if memory was published with SAWs then destroy it */
3342:   PetscCall(PetscObjectSAWsViewOff((PetscObject)*snes));
3343:   PetscTryTypeMethod((*snes), destroy);

3345:   if ((*snes)->dm) PetscCall(DMCoarsenHookRemove((*snes)->dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, *snes));
3346:   PetscCall(DMDestroy(&(*snes)->dm));
3347:   PetscCall(KSPDestroy(&(*snes)->ksp));
3348:   PetscCall(SNESLineSearchDestroy(&(*snes)->linesearch));

3350:   PetscCall(PetscFree((*snes)->kspconvctx));
3351:   if ((*snes)->ops->convergeddestroy) PetscCall((*(*snes)->ops->convergeddestroy)((*snes)->cnvP));
3352:   if ((*snes)->conv_hist_alloc) PetscCall(PetscFree2((*snes)->conv_hist, (*snes)->conv_hist_its));
3353:   PetscCall(SNESMonitorCancel((*snes)));
3354:   PetscCall(SNESConvergedReasonViewCancel((*snes)));
3355:   PetscCall(PetscHeaderDestroy(snes));
3356:   PetscFunctionReturn(PETSC_SUCCESS);
3357: }

3359: /* ----------- Routines to set solver parameters ---------- */

3361: /*@
3362:   SNESSetLagPreconditioner - Determines when the preconditioner is rebuilt in the nonlinear solve.

3364:   Logically Collective

3366:   Input Parameters:
3367: + snes - the `SNES` context
3368: - lag  - 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3369:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

3371:   Options Database Keys:
3372: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple `SNESSolve()`
3373: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3374: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple `SNESSolve()`
3375: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag

3377:   Level: intermediate

3379:   Notes:
3380:   The default is 1

3382:   The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or `SNESSetLagPreconditionerPersists()` was called

3384:   `SNESSetLagPreconditionerPersists()` allows using the same uniform lagging (for example every second linear solve) across multiple nonlinear solves.

3386: .seealso: [](ch_snes), `SNESSetTrustRegionTolerance()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESSetLagPreconditionerPersists()`,
3387:           `SNESSetLagJacobianPersists()`, `SNES`, `SNESSolve()`
3388: @*/
3389: PetscErrorCode SNESSetLagPreconditioner(SNES snes, PetscInt lag)
3390: {
3391:   PetscFunctionBegin;
3393:   PetscCheck(lag >= -2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag must be -2, -1, 1 or greater");
3394:   PetscCheck(lag, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag cannot be 0");
3396:   snes->lagpreconditioner = lag;
3397:   PetscFunctionReturn(PETSC_SUCCESS);
3398: }

3400: /*@
3401:   SNESSetGridSequence - sets the number of steps of grid sequencing that `SNES` will do

3403:   Logically Collective

3405:   Input Parameters:
3406: + snes  - the `SNES` context
3407: - steps - the number of refinements to do, defaults to 0

3409:   Options Database Key:
3410: . -snes_grid_sequence <steps> - Use grid sequencing to generate initial guess

3412:   Level: intermediate

3414:   Note:
3415:   Use `SNESGetSolution()` to extract the fine grid solution after grid sequencing.

3417: .seealso: [](ch_snes), `SNES`, `SNESSetTrustRegionTolerance()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetGridSequence()`,
3418:           `SNESetDM()`
3419: @*/
3420: PetscErrorCode SNESSetGridSequence(SNES snes, PetscInt steps)
3421: {
3422:   PetscFunctionBegin;
3425:   snes->gridsequence = steps;
3426:   PetscFunctionReturn(PETSC_SUCCESS);
3427: }

3429: /*@
3430:   SNESGetGridSequence - gets the number of steps of grid sequencing that `SNES` will do

3432:   Logically Collective

3434:   Input Parameter:
3435: . snes - the `SNES` context

3437:   Output Parameter:
3438: . steps - the number of refinements to do, defaults to 0

3440:   Level: intermediate

3442: .seealso: [](ch_snes), `SNESSetTrustRegionTolerance()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESSetGridSequence()`
3443: @*/
3444: PetscErrorCode SNESGetGridSequence(SNES snes, PetscInt *steps)
3445: {
3446:   PetscFunctionBegin;
3448:   *steps = snes->gridsequence;
3449:   PetscFunctionReturn(PETSC_SUCCESS);
3450: }

3452: /*@
3453:   SNESGetLagPreconditioner - Return how often the preconditioner is rebuilt

3455:   Not Collective

3457:   Input Parameter:
3458: . snes - the `SNES` context

3460:   Output Parameter:
3461: . lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3462:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

3464:   Level: intermediate

3466:   Notes:
3467:   The default is 1

3469:   The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

3471: .seealso: [](ch_snes), `SNES`, `SNESSetTrustRegionTolerance()`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`
3472: @*/
3473: PetscErrorCode SNESGetLagPreconditioner(SNES snes, PetscInt *lag)
3474: {
3475:   PetscFunctionBegin;
3477:   *lag = snes->lagpreconditioner;
3478:   PetscFunctionReturn(PETSC_SUCCESS);
3479: }

3481: /*@
3482:   SNESSetLagJacobian - Set when the Jacobian is rebuilt in the nonlinear solve. See `SNESSetLagPreconditioner()` for determining how
3483:   often the preconditioner is rebuilt.

3485:   Logically Collective

3487:   Input Parameters:
3488: + snes - the `SNES` context
3489: - lag  - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3490:          the Jacobian is built etc. -2 means rebuild at next chance but then never again

3492:   Options Database Keys:
3493: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple SNES solves
3494: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3495: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple SNES solves
3496: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag.

3498:   Level: intermediate

3500:   Notes:
3501:   The default is 1

3503:   The Jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

3505:   If  -1 is used before the very first nonlinear solve the CODE WILL FAIL! because no Jacobian is used, use -2 to indicate you want it recomputed
3506:   at the next Newton step but never again (unless it is reset to another value)

3508: .seealso: [](ch_snes), `SNES`, `SNESSetTrustRegionTolerance()`, `SNESGetLagPreconditioner()`, `SNESSetLagPreconditioner()`, `SNESGetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`
3509: @*/
3510: PetscErrorCode SNESSetLagJacobian(SNES snes, PetscInt lag)
3511: {
3512:   PetscFunctionBegin;
3514:   PetscCheck(lag >= -2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag must be -2, -1, 1 or greater");
3515:   PetscCheck(lag, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag cannot be 0");
3517:   snes->lagjacobian = lag;
3518:   PetscFunctionReturn(PETSC_SUCCESS);
3519: }

3521: /*@
3522:   SNESGetLagJacobian - Get how often the Jacobian is rebuilt. See `SNESGetLagPreconditioner()` to determine when the preconditioner is rebuilt

3524:   Not Collective

3526:   Input Parameter:
3527: . snes - the `SNES` context

3529:   Output Parameter:
3530: . lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3531:          the Jacobian is built etc.

3533:   Level: intermediate

3535:   Notes:
3536:   The default is 1

3538:   The jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or `SNESSetLagJacobianPersists()` was called.

3540: .seealso: [](ch_snes), `SNES`, `SNESSetTrustRegionTolerance()`, `SNESSetLagJacobian()`, `SNESSetLagPreconditioner()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`

3542: @*/
3543: PetscErrorCode SNESGetLagJacobian(SNES snes, PetscInt *lag)
3544: {
3545:   PetscFunctionBegin;
3547:   *lag = snes->lagjacobian;
3548:   PetscFunctionReturn(PETSC_SUCCESS);
3549: }

3551: /*@
3552:   SNESSetLagJacobianPersists - Set whether or not the Jacobian lagging persists through multiple nonlinear solves

3554:   Logically collective

3556:   Input Parameters:
3557: + snes - the `SNES` context
3558: - flg  - jacobian lagging persists if true

3560:   Options Database Keys:
3561: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple SNES solves
3562: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3563: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple SNES solves
3564: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag

3566:   Level: advanced

3568:   Notes:
3569:   Normally when `SNESSetLagJacobian()` is used, the Jacobian is always rebuilt at the beginning of each new nonlinear solve, this removes that behavior

3571:   This is useful both for nonlinear preconditioning, where it's appropriate to have the Jacobian be stale by
3572:   several solves, and for implicit time-stepping, where Jacobian lagging in the inner nonlinear solve over several
3573:   timesteps may present huge efficiency gains.

3575: .seealso: [](ch_snes), `SNES`, `SNESSetLagPreconditionerPersists()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetNPC()`
3576: @*/
3577: PetscErrorCode SNESSetLagJacobianPersists(SNES snes, PetscBool flg)
3578: {
3579:   PetscFunctionBegin;
3582:   snes->lagjac_persist = flg;
3583:   PetscFunctionReturn(PETSC_SUCCESS);
3584: }

3586: /*@
3587:   SNESSetLagPreconditionerPersists - Set whether or not the preconditioner lagging persists through multiple nonlinear solves

3589:   Logically Collective

3591:   Input Parameters:
3592: + snes - the `SNES` context
3593: - flg  - preconditioner lagging persists if true

3595:   Options Database Keys:
3596: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple SNES solves
3597: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3598: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple SNES solves
3599: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag

3601:   Level: developer

3603:   Notes:
3604:   Normally when `SNESSetLagPreconditioner()` is used, the preconditioner is always rebuilt at the beginning of each new nonlinear solve, this removes that behavior

3606:   This is useful both for nonlinear preconditioning, where it's appropriate to have the preconditioner be stale
3607:   by several solves, and for implicit time-stepping, where preconditioner lagging in the inner nonlinear solve over
3608:   several timesteps may present huge efficiency gains.

3610: .seealso: [](ch_snes), `SNES`, `SNESSetLagJacobianPersists()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetNPC()`, `SNESSetLagPreconditioner()`
3611: @*/
3612: PetscErrorCode SNESSetLagPreconditionerPersists(SNES snes, PetscBool flg)
3613: {
3614:   PetscFunctionBegin;
3617:   snes->lagpre_persist = flg;
3618:   PetscFunctionReturn(PETSC_SUCCESS);
3619: }

3621: /*@
3622:   SNESSetForceIteration - force `SNESSolve()` to take at least one iteration regardless of the initial residual norm

3624:   Logically Collective

3626:   Input Parameters:
3627: + snes  - the `SNES` context
3628: - force - `PETSC_TRUE` require at least one iteration

3630:   Options Database Key:
3631: . -snes_force_iteration <force> - Sets forcing an iteration

3633:   Level: intermediate

3635:   Note:
3636:   This is used sometimes with `TS` to prevent `TS` from detecting a false steady state solution

3638: .seealso: [](ch_snes), `SNES`, `TS`, `SNESSetTrustRegionTolerance()`, `SNESSetDivergenceTolerance()`
3639: @*/
3640: PetscErrorCode SNESSetForceIteration(SNES snes, PetscBool force)
3641: {
3642:   PetscFunctionBegin;
3644:   snes->forceiteration = force;
3645:   PetscFunctionReturn(PETSC_SUCCESS);
3646: }

3648: /*@
3649:   SNESGetForceIteration - Check whether or not `SNESSolve()` take at least one iteration regardless of the initial residual norm

3651:   Logically Collective

3653:   Input Parameter:
3654: . snes - the `SNES` context

3656:   Output Parameter:
3657: . force - `PETSC_TRUE` requires at least one iteration.

3659:   Level: intermediate

3661: .seealso: [](ch_snes), `SNES`, `SNESSetForceIteration()`, `SNESSetTrustRegionTolerance()`, `SNESSetDivergenceTolerance()`
3662: @*/
3663: PetscErrorCode SNESGetForceIteration(SNES snes, PetscBool *force)
3664: {
3665:   PetscFunctionBegin;
3667:   *force = snes->forceiteration;
3668:   PetscFunctionReturn(PETSC_SUCCESS);
3669: }

3671: /*@
3672:   SNESSetTolerances - Sets `SNES` various parameters used in convergence tests.

3674:   Logically Collective

3676:   Input Parameters:
3677: + snes   - the `SNES` context
3678: . abstol - absolute convergence tolerance
3679: . rtol   - relative convergence tolerance
3680: . stol   - convergence tolerance in terms of the norm of the change in the solution between steps,  || delta x || < stol*|| x ||
3681: . maxit  - maximum number of iterations, default 50.
3682: - maxf   - maximum number of function evaluations (-1 indicates no limit), default 1000

3684:   Options Database Keys:
3685: + -snes_atol <abstol>    - Sets abstol
3686: . -snes_rtol <rtol>      - Sets rtol
3687: . -snes_stol <stol>      - Sets stol
3688: . -snes_max_it <maxit>   - Sets maxit
3689: - -snes_max_funcs <maxf> - Sets maxf

3691:   Level: intermediate

3693: .seealso: [](ch_snes), `SNESolve()`, `SNES`, `SNESSetTrustRegionTolerance()`, `SNESSetDivergenceTolerance()`, `SNESSetForceIteration()`
3694: @*/
3695: PetscErrorCode SNESSetTolerances(SNES snes, PetscReal abstol, PetscReal rtol, PetscReal stol, PetscInt maxit, PetscInt maxf)
3696: {
3697:   PetscFunctionBegin;

3705:   if (abstol != (PetscReal)PETSC_DEFAULT) {
3706:     PetscCheck(abstol >= 0.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Absolute tolerance %g must be non-negative", (double)abstol);
3707:     snes->abstol = abstol;
3708:   }
3709:   if (rtol != (PetscReal)PETSC_DEFAULT) {
3710:     PetscCheck(rtol >= 0.0 && 1.0 > rtol, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Relative tolerance %g must be non-negative and less than 1.0", (double)rtol);
3711:     snes->rtol = rtol;
3712:   }
3713:   if (stol != (PetscReal)PETSC_DEFAULT) {
3714:     PetscCheck(stol >= 0.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Step tolerance %g must be non-negative", (double)stol);
3715:     snes->stol = stol;
3716:   }
3717:   if (maxit != PETSC_DEFAULT) {
3718:     PetscCheck(maxit >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Maximum number of iterations %" PetscInt_FMT " must be non-negative", maxit);
3719:     snes->max_its = maxit;
3720:   }
3721:   if (maxf != PETSC_DEFAULT) {
3722:     PetscCheck(maxf >= -1, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Maximum number of function evaluations %" PetscInt_FMT " must be -1 or nonnegative", maxf);
3723:     snes->max_funcs = maxf;
3724:   }
3725:   snes->tolerancesset = PETSC_TRUE;
3726:   PetscFunctionReturn(PETSC_SUCCESS);
3727: }

3729: /*@
3730:   SNESSetDivergenceTolerance - Sets the divergence tolerance used for the `SNES` divergence test.

3732:   Logically Collective

3734:   Input Parameters:
3735: + snes   - the `SNES` context
3736: - divtol - the divergence tolerance. Use -1 to deactivate the test, default is 1e4

3738:   Options Database Key:
3739: . -snes_divergence_tolerance <divtol> - Sets `divtol`

3741:   Level: intermediate

3743: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetTolerances()`, `SNESGetDivergenceTolerance`
3744: @*/
3745: PetscErrorCode SNESSetDivergenceTolerance(SNES snes, PetscReal divtol)
3746: {
3747:   PetscFunctionBegin;

3751:   if (divtol != (PetscReal)PETSC_DEFAULT) {
3752:     snes->divtol = divtol;
3753:   } else {
3754:     snes->divtol = 1.0e4;
3755:   }
3756:   PetscFunctionReturn(PETSC_SUCCESS);
3757: }

3759: /*@
3760:   SNESGetTolerances - Gets various parameters used in convergence tests.

3762:   Not Collective

3764:   Input Parameters:
3765: + snes  - the `SNES` context
3766: . atol  - absolute convergence tolerance
3767: . rtol  - relative convergence tolerance
3768: . stol  - convergence tolerance in terms of the norm
3769:            of the change in the solution between steps
3770: . maxit - maximum number of iterations
3771: - maxf  - maximum number of function evaluations

3773:   Level: intermediate

3775:   Note:
3776:   The user can specify `NULL` for any parameter that is not needed.

3778: .seealso: [](ch_snes), `SNES`, `SNESSetTolerances()`
3779: @*/
3780: PetscErrorCode SNESGetTolerances(SNES snes, PetscReal *atol, PetscReal *rtol, PetscReal *stol, PetscInt *maxit, PetscInt *maxf)
3781: {
3782:   PetscFunctionBegin;
3784:   if (atol) *atol = snes->abstol;
3785:   if (rtol) *rtol = snes->rtol;
3786:   if (stol) *stol = snes->stol;
3787:   if (maxit) *maxit = snes->max_its;
3788:   if (maxf) *maxf = snes->max_funcs;
3789:   PetscFunctionReturn(PETSC_SUCCESS);
3790: }

3792: /*@
3793:   SNESGetDivergenceTolerance - Gets divergence tolerance used in divergence test.

3795:   Not Collective

3797:   Input Parameters:
3798: + snes   - the `SNES` context
3799: - divtol - divergence tolerance

3801:   Level: intermediate

3803: .seealso: [](ch_snes), `SNES`, `SNESSetDivergenceTolerance()`
3804: @*/
3805: PetscErrorCode SNESGetDivergenceTolerance(SNES snes, PetscReal *divtol)
3806: {
3807:   PetscFunctionBegin;
3809:   if (divtol) *divtol = snes->divtol;
3810:   PetscFunctionReturn(PETSC_SUCCESS);
3811: }

3813: /*@
3814:   SNESSetTrustRegionTolerance - Sets the trust region parameter tolerance.

3816:   Logically Collective

3818:   Input Parameters:
3819: + snes - the `SNES` context
3820: - tol  - tolerance

3822:   Options Database Key:
3823: . -snes_tr_tol <tol> - Sets tol

3825:   Level: intermediate

3827: .seealso: [](ch_snes), `SNES`, `SNESNEWTONTR`, `SNESSetTolerances()`
3828: @*/
3829: PetscErrorCode SNESSetTrustRegionTolerance(SNES snes, PetscReal tol)
3830: {
3831:   PetscFunctionBegin;
3834:   snes->deltatol = tol;
3835:   PetscFunctionReturn(PETSC_SUCCESS);
3836: }

3838: PETSC_INTERN PetscErrorCode SNESMonitorRange_Private(SNES, PetscInt, PetscReal *);

3840: PetscErrorCode SNESMonitorLGRange(SNES snes, PetscInt n, PetscReal rnorm, void *monctx)
3841: {
3842:   PetscDrawLG      lg;
3843:   PetscReal        x, y, per;
3844:   PetscViewer      v = (PetscViewer)monctx;
3845:   static PetscReal prev; /* should be in the context */
3846:   PetscDraw        draw;

3848:   PetscFunctionBegin;
3850:   PetscCall(PetscViewerDrawGetDrawLG(v, 0, &lg));
3851:   if (!n) PetscCall(PetscDrawLGReset(lg));
3852:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
3853:   PetscCall(PetscDrawSetTitle(draw, "Residual norm"));
3854:   x = (PetscReal)n;
3855:   if (rnorm > 0.0) y = PetscLog10Real(rnorm);
3856:   else y = -15.0;
3857:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
3858:   if (n < 20 || !(n % 5) || snes->reason) {
3859:     PetscCall(PetscDrawLGDraw(lg));
3860:     PetscCall(PetscDrawLGSave(lg));
3861:   }

3863:   PetscCall(PetscViewerDrawGetDrawLG(v, 1, &lg));
3864:   if (!n) PetscCall(PetscDrawLGReset(lg));
3865:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
3866:   PetscCall(PetscDrawSetTitle(draw, "% elements > .2*max element"));
3867:   PetscCall(SNESMonitorRange_Private(snes, n, &per));
3868:   x = (PetscReal)n;
3869:   y = 100.0 * per;
3870:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
3871:   if (n < 20 || !(n % 5) || snes->reason) {
3872:     PetscCall(PetscDrawLGDraw(lg));
3873:     PetscCall(PetscDrawLGSave(lg));
3874:   }

3876:   PetscCall(PetscViewerDrawGetDrawLG(v, 2, &lg));
3877:   if (!n) {
3878:     prev = rnorm;
3879:     PetscCall(PetscDrawLGReset(lg));
3880:   }
3881:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
3882:   PetscCall(PetscDrawSetTitle(draw, "(norm -oldnorm)/oldnorm"));
3883:   x = (PetscReal)n;
3884:   y = (prev - rnorm) / prev;
3885:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
3886:   if (n < 20 || !(n % 5) || snes->reason) {
3887:     PetscCall(PetscDrawLGDraw(lg));
3888:     PetscCall(PetscDrawLGSave(lg));
3889:   }

3891:   PetscCall(PetscViewerDrawGetDrawLG(v, 3, &lg));
3892:   if (!n) PetscCall(PetscDrawLGReset(lg));
3893:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
3894:   PetscCall(PetscDrawSetTitle(draw, "(norm -oldnorm)/oldnorm*(% > .2 max)"));
3895:   x = (PetscReal)n;
3896:   y = (prev - rnorm) / (prev * per);
3897:   if (n > 2) { /*skip initial crazy value */
3898:     PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
3899:   }
3900:   if (n < 20 || !(n % 5) || snes->reason) {
3901:     PetscCall(PetscDrawLGDraw(lg));
3902:     PetscCall(PetscDrawLGSave(lg));
3903:   }
3904:   prev = rnorm;
3905:   PetscFunctionReturn(PETSC_SUCCESS);
3906: }

3908: /*@
3909:   SNESConverged - Run the convergence test and update the `SNESConvergedReason`.

3911:   Collective

3913:   Input Parameters:
3914: + snes  - the `SNES` context
3915: . it    - current iteration
3916: . xnorm - 2-norm of current iterate
3917: . snorm - 2-norm of current step
3918: - fnorm - 2-norm of function

3920:   Level: developer

3922:   Note:
3923:   This routine is called by the `SNESSolve()` implementations.
3924:   It does not typically need to be called by the user.

3926: .seealso: [](ch_snes), `SNES`, `SNESSolve`, `SNESSetConvergenceTest()`, `SNESGetConvergenceTest()`
3927: @*/
3928: PetscErrorCode SNESConverged(SNES snes, PetscInt it, PetscReal xnorm, PetscReal snorm, PetscReal fnorm)
3929: {
3930:   PetscFunctionBegin;
3931:   if (!snes->reason) {
3932:     if (snes->normschedule == SNES_NORM_ALWAYS) PetscUseTypeMethod(snes, converged, it, xnorm, snorm, fnorm, &snes->reason, snes->cnvP);
3933:     if (it == snes->max_its && !snes->reason) {
3934:       if (snes->normschedule == SNES_NORM_ALWAYS) {
3935:         PetscCall(PetscInfo(snes, "Maximum number of iterations has been reached: %" PetscInt_FMT "\n", snes->max_its));
3936:         snes->reason = SNES_DIVERGED_MAX_IT;
3937:       } else snes->reason = SNES_CONVERGED_ITS;
3938:     }
3939:   }
3940:   PetscFunctionReturn(PETSC_SUCCESS);
3941: }

3943: /*@
3944:   SNESMonitor - runs the user provided monitor routines, if they exist

3946:   Collective

3948:   Input Parameters:
3949: + snes  - nonlinear solver context obtained from `SNESCreate()`
3950: . iter  - iteration number
3951: - rnorm - relative norm of the residual

3953:   Level: developer

3955:   Note:
3956:   This routine is called by the `SNESSolve()` implementations.
3957:   It does not typically need to be called by the user.

3959: .seealso: [](ch_snes), `SNES`, `SNESMonitorSet()`
3960: @*/
3961: PetscErrorCode SNESMonitor(SNES snes, PetscInt iter, PetscReal rnorm)
3962: {
3963:   PetscInt i, n = snes->numbermonitors;

3965:   PetscFunctionBegin;
3966:   if (n > 0) SNESCheckFunctionNorm(snes, rnorm);
3967:   PetscCall(VecLockReadPush(snes->vec_sol));
3968:   for (i = 0; i < n; i++) PetscCall((*snes->monitor[i])(snes, iter, rnorm, snes->monitorcontext[i]));
3969:   PetscCall(VecLockReadPop(snes->vec_sol));
3970:   PetscFunctionReturn(PETSC_SUCCESS);
3971: }

3973: /* ------------ Routines to set performance monitoring options ----------- */

3975: /*MC
3976:     SNESMonitorFunction - functional form passed to `SNESMonitorSet()` to monitor convergence of nonlinear solver

3978:      Synopsis:
3979: #include <petscsnes.h>
3980:     PetscErrorCode SNESMonitorFunction(SNES snes, PetscInt its, PetscReal norm, void *mctx)

3982:      Collective

3984:     Input Parameters:
3985: +    snes - the `SNES` context
3986: .    its - iteration number
3987: .    norm - 2-norm function value (may be estimated)
3988: -    mctx - [optional] monitoring context

3990:    Level: advanced

3992: .seealso: [](ch_snes), `SNESMonitorSet()`, `SNESMonitorSet()`, `SNESMonitorGet()`
3993: M*/

3995: /*@C
3996:   SNESMonitorSet - Sets an ADDITIONAL function that is to be used at every
3997:   iteration of the nonlinear solver to display the iteration's
3998:   progress.

4000:   Logically Collective

4002:   Input Parameters:
4003: + snes           - the `SNES` context
4004: . f              - the monitor function,  for the calling sequence see `SNESMonitorFunction`
4005: . mctx           - [optional] user-defined context for private data for the monitor routine (use `NULL` if no context is desired)
4006: - monitordestroy - [optional] routine that frees monitor context (may be `NULL`)

4008:   Options Database Keys:
4009: + -snes_monitor               - sets `SNESMonitorDefault()`
4010: . -snes_monitor draw::draw_lg - sets line graph monitor,
4011: - -snes_monitor_cancel        - cancels all monitors that have been hardwired into a code by calls to `SNESMonitorSet()`, but does not cancel those set via
4012:                             the options database.

4014:   Level: intermediate

4016:   Note:
4017:   Several different monitoring routines may be set by calling
4018:   `SNESMonitorSet()` multiple times; all will be called in the
4019:   order in which they were set.

4021:   Fortran Note:
4022:   Only a single monitor function can be set for each `SNES` object

4024: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESMonitorDefault()`, `SNESMonitorCancel()`, `SNESMonitorFunction`
4025: @*/
4026: PetscErrorCode SNESMonitorSet(SNES snes, PetscErrorCode (*f)(SNES, PetscInt, PetscReal, void *), void *mctx, PetscErrorCode (*monitordestroy)(void **))
4027: {
4028:   PetscInt  i;
4029:   PetscBool identical;

4031:   PetscFunctionBegin;
4033:   for (i = 0; i < snes->numbermonitors; i++) {
4034:     PetscCall(PetscMonitorCompare((PetscErrorCode(*)(void))f, mctx, monitordestroy, (PetscErrorCode(*)(void))snes->monitor[i], snes->monitorcontext[i], snes->monitordestroy[i], &identical));
4035:     if (identical) PetscFunctionReturn(PETSC_SUCCESS);
4036:   }
4037:   PetscCheck(snes->numbermonitors < MAXSNESMONITORS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many monitors set");
4038:   snes->monitor[snes->numbermonitors]          = f;
4039:   snes->monitordestroy[snes->numbermonitors]   = monitordestroy;
4040:   snes->monitorcontext[snes->numbermonitors++] = (void *)mctx;
4041:   PetscFunctionReturn(PETSC_SUCCESS);
4042: }

4044: /*@
4045:   SNESMonitorCancel - Clears all the monitor functions for a `SNES` object.

4047:   Logically Collective

4049:   Input Parameter:
4050: . snes - the `SNES` context

4052:   Options Database Key:
4053: . -snes_monitor_cancel - cancels all monitors that have been hardwired
4054:     into a code by calls to `SNESMonitorSet()`, but does not cancel those
4055:     set via the options database

4057:   Level: intermediate

4059:   Note:
4060:   There is no way to clear one specific monitor from a `SNES` object.

4062: .seealso: [](ch_snes), `SNES`, `SNESMonitorGet()`, `SNESMonitorDefault()`, `SNESMonitorSet()`
4063: @*/
4064: PetscErrorCode SNESMonitorCancel(SNES snes)
4065: {
4066:   PetscInt i;

4068:   PetscFunctionBegin;
4070:   for (i = 0; i < snes->numbermonitors; i++) {
4071:     if (snes->monitordestroy[i]) PetscCall((*snes->monitordestroy[i])(&snes->monitorcontext[i]));
4072:   }
4073:   snes->numbermonitors = 0;
4074:   PetscFunctionReturn(PETSC_SUCCESS);
4075: }

4077: /*MC
4078:     SNESConvergenceTestFunction - functional form used for testing of convergence of nonlinear solver

4080:      Synopsis:
4081: #include <petscsnes.h>
4082:      PetscErrorCode SNESConvergenceTest(SNES snes, PetscInt it, PetscReal xnorm, PetscReal gnorm, PetscReal f, SNESConvergedReason *reason, void *cctx)

4084:      Collective

4086:     Input Parameters:
4087: +    snes - the `SNES` context
4088: .    it - current iteration (0 is the first and is before any Newton step)
4089: .    xnorm - 2-norm of current iterate
4090: .    gnorm - 2-norm of current step
4091: .    f - 2-norm of function
4092: -    cctx - [optional] convergence context

4094:     Output Parameter:
4095: .    reason - reason for convergence/divergence, only needs to be set when convergence or divergence is detected

4097:    Level: intermediate

4099: .seealso: [](ch_snes), `SNES`, `SNESSolve`, `SNESSetConvergenceTest()`, `SNESGetConvergenceTest()`
4100: M*/

4102: /*@C
4103:   SNESSetConvergenceTest - Sets the function that is to be used
4104:   to test for convergence of the nonlinear iterative solution.

4106:   Logically Collective

4108:   Input Parameters:
4109: + snes                        - the `SNES` context
4110: . SNESConvergenceTestFunction - routine to test for convergence
4111: . cctx                        - [optional] context for private data for the convergence routine  (may be `NULL`)
4112: - destroy                     - [optional] destructor for the context (may be `NULL`; `PETSC_NULL_FUNCTION` in Fortran)

4114:   Level: advanced

4116: .seealso: [](ch_snes), `SNES`, `SNESConvergedDefault()`, `SNESConvergedSkip()`, `SNESConvergenceTestFunction`
4117: @*/
4118: PetscErrorCode SNESSetConvergenceTest(SNES snes, PetscErrorCode (*SNESConvergenceTestFunction)(SNES, PetscInt, PetscReal, PetscReal, PetscReal, SNESConvergedReason *, void *), void *cctx, PetscErrorCode (*destroy)(void *))
4119: {
4120:   PetscFunctionBegin;
4122:   if (!SNESConvergenceTestFunction) SNESConvergenceTestFunction = SNESConvergedSkip;
4123:   if (snes->ops->convergeddestroy) PetscCall((*snes->ops->convergeddestroy)(snes->cnvP));
4124:   snes->ops->converged        = SNESConvergenceTestFunction;
4125:   snes->ops->convergeddestroy = destroy;
4126:   snes->cnvP                  = cctx;
4127:   PetscFunctionReturn(PETSC_SUCCESS);
4128: }

4130: /*@
4131:   SNESGetConvergedReason - Gets the reason the `SNES` iteration was stopped.

4133:   Not Collective

4135:   Input Parameter:
4136: . snes - the `SNES` context

4138:   Output Parameter:
4139: . reason - negative value indicates diverged, positive value converged, see `SNESConvergedReason` for the individual convergence tests for complete lists

4141:   Options Database Key:
4142: . -snes_converged_reason - prints the reason to standard out

4144:   Level: intermediate

4146:   Note:
4147:   Should only be called after the call the `SNESSolve()` is complete, if it is called earlier it returns the value `SNES__CONVERGED_ITERATING`.

4149: .seealso: [](ch_snes), `SNESSolve()`, `SNESSetConvergenceTest()`, `SNESSetConvergedReason()`, `SNESConvergedReason`, `SNESGetConvergedReasonString()`
4150: @*/
4151: PetscErrorCode SNESGetConvergedReason(SNES snes, SNESConvergedReason *reason)
4152: {
4153:   PetscFunctionBegin;
4155:   PetscAssertPointer(reason, 2);
4156:   *reason = snes->reason;
4157:   PetscFunctionReturn(PETSC_SUCCESS);
4158: }

4160: /*@C
4161:   SNESGetConvergedReasonString - Return a human readable string for `SNESConvergedReason`

4163:   Not Collective

4165:   Input Parameter:
4166: . snes - the `SNES` context

4168:   Output Parameter:
4169: . strreason - a human readable string that describes `SNES` converged reason

4171:   Level: beginner

4173: .seealso: [](ch_snes), `SNES`, `SNESGetConvergedReason()`
4174: @*/
4175: PetscErrorCode SNESGetConvergedReasonString(SNES snes, const char **strreason)
4176: {
4177:   PetscFunctionBegin;
4179:   PetscAssertPointer(strreason, 2);
4180:   *strreason = SNESConvergedReasons[snes->reason];
4181:   PetscFunctionReturn(PETSC_SUCCESS);
4182: }

4184: /*@
4185:   SNESSetConvergedReason - Sets the reason the `SNES` iteration was stopped.

4187:   Not Collective

4189:   Input Parameters:
4190: + snes   - the `SNES` context
4191: - reason - negative value indicates diverged, positive value converged, see `SNESConvergedReason` or the
4192:             manual pages for the individual convergence tests for complete lists

4194:   Level: developer

4196:   Developer Note:
4197:   Called inside the various `SNESSolve()` implementations

4199: .seealso: [](ch_snes), `SNESGetConvergedReason()`, `SNESSetConvergenceTest()`, `SNESConvergedReason`
4200: @*/
4201: PetscErrorCode SNESSetConvergedReason(SNES snes, SNESConvergedReason reason)
4202: {
4203:   PetscFunctionBegin;
4205:   PetscCheck(!snes->errorifnotconverged || reason > 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_PLIB, "SNES code should have previously errored due to negative reason");
4206:   snes->reason = reason;
4207:   PetscFunctionReturn(PETSC_SUCCESS);
4208: }

4210: /*@
4211:   SNESSetConvergenceHistory - Sets the arrays used to hold the convergence history.

4213:   Logically Collective

4215:   Input Parameters:
4216: + snes  - iterative context obtained from `SNESCreate()`
4217: . a     - array to hold history, this array will contain the function norms computed at each step
4218: . its   - integer array holds the number of linear iterations for each solve.
4219: . na    - size of `a` and `its`
4220: - reset - `PETSC_TRUE` indicates each new nonlinear solve resets the history counter to zero,
4221:            else it continues storing new values for new nonlinear solves after the old ones

4223:   Level: intermediate

4225:   Notes:
4226:   If 'a' and 'its' are `NULL` then space is allocated for the history. If 'na' `PETSC_DECIDE` or `PETSC_DEFAULT` then a
4227:   default array of length 10000 is allocated.

4229:   This routine is useful, e.g., when running a code for purposes
4230:   of accurate performance monitoring, when no I/O should be done
4231:   during the section of code that is being timed.

4233:   If the arrays run out of space after a number of iterations then the later values are not saved in the history

4235: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESGetConvergenceHistory()`
4236: @*/
4237: PetscErrorCode SNESSetConvergenceHistory(SNES snes, PetscReal a[], PetscInt its[], PetscInt na, PetscBool reset)
4238: {
4239:   PetscFunctionBegin;
4241:   if (a) PetscAssertPointer(a, 2);
4242:   if (its) PetscAssertPointer(its, 3);
4243:   if (!a) {
4244:     if (na == PETSC_DECIDE || na == PETSC_DEFAULT) na = 1000;
4245:     PetscCall(PetscCalloc2(na, &a, na, &its));
4246:     snes->conv_hist_alloc = PETSC_TRUE;
4247:   }
4248:   snes->conv_hist       = a;
4249:   snes->conv_hist_its   = its;
4250:   snes->conv_hist_max   = (size_t)na;
4251:   snes->conv_hist_len   = 0;
4252:   snes->conv_hist_reset = reset;
4253:   PetscFunctionReturn(PETSC_SUCCESS);
4254: }

4256: #if defined(PETSC_HAVE_MATLAB)
4257:   #include <engine.h> /* MATLAB include file */
4258:   #include <mex.h>    /* MATLAB include file */

4260: PETSC_EXTERN mxArray *SNESGetConvergenceHistoryMatlab(SNES snes)
4261: {
4262:   mxArray   *mat;
4263:   PetscInt   i;
4264:   PetscReal *ar;

4266:   mat = mxCreateDoubleMatrix(snes->conv_hist_len, 1, mxREAL);
4267:   ar  = (PetscReal *)mxGetData(mat);
4268:   for (i = 0; i < snes->conv_hist_len; i++) ar[i] = snes->conv_hist[i];
4269:   return mat;
4270: }
4271: #endif

4273: /*@C
4274:   SNESGetConvergenceHistory - Gets the arrays used to hold the convergence history.

4276:   Not Collective

4278:   Input Parameter:
4279: . snes - iterative context obtained from `SNESCreate()`

4281:   Output Parameters:
4282: + a   - array to hold history, usually was set with `SNESSetConvergenceHistory()`
4283: . its - integer array holds the number of linear iterations (or
4284:          negative if not converged) for each solve.
4285: - na  - size of `a` and `its`

4287:   Level: intermediate

4289:   Note:
4290:   This routine is useful, e.g., when running a code for purposes
4291:   of accurate performance monitoring, when no I/O should be done
4292:   during the section of code that is being timed.

4294:   Fortran Note:
4295:   The calling sequence for this routine in Fortran is
4296: .vb
4297:     call SNESGetConvergenceHistory(SNES snes, integer na, integer ierr)
4298: .ve

4300: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetConvergenceHistory()`
4301: @*/
4302: PetscErrorCode SNESGetConvergenceHistory(SNES snes, PetscReal *a[], PetscInt *its[], PetscInt *na)
4303: {
4304:   PetscFunctionBegin;
4306:   if (a) *a = snes->conv_hist;
4307:   if (its) *its = snes->conv_hist_its;
4308:   if (na) *na = (PetscInt)snes->conv_hist_len;
4309:   PetscFunctionReturn(PETSC_SUCCESS);
4310: }

4312: /*@C
4313:   SNESSetUpdate - Sets the general-purpose update function called
4314:   at the beginning of every iteration of the nonlinear solve. Specifically
4315:   it is called just before the Jacobian is "evaluated".

4317:   Logically Collective

4319:   Input Parameters:
4320: + snes - The nonlinear solver context
4321: - func - The function

4323:   Calling sequence of `func`:
4324: + snes - the nonlinear solver context
4325: - step - The current step of the iteration

4327:   Level: advanced

4329:   Notes:
4330:   This is NOT what one uses to update the ghost points before a function evaluation, that should be done at the beginning of your function provided
4331:   to `SNESSetFunction()`, or `SNESSetPicard()`
4332:   This is not used by most users.

4334:   There are a variety of function hooks one many set that are called at different stages of the nonlinear solution process, see the functions listed below.

4336: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetJacobian()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESNewtonTRSetPreCheck()`, `SNESNewtonTRSetPostCheck()`,
4337:          `SNESMonitorSet()`, `SNESSetDivergenceTest()`
4338: @*/
4339: PetscErrorCode SNESSetUpdate(SNES snes, PetscErrorCode (*func)(SNES snes, PetscInt step))
4340: {
4341:   PetscFunctionBegin;
4343:   snes->ops->update = func;
4344:   PetscFunctionReturn(PETSC_SUCCESS);
4345: }

4347: /*@C
4348:   SNESConvergedReasonView - Displays the reason a `SNES` solve converged or diverged to a viewer

4350:   Collective

4352:   Input Parameters:
4353: + snes   - iterative context obtained from `SNESCreate()`
4354: - viewer - the viewer to display the reason

4356:   Options Database Keys:
4357: + -snes_converged_reason          - print reason for converged or diverged, also prints number of iterations
4358: - -snes_converged_reason ::failed - only print reason and number of iterations when diverged

4360:   Level: beginner

4362:   Note:
4363:   To change the format of the output call `PetscViewerPushFormat`(viewer,format) before this call. Use `PETSC_VIEWER_DEFAULT` for the default,
4364:   use `PETSC_VIEWER_FAILED` to only display a reason if it fails.

4366: .seealso: [](ch_snes), `SNESConvergedReason`, `PetscViewer`, `SNES`,
4367:           `SNESCreate()`, `SNESSetUp()`, `SNESDestroy()`, `SNESSetTolerances()`, `SNESConvergedDefault()`, `SNESGetConvergedReason()`,
4368:           `SNESConvergedReasonViewFromOptions()`,
4369:           `PetscViewerPushFormat()`, `PetscViewerPopFormat()`
4370: @*/
4371: PetscErrorCode SNESConvergedReasonView(SNES snes, PetscViewer viewer)
4372: {
4373:   PetscViewerFormat format;
4374:   PetscBool         isAscii;

4376:   PetscFunctionBegin;
4377:   if (!viewer) viewer = PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes));
4378:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &isAscii));
4379:   if (isAscii) {
4380:     PetscCall(PetscViewerGetFormat(viewer, &format));
4381:     PetscCall(PetscViewerASCIIAddTab(viewer, ((PetscObject)snes)->tablevel));
4382:     if (format == PETSC_VIEWER_ASCII_INFO_DETAIL) {
4383:       DM       dm;
4384:       Vec      u;
4385:       PetscDS  prob;
4386:       PetscInt Nf, f;
4387:       PetscErrorCode (**exactSol)(PetscInt, PetscReal, const PetscReal[], PetscInt, PetscScalar[], void *);
4388:       void    **exactCtx;
4389:       PetscReal error;

4391:       PetscCall(SNESGetDM(snes, &dm));
4392:       PetscCall(SNESGetSolution(snes, &u));
4393:       PetscCall(DMGetDS(dm, &prob));
4394:       PetscCall(PetscDSGetNumFields(prob, &Nf));
4395:       PetscCall(PetscMalloc2(Nf, &exactSol, Nf, &exactCtx));
4396:       for (f = 0; f < Nf; ++f) PetscCall(PetscDSGetExactSolution(prob, f, &exactSol[f], &exactCtx[f]));
4397:       PetscCall(DMComputeL2Diff(dm, 0.0, exactSol, exactCtx, u, &error));
4398:       PetscCall(PetscFree2(exactSol, exactCtx));
4399:       if (error < 1.0e-11) PetscCall(PetscViewerASCIIPrintf(viewer, "L_2 Error: < 1.0e-11\n"));
4400:       else PetscCall(PetscViewerASCIIPrintf(viewer, "L_2 Error: %g\n", (double)error));
4401:     }
4402:     if (snes->reason > 0 && format != PETSC_VIEWER_FAILED) {
4403:       if (((PetscObject)snes)->prefix) {
4404:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear %s solve converged due to %s iterations %" PetscInt_FMT "\n", ((PetscObject)snes)->prefix, SNESConvergedReasons[snes->reason], snes->iter));
4405:       } else {
4406:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear solve converged due to %s iterations %" PetscInt_FMT "\n", SNESConvergedReasons[snes->reason], snes->iter));
4407:       }
4408:     } else if (snes->reason <= 0) {
4409:       if (((PetscObject)snes)->prefix) {
4410:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear %s solve did not converge due to %s iterations %" PetscInt_FMT "\n", ((PetscObject)snes)->prefix, SNESConvergedReasons[snes->reason], snes->iter));
4411:       } else {
4412:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear solve did not converge due to %s iterations %" PetscInt_FMT "\n", SNESConvergedReasons[snes->reason], snes->iter));
4413:       }
4414:     }
4415:     PetscCall(PetscViewerASCIISubtractTab(viewer, ((PetscObject)snes)->tablevel));
4416:   }
4417:   PetscFunctionReturn(PETSC_SUCCESS);
4418: }

4420: /*@C
4421:   SNESConvergedReasonViewSet - Sets an ADDITIONAL function that is to be used at the
4422:   end of the nonlinear solver to display the convergence reason of the nonlinear solver.

4424:   Logically Collective

4426:   Input Parameters:
4427: + snes              - the `SNES` context
4428: . f                 - the `SNESConvergedReason` view function
4429: . vctx              - [optional] user-defined context for private data for the `SNESConvergedReason` view function (use `NULL` if no context is desired)
4430: - reasonviewdestroy - [optional] routine that frees the context (may be `NULL`)

4432:   Calling sequence of `f`:
4433: + snes - the `SNES` context
4434: - vctx - [optional] user-defined context for private data for the function

4436:   Calling sequence of `reasonviewerdestroy`:
4437: . vctx - [optional] user-defined context for private data for the function

4439:   Options Database Keys:
4440: + -snes_converged_reason             - sets a default `SNESConvergedReasonView()`
4441: - -snes_converged_reason_view_cancel - cancels all converged reason viewers that have been hardwired into a code by
4442:                             calls to `SNESConvergedReasonViewSet()`, but does not cancel those set via the options database.

4444:   Level: intermediate

4446:   Note:
4447:   Several different converged reason view routines may be set by calling
4448:   `SNESConvergedReasonViewSet()` multiple times; all will be called in the
4449:   order in which they were set.

4451: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESConvergedReason`, `SNESGetConvergedReason()`, `SNESConvergedReasonView()`, `SNESConvergedReasonViewCancel()`
4452: @*/
4453: PetscErrorCode SNESConvergedReasonViewSet(SNES snes, PetscErrorCode (*f)(SNES snes, void *vctx), void *vctx, PetscErrorCode (*reasonviewdestroy)(void **vctx))
4454: {
4455:   PetscInt  i;
4456:   PetscBool identical;

4458:   PetscFunctionBegin;
4460:   for (i = 0; i < snes->numberreasonviews; i++) {
4461:     PetscCall(PetscMonitorCompare((PetscErrorCode(*)(void))f, vctx, reasonviewdestroy, (PetscErrorCode(*)(void))snes->reasonview[i], snes->reasonviewcontext[i], snes->reasonviewdestroy[i], &identical));
4462:     if (identical) PetscFunctionReturn(PETSC_SUCCESS);
4463:   }
4464:   PetscCheck(snes->numberreasonviews < MAXSNESREASONVIEWS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many SNES reasonview set");
4465:   snes->reasonview[snes->numberreasonviews]          = f;
4466:   snes->reasonviewdestroy[snes->numberreasonviews]   = reasonviewdestroy;
4467:   snes->reasonviewcontext[snes->numberreasonviews++] = (void *)vctx;
4468:   PetscFunctionReturn(PETSC_SUCCESS);
4469: }

4471: /*@
4472:   SNESConvergedReasonViewFromOptions - Processes command line options to determine if/how a `SNESConvergedReason` is to be viewed at the end of `SNESSolve()`
4473:   All the user-provided convergedReasonView routines will be involved as well, if they exist.

4475:   Collective

4477:   Input Parameter:
4478: . snes - the `SNES` object

4480:   Level: advanced

4482: .seealso: [](ch_snes), `SNES`, `SNESConvergedReason`, `SNESConvergedReasonViewSet()`, `SNESCreate()`, `SNESSetUp()`, `SNESDestroy()`,
4483:           `SNESSetTolerances()`, `SNESConvergedDefault()`, `SNESGetConvergedReason()`, `SNESConvergedReasonView()`
4484: @*/
4485: PetscErrorCode SNESConvergedReasonViewFromOptions(SNES snes)
4486: {
4487:   PetscViewer       viewer;
4488:   PetscBool         flg;
4489:   static PetscBool  incall = PETSC_FALSE;
4490:   PetscViewerFormat format;
4491:   PetscInt          i;

4493:   PetscFunctionBegin;
4494:   if (incall) PetscFunctionReturn(PETSC_SUCCESS);
4495:   incall = PETSC_TRUE;

4497:   /* All user-provided viewers are called first, if they exist. */
4498:   for (i = 0; i < snes->numberreasonviews; i++) PetscCall((*snes->reasonview[i])(snes, snes->reasonviewcontext[i]));

4500:   /* Call PETSc default routine if users ask for it */
4501:   PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_converged_reason", &viewer, &format, &flg));
4502:   if (flg) {
4503:     PetscCall(PetscViewerPushFormat(viewer, format));
4504:     PetscCall(SNESConvergedReasonView(snes, viewer));
4505:     PetscCall(PetscViewerPopFormat(viewer));
4506:     PetscCall(PetscViewerDestroy(&viewer));
4507:   }
4508:   incall = PETSC_FALSE;
4509:   PetscFunctionReturn(PETSC_SUCCESS);
4510: }

4512: /*@
4513:   SNESSolve - Solves a nonlinear system F(x) = b.

4515:   Collective

4517:   Input Parameters:
4518: + snes - the `SNES` context
4519: . b    - the constant part of the equation F(x) = b, or `NULL` to use zero.
4520: - x    - the solution vector.

4522:   Level: beginner

4524:   Note:
4525:   The user should initialize the vector, `x`, with the initial guess
4526:   for the nonlinear solve prior to calling `SNESSolve()` or use `SNESSetInitialSolution()`.  In particular,
4527:   to employ an initial guess of zero, the user should explicitly set
4528:   this vector to zero by calling `VecSet()`.

4530: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESDestroy()`, `SNESSetFunction()`, `SNESSetJacobian()`, `SNESSetGridSequence()`, `SNESGetSolution()`,
4531:           `SNESNewtonTRSetPreCheck()`, `SNESNewtonTRGetPreCheck()`, `SNESNewtonTRSetPostCheck()`, `SNESNewtonTRGetPostCheck()`,
4532:           `SNESLineSearchSetPostCheck()`, `SNESLineSearchGetPostCheck()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchGetPreCheck()`, `SNESSetInitialSolution()`
4533: @*/
4534: PetscErrorCode SNESSolve(SNES snes, Vec b, Vec x)
4535: {
4536:   PetscBool flg;
4537:   PetscInt  grid;
4538:   Vec       xcreated = NULL;
4539:   DM        dm;

4541:   PetscFunctionBegin;
4544:   if (x) PetscCheckSameComm(snes, 1, x, 3);
4546:   if (b) PetscCheckSameComm(snes, 1, b, 2);

4548:   /* High level operations using the nonlinear solver */
4549:   {
4550:     PetscViewer       viewer;
4551:     PetscViewerFormat format;
4552:     PetscInt          num;
4553:     PetscBool         flg;
4554:     static PetscBool  incall = PETSC_FALSE;

4556:     if (!incall) {
4557:       /* Estimate the convergence rate of the discretization */
4558:       PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_convergence_estimate", &viewer, &format, &flg));
4559:       if (flg) {
4560:         PetscConvEst conv;
4561:         DM           dm;
4562:         PetscReal   *alpha; /* Convergence rate of the solution error for each field in the L_2 norm */
4563:         PetscInt     Nf;

4565:         incall = PETSC_TRUE;
4566:         PetscCall(SNESGetDM(snes, &dm));
4567:         PetscCall(DMGetNumFields(dm, &Nf));
4568:         PetscCall(PetscCalloc1(Nf, &alpha));
4569:         PetscCall(PetscConvEstCreate(PetscObjectComm((PetscObject)snes), &conv));
4570:         PetscCall(PetscConvEstSetSolver(conv, (PetscObject)snes));
4571:         PetscCall(PetscConvEstSetFromOptions(conv));
4572:         PetscCall(PetscConvEstSetUp(conv));
4573:         PetscCall(PetscConvEstGetConvRate(conv, alpha));
4574:         PetscCall(PetscViewerPushFormat(viewer, format));
4575:         PetscCall(PetscConvEstRateView(conv, alpha, viewer));
4576:         PetscCall(PetscViewerPopFormat(viewer));
4577:         PetscCall(PetscViewerDestroy(&viewer));
4578:         PetscCall(PetscConvEstDestroy(&conv));
4579:         PetscCall(PetscFree(alpha));
4580:         incall = PETSC_FALSE;
4581:       }
4582:       /* Adaptively refine the initial grid */
4583:       num = 1;
4584:       PetscCall(PetscOptionsGetInt(NULL, ((PetscObject)snes)->prefix, "-snes_adapt_initial", &num, &flg));
4585:       if (flg) {
4586:         DMAdaptor adaptor;

4588:         incall = PETSC_TRUE;
4589:         PetscCall(DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor));
4590:         PetscCall(DMAdaptorSetSolver(adaptor, snes));
4591:         PetscCall(DMAdaptorSetSequenceLength(adaptor, num));
4592:         PetscCall(DMAdaptorSetFromOptions(adaptor));
4593:         PetscCall(DMAdaptorSetUp(adaptor));
4594:         PetscCall(DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_INITIAL, &dm, &x));
4595:         PetscCall(DMAdaptorDestroy(&adaptor));
4596:         incall = PETSC_FALSE;
4597:       }
4598:       /* Use grid sequencing to adapt */
4599:       num = 0;
4600:       PetscCall(PetscOptionsGetInt(NULL, ((PetscObject)snes)->prefix, "-snes_adapt_sequence", &num, NULL));
4601:       if (num) {
4602:         DMAdaptor adaptor;

4604:         incall = PETSC_TRUE;
4605:         PetscCall(DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor));
4606:         PetscCall(DMAdaptorSetSolver(adaptor, snes));
4607:         PetscCall(DMAdaptorSetSequenceLength(adaptor, num));
4608:         PetscCall(DMAdaptorSetFromOptions(adaptor));
4609:         PetscCall(DMAdaptorSetUp(adaptor));
4610:         PetscCall(DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_SEQUENTIAL, &dm, &x));
4611:         PetscCall(DMAdaptorDestroy(&adaptor));
4612:         incall = PETSC_FALSE;
4613:       }
4614:     }
4615:   }
4616:   if (!x) x = snes->vec_sol;
4617:   if (!x) {
4618:     PetscCall(SNESGetDM(snes, &dm));
4619:     PetscCall(DMCreateGlobalVector(dm, &xcreated));
4620:     x = xcreated;
4621:   }
4622:   PetscCall(SNESViewFromOptions(snes, NULL, "-snes_view_pre"));

4624:   for (grid = 0; grid < snes->gridsequence; grid++) PetscCall(PetscViewerASCIIPushTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes))));
4625:   for (grid = 0; grid < snes->gridsequence + 1; grid++) {
4626:     /* set solution vector */
4627:     if (!grid) PetscCall(PetscObjectReference((PetscObject)x));
4628:     PetscCall(VecDestroy(&snes->vec_sol));
4629:     snes->vec_sol = x;
4630:     PetscCall(SNESGetDM(snes, &dm));

4632:     /* set affine vector if provided */
4633:     if (b) PetscCall(PetscObjectReference((PetscObject)b));
4634:     PetscCall(VecDestroy(&snes->vec_rhs));
4635:     snes->vec_rhs = b;

4637:     if (snes->vec_rhs) PetscCheck(snes->vec_func != snes->vec_rhs, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Right hand side vector cannot be function vector");
4638:     PetscCheck(snes->vec_func != snes->vec_sol, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Solution vector cannot be function vector");
4639:     PetscCheck(snes->vec_rhs != snes->vec_sol, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Solution vector cannot be right hand side vector");
4640:     if (!snes->vec_sol_update /* && snes->vec_sol */) PetscCall(VecDuplicate(snes->vec_sol, &snes->vec_sol_update));
4641:     PetscCall(DMShellSetGlobalVector(dm, snes->vec_sol));
4642:     PetscCall(SNESSetUp(snes));

4644:     if (!grid) {
4645:       if (snes->ops->computeinitialguess) PetscCallBack("SNES callback initial guess", (*snes->ops->computeinitialguess)(snes, snes->vec_sol, snes->initialguessP));
4646:     }

4648:     if (snes->conv_hist_reset) snes->conv_hist_len = 0;
4649:     if (snes->counters_reset) {
4650:       snes->nfuncs      = 0;
4651:       snes->linear_its  = 0;
4652:       snes->numFailures = 0;
4653:     }

4655:     snes->reason = SNES_CONVERGED_ITERATING;
4656:     PetscCall(PetscLogEventBegin(SNES_Solve, snes, 0, 0, 0));
4657:     PetscUseTypeMethod(snes, solve);
4658:     PetscCall(PetscLogEventEnd(SNES_Solve, snes, 0, 0, 0));
4659:     PetscCheck(snes->reason, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Internal error, solver %s returned without setting converged reason", ((PetscObject)snes)->type_name);
4660:     snes->domainerror = PETSC_FALSE; /* clear the flag if it has been set */

4662:     if (snes->lagjac_persist) snes->jac_iter += snes->iter;
4663:     if (snes->lagpre_persist) snes->pre_iter += snes->iter;

4665:     PetscCall(PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_test_local_min", NULL, NULL, &flg));
4666:     if (flg && !PetscPreLoadingOn) PetscCall(SNESTestLocalMin(snes));
4667:     /* Call converged reason views. This may involve user-provided viewers as well */
4668:     PetscCall(SNESConvergedReasonViewFromOptions(snes));

4670:     if (snes->errorifnotconverged) PetscCheck(snes->reason >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_NOT_CONVERGED, "SNESSolve has not converged");
4671:     if (snes->reason < 0) break;
4672:     if (grid < snes->gridsequence) {
4673:       DM  fine;
4674:       Vec xnew;
4675:       Mat interp;

4677:       PetscCall(DMRefine(snes->dm, PetscObjectComm((PetscObject)snes), &fine));
4678:       PetscCheck(fine, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_INCOMP, "DMRefine() did not perform any refinement, cannot continue grid sequencing");
4679:       PetscCall(DMCreateInterpolation(snes->dm, fine, &interp, NULL));
4680:       PetscCall(DMCreateGlobalVector(fine, &xnew));
4681:       PetscCall(MatInterpolate(interp, x, xnew));
4682:       PetscCall(DMInterpolate(snes->dm, interp, fine));
4683:       PetscCall(MatDestroy(&interp));
4684:       x = xnew;

4686:       PetscCall(SNESReset(snes));
4687:       PetscCall(SNESSetDM(snes, fine));
4688:       PetscCall(SNESResetFromOptions(snes));
4689:       PetscCall(DMDestroy(&fine));
4690:       PetscCall(PetscViewerASCIIPopTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes))));
4691:     }
4692:   }
4693:   PetscCall(SNESViewFromOptions(snes, NULL, "-snes_view"));
4694:   PetscCall(VecViewFromOptions(snes->vec_sol, (PetscObject)snes, "-snes_view_solution"));
4695:   PetscCall(DMMonitor(snes->dm));
4696:   PetscCall(SNESMonitorPauseFinal_Internal(snes));

4698:   PetscCall(VecDestroy(&xcreated));
4699:   PetscCall(PetscObjectSAWsBlock((PetscObject)snes));
4700:   PetscFunctionReturn(PETSC_SUCCESS);
4701: }

4703: /* --------- Internal routines for SNES Package --------- */

4705: /*@C
4706:   SNESSetType - Sets the method for the nonlinear solver.

4708:   Collective

4710:   Input Parameters:
4711: + snes - the `SNES` context
4712: - type - a known method

4714:   Options Database Key:
4715: . -snes_type <type> - Sets the method; use -help for a list
4716:    of available methods (for instance, newtonls or newtontr)

4718:   Level: intermediate

4720:   Notes:
4721:   See "petsc/include/petscsnes.h" for available methods (for instance)
4722: +    `SNESNEWTONLS` - Newton's method with line search
4723:   (systems of nonlinear equations)
4724: -    `SNESNEWTONTR` - Newton's method with trust region
4725:   (systems of nonlinear equations)

4727:   Normally, it is best to use the `SNESSetFromOptions()` command and then
4728:   set the `SNES` solver type from the options database rather than by using
4729:   this routine.  Using the options database provides the user with
4730:   maximum flexibility in evaluating the many nonlinear solvers.
4731:   The `SNESSetType()` routine is provided for those situations where it
4732:   is necessary to set the nonlinear solver independently of the command
4733:   line or options database.  This might be the case, for example, when
4734:   the choice of solver changes during the execution of the program,
4735:   and the user's application is taking responsibility for choosing the
4736:   appropriate method.

4738:   Developer Note:
4739:   `SNESRegister()` adds a constructor for a new `SNESType` to `SNESList`, `SNESSetType()` locates
4740:   the constructor in that list and calls it to create the specific object.

4742: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESType`, `SNESCreate()`, `SNESDestroy()`, `SNESGetType()`, `SNESSetFromOptions()`
4743: @*/
4744: PetscErrorCode SNESSetType(SNES snes, SNESType type)
4745: {
4746:   PetscBool match;
4747:   PetscErrorCode (*r)(SNES);

4749:   PetscFunctionBegin;
4751:   PetscAssertPointer(type, 2);

4753:   PetscCall(PetscObjectTypeCompare((PetscObject)snes, type, &match));
4754:   if (match) PetscFunctionReturn(PETSC_SUCCESS);

4756:   PetscCall(PetscFunctionListFind(SNESList, type, &r));
4757:   PetscCheck(r, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_UNKNOWN_TYPE, "Unable to find requested SNES type %s", type);
4758:   /* Destroy the previous private SNES context */
4759:   PetscTryTypeMethod(snes, destroy);
4760:   /* Reinitialize function pointers in SNESOps structure */
4761:   snes->ops->setup          = NULL;
4762:   snes->ops->solve          = NULL;
4763:   snes->ops->view           = NULL;
4764:   snes->ops->setfromoptions = NULL;
4765:   snes->ops->destroy        = NULL;

4767:   /* It may happen the user has customized the line search before calling SNESSetType */
4768:   if (((PetscObject)snes)->type_name) PetscCall(SNESLineSearchDestroy(&snes->linesearch));

4770:   /* Call the SNESCreate_XXX routine for this particular Nonlinear solver */
4771:   snes->setupcalled = PETSC_FALSE;

4773:   PetscCall(PetscObjectChangeTypeName((PetscObject)snes, type));
4774:   PetscCall((*r)(snes));
4775:   PetscFunctionReturn(PETSC_SUCCESS);
4776: }

4778: /*@C
4779:   SNESGetType - Gets the `SNES` method type and name (as a string).

4781:   Not Collective

4783:   Input Parameter:
4784: . snes - nonlinear solver context

4786:   Output Parameter:
4787: . type - `SNES` method (a character string)

4789:   Level: intermediate

4791: .seealso: [](ch_snes), `SNESSetType()`, `SNESType`, `SNESSetFromOptions()`, `SNES`
4792: @*/
4793: PetscErrorCode SNESGetType(SNES snes, SNESType *type)
4794: {
4795:   PetscFunctionBegin;
4797:   PetscAssertPointer(type, 2);
4798:   *type = ((PetscObject)snes)->type_name;
4799:   PetscFunctionReturn(PETSC_SUCCESS);
4800: }

4802: /*@
4803:   SNESSetSolution - Sets the solution vector for use by the `SNES` routines.

4805:   Logically Collective

4807:   Input Parameters:
4808: + snes - the `SNES` context obtained from `SNESCreate()`
4809: - u    - the solution vector

4811:   Level: beginner

4813: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESGetSolution()`, `Vec`
4814: @*/
4815: PetscErrorCode SNESSetSolution(SNES snes, Vec u)
4816: {
4817:   DM dm;

4819:   PetscFunctionBegin;
4822:   PetscCall(PetscObjectReference((PetscObject)u));
4823:   PetscCall(VecDestroy(&snes->vec_sol));

4825:   snes->vec_sol = u;

4827:   PetscCall(SNESGetDM(snes, &dm));
4828:   PetscCall(DMShellSetGlobalVector(dm, u));
4829:   PetscFunctionReturn(PETSC_SUCCESS);
4830: }

4832: /*@
4833:   SNESGetSolution - Returns the vector where the approximate solution is
4834:   stored. This is the fine grid solution when using `SNESSetGridSequence()`.

4836:   Not Collective, but `x` is parallel if `snes` is parallel

4838:   Input Parameter:
4839: . snes - the `SNES` context

4841:   Output Parameter:
4842: . x - the solution

4844:   Level: intermediate

4846: .seealso: [](ch_snes), `SNESSetSolution()`, `SNESSolve()`, `SNES`, `SNESGetSolutionUpdate()`, `SNESGetFunction()`
4847: @*/
4848: PetscErrorCode SNESGetSolution(SNES snes, Vec *x)
4849: {
4850:   PetscFunctionBegin;
4852:   PetscAssertPointer(x, 2);
4853:   *x = snes->vec_sol;
4854:   PetscFunctionReturn(PETSC_SUCCESS);
4855: }

4857: /*@
4858:   SNESGetSolutionUpdate - Returns the vector where the solution update is
4859:   stored.

4861:   Not Collective, but `x` is parallel if `snes` is parallel

4863:   Input Parameter:
4864: . snes - the `SNES` context

4866:   Output Parameter:
4867: . x - the solution update

4869:   Level: advanced

4871: .seealso: [](ch_snes), `SNES`, `SNESGetSolution()`, `SNESGetFunction()`
4872: @*/
4873: PetscErrorCode SNESGetSolutionUpdate(SNES snes, Vec *x)
4874: {
4875:   PetscFunctionBegin;
4877:   PetscAssertPointer(x, 2);
4878:   *x = snes->vec_sol_update;
4879:   PetscFunctionReturn(PETSC_SUCCESS);
4880: }

4882: /*@C
4883:   SNESGetFunction - Returns the function that defines the nonlinear system set with `SNESSetFunction()`

4885:   Not Collective, but `r` is parallel if `snes` is parallel. Collective if `r` is requested, but has not been created yet.

4887:   Input Parameter:
4888: . snes - the `SNES` context

4890:   Output Parameters:
4891: + r   - the vector that is used to store residuals (or `NULL` if you don't want it)
4892: . f   - the function (or `NULL` if you don't want it);  for calling sequence see `SNESFunction`
4893: - ctx - the function context (or `NULL` if you don't want it)

4895:   Level: advanced

4897:   Note:
4898:   The vector `r` DOES NOT, in general, contain the current value of the `SNES` nonlinear function

4900: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetFunction()`, `SNESGetSolution()`, `SNESFunction`
4901: @*/
4902: PetscErrorCode SNESGetFunction(SNES snes, Vec *r, PetscErrorCode (**f)(SNES, Vec, Vec, void *), void **ctx)
4903: {
4904:   DM dm;

4906:   PetscFunctionBegin;
4908:   if (r) {
4909:     if (!snes->vec_func) {
4910:       if (snes->vec_rhs) {
4911:         PetscCall(VecDuplicate(snes->vec_rhs, &snes->vec_func));
4912:       } else if (snes->vec_sol) {
4913:         PetscCall(VecDuplicate(snes->vec_sol, &snes->vec_func));
4914:       } else if (snes->dm) {
4915:         PetscCall(DMCreateGlobalVector(snes->dm, &snes->vec_func));
4916:       }
4917:     }
4918:     *r = snes->vec_func;
4919:   }
4920:   PetscCall(SNESGetDM(snes, &dm));
4921:   PetscCall(DMSNESGetFunction(dm, f, ctx));
4922:   PetscFunctionReturn(PETSC_SUCCESS);
4923: }

4925: /*@C
4926:   SNESGetNGS - Returns the function and context set with `SNESSetNGS()`

4928:   Input Parameter:
4929: . snes - the `SNES` context

4931:   Output Parameters:
4932: + f   - the function (or `NULL`) see `SNESSetNGS()` for details
4933: - ctx - the function context (or `NULL`)

4935:   Level: advanced

4937: .seealso: [](ch_snes), `SNESSetNGS()`, `SNESGetFunction()`
4938: @*/
4939: PetscErrorCode SNESGetNGS(SNES snes, PetscErrorCode (**f)(SNES, Vec, Vec, void *), void **ctx)
4940: {
4941:   DM dm;

4943:   PetscFunctionBegin;
4945:   PetscCall(SNESGetDM(snes, &dm));
4946:   PetscCall(DMSNESGetNGS(dm, f, ctx));
4947:   PetscFunctionReturn(PETSC_SUCCESS);
4948: }

4950: /*@C
4951:   SNESSetOptionsPrefix - Sets the prefix used for searching for all
4952:   `SNES` options in the database.

4954:   Logically Collective

4956:   Input Parameters:
4957: + snes   - the `SNES` context
4958: - prefix - the prefix to prepend to all option names

4960:   Level: advanced

4962:   Note:
4963:   A hyphen (-) must NOT be given at the beginning of the prefix name.
4964:   The first character of all runtime options is AUTOMATICALLY the hyphen.

4966: .seealso: [](ch_snes), `SNES`, `SNESSetFromOptions()`, `SNESAppendOptionsPrefix()`
4967: @*/
4968: PetscErrorCode SNESSetOptionsPrefix(SNES snes, const char prefix[])
4969: {
4970:   PetscFunctionBegin;
4972:   PetscCall(PetscObjectSetOptionsPrefix((PetscObject)snes, prefix));
4973:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
4974:   if (snes->linesearch) {
4975:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
4976:     PetscCall(PetscObjectSetOptionsPrefix((PetscObject)snes->linesearch, prefix));
4977:   }
4978:   PetscCall(KSPSetOptionsPrefix(snes->ksp, prefix));
4979:   PetscFunctionReturn(PETSC_SUCCESS);
4980: }

4982: /*@C
4983:   SNESAppendOptionsPrefix - Appends to the prefix used for searching for all
4984:   `SNES` options in the database.

4986:   Logically Collective

4988:   Input Parameters:
4989: + snes   - the `SNES` context
4990: - prefix - the prefix to prepend to all option names

4992:   Level: advanced

4994:   Note:
4995:   A hyphen (-) must NOT be given at the beginning of the prefix name.
4996:   The first character of all runtime options is AUTOMATICALLY the hyphen.

4998: .seealso: [](ch_snes), `SNESGetOptionsPrefix()`, `SNESSetOptionsPrefix()`
4999: @*/
5000: PetscErrorCode SNESAppendOptionsPrefix(SNES snes, const char prefix[])
5001: {
5002:   PetscFunctionBegin;
5004:   PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)snes, prefix));
5005:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
5006:   if (snes->linesearch) {
5007:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
5008:     PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)snes->linesearch, prefix));
5009:   }
5010:   PetscCall(KSPAppendOptionsPrefix(snes->ksp, prefix));
5011:   PetscFunctionReturn(PETSC_SUCCESS);
5012: }

5014: /*@C
5015:   SNESGetOptionsPrefix - Gets the prefix used for searching for all
5016:   `SNES` options in the database.

5018:   Not Collective

5020:   Input Parameter:
5021: . snes - the `SNES` context

5023:   Output Parameter:
5024: . prefix - pointer to the prefix string used

5026:   Level: advanced

5028:   Fortran Note:
5029:   The user should pass in a string 'prefix' of
5030:   sufficient length to hold the prefix.

5032: .seealso: [](ch_snes), `SNES`, `SNESSetOptionsPrefix()`, `SNESAppendOptionsPrefix()`
5033: @*/
5034: PetscErrorCode SNESGetOptionsPrefix(SNES snes, const char *prefix[])
5035: {
5036:   PetscFunctionBegin;
5038:   PetscCall(PetscObjectGetOptionsPrefix((PetscObject)snes, prefix));
5039:   PetscFunctionReturn(PETSC_SUCCESS);
5040: }

5042: /*@C
5043:   SNESRegister - Adds a method to the nonlinear solver package.

5045:   Not Collective

5047:   Input Parameters:
5048: + sname    - name of a new user-defined solver
5049: - function - routine to create method context

5051:   Level: advanced

5053:   Note:
5054:   `SNESRegister()` may be called multiple times to add several user-defined solvers.

5056:   Example Usage:
5057: .vb
5058:    SNESRegister("my_solver", MySolverCreate);
5059: .ve

5061:   Then, your solver can be chosen with the procedural interface via
5062: $     SNESSetType(snes, "my_solver")
5063:   or at runtime via the option
5064: $     -snes_type my_solver

5066: .seealso: [](ch_snes), `SNESRegisterAll()`, `SNESRegisterDestroy()`
5067: @*/
5068: PetscErrorCode SNESRegister(const char sname[], PetscErrorCode (*function)(SNES))
5069: {
5070:   PetscFunctionBegin;
5071:   PetscCall(SNESInitializePackage());
5072:   PetscCall(PetscFunctionListAdd(&SNESList, sname, function));
5073:   PetscFunctionReturn(PETSC_SUCCESS);
5074: }

5076: PetscErrorCode SNESTestLocalMin(SNES snes)
5077: {
5078:   PetscInt    N, i, j;
5079:   Vec         u, uh, fh;
5080:   PetscScalar value;
5081:   PetscReal   norm;

5083:   PetscFunctionBegin;
5084:   PetscCall(SNESGetSolution(snes, &u));
5085:   PetscCall(VecDuplicate(u, &uh));
5086:   PetscCall(VecDuplicate(u, &fh));

5088:   /* currently only works for sequential */
5089:   PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "Testing FormFunction() for local min\n"));
5090:   PetscCall(VecGetSize(u, &N));
5091:   for (i = 0; i < N; i++) {
5092:     PetscCall(VecCopy(u, uh));
5093:     PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "i = %" PetscInt_FMT "\n", i));
5094:     for (j = -10; j < 11; j++) {
5095:       value = PetscSign(j) * PetscExpReal(PetscAbs(j) - 10.0);
5096:       PetscCall(VecSetValue(uh, i, value, ADD_VALUES));
5097:       PetscCall(SNESComputeFunction(snes, uh, fh));
5098:       PetscCall(VecNorm(fh, NORM_2, &norm));
5099:       PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "       j norm %" PetscInt_FMT " %18.16e\n", j, (double)norm));
5100:       value = -value;
5101:       PetscCall(VecSetValue(uh, i, value, ADD_VALUES));
5102:     }
5103:   }
5104:   PetscCall(VecDestroy(&uh));
5105:   PetscCall(VecDestroy(&fh));
5106:   PetscFunctionReturn(PETSC_SUCCESS);
5107: }

5109: /*@
5110:   SNESKSPSetUseEW - Sets `SNES` to the use Eisenstat-Walker method for
5111:   computing relative tolerance for linear solvers within an inexact
5112:   Newton method.

5114:   Logically Collective

5116:   Input Parameters:
5117: + snes - `SNES` context
5118: - flag - `PETSC_TRUE` or `PETSC_FALSE`

5120:   Options Database Keys:
5121: + -snes_ksp_ew                       - use Eisenstat-Walker method for determining linear system convergence
5122: . -snes_ksp_ew_version ver           - version of  Eisenstat-Walker method
5123: . -snes_ksp_ew_rtol0 <rtol0>         - Sets rtol0
5124: . -snes_ksp_ew_rtolmax <rtolmax>     - Sets rtolmax
5125: . -snes_ksp_ew_gamma <gamma>         - Sets gamma
5126: . -snes_ksp_ew_alpha <alpha>         - Sets alpha
5127: . -snes_ksp_ew_alpha2 <alpha2>       - Sets alpha2
5128: - -snes_ksp_ew_threshold <threshold> - Sets threshold

5130:   Level: advanced

5132:   Note:
5133:   The default is to use a constant relative tolerance for
5134:   the inner linear solvers.  Alternatively, one can use the
5135:   Eisenstat-Walker method, where the relative convergence tolerance
5136:   is reset at each Newton iteration according progress of the nonlinear
5137:   solver.

5139:   References:
5140: .  - * S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an inexact Newton method", SISC 17 (1), pp.16-32, 1996.

5142: .seealso: [](ch_snes), `KSP`, `SNES`, `SNESKSPGetUseEW()`, `SNESKSPGetParametersEW()`, `SNESKSPSetParametersEW()`
5143: @*/
5144: PetscErrorCode SNESKSPSetUseEW(SNES snes, PetscBool flag)
5145: {
5146:   PetscFunctionBegin;
5149:   snes->ksp_ewconv = flag;
5150:   PetscFunctionReturn(PETSC_SUCCESS);
5151: }

5153: /*@
5154:   SNESKSPGetUseEW - Gets if `SNES` is using Eisenstat-Walker method
5155:   for computing relative tolerance for linear solvers within an
5156:   inexact Newton method.

5158:   Not Collective

5160:   Input Parameter:
5161: . snes - `SNES` context

5163:   Output Parameter:
5164: . flag - `PETSC_TRUE` or `PETSC_FALSE`

5166:   Level: advanced

5168: .seealso: [](ch_snes), `SNESKSPSetUseEW()`, `SNESKSPGetParametersEW()`, `SNESKSPSetParametersEW()`
5169: @*/
5170: PetscErrorCode SNESKSPGetUseEW(SNES snes, PetscBool *flag)
5171: {
5172:   PetscFunctionBegin;
5174:   PetscAssertPointer(flag, 2);
5175:   *flag = snes->ksp_ewconv;
5176:   PetscFunctionReturn(PETSC_SUCCESS);
5177: }

5179: /*@
5180:   SNESKSPSetParametersEW - Sets parameters for Eisenstat-Walker
5181:   convergence criteria for the linear solvers within an inexact
5182:   Newton method.

5184:   Logically Collective

5186:   Input Parameters:
5187: + snes      - `SNES` context
5188: . version   - version 1, 2 (default is 2), 3 or 4
5189: . rtol_0    - initial relative tolerance (0 <= rtol_0 < 1)
5190: . rtol_max  - maximum relative tolerance (0 <= rtol_max < 1)
5191: . gamma     - multiplicative factor for version 2 rtol computation
5192:              (0 <= gamma2 <= 1)
5193: . alpha     - power for version 2 rtol computation (1 < alpha <= 2)
5194: . alpha2    - power for safeguard
5195: - threshold - threshold for imposing safeguard (0 < threshold < 1)

5197:   Level: advanced

5199:   Notes:
5200:   Version 3 was contributed by Luis Chacon, June 2006.

5202:   Use `PETSC_DEFAULT` to retain the default for any of the parameters.

5204: .seealso: [](ch_snes), `SNES`, `SNESKSPSetUseEW()`, `SNESKSPGetUseEW()`, `SNESKSPGetParametersEW()`
5205: @*/
5206: PetscErrorCode SNESKSPSetParametersEW(SNES snes, PetscInt version, PetscReal rtol_0, PetscReal rtol_max, PetscReal gamma, PetscReal alpha, PetscReal alpha2, PetscReal threshold)
5207: {
5208:   SNESKSPEW *kctx;

5210:   PetscFunctionBegin;
5212:   kctx = (SNESKSPEW *)snes->kspconvctx;
5213:   PetscCheck(kctx, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "No Eisenstat-Walker context existing");

5222:   if (version != PETSC_DEFAULT) kctx->version = version;
5223:   if (rtol_0 != (PetscReal)PETSC_DEFAULT) kctx->rtol_0 = rtol_0;
5224:   if (rtol_max != (PetscReal)PETSC_DEFAULT) kctx->rtol_max = rtol_max;
5225:   if (gamma != (PetscReal)PETSC_DEFAULT) kctx->gamma = gamma;
5226:   if (alpha != (PetscReal)PETSC_DEFAULT) kctx->alpha = alpha;
5227:   if (alpha2 != (PetscReal)PETSC_DEFAULT) kctx->alpha2 = alpha2;
5228:   if (threshold != (PetscReal)PETSC_DEFAULT) kctx->threshold = threshold;

5230:   PetscCheck(kctx->version >= 1 && kctx->version <= 4, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Only versions 1 to 4 are supported: %" PetscInt_FMT, kctx->version);
5231:   PetscCheck(kctx->rtol_0 >= 0.0 && kctx->rtol_0 < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= rtol_0 < 1.0: %g", (double)kctx->rtol_0);
5232:   PetscCheck(kctx->rtol_max >= 0.0 && kctx->rtol_max < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= rtol_max (%g) < 1.0", (double)kctx->rtol_max);
5233:   PetscCheck(kctx->gamma >= 0.0 && kctx->gamma <= 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= gamma (%g) <= 1.0", (double)kctx->gamma);
5234:   PetscCheck(kctx->alpha > 1.0 && kctx->alpha <= 2.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "1.0 < alpha (%g) <= 2.0", (double)kctx->alpha);
5235:   PetscCheck(kctx->threshold > 0.0 && kctx->threshold < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 < threshold (%g) < 1.0", (double)kctx->threshold);
5236:   PetscFunctionReturn(PETSC_SUCCESS);
5237: }

5239: /*@
5240:   SNESKSPGetParametersEW - Gets parameters for Eisenstat-Walker
5241:   convergence criteria for the linear solvers within an inexact
5242:   Newton method.

5244:   Not Collective

5246:   Input Parameter:
5247: . snes - `SNES` context

5249:   Output Parameters:
5250: + version   - version 1, 2 (default is 2), 3 or 4
5251: . rtol_0    - initial relative tolerance (0 <= rtol_0 < 1)
5252: . rtol_max  - maximum relative tolerance (0 <= rtol_max < 1)
5253: . gamma     - multiplicative factor for version 2 rtol computation (0 <= gamma2 <= 1)
5254: . alpha     - power for version 2 rtol computation (1 < alpha <= 2)
5255: . alpha2    - power for safeguard
5256: - threshold - threshold for imposing safeguard (0 < threshold < 1)

5258:   Level: advanced

5260: .seealso: [](ch_snes), `SNES`, `SNESKSPSetUseEW()`, `SNESKSPGetUseEW()`, `SNESKSPSetParametersEW()`
5261: @*/
5262: PetscErrorCode SNESKSPGetParametersEW(SNES snes, PetscInt *version, PetscReal *rtol_0, PetscReal *rtol_max, PetscReal *gamma, PetscReal *alpha, PetscReal *alpha2, PetscReal *threshold)
5263: {
5264:   SNESKSPEW *kctx;

5266:   PetscFunctionBegin;
5268:   kctx = (SNESKSPEW *)snes->kspconvctx;
5269:   PetscCheck(kctx, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "No Eisenstat-Walker context existing");
5270:   if (version) *version = kctx->version;
5271:   if (rtol_0) *rtol_0 = kctx->rtol_0;
5272:   if (rtol_max) *rtol_max = kctx->rtol_max;
5273:   if (gamma) *gamma = kctx->gamma;
5274:   if (alpha) *alpha = kctx->alpha;
5275:   if (alpha2) *alpha2 = kctx->alpha2;
5276:   if (threshold) *threshold = kctx->threshold;
5277:   PetscFunctionReturn(PETSC_SUCCESS);
5278: }

5280: PetscErrorCode KSPPreSolve_SNESEW(KSP ksp, Vec b, Vec x, void *ctx)
5281: {
5282:   SNES       snes = (SNES)ctx;
5283:   SNESKSPEW *kctx = (SNESKSPEW *)snes->kspconvctx;
5284:   PetscReal  rtol = PETSC_DEFAULT, stol;

5286:   PetscFunctionBegin;
5287:   if (!snes->ksp_ewconv) PetscFunctionReturn(PETSC_SUCCESS);
5288:   if (!snes->iter) {
5289:     rtol = kctx->rtol_0; /* first time in, so use the original user rtol */
5290:     PetscCall(VecNorm(snes->vec_func, NORM_2, &kctx->norm_first));
5291:   } else {
5292:     PetscCheck(kctx->version >= 1 && kctx->version <= 4, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Only versions 1-4 are supported: %" PetscInt_FMT, kctx->version);
5293:     if (kctx->version == 1) {
5294:       rtol = PetscAbsReal(snes->norm - kctx->lresid_last) / kctx->norm_last;
5295:       stol = PetscPowReal(kctx->rtol_last, kctx->alpha2);
5296:       if (stol > kctx->threshold) rtol = PetscMax(rtol, stol);
5297:     } else if (kctx->version == 2) {
5298:       rtol = kctx->gamma * PetscPowReal(snes->norm / kctx->norm_last, kctx->alpha);
5299:       stol = kctx->gamma * PetscPowReal(kctx->rtol_last, kctx->alpha);
5300:       if (stol > kctx->threshold) rtol = PetscMax(rtol, stol);
5301:     } else if (kctx->version == 3) { /* contributed by Luis Chacon, June 2006. */
5302:       rtol = kctx->gamma * PetscPowReal(snes->norm / kctx->norm_last, kctx->alpha);
5303:       /* safeguard: avoid sharp decrease of rtol */
5304:       stol = kctx->gamma * PetscPowReal(kctx->rtol_last, kctx->alpha);
5305:       stol = PetscMax(rtol, stol);
5306:       rtol = PetscMin(kctx->rtol_0, stol);
5307:       /* safeguard: avoid oversolving */
5308:       stol = kctx->gamma * (kctx->norm_first * snes->rtol) / snes->norm;
5309:       stol = PetscMax(rtol, stol);
5310:       rtol = PetscMin(kctx->rtol_0, stol);
5311:     } else /* if (kctx->version == 4) */ {
5312:       /* H.-B. An et al. Journal of Computational and Applied Mathematics 200 (2007) 47-60 */
5313:       PetscReal ared = PetscAbsReal(kctx->norm_last - snes->norm);
5314:       PetscReal pred = PetscAbsReal(kctx->norm_last - kctx->lresid_last);
5315:       PetscReal rk   = ared / pred;
5316:       if (rk < kctx->v4_p1) rtol = 1. - 2. * kctx->v4_p1;
5317:       else if (rk < kctx->v4_p2) rtol = kctx->rtol_last;
5318:       else if (rk < kctx->v4_p3) rtol = kctx->v4_m1 * kctx->rtol_last;
5319:       else rtol = kctx->v4_m2 * kctx->rtol_last;

5321:       if (kctx->rtol_last_2 > kctx->v4_m3 && kctx->rtol_last > kctx->v4_m3 && kctx->rk_last_2 < kctx->v4_p1 && kctx->rk_last < kctx->v4_p1) rtol = kctx->v4_m4 * kctx->rtol_last;
5322:       kctx->rtol_last_2 = kctx->rtol_last;
5323:       kctx->rk_last_2   = kctx->rk_last;
5324:       kctx->rk_last     = rk;
5325:     }
5326:   }
5327:   /* safeguard: avoid rtol greater than rtol_max */
5328:   rtol = PetscMin(rtol, kctx->rtol_max);
5329:   PetscCall(KSPSetTolerances(ksp, rtol, PETSC_DEFAULT, PETSC_DEFAULT, PETSC_DEFAULT));
5330:   PetscCall(PetscInfo(snes, "iter %" PetscInt_FMT ", Eisenstat-Walker (version %" PetscInt_FMT ") KSP rtol=%g\n", snes->iter, kctx->version, (double)rtol));
5331:   PetscFunctionReturn(PETSC_SUCCESS);
5332: }

5334: PetscErrorCode KSPPostSolve_SNESEW(KSP ksp, Vec b, Vec x, void *ctx)
5335: {
5336:   SNES       snes = (SNES)ctx;
5337:   SNESKSPEW *kctx = (SNESKSPEW *)snes->kspconvctx;
5338:   PCSide     pcside;
5339:   Vec        lres;

5341:   PetscFunctionBegin;
5342:   if (!snes->ksp_ewconv) PetscFunctionReturn(PETSC_SUCCESS);
5343:   PetscCall(KSPGetTolerances(ksp, &kctx->rtol_last, NULL, NULL, NULL));
5344:   kctx->norm_last = snes->norm;
5345:   if (kctx->version == 1 || kctx->version == 4) {
5346:     PC        pc;
5347:     PetscBool getRes;

5349:     PetscCall(KSPGetPC(ksp, &pc));
5350:     PetscCall(PetscObjectTypeCompare((PetscObject)pc, PCNONE, &getRes));
5351:     if (!getRes) {
5352:       KSPNormType normtype;

5354:       PetscCall(KSPGetNormType(ksp, &normtype));
5355:       getRes = (PetscBool)(normtype == KSP_NORM_UNPRECONDITIONED);
5356:     }
5357:     PetscCall(KSPGetPCSide(ksp, &pcside));
5358:     if (pcside == PC_RIGHT || getRes) { /* KSP residual is true linear residual */
5359:       PetscCall(KSPGetResidualNorm(ksp, &kctx->lresid_last));
5360:     } else {
5361:       /* KSP residual is preconditioned residual */
5362:       /* compute true linear residual norm */
5363:       Mat J;
5364:       PetscCall(KSPGetOperators(ksp, &J, NULL));
5365:       PetscCall(VecDuplicate(b, &lres));
5366:       PetscCall(MatMult(J, x, lres));
5367:       PetscCall(VecAYPX(lres, -1.0, b));
5368:       PetscCall(VecNorm(lres, NORM_2, &kctx->lresid_last));
5369:       PetscCall(VecDestroy(&lres));
5370:     }
5371:   }
5372:   PetscFunctionReturn(PETSC_SUCCESS);
5373: }

5375: /*@
5376:   SNESGetKSP - Returns the `KSP` context for a `SNES` solver.

5378:   Not Collective, but if `snes` is parallel, then `ksp` is parallel

5380:   Input Parameter:
5381: . snes - the `SNES` context

5383:   Output Parameter:
5384: . ksp - the `KSP` context

5386:   Level: beginner

5388:   Notes:
5389:   The user can then directly manipulate the `KSP` context to set various
5390:   options, etc.  Likewise, the user can then extract and manipulate the
5391:   `PC` contexts as well.

5393:   Some `SNESType`s do not use a `KSP` but a `KSP` is still returned by this function

5395: .seealso: [](ch_snes), `SNES`, `KSP`, `PC`, `KSPGetPC()`, `SNESCreate()`, `KSPCreate()`, `SNESSetKSP()`
5396: @*/
5397: PetscErrorCode SNESGetKSP(SNES snes, KSP *ksp)
5398: {
5399:   PetscFunctionBegin;
5401:   PetscAssertPointer(ksp, 2);

5403:   if (!snes->ksp) {
5404:     PetscCall(KSPCreate(PetscObjectComm((PetscObject)snes), &snes->ksp));
5405:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->ksp, (PetscObject)snes, 1));

5407:     PetscCall(KSPSetPreSolve(snes->ksp, KSPPreSolve_SNESEW, snes));
5408:     PetscCall(KSPSetPostSolve(snes->ksp, KSPPostSolve_SNESEW, snes));

5410:     PetscCall(KSPMonitorSetFromOptions(snes->ksp, "-snes_monitor_ksp", "snes_preconditioned_residual", snes));
5411:     PetscCall(PetscObjectSetOptions((PetscObject)snes->ksp, ((PetscObject)snes)->options));
5412:   }
5413:   *ksp = snes->ksp;
5414:   PetscFunctionReturn(PETSC_SUCCESS);
5415: }

5417: #include <petsc/private/dmimpl.h>
5418: /*@
5419:   SNESSetDM - Sets the `DM` that may be used by some nonlinear solvers or their underlying preconditioners

5421:   Logically Collective

5423:   Input Parameters:
5424: + snes - the nonlinear solver context
5425: - dm   - the `DM`, cannot be `NULL`

5427:   Level: intermediate

5429:   Note:
5430:   A `DM` can only be used for solving one problem at a time because information about the problem is stored on the `DM`,
5431:   even when not using interfaces like `DMSNESSetFunction()`.  Use `DMClone()` to get a distinct `DM` when solving different
5432:   problems using the same function space.

5434: .seealso: [](ch_snes), `DM`, `SNES`, `SNESGetDM()`, `KSPSetDM()`, `KSPGetDM()`
5435: @*/
5436: PetscErrorCode SNESSetDM(SNES snes, DM dm)
5437: {
5438:   KSP    ksp;
5439:   DMSNES sdm;

5441:   PetscFunctionBegin;
5444:   PetscCall(PetscObjectReference((PetscObject)dm));
5445:   if (snes->dm) { /* Move the DMSNES context over to the new DM unless the new DM already has one */
5446:     if (snes->dm->dmsnes && !dm->dmsnes) {
5447:       PetscCall(DMCopyDMSNES(snes->dm, dm));
5448:       PetscCall(DMGetDMSNES(snes->dm, &sdm));
5449:       if (sdm->originaldm == snes->dm) sdm->originaldm = dm; /* Grant write privileges to the replacement DM */
5450:     }
5451:     PetscCall(DMCoarsenHookRemove(snes->dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, snes));
5452:     PetscCall(DMDestroy(&snes->dm));
5453:   }
5454:   snes->dm     = dm;
5455:   snes->dmAuto = PETSC_FALSE;

5457:   PetscCall(SNESGetKSP(snes, &ksp));
5458:   PetscCall(KSPSetDM(ksp, dm));
5459:   PetscCall(KSPSetDMActive(ksp, PETSC_FALSE));
5460:   if (snes->npc) {
5461:     PetscCall(SNESSetDM(snes->npc, snes->dm));
5462:     PetscCall(SNESSetNPCSide(snes, snes->npcside));
5463:   }
5464:   PetscFunctionReturn(PETSC_SUCCESS);
5465: }

5467: /*@
5468:   SNESGetDM - Gets the `DM` that may be used by some solvers/preconditioners

5470:   Not Collective but dm obtained is parallel on snes

5472:   Input Parameter:
5473: . snes - the `SNES` context

5475:   Output Parameter:
5476: . dm - the `DM`

5478:   Level: intermediate

5480: .seealso: [](ch_snes), `DM`, `SNES`, `SNESSetDM()`, `KSPSetDM()`, `KSPGetDM()`
5481: @*/
5482: PetscErrorCode SNESGetDM(SNES snes, DM *dm)
5483: {
5484:   PetscFunctionBegin;
5486:   if (!snes->dm) {
5487:     PetscCall(DMShellCreate(PetscObjectComm((PetscObject)snes), &snes->dm));
5488:     snes->dmAuto = PETSC_TRUE;
5489:   }
5490:   *dm = snes->dm;
5491:   PetscFunctionReturn(PETSC_SUCCESS);
5492: }

5494: /*@
5495:   SNESSetNPC - Sets the nonlinear preconditioner to be used.

5497:   Collective

5499:   Input Parameters:
5500: + snes - iterative context obtained from `SNESCreate()`
5501: - npc  - the nonlinear preconditioner object

5503:   Level: developer

5505:   Notes:
5506:   Use `SNESGetNPC()` to retrieve the preconditioner context (for example,
5507:   to configure it using the API).

5509:   Only some `SNESType` can use a nonlinear preconditioner

5511: .seealso: [](ch_snes), `SNES`, `SNESNGS`, `SNESFAS`, `SNESGetNPC()`, `SNESHasNPC()`
5512: @*/
5513: PetscErrorCode SNESSetNPC(SNES snes, SNES npc)
5514: {
5515:   PetscFunctionBegin;
5518:   PetscCheckSameComm(snes, 1, npc, 2);
5519:   PetscCall(PetscObjectReference((PetscObject)npc));
5520:   PetscCall(SNESDestroy(&snes->npc));
5521:   snes->npc = npc;
5522:   PetscFunctionReturn(PETSC_SUCCESS);
5523: }

5525: /*@
5526:   SNESGetNPC - Gets a nonlinear preconditioning solver SNES` to be used to precondition the original nonlinear solver.

5528:   Not Collective; but any changes to the obtained the npc object must be applied collectively

5530:   Input Parameter:
5531: . snes - iterative context obtained from `SNESCreate()`

5533:   Output Parameter:
5534: . pc - preconditioner context

5536:   Options Database Key:
5537: . -npc_snes_type <type> - set the type of the `SNES` to use as the nonlinear preconditioner

5539:   Level: developer

5541:   Notes:
5542:   If a `SNES` was previously set with `SNESSetNPC()` then that value is returned, otherwise a new `SNES` object is created.

5544:   The (preconditioner) `SNES` returned automatically inherits the same nonlinear function and Jacobian supplied to the original
5545:   `SNES`

5547: .seealso: [](ch_snes), `SNESSetNPC()`, `SNESHasNPC()`, `SNES`, `SNESCreate()`
5548: @*/
5549: PetscErrorCode SNESGetNPC(SNES snes, SNES *pc)
5550: {
5551:   const char *optionsprefix;

5553:   PetscFunctionBegin;
5555:   PetscAssertPointer(pc, 2);
5556:   if (!snes->npc) {
5557:     void *ctx;

5559:     PetscCall(SNESCreate(PetscObjectComm((PetscObject)snes), &snes->npc));
5560:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->npc, (PetscObject)snes, 1));
5561:     PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
5562:     PetscCall(SNESSetOptionsPrefix(snes->npc, optionsprefix));
5563:     PetscCall(SNESAppendOptionsPrefix(snes->npc, "npc_"));
5564:     PetscCall(SNESGetApplicationContext(snes, &ctx));
5565:     PetscCall(SNESSetApplicationContext(snes->npc, ctx));
5566:     PetscCall(SNESSetCountersReset(snes->npc, PETSC_FALSE));
5567:   }
5568:   *pc = snes->npc;
5569:   PetscFunctionReturn(PETSC_SUCCESS);
5570: }

5572: /*@
5573:   SNESHasNPC - Returns whether a nonlinear preconditioner exists

5575:   Not Collective

5577:   Input Parameter:
5578: . snes - iterative context obtained from `SNESCreate()`

5580:   Output Parameter:
5581: . has_npc - whether the `SNES` has a nonlinear preconditioner or not

5583:   Level: developer

5585: .seealso: [](ch_snes), `SNESSetNPC()`, `SNESGetNPC()`
5586: @*/
5587: PetscErrorCode SNESHasNPC(SNES snes, PetscBool *has_npc)
5588: {
5589:   PetscFunctionBegin;
5591:   *has_npc = (PetscBool)(snes->npc ? PETSC_TRUE : PETSC_FALSE);
5592:   PetscFunctionReturn(PETSC_SUCCESS);
5593: }

5595: /*@
5596:   SNESSetNPCSide - Sets the nonlinear preconditioning side.

5598:   Logically Collective

5600:   Input Parameter:
5601: . snes - iterative context obtained from `SNESCreate()`

5603:   Output Parameter:
5604: . side - the preconditioning side, where side is one of
5605: .vb
5606:       PC_LEFT - left preconditioning
5607:       PC_RIGHT - right preconditioning (default for most nonlinear solvers)
5608: .ve

5610:   Options Database Key:
5611: . -snes_npc_side <right,left> - nonlinear preconditioner side

5613:   Level: intermediate

5615:   Note:
5616:   `SNESNRICHARDSON` and `SNESNCG` only support left preconditioning.

5618: .seealso: [](ch_snes), `SNES`, `SNESNRICHARDSON`, `SNESNCG`, `SNESType`, `SNESGetNPCSide()`, `KSPSetPCSide()`, `PC_LEFT`, `PC_RIGHT`, `PCSide`
5619: @*/
5620: PetscErrorCode SNESSetNPCSide(SNES snes, PCSide side)
5621: {
5622:   PetscFunctionBegin;
5625:   if (side == PC_SIDE_DEFAULT) side = PC_RIGHT;
5626:   PetscCheck((side == PC_LEFT) || (side == PC_RIGHT), PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONG, "Only PC_LEFT and PC_RIGHT are supported");
5627:   snes->npcside = side;
5628:   PetscFunctionReturn(PETSC_SUCCESS);
5629: }

5631: /*@
5632:   SNESGetNPCSide - Gets the preconditioning side.

5634:   Not Collective

5636:   Input Parameter:
5637: . snes - iterative context obtained from `SNESCreate()`

5639:   Output Parameter:
5640: . side - the preconditioning side, where side is one of
5641: .vb
5642:       `PC_LEFT` - left preconditioning
5643:       `PC_RIGHT` - right preconditioning (default for most nonlinear solvers)
5644: .ve

5646:   Level: intermediate

5648: .seealso: [](ch_snes), `SNES`, `SNESSetNPCSide()`, `KSPGetPCSide()`, `PC_LEFT`, `PC_RIGHT`, `PCSide`
5649: @*/
5650: PetscErrorCode SNESGetNPCSide(SNES snes, PCSide *side)
5651: {
5652:   PetscFunctionBegin;
5654:   PetscAssertPointer(side, 2);
5655:   *side = snes->npcside;
5656:   PetscFunctionReturn(PETSC_SUCCESS);
5657: }

5659: /*@
5660:   SNESSetLineSearch - Sets the linesearch to be used for `SNES`

5662:   Collective

5664:   Input Parameters:
5665: + snes       - iterative context obtained from `SNESCreate()`
5666: - linesearch - the linesearch object

5668:   Level: developer

5670:   Note:
5671:   This is almost never used, rather one uses `SNESGetLineSearch()` to retrieve the line search and set options on it
5672:   to configure it using the API).

5674: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`
5675: @*/
5676: PetscErrorCode SNESSetLineSearch(SNES snes, SNESLineSearch linesearch)
5677: {
5678:   PetscFunctionBegin;
5681:   PetscCheckSameComm(snes, 1, linesearch, 2);
5682:   PetscCall(PetscObjectReference((PetscObject)linesearch));
5683:   PetscCall(SNESLineSearchDestroy(&snes->linesearch));

5685:   snes->linesearch = linesearch;

5687:   PetscFunctionReturn(PETSC_SUCCESS);
5688: }

5690: /*@
5691:   SNESGetLineSearch - Returns the line search context possibly set with `SNESSetLineSearch()`
5692:   or creates a default line search instance associated with the `SNES` and returns it.

5694:   Not Collective

5696:   Input Parameter:
5697: . snes - iterative context obtained from `SNESCreate()`

5699:   Output Parameter:
5700: . linesearch - linesearch context

5702:   Level: beginner

5704: .seealso: [](ch_snes), `SNESLineSearch`, `SNESSetLineSearch()`, `SNESLineSearchCreate()`
5705: @*/
5706: PetscErrorCode SNESGetLineSearch(SNES snes, SNESLineSearch *linesearch)
5707: {
5708:   const char *optionsprefix;

5710:   PetscFunctionBegin;
5712:   PetscAssertPointer(linesearch, 2);
5713:   if (!snes->linesearch) {
5714:     PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
5715:     PetscCall(SNESLineSearchCreate(PetscObjectComm((PetscObject)snes), &snes->linesearch));
5716:     PetscCall(SNESLineSearchSetSNES(snes->linesearch, snes));
5717:     PetscCall(SNESLineSearchAppendOptionsPrefix(snes->linesearch, optionsprefix));
5718:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->linesearch, (PetscObject)snes, 1));
5719:   }
5720:   *linesearch = snes->linesearch;
5721:   PetscFunctionReturn(PETSC_SUCCESS);
5722: }