Actual source code: ex142.c

  1: static char help[] = "Test sequential r2c/c2r FFTW without PETSc interface \n\n";

  3: /*
  4:   Compiling the code:
  5:       This code uses the real numbers version of PETSc
  6: */

  8: #include <petscmat.h>
  9: #include <fftw3.h>

 11: int main(int argc,char **args)
 12: {
 13:   typedef enum {RANDOM, CONSTANT, TANH, NUM_FUNCS} FuncType;
 14:   const char      *funcNames[NUM_FUNCS] = {"random", "constant", "tanh"};
 15:   PetscMPIInt     size;
 16:   int             n = 10,N,Ny,ndim=4,i,dim[4],DIM;
 17:   Vec             x,y,z;
 18:   PetscScalar     s;
 19:   PetscRandom     rdm;
 20:   PetscReal       enorm;
 21:   PetscInt        func     = RANDOM;
 22:   FuncType        function = RANDOM;
 23:   PetscBool       view     = PETSC_FALSE;
 24:   PetscErrorCode  ierr;
 25:   PetscScalar     *x_array,*y_array,*z_array;
 26:   fftw_plan       fplan,bplan;

 28:   PetscInitialize(&argc,&args,(char*)0,help);
 29: #if defined(PETSC_USE_COMPLEX)
 30:   SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP, "This example requires real numbers");
 31: #endif

 33:   MPI_Comm_size(PETSC_COMM_WORLD, &size);
 35:   PetscOptionsBegin(PETSC_COMM_WORLD, NULL, "FFTW Options", "ex142");
 36:   PetscOptionsEList("-function", "Function type", "ex142", funcNames, NUM_FUNCS, funcNames[function], &func, NULL);
 37:   PetscOptionsBool("-vec_view draw", "View the functions", "ex142", view, &view, NULL);
 38:   function = (FuncType) func;
 39:   PetscOptionsEnd();

 41:   for (DIM = 0; DIM < ndim; DIM++) {
 42:     dim[DIM] = n;  /* size of real space vector in DIM-dimension */
 43:   }
 44:   PetscRandomCreate(PETSC_COMM_SELF, &rdm);
 45:   PetscRandomSetFromOptions(rdm);

 47:   for (DIM = 1; DIM < 5; DIM++) {
 48:     /* create vectors of length N=dim[0]*dim[1]* ...*dim[DIM-1] */
 49:     /*----------------------------------------------------------*/
 50:     N = Ny = 1;
 51:     for (i = 0; i < DIM-1; i++) {
 52:       N *= dim[i];
 53:     }
 54:     Ny = N; Ny *= 2*(dim[DIM-1]/2 + 1); /* add padding elements to output vector y */
 55:     N *= dim[DIM-1];

 57:     PetscPrintf(PETSC_COMM_SELF, "\n %d-D: FFTW on vector of size %d \n",DIM,N);
 58:     VecCreateSeq(PETSC_COMM_SELF,N,&x);
 59:     PetscObjectSetName((PetscObject) x, "Real space vector");

 61:     VecCreateSeq(PETSC_COMM_SELF,Ny,&y);
 62:     PetscObjectSetName((PetscObject) y, "Frequency space vector");

 64:     VecDuplicate(x,&z);
 65:     PetscObjectSetName((PetscObject) z, "Reconstructed vector");

 67:     /* Set fftw plan                    */
 68:     /*----------------------------------*/
 69:     VecGetArray(x,&x_array);
 70:     VecGetArray(y,&y_array);
 71:     VecGetArray(z,&z_array);

 73:     unsigned int flags = FFTW_ESTIMATE; /*or FFTW_MEASURE */
 74:     /* The data in the in/out arrays is overwritten during FFTW_MEASURE planning, so such planning
 75:      should be done before the input is initialized by the user. */
 76:     PetscPrintf(PETSC_COMM_SELF,"DIM: %d, N %d, Ny %d\n",DIM,N,Ny);

 78:     switch (DIM) {
 79:     case 1:
 80:       fplan = fftw_plan_dft_r2c_1d(dim[0], (double*)x_array, (fftw_complex*)y_array, flags);
 81:       bplan = fftw_plan_dft_c2r_1d(dim[0], (fftw_complex*)y_array, (double*)z_array, flags);
 82:       break;
 83:     case 2:
 84:       fplan = fftw_plan_dft_r2c_2d(dim[0],dim[1],(double*)x_array, (fftw_complex*)y_array,flags);
 85:       bplan = fftw_plan_dft_c2r_2d(dim[0],dim[1],(fftw_complex*)y_array,(double*)z_array,flags);
 86:       break;
 87:     case 3:
 88:       fplan = fftw_plan_dft_r2c_3d(dim[0],dim[1],dim[2],(double*)x_array, (fftw_complex*)y_array,flags);
 89:       bplan = fftw_plan_dft_c2r_3d(dim[0],dim[1],dim[2],(fftw_complex*)y_array,(double*)z_array,flags);
 90:       break;
 91:     default:
 92:       fplan = fftw_plan_dft_r2c(DIM,(int*)dim,(double*)x_array, (fftw_complex*)y_array,flags);
 93:       bplan = fftw_plan_dft_c2r(DIM,(int*)dim,(fftw_complex*)y_array,(double*)z_array,flags);
 94:       break;
 95:     }

 97:     VecRestoreArray(x,&x_array);
 98:     VecRestoreArray(y,&y_array);
 99:     VecRestoreArray(z,&z_array);

101:     /* Initialize Real space vector x:
102:        The data in the in/out arrays is overwritten during FFTW_MEASURE planning, so planning
103:        should be done before the input is initialized by the user.
104:     --------------------------------------------------------*/
105:     if (function == RANDOM) {
106:       VecSetRandom(x, rdm);
107:     } else if (function == CONSTANT) {
108:       VecSet(x, 1.0);
109:     } else if (function == TANH) {
110:       VecGetArray(x, &x_array);
111:       for (i = 0; i < N; ++i) {
112:         x_array[i] = tanh((i - N/2.0)*(10.0/N));
113:       }
114:       VecRestoreArray(x, &x_array);
115:     }
116:     if (view) {
117:       VecView(x, PETSC_VIEWER_STDOUT_WORLD);
118:     }

120:     /* FFT - also test repeated transformation   */
121:     /*-------------------------------------------*/
122:     VecGetArray(x,&x_array);
123:     VecGetArray(y,&y_array);
124:     VecGetArray(z,&z_array);
125:     for (i=0; i<4; i++) {
126:       /* FFTW_FORWARD */
127:       fftw_execute(fplan);

129:       /* FFTW_BACKWARD: destroys its input array 'y_array' even for out-of-place transforms! */
130:       fftw_execute(bplan);
131:     }
132:     VecRestoreArray(x,&x_array);
133:     VecRestoreArray(y,&y_array);
134:     VecRestoreArray(z,&z_array);

136:     /* Compare x and z. FFTW computes an unnormalized DFT, thus z = N*x */
137:     /*------------------------------------------------------------------*/
138:     s    = 1.0/(PetscReal)N;
139:     VecScale(z,s);
140:     if (view) VecView(x, PETSC_VIEWER_DRAW_WORLD);
141:     if (view) VecView(z, PETSC_VIEWER_DRAW_WORLD);
142:     VecAXPY(z,-1.0,x);
143:     VecNorm(z,NORM_1,&enorm);
144:     if (enorm > 1.e-11) {
145:       PetscPrintf(PETSC_COMM_SELF,"  Error norm of |x - z| %g\n",(double)enorm);
146:     }

148:     /* free spaces */
149:     fftw_destroy_plan(fplan);
150:     fftw_destroy_plan(bplan);
151:     VecDestroy(&x);
152:     VecDestroy(&y);
153:     VecDestroy(&z);
154:   }
155:   PetscRandomDestroy(&rdm);
156:   PetscFinalize();
157:   return 0;
158: }

160: /*TEST

162:    build:
163:      requires: fftw !complex

165:    test:
166:      output_file: output/ex142.out

168: TEST*/