Actual source code: ex5.c


  2: static char help[] = "Scatters from a parallel vector to a sequential vector.\n\
  3: This does case when we are merely selecting the local part of the\n\
  4: parallel vector.\n\n";

  6: #include <petscvec.h>

  8: int main(int argc,char **argv)
  9: {
 10:   PetscMPIInt    size,rank;
 11:   PetscInt       n = 5,i;
 12:   PetscScalar    value;
 13:   Vec            x,y;
 14:   IS             is1,is2;
 15:   VecScatter     ctx = 0;

 17:   PetscInitialize(&argc,&argv,(char*)0,help);
 18:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 19:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 21:   /* create two vectors */
 22:   VecCreate(PETSC_COMM_WORLD,&x);
 23:   VecSetSizes(x,PETSC_DECIDE,size*n);
 24:   VecSetFromOptions(x);
 25:   VecCreateSeq(PETSC_COMM_SELF,n,&y);

 27:   /* create two index sets */
 28:   ISCreateStride(PETSC_COMM_SELF,n,n*rank,1,&is1);
 29:   ISCreateStride(PETSC_COMM_SELF,n,0,1,&is2);

 31:   /* each processor inserts the entire vector */
 32:   /* this is redundant but tests assembly */
 33:   for (i=0; i<n*size; i++) {
 34:     value = (PetscScalar) i;
 35:     VecSetValues(x,1,&i,&value,INSERT_VALUES);
 36:   }
 37:   VecAssemblyBegin(x);
 38:   VecAssemblyEnd(x);
 39:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

 41:   VecScatterCreate(x,is1,y,is2,&ctx);
 42:   VecScatterBegin(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
 43:   VecScatterEnd(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
 44:   VecScatterDestroy(&ctx);

 46:   if (rank == 0) {
 47:     PetscPrintf(PETSC_COMM_SELF,"----\n");
 48:     VecView(y,PETSC_VIEWER_STDOUT_SELF);
 49:   }

 51:   VecDestroy(&x);
 52:   VecDestroy(&y);
 53:   ISDestroy(&is1);
 54:   ISDestroy(&is2);

 56:   PetscFinalize();
 57:   return 0;
 58: }

 60: /*TEST

 62:      test:
 63:        nsize: 2

 65: TEST*/