Actual source code: ex24.c

  2: static char help[] = "Scatters from a parallel vector to a sequential vector.\n\
  3: Tests where the local part of the scatter is a copy.\n\n";

 5:  #include petscvec.h

  9: int main(int argc,char **argv)
 10: {
 12:   PetscMPIInt    size,rank;
 13:   PetscInt       n = 5,i,*blks,bs = 1,m = 2;
 14:   PetscScalar    value;
 15:   Vec            x,y;
 16:   IS             is1,is2;
 17:   VecScatter     ctx = 0;
 18:   PetscViewer    sviewer;

 20:   PetscInitialize(&argc,&argv,(char*)0,help);

 22:   PetscOptionsGetInt(PETSC_NULL,"-n",&n,PETSC_NULL);
 23:   PetscOptionsGetInt(PETSC_NULL,"-bs",&bs,PETSC_NULL);

 25:   MPI_Comm_size(PETSC_COMM_WORLD,&size);
 26:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 28:   /* create two vectors */
 29:   VecCreate(PETSC_COMM_WORLD,&x);
 30:   VecSetSizes(x,PETSC_DECIDE,size*bs*n);
 31:   VecSetFromOptions(x);

 33:   /* create two index sets */
 34:   if (rank < size-1) {
 35:     m = n + 2;
 36:   } else {
 37:     m = n;
 38:   }
 39:   PetscMalloc((m)*sizeof(PetscInt),&blks);
 40:   blks[0] = n*rank*bs;
 41:   for (i=1; i<m; i++) {
 42:     blks[i] = blks[i-1] + bs;
 43:   }
 44:   ISCreateBlock(PETSC_COMM_SELF,bs,m,blks,&is1);
 45:   PetscFree(blks);

 47:   VecCreateSeq(PETSC_COMM_SELF,bs*m,&y);
 48:   ISCreateStride(PETSC_COMM_SELF,bs*m,0,1,&is2);

 50:   /* each processor inserts the entire vector */
 51:   /* this is redundant but tests assembly */
 52:   for (i=0; i<bs*n*size; i++) {
 53:     value = (PetscScalar) i;
 54:     VecSetValues(x,1,&i,&value,INSERT_VALUES);
 55:   }
 56:   VecAssemblyBegin(x);
 57:   VecAssemblyEnd(x);
 58:   VecView(x,PETSC_VIEWER_STDOUT_WORLD);

 60:   VecScatterCreate(x,is1,y,is2,&ctx);
 61:   VecScatterBegin(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);
 62:   VecScatterEnd(ctx,x,y,INSERT_VALUES,SCATTER_FORWARD);

 64:   PetscSynchronizedPrintf(PETSC_COMM_WORLD,"----\n");
 65:   PetscViewerGetSingleton(PETSC_VIEWER_STDOUT_WORLD,&sviewer);
 66:   VecView(y,sviewer); fflush(stdout);
 67:   PetscViewerRestoreSingleton(PETSC_VIEWER_STDOUT_WORLD,&sviewer);
 68:   PetscSynchronizedFlush(PETSC_COMM_WORLD);

 70:   VecScatterDestroy(ctx);

 72:   VecDestroy(x);
 73:   VecDestroy(y);
 74:   ISDestroy(is1);
 75:   ISDestroy(is2);

 77:   PetscFinalize();
 78:   return 0;
 79: }
 80: