Actual source code: ex12.c


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

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

 20:   MPI_Comm_size(PETSC_COMM_WORLD, &size);
 21:   MPI_Comm_rank(PETSC_COMM_WORLD, &rank);

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

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

 33:   /* each processor inserts the entire vector */
 34:   /* this is redundant but tests assembly */
 35:   for (i = 0; i < n; i++) {
 36:     value = (PetscScalar)(i + 10 * rank);
 37:     VecSetValues(y, 1, &i, &value, INSERT_VALUES);
 38:   }
 39:   VecAssemblyBegin(y);
 40:   VecAssemblyEnd(y);

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

 47:   VecView(x, PETSC_VIEWER_STDOUT_WORLD);

 49:   VecDestroy(&x);
 50:   VecDestroy(&y);
 51:   ISDestroy(&is1);
 52:   ISDestroy(&is2);

 54:   PetscFinalize();
 55:   return 0;
 56: }

 58: /*TEST

 60:    test:
 61:       nsize: 2

 63: TEST*/