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;
17: PetscFunctionBeginUser;
18: PetscCall(PetscInitialize(&argc, &argv, (char *)0, help));
20: PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
21: PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
23: /* create two vectors */
24: PetscCall(VecCreate(PETSC_COMM_WORLD, &x));
25: PetscCall(VecSetSizes(x, PETSC_DECIDE, size * n));
26: PetscCall(VecSetFromOptions(x));
27: PetscCall(VecCreateSeq(PETSC_COMM_SELF, n, &y));
29: /* create two index sets */
30: PetscCall(ISCreateStride(PETSC_COMM_SELF, n, n * rank, 1, &is1));
31: PetscCall(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: PetscCall(VecSetValues(y, 1, &i, &value, INSERT_VALUES));
38: }
39: PetscCall(VecAssemblyBegin(y));
40: PetscCall(VecAssemblyEnd(y));
42: PetscCall(VecScatterCreate(y, is2, x, is1, &ctx));
43: PetscCall(VecScatterBegin(ctx, y, x, INSERT_VALUES, SCATTER_FORWARD));
44: PetscCall(VecScatterEnd(ctx, y, x, INSERT_VALUES, SCATTER_FORWARD));
45: PetscCall(VecScatterDestroy(&ctx));
47: PetscCall(VecView(x, PETSC_VIEWER_STDOUT_WORLD));
49: PetscCall(VecDestroy(&x));
50: PetscCall(VecDestroy(&y));
51: PetscCall(ISDestroy(&is1));
52: PetscCall(ISDestroy(&is2));
54: PetscCall(PetscFinalize());
55: return 0;
56: }
58: /*TEST
60: test:
61: nsize: 2
63: TEST*/