Actual source code: ex12.c
1: static char help[] = "Scatters from a sequential vector to a parallel vector.\n\
2: This does case when we are merely selecting the local part of the\n\
3: parallel vector.\n";
5: #include <petscvec.h>
7: int main(int argc, char **argv)
8: {
9: PetscMPIInt size, rank;
10: PetscInt n = 5, i;
11: PetscScalar value;
12: Vec x, y;
13: IS is1, is2;
14: VecScatter ctx = 0;
16: PetscFunctionBeginUser;
17: PetscCall(PetscInitialize(&argc, &argv, NULL, help));
19: PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
20: PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
22: /* create two vectors */
23: PetscCall(VecCreate(PETSC_COMM_WORLD, &x));
24: PetscCall(VecSetSizes(x, PETSC_DECIDE, size * n));
25: PetscCall(VecSetFromOptions(x));
26: PetscCall(VecCreateSeq(PETSC_COMM_SELF, n, &y));
28: /* create two index sets */
29: PetscCall(ISCreateStride(PETSC_COMM_SELF, n, n * rank, 1, &is1));
30: PetscCall(ISCreateStride(PETSC_COMM_SELF, n, 0, 1, &is2));
32: /* each processor inserts the entire vector */
33: /* this is redundant but tests assembly */
34: for (i = 0; i < n; i++) {
35: value = (PetscScalar)(i + 10 * rank);
36: PetscCall(VecSetValues(y, 1, &i, &value, INSERT_VALUES));
37: }
38: PetscCall(VecAssemblyBegin(y));
39: PetscCall(VecAssemblyEnd(y));
41: PetscCall(VecScatterCreate(y, is2, x, is1, &ctx));
42: PetscCall(VecScatterBegin(ctx, y, x, INSERT_VALUES, SCATTER_FORWARD));
43: PetscCall(VecScatterEnd(ctx, y, x, INSERT_VALUES, SCATTER_FORWARD));
44: PetscCall(VecScatterDestroy(&ctx));
46: PetscCall(VecView(x, PETSC_VIEWER_STDOUT_WORLD));
48: PetscCall(VecDestroy(&x));
49: PetscCall(VecDestroy(&y));
50: PetscCall(ISDestroy(&is1));
51: PetscCall(ISDestroy(&is2));
53: PetscCall(PetscFinalize());
54: return 0;
55: }
57: /*TEST
59: test:
60: nsize: 2
62: TEST*/