Actual source code: ex14.c
1: static char help[] = "Scatters from a sequential vector to a parallel vector.\n\
2: This does the tricky case.\n\n";
4: #include <petscvec.h>
6: int main(int argc, char **argv)
7: {
8: PetscInt n = 5, N;
9: PetscMPIInt size, rank;
10: PetscScalar value, zero = 0.0;
11: Vec x, y;
12: IS is1, is2;
13: VecScatter ctx = 0;
15: PetscFunctionBeginUser;
16: PetscCall(PetscInitialize(&argc, &argv, NULL, help));
17: PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
18: PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
20: /* create two vectors */
21: N = size * n;
22: PetscCall(VecCreate(PETSC_COMM_WORLD, &y));
23: PetscCall(VecSetSizes(y, PETSC_DECIDE, N));
24: PetscCall(VecSetFromOptions(y));
25: PetscCall(VecCreateSeq(PETSC_COMM_SELF, N, &x));
27: /* create two index sets */
28: PetscCall(ISCreateStride(PETSC_COMM_SELF, n, 0, 1, &is1));
29: PetscCall(ISCreateStride(PETSC_COMM_SELF, n, rank, 1, &is2));
31: value = rank + 1;
32: PetscCall(VecSet(x, value));
33: PetscCall(VecSet(y, zero));
35: PetscCall(VecScatterCreate(x, is1, y, is2, &ctx));
36: PetscCall(VecScatterBegin(ctx, x, y, ADD_VALUES, SCATTER_FORWARD));
37: PetscCall(VecScatterEnd(ctx, x, y, ADD_VALUES, SCATTER_FORWARD));
38: PetscCall(VecScatterDestroy(&ctx));
40: PetscCall(VecView(y, PETSC_VIEWER_STDOUT_WORLD));
42: PetscCall(VecDestroy(&x));
43: PetscCall(VecDestroy(&y));
44: PetscCall(ISDestroy(&is1));
45: PetscCall(ISDestroy(&is2));
47: PetscCall(PetscFinalize());
48: return 0;
49: }
51: /*TEST
53: test:
54: nsize: 2
56: TEST*/