Actual source code: ex14.c
2: static char help[] = "Scatters from a sequential vector to a parallel vector.\n\
3: This does the tricky case.\n\n";
5: #include <petscvec.h>
7: int main(int argc, char **argv)
8: {
9: PetscInt n = 5, N;
10: PetscMPIInt size, rank;
11: PetscScalar value, zero = 0.0;
12: Vec x, y;
13: IS is1, is2;
14: VecScatter ctx = 0;
16: PetscFunctionBeginUser;
17: PetscCall(PetscInitialize(&argc, &argv, (char *)0, help));
18: PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
19: PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
21: /* create two vectors */
22: N = size * n;
23: PetscCall(VecCreate(PETSC_COMM_WORLD, &y));
24: PetscCall(VecSetSizes(y, PETSC_DECIDE, N));
25: PetscCall(VecSetFromOptions(y));
26: PetscCall(VecCreateSeq(PETSC_COMM_SELF, N, &x));
28: /* create two index sets */
29: PetscCall(ISCreateStride(PETSC_COMM_SELF, n, 0, 1, &is1));
30: PetscCall(ISCreateStride(PETSC_COMM_SELF, n, rank, 1, &is2));
32: value = rank + 1;
33: PetscCall(VecSet(x, value));
34: PetscCall(VecSet(y, zero));
36: PetscCall(VecScatterCreate(x, is1, y, is2, &ctx));
37: PetscCall(VecScatterBegin(ctx, x, y, ADD_VALUES, SCATTER_FORWARD));
38: PetscCall(VecScatterEnd(ctx, x, y, ADD_VALUES, SCATTER_FORWARD));
39: PetscCall(VecScatterDestroy(&ctx));
41: PetscCall(VecView(y, PETSC_VIEWER_STDOUT_WORLD));
43: PetscCall(VecDestroy(&x));
44: PetscCall(VecDestroy(&y));
45: PetscCall(ISDestroy(&is1));
46: PetscCall(ISDestroy(&is2));
48: PetscCall(PetscFinalize());
49: return 0;
50: }
52: /*TEST
54: test:
55: nsize: 2
57: TEST*/