Actual source code: ex9.c
1: static char help[] = "Scatters from a parallel vector to a sequential vector.\n\n";
3: #include <petscvec.h>
5: int main(int argc, char **argv)
6: {
7: PetscInt n = 5, i, idx2[3] = {0, 2, 3}, idx1[3] = {0, 1, 2};
8: PetscMPIInt size, rank;
9: PetscScalar value;
10: Vec x, y;
11: IS is1, is2;
12: VecScatter ctx = 0;
14: PetscFunctionBeginUser;
15: PetscCall(PetscInitialize(&argc, &argv, (char *)0, help));
16: PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
17: PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
19: /* create two vectors */
20: PetscCall(VecCreate(PETSC_COMM_WORLD, &x));
21: PetscCall(VecSetSizes(x, PETSC_DECIDE, size * n));
22: PetscCall(VecSetFromOptions(x));
23: PetscCall(VecCreateSeq(PETSC_COMM_SELF, n, &y));
25: /* create two index sets */
26: PetscCall(ISCreateGeneral(PETSC_COMM_SELF, 3, idx1, PETSC_COPY_VALUES, &is1));
27: PetscCall(ISCreateGeneral(PETSC_COMM_SELF, 3, idx2, PETSC_COPY_VALUES, &is2));
29: /* fill local part of parallel vector */
30: for (i = n * rank; i < n * (rank + 1); i++) {
31: value = (PetscScalar)i;
32: PetscCall(VecSetValues(x, 1, &i, &value, INSERT_VALUES));
33: }
34: PetscCall(VecAssemblyBegin(x));
35: PetscCall(VecAssemblyEnd(x));
37: PetscCall(VecView(x, PETSC_VIEWER_STDOUT_WORLD));
39: PetscCall(VecSet(y, -1.0));
41: PetscCall(VecScatterCreate(x, is1, y, is2, &ctx));
42: PetscCall(VecScatterBegin(ctx, x, y, INSERT_VALUES, SCATTER_FORWARD));
43: PetscCall(VecScatterEnd(ctx, x, y, INSERT_VALUES, SCATTER_FORWARD));
44: PetscCall(VecScatterDestroy(&ctx));
46: if (rank == 0) {
47: PetscCall(PetscPrintf(PETSC_COMM_SELF, "scattered vector\n"));
48: PetscCall(VecView(y, PETSC_VIEWER_STDOUT_SELF));
49: }
50: PetscCall(ISDestroy(&is1));
51: PetscCall(ISDestroy(&is2));
52: PetscCall(VecDestroy(&x));
53: PetscCall(VecDestroy(&y));
55: PetscCall(PetscFinalize());
56: return 0;
57: }
59: /*TEST
61: test:
62: nsize: 2
64: TEST*/