Actual source code: ex11.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: PetscMPIInt size, rank;
8: PetscInt i, N;
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, rank + 1, PETSC_DECIDE));
22: PetscCall(VecSetFromOptions(x));
23: PetscCall(VecGetSize(x, &N));
24: PetscCall(VecCreateSeq(PETSC_COMM_SELF, N - rank, &y));
26: /* create two index sets */
27: PetscCall(ISCreateStride(PETSC_COMM_SELF, N - rank, rank, 1, &is1));
28: PetscCall(ISCreateStride(PETSC_COMM_SELF, N - rank, 0, 1, &is2));
30: /* fill parallel vector: note this is not efficient way*/
31: for (i = 0; i < N; i++) {
32: value = (PetscScalar)i;
33: PetscCall(VecSetValues(x, 1, &i, &value, INSERT_VALUES));
34: }
35: PetscCall(VecAssemblyBegin(x));
36: PetscCall(VecAssemblyEnd(x));
37: PetscCall(VecSet(y, -1.0));
39: PetscCall(VecView(x, PETSC_VIEWER_STDOUT_WORLD));
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, "----\n"));
48: PetscCall(VecView(y, PETSC_VIEWER_STDOUT_SELF));
49: }
51: PetscCall(ISDestroy(&is1));
52: PetscCall(ISDestroy(&is2));
53: PetscCall(VecDestroy(&x));
54: PetscCall(VecDestroy(&y));
56: PetscCall(PetscFinalize());
57: return 0;
58: }
60: /*TEST
62: test:
63: nsize: 2
65: test:
66: suffix: bts
67: nsize: 2
68: args: -vec_assembly_legacy
69: output_file: output/ex11_1.out
71: TEST*/