Actual source code: ex11.c
2: static char help[] = "Scatters from a parallel vector to a sequential vector.\n\n";
4: #include <petscvec.h>
6: int main(int argc, char **argv)
7: {
8: PetscMPIInt size, rank;
9: PetscInt i, N;
10: PetscScalar value;
11: Vec x, y;
12: IS is1, is2;
13: VecScatter ctx = 0;
15: PetscFunctionBeginUser;
16: PetscCall(PetscInitialize(&argc, &argv, (char *)0, help));
17: PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
18: PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
20: /* create two vectors */
21: PetscCall(VecCreate(PETSC_COMM_WORLD, &x));
22: PetscCall(VecSetSizes(x, rank + 1, PETSC_DECIDE));
23: PetscCall(VecSetFromOptions(x));
24: PetscCall(VecGetSize(x, &N));
25: PetscCall(VecCreateSeq(PETSC_COMM_SELF, N - rank, &y));
27: /* create two index sets */
28: PetscCall(ISCreateStride(PETSC_COMM_SELF, N - rank, rank, 1, &is1));
29: PetscCall(ISCreateStride(PETSC_COMM_SELF, N - rank, 0, 1, &is2));
31: /* fill parallel vector: note this is not efficient way*/
32: for (i = 0; i < N; i++) {
33: value = (PetscScalar)i;
34: PetscCall(VecSetValues(x, 1, &i, &value, INSERT_VALUES));
35: }
36: PetscCall(VecAssemblyBegin(x));
37: PetscCall(VecAssemblyEnd(x));
38: PetscCall(VecSet(y, -1.0));
40: PetscCall(VecView(x, PETSC_VIEWER_STDOUT_WORLD));
42: PetscCall(VecScatterCreate(x, is1, y, is2, &ctx));
43: PetscCall(VecScatterBegin(ctx, x, y, INSERT_VALUES, SCATTER_FORWARD));
44: PetscCall(VecScatterEnd(ctx, x, y, INSERT_VALUES, SCATTER_FORWARD));
45: PetscCall(VecScatterDestroy(&ctx));
47: if (rank == 0) {
48: PetscCall(PetscPrintf(PETSC_COMM_SELF, "----\n"));
49: PetscCall(VecView(y, PETSC_VIEWER_STDOUT_SELF));
50: }
52: PetscCall(ISDestroy(&is1));
53: PetscCall(ISDestroy(&is2));
54: PetscCall(VecDestroy(&x));
55: PetscCall(VecDestroy(&y));
57: PetscCall(PetscFinalize());
58: return 0;
59: }
61: /*TEST
63: test:
64: nsize: 2
66: test:
67: suffix: bts
68: nsize: 2
69: args: -vec_assembly_legacy
70: output_file: output/ex11_1.out
72: TEST*/