Actual source code: ex10.c
1: static char help[] = "Scatters from a parallel vector to a sequential vector.\n\
2: uses block index sets\n\n";
4: #include <petscvec.h>
6: int main(int argc, char **argv)
7: {
8: PetscInt bs = 1, n = 5, ix0[3] = {5, 7, 9}, ix1[3] = {2, 3, 4}, i, iy0[3] = {1, 2, 4}, iy1[3] = {0, 1, 3};
9: PetscMPIInt size, rank;
10: PetscScalar value;
11: Vec x, y;
12: IS isx, isy;
13: VecScatter ctx = 0, newctx;
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: PetscCheck(size == 2, PETSC_COMM_WORLD, PETSC_ERR_WRONG_MPI_SIZE, "Must run with 2 processors");
22: PetscCall(PetscOptionsGetInt(NULL, NULL, "-bs", &bs, NULL));
23: n = bs * n;
25: /* create two vectors */
26: PetscCall(VecCreate(PETSC_COMM_WORLD, &x));
27: PetscCall(VecSetSizes(x, PETSC_DECIDE, size * n));
28: PetscCall(VecSetFromOptions(x));
29: PetscCall(VecCreateSeq(PETSC_COMM_SELF, n, &y));
31: /* create two index sets */
32: if (rank == 0) {
33: PetscCall(ISCreateBlock(PETSC_COMM_SELF, bs, 3, ix0, PETSC_COPY_VALUES, &isx));
34: PetscCall(ISCreateBlock(PETSC_COMM_SELF, bs, 3, iy0, PETSC_COPY_VALUES, &isy));
35: } else {
36: PetscCall(ISCreateBlock(PETSC_COMM_SELF, bs, 3, ix1, PETSC_COPY_VALUES, &isx));
37: PetscCall(ISCreateBlock(PETSC_COMM_SELF, bs, 3, iy1, PETSC_COPY_VALUES, &isy));
38: }
40: /* fill local part of parallel vector */
41: for (i = n * rank; i < n * (rank + 1); i++) {
42: value = (PetscScalar)i;
43: PetscCall(VecSetValues(x, 1, &i, &value, INSERT_VALUES));
44: }
45: PetscCall(VecAssemblyBegin(x));
46: PetscCall(VecAssemblyEnd(x));
48: PetscCall(VecView(x, PETSC_VIEWER_STDOUT_WORLD));
50: /* fill local part of parallel vector */
51: for (i = 0; i < n; i++) {
52: value = -(PetscScalar)(i + 100 * rank);
53: PetscCall(VecSetValues(y, 1, &i, &value, INSERT_VALUES));
54: }
55: PetscCall(VecAssemblyBegin(y));
56: PetscCall(VecAssemblyEnd(y));
58: PetscCall(VecScatterCreate(x, isx, y, isy, &ctx));
59: PetscCall(VecScatterCopy(ctx, &newctx));
60: PetscCall(VecScatterDestroy(&ctx));
62: PetscCall(VecScatterBegin(newctx, y, x, INSERT_VALUES, SCATTER_REVERSE));
63: PetscCall(VecScatterEnd(newctx, y, x, INSERT_VALUES, SCATTER_REVERSE));
64: PetscCall(VecScatterDestroy(&newctx));
66: PetscCall(VecView(x, PETSC_VIEWER_STDOUT_WORLD));
68: PetscCall(ISDestroy(&isx));
69: PetscCall(ISDestroy(&isy));
70: PetscCall(VecDestroy(&x));
71: PetscCall(VecDestroy(&y));
73: PetscCall(PetscFinalize());
74: return 0;
75: }
77: /*TEST
79: test:
80: nsize: 2
82: TEST*/