Actual source code: ex7.c
1: static char help[] = "Test vecscatter of different block sizes across processes\n\n";
3: #include <petscvec.h>
4: int main(int argc, char **argv)
5: {
6: PetscInt i, bs, n, low, high;
7: PetscMPIInt nproc, rank;
8: Vec x, y, z;
9: IS ix, iy;
10: VecScatter vscat;
11: const PetscScalar *yv;
13: PetscFunctionBeginUser;
14: PetscCall(PetscInitialize(&argc, &argv, (char *)0, help));
15: PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &nproc));
16: PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
17: PetscCheck(nproc == 2, PETSC_COMM_WORLD, PETSC_ERR_WRONG_MPI_SIZE, "This test can only run on two MPI ranks");
19: /* Create an MPI vector x of size 12 on two processes, and set x = {0, 1, 2, .., 11} */
20: PetscCall(VecCreateMPI(PETSC_COMM_WORLD, 6, PETSC_DECIDE, &x));
21: PetscCall(VecGetOwnershipRange(x, &low, &high));
22: for (i = low; i < high; i++) PetscCall(VecSetValue(x, i, (PetscScalar)i, INSERT_VALUES));
23: PetscCall(VecAssemblyBegin(x));
24: PetscCall(VecAssemblyEnd(x));
26: /* Create a seq vector y, and a parallel to sequential (PtoS) vecscatter to scatter x to y */
27: if (rank == 0) {
28: /* On rank 0, seq y is of size 6. We will scatter x[0,1,2,6,7,8] to y[0,1,2,3,4,5] using IS with bs=3 */
29: PetscInt idx[2] = {0, 2};
30: PetscInt idy[2] = {0, 1};
31: n = 6;
32: bs = 3;
33: PetscCall(VecCreateSeq(PETSC_COMM_SELF, n, &y));
34: PetscCall(ISCreateBlock(PETSC_COMM_SELF, bs, 2, idx, PETSC_COPY_VALUES, &ix));
35: PetscCall(ISCreateBlock(PETSC_COMM_SELF, bs, 2, idy, PETSC_COPY_VALUES, &iy));
36: } else {
37: /* On rank 1, seq y is of size 4. We will scatter x[4,5,10,11] to y[0,1,2,3] using IS with bs=2 */
38: PetscInt idx[2] = {2, 5};
39: PetscInt idy[2] = {0, 1};
40: n = 4;
41: bs = 2;
42: PetscCall(VecCreateSeq(PETSC_COMM_SELF, n, &y));
43: PetscCall(ISCreateBlock(PETSC_COMM_SELF, bs, 2, idx, PETSC_COPY_VALUES, &ix));
44: PetscCall(ISCreateBlock(PETSC_COMM_SELF, bs, 2, idy, PETSC_COPY_VALUES, &iy));
45: }
46: PetscCall(VecScatterCreate(x, ix, y, iy, &vscat));
48: /* Do the vecscatter */
49: PetscCall(VecScatterBegin(vscat, x, y, INSERT_VALUES, SCATTER_FORWARD));
50: PetscCall(VecScatterEnd(vscat, x, y, INSERT_VALUES, SCATTER_FORWARD));
52: /* Print y. Since y is sequential, we put y in a parallel z to print its value on both ranks */
53: PetscCall(VecGetArrayRead(y, &yv));
54: PetscCall(VecCreateMPIWithArray(PETSC_COMM_WORLD, 1, n, PETSC_DECIDE, yv, &z));
55: PetscCall(VecView(z, PETSC_VIEWER_STDOUT_WORLD));
56: PetscCall(VecRestoreArrayRead(y, &yv));
58: PetscCall(ISDestroy(&ix));
59: PetscCall(ISDestroy(&iy));
60: PetscCall(VecDestroy(&x));
61: PetscCall(VecDestroy(&y));
62: PetscCall(VecDestroy(&z));
63: PetscCall(VecScatterDestroy(&vscat));
65: PetscCall(PetscFinalize());
66: return 0;
67: }
69: /*TEST
71: test:
72: nsize: 2
73: args:
74: requires:
75: TEST*/