Actual source code: zerorows.c
1: #include <petsc/private/matimpl.h>
2: #include <petscsf.h>
4: /* this function maps rows to locally owned rows */
5: PETSC_INTERN PetscErrorCode MatZeroRowsMapLocal_Private(Mat A, PetscInt N, const PetscInt *rows, PetscInt *nr, PetscInt **olrows)
6: {
7: PetscInt *owners = A->rmap->range;
8: PetscInt n = A->rmap->n;
9: PetscSF sf;
10: PetscInt *lrows;
11: PetscSFNode *rrows;
12: PetscMPIInt rank, p = 0;
13: PetscInt r, len = 0;
15: PetscFunctionBegin;
16: /* Create SF where leaves are input rows and roots are owned rows */
17: PetscCallMPI(MPI_Comm_rank(PetscObjectComm((PetscObject)A), &rank));
18: PetscCall(PetscMalloc1(n, &lrows));
19: for (r = 0; r < n; ++r) lrows[r] = -1;
20: if (!A->nooffproczerorows) PetscCall(PetscMalloc1(N, &rrows));
21: for (r = 0; r < N; ++r) {
22: const PetscInt idx = rows[r];
23: PetscCheck(idx >= 0 && A->rmap->N > idx, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Row %" PetscInt_FMT " out of range [0,%" PetscInt_FMT ")", idx, A->rmap->N);
24: if (idx < owners[p] || owners[p + 1] <= idx) { /* short-circuit the search if the last p owns this row too */
25: PetscCall(PetscLayoutFindOwner(A->rmap, idx, &p));
26: }
27: if (A->nooffproczerorows) {
28: PetscCheck(p == rank, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "MAT_NO_OFF_PROC_ZERO_ROWS set, but row %" PetscInt_FMT " is not owned by rank %d", idx, rank);
29: lrows[len++] = idx - owners[p];
30: } else {
31: rrows[r].rank = p;
32: rrows[r].index = rows[r] - owners[p];
33: }
34: }
35: if (!A->nooffproczerorows) {
36: PetscCall(PetscSFCreate(PetscObjectComm((PetscObject)A), &sf));
37: PetscCall(PetscSFSetGraph(sf, n, N, NULL, PETSC_OWN_POINTER, rrows, PETSC_OWN_POINTER));
38: /* Collect flags for rows to be zeroed */
39: PetscCall(PetscSFReduceBegin(sf, MPIU_INT, (PetscInt *)rows, lrows, MPI_LOR));
40: PetscCall(PetscSFReduceEnd(sf, MPIU_INT, (PetscInt *)rows, lrows, MPI_LOR));
41: PetscCall(PetscSFDestroy(&sf));
42: /* Compress and put in row numbers */
43: for (r = 0; r < n; ++r)
44: if (lrows[r] >= 0) lrows[len++] = r;
45: }
46: if (nr) *nr = len;
47: if (olrows) *olrows = lrows;
48: PetscFunctionReturn(PETSC_SUCCESS);
49: }