Actual source code: spqmd.c
2: #include <petscmat.h>
3: #include <petsc/private/matorderimpl.h>
5: /*
6: MatGetOrdering_QMD - Find the Quotient Minimum Degree ordering of a given matrix.
7: */
8: PETSC_INTERN PetscErrorCode MatGetOrdering_QMD(Mat mat, MatOrderingType type, IS *row, IS *col)
9: {
10: PetscInt i, *deg, *marker, *rchset, *nbrhd, *qsize, *qlink, nofsub, *iperm, nrow, *perm;
11: const PetscInt *ia, *ja;
12: PetscBool done;
14: PetscFunctionBegin;
15: PetscCall(MatGetRowIJ(mat, 1, PETSC_TRUE, PETSC_TRUE, &nrow, &ia, &ja, &done));
16: PetscCheck(done, PetscObjectComm((PetscObject)mat), PETSC_ERR_SUP, "Cannot get rows for matrix");
18: PetscCall(PetscMalloc1(nrow, &perm));
19: PetscCall(PetscMalloc5(nrow, &iperm, nrow, °, nrow, &marker, nrow, &rchset, nrow, &nbrhd));
20: PetscCall(PetscMalloc2(nrow, &qsize, nrow, &qlink));
21: /* WARNING - genqmd trashes ja */
22: PetscCall(SPARSEPACKgenqmd(&nrow, ia, ja, perm, iperm, deg, marker, rchset, nbrhd, qsize, qlink, &nofsub));
23: PetscCall(MatRestoreRowIJ(mat, 1, PETSC_TRUE, PETSC_TRUE, NULL, &ia, &ja, &done));
25: PetscCall(PetscFree2(qsize, qlink));
26: PetscCall(PetscFree5(iperm, deg, marker, rchset, nbrhd));
27: for (i = 0; i < nrow; i++) perm[i]--;
28: PetscCall(ISCreateGeneral(PETSC_COMM_SELF, nrow, perm, PETSC_COPY_VALUES, row));
29: PetscCall(ISCreateGeneral(PETSC_COMM_SELF, nrow, perm, PETSC_OWN_POINTER, col));
30: PetscFunctionReturn(PETSC_SUCCESS);
31: }