1 #include <petscmat.h>
2 #include <petsc/private/matorderimpl.h>
3
4 /*
5 MatGetOrdering_QMD - Find the Quotient Minimum Degree ordering of a given matrix.
6 */
MatGetOrdering_QMD(Mat mat,MatOrderingType type,IS * row,IS * col)7 PETSC_INTERN PetscErrorCode MatGetOrdering_QMD(Mat mat, MatOrderingType type, IS *row, IS *col)
8 {
9 PetscInt i, *deg, *marker, *rchset, *nbrhd, *qsize, *qlink, nofsub, *iperm, nrow, *perm;
10 const PetscInt *ia, *ja;
11 PetscBool done;
12
13 PetscFunctionBegin;
14 PetscCall(MatGetRowIJ(mat, 1, PETSC_TRUE, PETSC_TRUE, &nrow, &ia, &ja, &done));
15 PetscCheck(done, PetscObjectComm((PetscObject)mat), PETSC_ERR_SUP, "Cannot get rows for matrix");
16
17 PetscCall(PetscMalloc1(nrow, &perm));
18 PetscCall(PetscMalloc5(nrow, &iperm, nrow, °, nrow, &marker, nrow, &rchset, nrow, &nbrhd));
19 PetscCall(PetscMalloc2(nrow, &qsize, nrow, &qlink));
20 /* WARNING - genqmd trashes ja */
21 PetscCall(SPARSEPACKgenqmd(&nrow, ia, ja, perm, iperm, deg, marker, rchset, nbrhd, qsize, qlink, &nofsub));
22 PetscCall(MatRestoreRowIJ(mat, 1, PETSC_TRUE, PETSC_TRUE, NULL, &ia, &ja, &done));
23
24 PetscCall(PetscFree2(qsize, qlink));
25 PetscCall(PetscFree5(iperm, deg, marker, rchset, nbrhd));
26 for (i = 0; i < nrow; i++) perm[i]--;
27 PetscCall(ISCreateGeneral(PETSC_COMM_SELF, nrow, perm, PETSC_COPY_VALUES, row));
28 PetscCall(ISCreateGeneral(PETSC_COMM_SELF, nrow, perm, PETSC_OWN_POINTER, col));
29 PetscFunctionReturn(PETSC_SUCCESS);
30 }
31