1 #include <petscmat.h>
2 #include <petsc/private/matorderimpl.h>
3
4 /*
5 MatGetOrdering_RCM - Find the Reverse Cuthill-McKee ordering of a given matrix.
6 */
MatGetOrdering_RCM(Mat mat,MatOrderingType type,IS * row,IS * col)7 PETSC_INTERN PetscErrorCode MatGetOrdering_RCM(Mat mat, MatOrderingType type, IS *row, IS *col)
8 {
9 PetscInt i, *mask, *xls, 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(PetscMalloc3(nrow, &mask, nrow, &perm, 2 * nrow, &xls));
18 PetscCall(SPARSEPACKgenrcm(&nrow, ia, ja, perm, mask, xls));
19 PetscCall(MatRestoreRowIJ(mat, 1, PETSC_TRUE, PETSC_TRUE, NULL, &ia, &ja, &done));
20
21 /* shift because Sparsepack indices start at one */
22 for (i = 0; i < nrow; i++) perm[i]--;
23 PetscCall(ISCreateGeneral(PETSC_COMM_SELF, nrow, perm, PETSC_COPY_VALUES, row));
24 PetscCall(ISCreateGeneral(PETSC_COMM_SELF, nrow, perm, PETSC_COPY_VALUES, col));
25 PetscCall(PetscFree3(mask, perm, xls));
26 PetscFunctionReturn(PETSC_SUCCESS);
27 }
28