Actual source code: sprcm.c


  2: #include <petscmat.h>
  3: #include <petsc/private/matorderimpl.h>

  5: /*
  6:     MatGetOrdering_RCM - Find the Reverse Cuthill-McKee ordering of a given matrix.
  7: */
  8: PETSC_INTERN PetscErrorCode MatGetOrdering_RCM(Mat mat, MatOrderingType type, IS *row, IS *col)
  9: {
 10:   PetscInt        i, *mask, *xls, 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(PetscMalloc3(nrow, &mask, nrow, &perm, 2 * nrow, &xls));
 19:   PetscCall(SPARSEPACKgenrcm(&nrow, ia, ja, perm, mask, xls));
 20:   PetscCall(MatRestoreRowIJ(mat, 1, PETSC_TRUE, PETSC_TRUE, NULL, &ia, &ja, &done));

 22:   /* shift because Sparsepack indices start at one */
 23:   for (i = 0; i < nrow; i++) perm[i]--;
 24:   PetscCall(ISCreateGeneral(PETSC_COMM_SELF, nrow, perm, PETSC_COPY_VALUES, row));
 25:   PetscCall(ISCreateGeneral(PETSC_COMM_SELF, nrow, perm, PETSC_COPY_VALUES, col));
 26:   PetscCall(PetscFree3(mask, perm, xls));
 27:   PetscFunctionReturn(PETSC_SUCCESS);
 28: }