Actual source code: spnd.c

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

  4: /*
  5:     MatGetOrdering_ND - Find the nested dissection ordering of a given matrix.
  6: */
  7: PETSC_INTERN PetscErrorCode MatGetOrdering_ND(Mat mat, MatOrderingType type, IS *row, IS *col)
  8: {
  9:   PetscInt        i, *mask, *xls, *ls, nrow, *perm;
 10:   const PetscInt *ia, *ja;
 11:   PetscBool       done;
 12:   Mat             B = NULL;

 14:   PetscFunctionBegin;
 15:   PetscCall(MatGetRowIJ(mat, 1, PETSC_TRUE, PETSC_TRUE, &nrow, &ia, &ja, &done));
 16:   if (!done) {
 17:     PetscCall(MatConvert(mat, MATAIJ, MAT_INITIAL_MATRIX, &B));
 18:     PetscCall(MatGetRowIJ(B, 1, PETSC_TRUE, PETSC_TRUE, &nrow, &ia, &ja, &done));
 19:   }

 21:   PetscCall(PetscMalloc4(nrow, &mask, nrow, &perm, nrow + 1, &xls, nrow, &ls));
 22:   PetscCall(SPARSEPACKgennd(&nrow, ia, ja, mask, perm, xls, ls));
 23:   if (B) {
 24:     PetscCall(MatRestoreRowIJ(B, 1, PETSC_TRUE, PETSC_TRUE, NULL, &ia, &ja, &done));
 25:     PetscCall(MatDestroy(&B));
 26:   } else {
 27:     PetscCall(MatRestoreRowIJ(mat, 1, PETSC_TRUE, PETSC_TRUE, NULL, &ia, &ja, &done));
 28:   }

 30:   /* shift because Sparsepack indices start at one */
 31:   for (i = 0; i < nrow; i++) perm[i]--;

 33:   PetscCall(ISCreateGeneral(PETSC_COMM_SELF, nrow, perm, PETSC_COPY_VALUES, row));
 34:   PetscCall(ISCreateGeneral(PETSC_COMM_SELF, nrow, perm, PETSC_COPY_VALUES, col));
 35:   PetscCall(PetscFree4(mask, perm, xls, ls));
 36:   PetscFunctionReturn(PETSC_SUCCESS);
 37: }