MatGetOrdering#

Gets a reordering for a matrix to reduce fill or to improve numerical stability of LU factorization.

Synopsis#

#include "petscmat.h" 
PetscErrorCode MatGetOrdering(Mat mat, MatOrderingType type, IS *rperm, IS *cperm)

Collective

Input Parameters#

mat - the matrix
type - type of reordering, one of the following

      MATORDERINGNATURAL_OR_ND - Nested dissection unless matrix is SBAIJ then it is natural
      MATORDERINGNATURAL - Natural
      MATORDERINGND - Nested Dissection
      MATORDERING1WD - One-way Dissection
      MATORDERINGRCM - Reverse Cuthill-McKee
      MATORDERINGQMD - Quotient Minimum Degree
      MATORDERINGEXTERNAL - Use an ordering internal to the factorzation package and do not compute or use PETSc's

Output Parameters#

rperm - row permutation indices
cperm - column permutation indices

Options Database Key#

-mat_view_ordering draw - plots matrix nonzero structure in new ordering
-pc_factor_mat_ordering_type <nd,natural,..> - ordering to use with PCs based on factorization, MATLU, MATILU, MATCHOLESKY, MATICC`

Notes#

This DOES NOT actually reorder the matrix; it merely returns two index sets that define a reordering. This is usually not used directly, rather use the options PCFactorSetMatOrderingType()

The user can define additional orderings; see MatOrderingRegister().

These are generally only implemented for sequential sparse matrices.

Some external packages that PETSc can use for direct factorization such as SuperLU_DIST do not accept orderings provided by this call.

If MATORDERINGEXTERNAL is used then PETSc does not compute an ordering and utilizes one built into the factorization package

Level#

intermediate

Location#

src/mat/order/sorder.c

Examples#

src/ksp/ksp/tutorials/ex10.c
src/mat/tutorials/ex1.c
src/ksp/ksp/tutorials/ex18.c

Index of all MatOrderings routines
Table of Contents for all manual pages
Index of all manual pages