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

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