petsc-main 2021-04-20
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Gets a reordering for a matrix to reduce fill or to improve numerical stability of LU factorization.


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

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
     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, LU, ILU, Cholesky, ICC


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

fill, reordering, natural, Nested Dissection, One-way Dissection, Cholesky, Reverse Cuthill-McKee, Quotient Minimum Degree

See Also

MatOrderingRegister(), PCFactorSetMatOrderingType(), MatColoring, MatColoringCreate()







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