MatGetLocalSubMatrix#

Gets a reference to a submatrix specified in local numbering

Synopsis#

#include "petscmat.h" 
PetscErrorCode MatGetLocalSubMatrix(Mat mat, IS isrow, IS iscol, Mat *submat)

Not Collective

Input Parameters#

  • mat - matrix to extract local submatrix from

  • isrow - local row indices for submatrix

  • iscol - local column indices for submatrix

Output Parameter#

  • submat - the submatrix

Notes#

The submat should be returned with MatRestoreLocalSubMatrix().

Depending on the format of mat, the returned submat may not implement MatMult(). Its communicator may be the same as mat, it may be PETSC_COMM_SELF, or some other subcomm of mat’s.

The submat always implements MatSetValuesLocal(). If isrow and iscol have the same block size, then MatSetValuesBlockedLocal() will also be implemented.

The mat must have had a ISLocalToGlobalMapping provided to it with MatSetLocalToGlobalMapping(). Matrices obtained with DMCreateMatrix() generally already have the local to global mapping provided.

See Also#

MatRestoreLocalSubMatrix(), MatCreateLocalRef(), MatSetLocalToGlobalMapping()

Level#

intermediate

Location#

src/mat/interface/matrix.c

Examples#

src/snes/tutorials/ex28.c.html
src/ts/tutorials/ex14.c.html

Implementations#

MatGetLocalSubMatrix_IS in src/mat/impls/is/matis.c
MatGetLocalSubMatrix_Nest in src/mat/impls/nest/matnest.c


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