# MatSubMatrixVirtualUpdate#

Updates a MATSUBMATRIX virtual submatrix

## Synopsis#

#include "petscmat.h"
PetscErrorCode MatSubMatrixVirtualUpdate(Mat N, Mat A, IS isrow, IS iscol)


Collective

## Input Parameters#

• N - submatrix to update

• A - full matrix in the submatrix

• isrow - rows in the update (same as the first time the submatrix was created)

• iscol - columns in the update (same as the first time the submatrix was created)

## Note#

Most will use MatCreateSubMatrix() which provides a more efficient representation if it is available.

MATSUBMATRIX, MatCreateSubMatrixVirtual()`