petsc-3.7.7 2017-09-25

MatCreateSubMatrix

Creates a composite matrix that acts as a submatrix

#include "petscmat.h" 
PetscErrorCode  MatCreateSubMatrix(Mat A,IS isrow,IS iscol,Mat *newmat)

Collective on Mat

	A	- matrix that we will extract a submatrix of
	isrow	- rows to be present in the submatrix
	iscol	- columns to be present in the submatrix

newmat -new matrix

Most will use MatGetSubMatrix which provides a more efficient representation if it is available.