petsc-3.3-p7 2013-05-11

MatMFFDSetType

Sets the method that is used to compute the differencing parameter for finite differene matrix-free formulations.

#include "petscmat.h"   
PetscErrorCode  MatMFFDSetType(Mat mat,const MatMFFDType ftype)

	mat	- the "matrix-free" matrix created via MatCreateSNESMF(), or MatCreateMFFD() or MatSetType(mat,MATMFFD);
	ftype	- the type requested, either MATMFFD_WP or MATMFFD_DS

For example, such routines can compute h for use in Jacobian-vector products of the form

F(x+ha) - F(x) F'(u)a ~= ---------------- h