petsc-3.3-p7 2013-05-11

DMMeshCreateMatrix

Creates a matrix with the correct parallel layout required for computing the Jacobian on a function defined using the information in the Section.

#include "petscdmmesh.h"   
PetscErrorCode DMMeshCreateMatrix(DM dm, SectionReal section, const MatType mtype, Mat *J)

Collective on DMMesh

	mesh	- the mesh object
	section	- the section which determines data layout
	mtype	- Supported types are MATSEQAIJ, MATMPIAIJ, MATSEQBAIJ, MATMPIBAIJ, MATSEQSBAIJ, MATMPISBAIJ, or any type which inherits from one of these (such as MATAIJ, MATLUSOL, etc.).

J -matrix with the correct nonzero preallocation (obviously without the correct Jacobian values)

Notes: This properly preallocates the number of nonzeros in the sparse matrix so you do not need to do it yourself.