# MatStoreValues#

Stashes a copy of the matrix values; this allows, for example, reuse of the linear part of a Jacobian, while recomputing the nonlinear portion.

## Synopsis#

#include "petscmat.h"
PetscErrorCode MatStoreValues(Mat mat)


Logically Collect

## Input Parameters#

• mat - the matrix (currently only MATAIJ matrices support this option)

## Common Usage, with SNESSolve()#

Create Jacobian matrix

Set linear terms into matrix

Apply boundary conditions to matrix, at this time matrix must have

final nonzero structure (i.e. setting the nonlinear terms and applying

boundary conditions again will not change the nonzero structure

ierr = MatSetOption(mat,MAT_NEW_NONZERO_LOCATIONS,PETSC_FALSE);

ierr = MatStoreValues(mat);

Call SNESSetJacobian() with matrix

In your Jacobian routine

ierr = MatRetrieveValues(mat);

Set nonlinear terms in matrix


## Common Usage without SNESSolve(), i.e. when you handle nonlinear solve yourself#

// build linear portion of Jacobian

ierr = MatSetOption(mat,MAT_NEW_NONZERO_LOCATIONS,PETSC_FALSE);

ierr = MatStoreValues(mat);

loop over nonlinear iterations

ierr = MatRetrieveValues(mat);

// call MatSetValues(mat,...) to set nonliner portion of Jacobian

// call MatAssemblyBegin/End() on matrix

Solve linear system with Jacobian

endloop


## Notes#

Matrix must already be assemblied before calling this routine Must set the matrix option MatSetOption(mat,MAT_NEW_NONZERO_LOCATIONS,PETSC_FALSE); before calling this routine.

When this is called multiple times it overwrites the previous set of stored values and does not allocated additional space.

MatRetrieveValues()