MatStoreValues#

Stashes a copy of the matrix values; this allows reusing of the linear part of a Jacobian, while recomputing only the nonlinear portion.

Synopsis#

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

Logically Collect

Input Parameter#

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

Usage#

    Using SNES
    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
    MatSetOption(mat,MAT_NEW_NONZERO_LOCATIONS,PETSC_FALSE);
    MatStoreValues(mat);
    Call SNESSetJacobian() with matrix
    In your Jacobian routine
      MatRetrieveValues(mat);
      Set nonlinear terms in matrix

    Without `SNESSolve()`, i.e. when you handle nonlinear solve yourself:
    // build linear portion of Jacobian
    MatSetOption(mat,MAT_NEW_NONZERO_LOCATIONS,PETSC_FALSE);
    MatStoreValues(mat);
    loop over nonlinear iterations
       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 assembled 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.