petsc-3.7.7 2017-09-25

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)

Collect on Mat

Input Parameters

mat -the matrix (currently only AIJ 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.