petsc-3.4.5 2014-06-29

MatSetUnfactored

Resets a factored matrix to be treated as unfactored.

Synopsis

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

Logically Collective on Mat

Input Parameter

mat -the factored matrix to be reset

Notes

This routine should be used only with factored matrices formed by in-place factorization via ILU(0) (or by in-place LU factorization for the MATSEQDENSE format). This option can save memory, for example, when solving nonlinear systems with a matrix-free Newton-Krylov method and a matrix-based, in-place ILU(0) preconditioner.

Note that one can specify in-place ILU(0) factorization by calling

     PCType(pc,PCILU);
     PCFactorSeUseInPlace(pc);

or by using the options -pc_type ilu -pc_factor_in_place

In-place factorization ILU(0) can also be used as a local solver for the blocks within the block Jacobi or additive Schwarz methods (runtime option: -sub_pc_factor_in_place). See the discussion of these preconditioners in the <a href="../../docs/manual.pdf#ch_pc">PC chapter of the users manual</a> for details on setting local solver options.

Most users should employ the simplified KSP interface for linear solvers instead of working directly with matrix algebra routines such as this. See, e.g., KSPCreate().

MatSetUnfactored

Synopsis

Input Parameter

Notes

See Also