SNESSetUseMatrixFree#

indicates that SNES should use matrix free finite difference matrix vector products to apply the Jacobian.

Synopsis#

#include "petscsnes.h"  
PetscErrorCode SNESSetUseMatrixFree(SNES snes, PetscBool mf_operator, PetscBool mf)

Logically Collective

Input Parameters#

  • snes - SNES context

  • mf_operator - use matrix-free only for the Amat used by SNESSetJacobian(), this means the user provided Pmat will continue to be used

  • mf - use matrix-free for both the Amat and Pmat used by SNESSetJacobian(), both the Amat and Pmat set in SNESSetJacobian() will be ignored. With this option no matrix element based preconditioners can be used in the linear solve since the matrix won’t be explicitly available

Options Database Keys#

  • -snes_mf_operator - use matrix free only for the mat operator

  • -snes_mf - use matrix-free for both the mat and pmat operator

  • -snes_fd_color - compute the Jacobian via coloring and finite differences.

  • -snes_fd - compute the Jacobian via finite differences (slow)

Note#

SNES supports three approaches for computing (approximate) Jacobians: user provided via SNESSetJacobian(), matrix-free, and computing explicitly with finite differences and coloring using MatFDColoring. It is also possible to use automatic differentiation and the MatFDColoring object.

See Also#

SNES: Nonlinear Solvers, SNES, SNESGetUseMatrixFree(), MatCreateSNESMF(), SNESComputeJacobianDefaultColor()

Level#

intermediate

Location#

src/snes/interface/snes.c

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