SNESComputeJacobianDefault#
Computes the Jacobian using finite differences.
Synopsis#
#include "petscsnes.h"
PetscErrorCode SNESComputeJacobianDefault(SNES snes, Vec x1, Mat J, Mat B, void *ctx)
Collective
Input Parameters#
snes - the
SNEScontextx1 - compute Jacobian at this point
ctx - application’s function context, as set with
SNESSetFunction()
Output Parameters#
J - Jacobian matrix (not altered in this routine)
B - newly computed Jacobian matrix to use with preconditioner (generally the same as
J)
Options Database Keys#
-snes_fd - Activates
SNESComputeJacobianDefault()-snes_fd_coloring - Activates a faster computation that uses a graph coloring of the matrix
-snes_test_err - Square root of function error tolerance, default square root of machine epsilon (1.e-8 in double, 3.e-4 in single)
-mat_fd_type - Either wp or ds (see
MATMFFD_WPorMATMFFD_DS)
Notes#
This routine is slow and expensive, and is not currently optimized
to take advantage of sparsity in the problem. Although
SNESComputeJacobianDefault() is not recommended for general use
in large-scale applications, It can be useful in checking the
correctness of a user-provided Jacobian.
An alternative routine that uses coloring to exploit matrix sparsity is
SNESComputeJacobianDefaultColor().
This routine ignores the maximum number of function evaluations set with SNESSetTolerances() and the function
evaluations it performs are not counted in what is returned by of SNESGetNumberFunctionEvals().
This function can be provided to SNESSetJacobian() along with a dense matrix to hold the Jacobian
Developer Note#
The function has a poorly chosen name since it does not mention the use of finite differences
See Also#
SNES: Nonlinear Solvers, SNES, SNESSetJacobian(), SNESComputeJacobianDefaultColor(), MatCreateSNESMF()
Level#
intermediate
Location#
Examples#
src/ts/tutorials/ex4.c
src/ts/tutorials/ex15.c
src/ts/tutorials/ex17.c
src/ts/tutorials/ex10.c
Index of all SNES routines
Table of Contents for all manual pages
Index of all manual pages