MatMFFDSetFunctionError#
Sets the error_rel for the approximation of matrix-vector products using finite differences with the MATMFFD matrix
Synopsis#
#include "petscmat.h"   
PetscErrorCode MatMFFDSetFunctionError(Mat mat, PetscReal error)
Logically Collective
Input Parameters#
- mat - the - MATMFFDmatrix-free matrix
- error - relative error (should be set to the square root of the relative error in the function evaluations) 
Options Database Key#
- -mat_mffd_err <error_rel> - Sets error_rel 
Note#
The default matrix-free matrix-vector product routine computes
     F'(u)*a = [F(u+h*a) - F(u)]/h where
     h = error_rel*u'a/||a||^2                        if  |u'a| > umin*||a||_{1}
       = error_rel*umin*sign(u'a)*||a||_{1}/||a||^2   else
See Also#
Matrices, Mat, MATMFFD, MatCreateSNESMF(), MatMFFDGetH(), MatCreateMFFD(),
MatMFFDSetHHistory(), MatMFFDResetHHistory()
Level#
advanced
Location#
Implementations#
MatMFFDSetFunctionError_MFFD() in src/mat/impls/mffd/mffd.c
Index of all Mat routines
Table of Contents for all manual pages
Index of all manual pages