MatSNESMFSetFunctionError

 Sets the error_rel for the approximation of matrix-vector products using finite differences.

Synopsis

#include "petscsnes.h"   
int MatSNESMFSetFunctionError(Mat mat,PetscReal error)
Collective on Mat

Input Parameters

mat - the matrix free matrix created via MatCreateSNESMF()
error_rel - relative error (should be set to the square root of the relative error in the function evaluations)

Options Database Keys

Notes

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

Keywords

SNES, matrix-free, parameters

See Also

MatCreateSNESMF(),MatSNESMFGetH(),
MatSNESMFSetHHistory(), MatSNESMFResetHHistory(), MatSNESMFKSPMonitor()

Level:advanced
Location:src/snes/mf/snesmfj.c
Index of all SNESMF routines
Table of Contents for all manual pages
Index of all manual pages

-snes_mf_err <error_rel> - Sets error_rel