petsc-3.13.6 2020-09-29
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MatMFFDSetFunctionError

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

Synopsis

#include "petscmat.h"   
PetscErrorCode  MatMFFDSetFunctionError(Mat mat,PetscReal error)
Logically Collective on Mat

Input Parameters

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

Options Database Keys

-mat_mffd_err <error_rel> -Sets error_rel

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

See Also

MatCreateSNESMF(),MatMFFDGetH(), MatCreateMFFD(), MATMFFD
MatMFFDSetHHistory(), MatMFFDResetHHistory()

Level

advanced

Location

src/mat/impls/mffd/mffd.c

Implementations

MatMFFDSetFunctionError_MFFD in src/mat/impls/mffd/mffd.c

Index of all Mat routines
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Index of all manual pages