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 MATMFFD matrix-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

src/mat/impls/mffd/mffd.c

Implementations

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

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