# MatSNESMFMoreSetParameters
Sets the parameters for the approximation of matrix-vector products using finite differences, see  `MatCreateSNESMFMore()` 
## Synopsis
```
#include "petscsnes.h"   
PetscErrorCode MatSNESMFMoreSetParameters(Mat mat, PetscReal error, PetscReal umin, PetscReal h)
```

## Input Parameters

- ***mat -*** the matrix
- ***error_rel -*** relative error (should be set to the square root of the relative error in the function evaluations)
- ***umin -*** minimum allowable u-value
- ***h -*** differencing parameter



## Options Database Keys

- ***-snes_mf_err <error_rel> -*** see `MatCreateSNESMF()`
- ***-snes_mf_umin <umin> -*** see `MatCreateSNESMF()`
- ***-snes_mf_compute_err -*** compute the square root or relative error in function
- ***-snes_mf_freq_err <freq> -*** set the frequency to recompute the parameters
- ***-snes_mf_jorge -*** use the method of Jorge More





## Note
If the user sets the parameter h directly, then this value will be used
instead of the default computation as discussed in `MatCreateSNESMFMore()`


## See Also
 `MatCreateSNESMF()`, `MatCreateSNESMFMore()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/interface/noise/snesmfj2.c.html#MatSNESMFMoreSetParameters">src/snes/interface/noise/snesmfj2.c</A>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/snes/interface/noise/snesmfj2.c)


[Index of all SNES routines](index.md)  
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