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# MatMFFDDSSetUmin
Sets the "umin" parameter used by the PETSc routine for computing the differencing parameter, h, which is used for matrix-free Jacobian-vector products for a `MATMFFD` matrix. 
## Synopsis
```
#include "petscmat.h"   
PetscErrorCode MatMFFDDSSetUmin(Mat A, PetscReal umin)
```

## Input Parameters

- ***A -*** the `MATMFFD` matrix
- ***umin -*** the parameter





## Note
See the manual page for `MatCreateSNESMF()` for a complete description of the
algorithm used to compute h.


## See Also
 `MATMFFD`, `MatMFFDSetFunctionError()`, `MatCreateSNESMF()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/mffd/mffddef.c.html#MatMFFDDSSetUmin">src/mat/impls/mffd/mffddef.c</A>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/mffd/mffddef.c.html#MatMFFDDSSetUmin_DS">MatMFFDDSSetUmin_DS in src/mat/impls/mffd/mffddef.c</A><BR>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/mat/impls/mffd/mffddef.c)


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