# DMSNESCreateJacobianMF
Create a `Mat` which computes the action of the Jacobian matrix-free 
## Synopsis
```
#include "petscdmplex.h" 
#include "petscsnes.h"   
PetscErrorCode DMSNESCreateJacobianMF(DM dm, Vec X, void *user, Mat *J)
```
Collective


## Input Parameters

- ***dm   -*** The `DM`
- ***X    -*** The evaluation point for the Jacobian
- ***user -*** A user context, or NULL



## Output Parameter

- ***J    -*** The `Mat`





## Note
Vec X is kept in `Mat` J, so updating X then updates the evaluation point.


## See Also
 `DM`, `DMSNESComputeJacobianAction()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/utils/dmplexsnes.c.html#DMSNESCreateJacobianMF">src/snes/utils/dmplexsnes.c</A>


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


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