:orphan:
# SNESSetJacobian
Sets the function to compute Jacobian as well as the location to store the matrix. 
## Synopsis
```
#include "petscsnes.h"  
PetscErrorCode SNESSetJacobian(SNES snes, Mat Amat, Mat Pmat, PetscErrorCode (*J)(SNES, Vec, Mat, Mat, void *), void *ctx)
```
Logically Collective


## Input Parameters

- ***snes -*** the `SNES` context
- ***Amat -*** the matrix that defines the (approximate) Jacobian
- ***Pmat -*** the matrix to be used in constructing the preconditioner, usually the same as `Amat`.
- ***J -*** Jacobian evaluation routine (if `NULL` then `SNES` retains any previously set value), see `SNESJacobianFunction` for details
- ***ctx -*** [optional] user-defined context for private data for the
Jacobian evaluation routine (may be `NULL`) (if `NULL` then `SNES` retains any previously set value)





## Notes
If the `Amat` matrix and `Pmat` matrix are different you must call `MatAssemblyBegin()`/`MatAssemblyEnd()` on
each matrix.

If you know the operator `Amat` has a null space you can use `MatSetNullSpace()` and `MatSetTransposeNullSpace()` to supply the null
space to `Amat` and the `KSP` solvers will automatically use that null space as needed during the solution process.

If using `SNESComputeJacobianDefaultColor()` to assemble a Jacobian, the `ctx` argument
must be a `MatFDColoring`.

Other defect-correction schemes can be used by computing a different matrix in place of the Jacobian.  One common
example is to use the "Picard linearization" which only differentiates through the highest order parts of each term using `SNESSetPicard()`


## See Also
 [](ch_snes), `SNES`, `KSPSetOperators()`, `SNESSetFunction()`, `MatMFFDComputeJacobian()`, `SNESComputeJacobianDefaultColor()`, `MatStructure`,
`SNESSetPicard()`, `SNESJacobianFunction`

## Level
beginner

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

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex1.c.html">src/snes/tutorials/ex1.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex12.c.html">src/snes/tutorials/ex12.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex14.c.html">src/snes/tutorials/ex14.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex15.c.html">src/snes/tutorials/ex15.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex18.c.html">src/snes/tutorials/ex18.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex1f.F90.html">src/snes/tutorials/ex1f.F90</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex2.c.html">src/snes/tutorials/ex2.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex22.c.html">src/snes/tutorials/ex22.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex28.c.html">src/snes/tutorials/ex28.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex3.c.html">src/snes/tutorials/ex3.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex35.c.html">src/snes/tutorials/ex35.c</A><BR>


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


[Index of all SNES routines](index.md)  
[Table of Contents for all manual pages](/manualpages/index.md)  
[Index of all manual pages](/manualpages/singleindex.md)