# TaoSetJacobianEqualityRoutine
Sets the function to compute the Jacobian (and its inverse) of the constraint function with respect to the equality variables. Used only for PDE-constrained optimization. 
## Synopsis
```
#include "petsctao.h" 
PetscErrorCode TaoSetJacobianEqualityRoutine(Tao tao, Mat J, Mat Jpre, PetscErrorCode (*func)(Tao, Vec, Mat, Mat, void *), void *ctx)
```
Logically collective


## Input Parameters

- ***tao  -*** the Tao context
- ***J    -*** Matrix used for the jacobian
- ***Jpre -*** Matrix that will be used operated on by PETSc preconditioner, can be same as J.
- ***func -*** Jacobian evaluation routine
- ***ctx  -*** [optional] user-defined context for private data for the
Jacobian evaluation routine (may be NULL)



## Calling sequence of func
```none
func(Tao tao,Vec x,Mat J,Mat Jpre,void *ctx);
```


- ***tao  -*** the Tao  context
- ***x    -*** input vector
- ***J    -*** Jacobian matrix
- ***Jpre -*** preconditioner matrix, usually the same as J
- ***ctx  -*** [optional] user-defined Jacobian context





## See Also
 `Tao`, `TaoComputeJacobianEquality()`, `TaoSetJacobianDesignRoutine()`, `TaoSetEqualityDesignIS()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/interface/taosolver_hj.c.html#TaoSetJacobianEqualityRoutine">src/tao/interface/taosolver_hj.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/constrained/tutorials/ex1.c.html">src/tao/constrained/tutorials/ex1.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/constrained/tutorials/maros.c.html">src/tao/constrained/tutorials/maros.c.html</A><BR>


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


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