:orphan:
# TaoBRGNSetRegularizerHessianRoutine
Sets the user-defined regularizer call-back function into the algorithm. 
## Synopsis
```
#include "petsctao.h" 
PetscErrorCode TaoBRGNSetRegularizerHessianRoutine(Tao tao, Mat Hreg, PetscErrorCode (*func)(Tao, Vec, Mat, void *), void *ctx)
```

## Input Parameters

- ***tao -*** the `Tao` context
- ***Hreg -*** user-created matrix for the Hessian of the regularization term
- ***func -*** function pointer for the regularizer Hessian evaluation
- ***ctx -*** user context for the regularizer Hessian



## Calling Sequence of `func`
```none
PetscErrorCode func(Tao tao, Vec u, Mat H, void *ctx)
```

- ***tao -*** the `Tao` context
- ***u -*** the location at which to compute the Hessian
- ***Hreg -*** user-created matrix for the Hessian of the regularization term
- ***ctx -*** user context for the regularizer Hessian





## See Also
 `Tao`, `Mat`, `TAOBRGN`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/leastsquares/impls/brgn/brgn.c.html#TaoBRGNSetRegularizerHessianRoutine">src/tao/leastsquares/impls/brgn/brgn.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/leastsquares/tutorials/tomography.c.html">src/tao/leastsquares/tutorials/tomography.c</A><BR>


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


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