:orphan:
# TaoADMMSetRegularizerHessianRoutine
Sets the user-defined regularizer Hessian call-back function, to be used for subsolverZ.
## Synopsis
```
#include "petsctao.h"
PetscErrorCode TaoADMMSetRegularizerHessianRoutine(Tao tao, Mat H, Mat Hpre, PetscErrorCode (*func)(Tao, Vec, Mat, Mat, void *), void *ctx)
```
Collective
## Input Parameters
- ***tao -*** the `Tao` context
- ***H -*** user-created matrix for the Hessian of the regularization term
- ***Hpre -*** user-created matrix for the preconditioner of Hessian of the regularization term
- ***func -*** function pointer for the regularizer Hessian evaluation
- ***ctx -*** user context for the regularizer Hessian
## See Also
`TAOADMM`
## Level
advanced
## Location
src/tao/constrained/impls/admm/admm.c
## Examples
src/tao/constrained/tutorials/tomographyADMM.c
---
[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/tao/constrained/impls/admm/admm.c)
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