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# TaoGetGradient
Gets the gradient evaluation routine for the function being optimized 
## Synopsis
```
#include "petsctao.h" 
PetscErrorCode TaoGetGradient(Tao tao, Vec *g, PetscErrorCode (**func)(Tao, Vec, Vec, void *), void **ctx)
```
Not Collective


## Input Parameter

- ***tao -*** the `Tao` context



## Output Parameters

- ***g -*** the vector to internally hold the gradient computation
- ***func -*** the gradient function
- ***ctx -*** user-defined context for private data for the gradient evaluation routine



## Calling sequence of `func`
```none
PetscErrorCode func(Tao tao, Vec x, Vec g, void *ctx);
```

- ***tao -*** the optimizer
- ***x -*** input vector
- ***g -*** gradient value (output)
- ***ctx -*** [optional] user-defined function context





## See Also
 [](ch_tao), `Tao`, `TaoSetObjective()`, `TaoSetHessian()`, `TaoSetObjectiveAndGradient()`, `TaoSetGradient()`

## Level
beginner

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

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


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


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