# TaoSetObjectiveAndGradient
Sets a combined objective function and gradient evaluation routine for the function to be optimized 
## Synopsis
```
#include "petsctao.h" 
PetscErrorCode TaoSetObjectiveAndGradient(Tao tao, Vec g, PetscErrorCode (*func)(Tao, Vec, PetscReal *, Vec, void *), void *ctx)
```
Logically collective


## Input Parameters

- ***tao -*** the Tao context
- ***g -*** [optional] the vector to internally hold the gradient computation
- ***func -*** the gradient function
- ***ctx -*** [optional] user-defined context for private data for the gradient evaluation
routine (may be NULL)



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


- ***x -*** input vector
- ***f -*** objective value (output)
- ***g -*** gradient value (output)
- ***ctx -*** [optional] user-defined function context





## Note
For some optimization methods using a combined function can be more eifficient.


## See Also
 `Tao`, `TaoSolve()`, `TaoSetObjective()`, `TaoSetHessian()`, `TaoSetGradient()`, `TaoGetObjectiveAndGradient()`

## Level
beginner

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

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ts/tutorials/ex20opt_ic.c.html">src/ts/tutorials/ex20opt_ic.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ts/tutorials/ex20opt_p.c.html">src/ts/tutorials/ex20opt_p.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/unconstrained/tutorials/burgers_spectral.c.html">src/tao/unconstrained/tutorials/burgers_spectral.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/unconstrained/tutorials/eptorsion1.c.html">src/tao/unconstrained/tutorials/eptorsion1.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/unconstrained/tutorials/eptorsion2.c.html">src/tao/unconstrained/tutorials/eptorsion2.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/unconstrained/tutorials/eptorsion2f.F90.html">src/tao/unconstrained/tutorials/eptorsion2f.F90.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/unconstrained/tutorials/eptorsion3.c.html">src/tao/unconstrained/tutorials/eptorsion3.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/unconstrained/tutorials/minsurf1.c.html">src/tao/unconstrained/tutorials/minsurf1.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/unconstrained/tutorials/minsurf2.c.html">src/tao/unconstrained/tutorials/minsurf2.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/unconstrained/tutorials/rosenbrock1.c.html">src/tao/unconstrained/tutorials/rosenbrock1.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/unconstrained/tutorials/rosenbrock1f.F90.html">src/tao/unconstrained/tutorials/rosenbrock1f.F90.html</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)  
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[Index of all manual pages](/docs/manualpages/singleindex.md)  
