# TaoLineSearchSetObjectiveRoutine
Sets the function evaluation routine for the line search 
## Synopsis
```
#include "petsctaolinesearch.h" 
PetscErrorCode TaoLineSearchSetObjectiveRoutine(TaoLineSearch ls, PetscErrorCode (*func)(TaoLineSearch ls, Vec x, PetscReal *, void *), void *ctx)
```
Logically Collective on TaoLineSearch


## Input Parameters

- ***ls -*** the TaoLineSearch context
- ***func -*** the objective function evaluation routine
- ***ctx -*** the (optional) user-defined context for private data



## Calling sequence of func
```none
func (TaoLinesearch ls, Vec x, PetscReal *f, void *ctx);
```


- ***x -*** input vector
- ***f -*** function value
- ***ctx (optional) user-*** defined context





## Note
Use this routine only if you want the line search objective
evaluation routine to be different from the Tao's objective
evaluation routine. If you use this routine you must also set
the line search gradient and/or function/gradient routine.


## Note
Some algorithms (lcl, gpcg) set their own objective routine for the
line search, application programmers should be wary of overriding the
default objective routine.


## See Also
 `TaoLineSearchCreate()`, `TaoLineSearchSetGradientRoutine()`, `TaoLineSearchSetObjectiveAndGradientRoutine()`, `TaoLineSearchUseTaoRoutines()`

## Level
beginner

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/linesearch/interface/taolinesearch.c.html#TaoLineSearchSetObjectiveRoutine">src/tao/linesearch/interface/taolinesearch.c</A>


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


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