:orphan:
# TaoLineSearchSetOptionsPrefix
Sets the prefix used for searching for all `TaoLineSearch` options in the database. 
## Synopsis
```
#include "petsctaolinesearch.h" 
PetscErrorCode TaoLineSearchSetOptionsPrefix(TaoLineSearch ls, const char p[])
```
Logically Collective


## Input Parameters

- ***ls -*** the `TaoLineSearch` context
- ***prefix -*** the prefix string to prepend to all `ls` option requests





## Notes
A hyphen (-) must NOT be given at the beginning of the prefix name.
The first character of all runtime options is AUTOMATICALLY the hyphen.

This is inherited from the `Tao` object so rarely needs to be set

For example, to distinguish between the runtime options for two
different line searches, one could call
```none
      TaoLineSearchSetOptionsPrefix(ls1,"sys1_")
      TaoLineSearchSetOptionsPrefix(ls2,"sys2_")
```


This would enable use of different options for each system, such as
```none
      -sys1_tao_ls_type mt
      -sys2_tao_ls_type armijo
```



## See Also
 [](ch_tao), `Tao`, `TaoLineSearch`, `TaoLineSearchAppendOptionsPrefix()`, `TaoLineSearchGetOptionsPrefix()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/linesearch/interface/taolinesearch.c.html#TaoLineSearchSetOptionsPrefix">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](/manualpages/index.md)  
[Index of all manual pages](/manualpages/singleindex.md)