:orphan:
# PetscOptionsBegin
Begins a set of queries on the options database that are related and should be displayed on the same window of a GUI that allows the user to set the options interactively. Often one should use `PetscObjectOptionsBegin()` rather than this call. 
## Synopsis
```
#include <petscoptions.h>
PetscErrorCode PetscOptionsBegin(MPI_Comm comm,const char prefix[],const char title[],const char mansec[])
```
Collective


## Input Parameters

- ***comm -*** communicator that shares GUI
- ***prefix -*** options prefix for all options displayed on window (optional)
- ***title -*** short descriptive text, for example "Krylov Solver Options"
- ***mansec -*** section of manual pages for options, for example `KSP` (optional)





## Notes
This is a macro that handles its own error checking, it does not return an error code.

The set of queries needs to be ended by a call to `PetscOptionsEnd()`.

One can add subheadings with `PetscOptionsHeadBegin()`.


## Developer Notes
`PetscOptionsPublish` is set in `PetscOptionsCheckInitial_Private()` with `-saws_options`. When `PetscOptionsPublish` is set the
loop between `PetscOptionsBegin()` and `PetscOptionsEnd()` is run THREE times with `PetscOptionsPublishCount` of values -1,0,1.
Otherwise the loop is run ONCE with a `PetscOptionsPublishCount` of 1.

- ***-1 -*** `PetscOptionsInt()` etc. just call `PetscOptionsGetInt()` etc.
- ***0  -*** The GUI objects are created in `PetscOptionsInt()` etc. and displayed in `PetscOptionsEnd()` and the options
database updated with user changes; `PetscOptionsGetInt()` etc. are also called.
- ***1 -*** `PetscOptionsInt()` etc. again call `PetscOptionsGetInt()` etc. (possibly getting new values), in addition the help message and
default values are printed if -help was given.
When `PetscOptionsObject.changedmethod` is set this causes `PetscOptionsPublishCount` to be reset to -2 (so in the next loop iteration it is -1)
and the whole process is repeated. This is to handle when, for example, the `KSPType` is changed thus changing the list of
options available so they need to be redisplayed so the user can change the. Changing `PetscOptionsObjects.changedmethod` is never
currently set.



## See Also
 `PetscOptionsGetReal()`, `PetscOptionsHasName()`, `PetscOptionsGetString()`, `PetscOptionsGetInt()`,
`PetscOptionsGetIntArray()`, `PetscOptionsGetRealArray()`, `PetscOptionsBool()`
`PetscOptionsInt()`, `PetscOptionsString()`, `PetscOptionsReal()`, `PetscOptionsBool()`,
`PetscOptionsName()`, `PetscOptionsEnd()`, `PetscOptionsHeadBegin()`,
`PetscOptionsStringArray()`, `PetscOptionsRealArray()`, `PetscOptionsScalar()`,
`PetscOptionsBoolGroupBegin()`, `PetscOptionsBoolGroup()`, `PetscOptionsBoolGroupEnd()`,
`PetscOptionsFList()`, `PetscOptionsEList()`, `PetscObjectOptionsBegin()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/include/petscoptions.h.html#PetscOptionsBegin">include/petscoptions.h</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/dt/dualspace/impls/lagrange/tutorials/ex1.c.html">src/dm/dt/dualspace/impls/lagrange/tutorials/ex1.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/dt/dualspace/impls/lagrange/tutorials/ex2.c.html">src/dm/dt/dualspace/impls/lagrange/tutorials/ex2.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/field/tutorials/ex1.c.html">src/dm/field/tutorials/ex1.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/forest/tutorials/ex1.c.html">src/dm/impls/forest/tutorials/ex1.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/plex/tutorials/ex10.c.html">src/dm/impls/plex/tutorials/ex10.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/plex/tutorials/ex11.c.html">src/dm/impls/plex/tutorials/ex11.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/plex/tutorials/ex13.c.html">src/dm/impls/plex/tutorials/ex13.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/plex/tutorials/ex5.c.html">src/dm/impls/plex/tutorials/ex5.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/plex/tutorials/ex6.c.html">src/dm/impls/plex/tutorials/ex6.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/plex/tutorials/ex8.c.html">src/dm/impls/plex/tutorials/ex8.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/plex/tutorials/ex9.c.html">src/dm/impls/plex/tutorials/ex9.c</A><BR>


---
[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/include/petscoptions.h)


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