# PCGetOperators
Gets the matrix associated with the linear system and possibly a different one associated with the preconditioner. 
## Synopsis
```
#include "petscksp.h" 
PetscErrorCode PCGetOperators(PC pc, Mat *Amat, Mat *Pmat)
```
Not collective, though parallel mats are returned if pc is parallel


## Input Parameter

- ***pc -*** the preconditioner context



## Output Parameters

- ***Amat -*** the matrix defining the linear system
- ***Pmat -*** the matrix from which the preconditioner is constructed, usually the same as Amat.





## Note
Does not increase the reference count of the matrices, so you should not destroy them

Alternative usage: If the operators have NOT been set with `KSPSetOperators()`/`PCSetOperators()` then the operators
are created in `PC` and returned to the user. In this case, if both operators
mat and pmat are requested, two DIFFERENT operators will be returned. If
only one is requested both operators in the PC will be the same (i.e. as
if one had called `KSPSetOperators()`/`PCSetOperators()` with the same argument for both Mats).
The user must set the sizes of the returned matrices and their type etc just
as if the user created them with `MatCreate()`. For example,

```none
         KSP/PCGetOperators(ksp/pc,&Amat,NULL); is equivalent to
           set size, type, etc of Amat

         MatCreate(comm,&mat);
         KSP/PCSetOperators(ksp/pc,Amat,Amat);
         PetscObjectDereference((PetscObject)mat);
           set size, type, etc of Amat
```


and

```none
         KSP/PCGetOperators(ksp/pc,&Amat,&Pmat); is equivalent to
           set size, type, etc of Amat and Pmat

         MatCreate(comm,&Amat);
         MatCreate(comm,&Pmat);
         KSP/PCSetOperators(ksp/pc,Amat,Pmat);
         PetscObjectDereference((PetscObject)Amat);
         PetscObjectDereference((PetscObject)Pmat);
           set size, type, etc of Amat and Pmat
```


The rationale for this support is so that when creating a `TS`, `SNES`, or `KSP` the hierarchy
of underlying objects (i.e. `SNES`, `KSP`, `PC`, `Mat`) and their lifespans can be completely
managed by the top most level object (i.e. the `TS`, `SNES`, or `KSP`). Another way to look
at this is when you create a `SNES` you do not NEED to create a `KSP` and attach it to
the `SNES` object (the `SNES` object manages it for you). Similarly when you create a KSP
you do not need to attach a `PC` to it (the `KSP` object manages the `PC` object for you).
Thus, why should YOU have to create the `Mat` and attach it to the `SNES`/`KSP`/`PC`, when
it can be created for you?


## See Also
 `PC`, `PCSetOperators()`, `KSPGetOperators()`, `KSPSetOperators()`, `PCGetOperatorsSet()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/interface/precon.c.html#PCGetOperators">src/ksp/pc/interface/precon.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex15f.F90.html">src/ksp/ksp/tutorials/ex15f.F90.html</A><BR>


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


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