:orphan:
# PetscSubcomm
A decomposition of an MPI communicator into subcommunicators 
## Synopsis
```
typedef struct _n_PetscSubcomm *PetscSubcomm;
```

## Values

- ***`PETSC_SUBCOMM_GENERAL` -*** similar to `MPI_Comm_split()` each process sets the new communicator (color) they will belong to and the order within that communicator
- ***`PETSC_SUBCOMM_CONTIGUOUS` -*** each new communicator contains a set of process with contiguous ranks in the original MPI communicator
- ***`PETSC_SUBCOMM_INTERLACED` -*** each new communictor contains a set of processes equally far apart in rank from the others in that new communicator



## Sample Usage
```none
       PetscSubcommCreate()
       PetscSubcommSetNumber()
       PetscSubcommSetType(PETSC_SUBCOMM_INTERLACED);
       ccomm = PetscSubcommChild()
       PetscSubcommDestroy()
```



## Example
Consider a communicator with six processes split into 3 subcommunicators.
```none
   PETSC_SUBCOMM_CONTIGUOUS - the first communicator contains rank 0,1  the second rank 2,3 and the third rank 4,5 in the original ordering of the original communicator
   PETSC_SUBCOMM_INTERLACED - the first communicator contains rank 0,3, the second 1,4 and the third 2,5
```





## Note
After a call to `PetscSubcommSetType()`, `PetscSubcommSetTypeGeneral()`, or `PetscSubcommSetFromOptions()` one may call
```none
     PetscSubcommChild() returns the associated subcommunicator on this process
     PetscSubcommContiguousParent() returns a parent communitor but with all child of the same subcommunicator having contiguous rank
```



## Developer Note
This is used in objects such as `PCREDUNDANT` to manage the subcommunicators on which the redundant computations
are performed.


## See Also
 `PetscSubcommCreate()`, `PetscSubcommSetNumber()`, `PetscSubcommSetType()`, `PetscSubcommView()`, `PetscSubcommSetFromOptions()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/include/petscsystypes.h.html#PetscSubcomm">include/petscsystypes.h</A>


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