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# PCASMSetLocalSubdomains
Sets the local subdomains (for this processor only) for the additive Schwarz preconditioner `PCASM`. 
## Synopsis
```
#include "petscpc.h" 
PetscErrorCode PCASMSetLocalSubdomains(PC pc, PetscInt n, IS is[], IS is_local[])
```
Collective


## Input Parameters

- ***pc -*** the preconditioner context
- ***n -*** the number of subdomains for this processor (default value = 1)
- ***is -*** the index set that defines the subdomains for this processor
(or `NULL` for PETSc to determine subdomains)
- ***is_local -*** the index sets that define the local part of the subdomains for this processor, not used unless PCASMType is PC_ASM_RESTRICT
(or `NULL` to not provide these)



## Options Database Key

- ***-pc_asm_local_blocks <blks> -*** Sets number of local blocks





## Notes
The `IS` numbering is in the parallel, global numbering of the vector for both is and is_local

By default the `PCASM` preconditioner uses 1 block per processor.

Use `PCASMSetTotalSubdomains()` to set the subdomains for all processors.

If is_local is provided and `PCASMType` is `PC_ASM_RESTRICT` then the solution only over the is_local region is interpolated
back to form the global solution (this is the standard restricted additive Schwarz method)

If the is_local is provided and `PCASMType` is `PC_ASM_INTERPOLATE` or `PC_ASM_NONE` then an error is generated since there is
no code to handle that case.


## See Also
 `PCASM`, `PCASMSetTotalSubdomains()`, `PCASMSetOverlap()`, `PCASMGetSubKSP()`,
`PCASMCreateSubdomains2D()`, `PCASMGetLocalSubdomains()`, `PCASMType`, `PCASMSetType()`, `PCGASM`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/asm/asm.c.html#PCASMSetLocalSubdomains">src/ksp/pc/impls/asm/asm.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex19.c.html">src/ksp/ksp/tutorials/ex19.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex76.c.html">src/ksp/ksp/tutorials/ex76.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex8.c.html">src/ksp/ksp/tutorials/ex8.c</A><BR>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/asm/asm.c.html#PCASMSetLocalSubdomains_ASM">PCASMSetLocalSubdomains_ASM in src/ksp/pc/impls/asm/asm.c</A><BR>


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


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[Index of all manual pages](/manualpages/singleindex.md)