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# PCDeflationSetReductionFactor
Set reduction factor for the `PCDEFLATION` 
## Synopsis
```
#include "petscksp.h" 
PetscErrorCode PCDeflationSetReductionFactor(PC pc, PetscInt red)
```
Logically Collective


## Input Parameters

- ***pc  -*** the preconditioner context
- ***red -*** reduction factor (or `PETSC_DETERMINE`)



## Options Database Key

- ***-pc_deflation_reduction_factor <-1> -*** reduction factor on bottom level coarse problem for `PCDEFLATION`



## Note
Default is computed based on the size of the coarse problem.




## See Also
 `PCTELESCOPE`, `PCDEFLATION`, `PCDeflationSetLevels()`

## Level
intermediate

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

## Implementations

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


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


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