# PCGAMGSetRankReductionFactors
Set a manual schedule for MPI rank reduction on coarse grids 
## Synopsis
```
#include "petscpc.h" 
#include "petscksp.h" 
PetscErrorCode PCGAMGSetRankReductionFactors(PC pc, PetscInt v[], PetscInt n)
```
Collective


## Input Parameters

- ***pc -*** the preconditioner context
- ***v -*** array of reduction factors. 0 for first value forces a reduction to one process/device on first level in CUDA
- ***n -*** number of values provided in array



## Options Database Key

- ***-pc_gamg_rank_reduction_factors <factors> -*** provide the schedule





## See Also
 `PCGAMG`, `PCGAMGSetProcEqLim()`, `PCGAMGSetCoarseEqLim()`

## Level
intermediate

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

## Implementations

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


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


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