# KSPPIPEGCRSetMmax
set the maximum number of previous directions `KSPPIPEGCR` will store for orthogonalization 
## Synopsis
```
#include "petscksp.h"  
PetscErrorCode KSPPIPEGCRSetMmax(KSP ksp, PetscInt mmax)
```
Logically Collective


## Input Parameters

- ***ksp -*** the Krylov space context
- ***mmax -*** the maximum number of previous directions to orthogonalize against



## Options Database Key

- ***-ksp_pipegcr_mmax <N> -*** maximum number of previous directions





## Note
mmax + 1 directions are stored (mmax previous ones along with a current one)
and whether all are used in each iteration also depends on the truncation strategy
(see `KSPPIPEGCRSetTruncationType`)


## See Also
 [](chapter_ksp), `KSPPIPEGCR`, `KSPPIPEGCRSetTruncationType()`, `KSPPIPEGCRSetNprealloc()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/impls/gcr/pipegcr/pipegcr.c.html#KSPPIPEGCRSetMmax">src/ksp/ksp/impls/gcr/pipegcr/pipegcr.c</A>


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


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