# KSPBCGSLSetEll
Sets the number of search directions in `KSPCBGSL` solver 
## Synopsis
```
#include "petscksp.h" 
PetscErrorCode KSPBCGSLSetEll(KSP ksp, PetscInt ell)
```
Logically Collective


## Input Parameters

- ***ksp -*** iterative context of type `KSPCBGSL`
- ***ell -*** number of search directions



## Options Database Keys

- ***-ksp_bcgsl_ell ell -*** Number of Krylov search directions





## Notes
For large ell it is common for the polynomial update problem to become singular (due to happy breakdown for smallish
test problems, but also for larger problems). Consequently, by default, the system is solved by pseudoinverse, which
allows the iteration to complete successfully. See `KSPBCGSLSetUsePseudoinverse()` to switch to a conventional solve.


## See Also
 [](chapter_ksp), `KSPBCGSLSetUsePseudoinverse()`, `KSP`, `KSPBCGSL`, `KSPBCGSLSetPol()`, `KSPBCGSLSetXRes()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/impls/bcgsl/bcgsl.c.html#KSPBCGSLSetEll">src/ksp/ksp/impls/bcgsl/bcgsl.c</A>


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


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