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# KSPSetComputeEigenvalues
Sets a flag so that the extreme eigenvalues values will be calculated via a Lanczos or Arnoldi process as the linear system is solved. 
## Synopsis
```
#include "petscksp.h" 
#include "petscmat.h" 
PetscErrorCode KSPSetComputeEigenvalues(KSP ksp, PetscBool flg)
```
Logically Collective


## Input Parameters

- ***ksp -*** iterative context obtained from `KSPCreate()`
- ***flg -*** `PETSC_TRUE` or `PETSC_FALSE`





## Note
Currently this option is not valid for all iterative methods.


## See Also
 [](ch_ksp), `KSPComputeEigenvalues()`, `KSPComputeEigenvaluesExplicitly()`, `KSP`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/interface/itfunc.c.html#KSPSetComputeEigenvalues">src/ksp/ksp/interface/itfunc.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex71.c.html">src/ksp/ksp/tutorials/ex71.c</A><BR>


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