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


## Input Parameters

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



## Options Database Key

- ***-ksp_monitor_singular_value -*** Activates `KSPSetComputeSingularValues()`



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

Many users may just want to use the monitoring routine
`KSPMonitorSingularValue()` (which can be set with option -ksp_monitor_singular_value)
to print the singular values at each iteration of the linear solve.




## See Also
 [](chapter_ksp), `KSPComputeExtremeSingularValues()`, `KSPMonitorSingularValue()`, `KSP`

## Level
advanced

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

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex56.c.html">src/ksp/ksp/tutorials/ex56.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex59.c.html">src/ksp/ksp/tutorials/ex59.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex30.c.html">src/snes/tutorials/ex30.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex56.c.html">src/snes/tutorials/ex56.c.html</A><BR>


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


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[Index of all manual pages](/docs/manualpages/singleindex.md)  
