# KSPSetUseFischerGuess
Use the Paul Fischer algorithm or its variants to compute initial guesses for a set of solves with related right hand sides 
## Synopsis
```
#include "petscksp.h" 
PetscErrorCode KSPSetUseFischerGuess(KSP ksp, PetscInt model, PetscInt size)
```
Logically Collective on ksp


## Input Parameters

- ***ksp -*** the Krylov context
- ***model -*** use model 1, model 2, model 3, or any other number to turn it off
- ***size -*** size of subspace used to generate initial guess



## Options Database Key

- ***-ksp_fischer_guess <model,size> -*** uses the Fischer initial guess generator for repeated linear solves





## See Also
 [](chapter_ksp), `KSP`, `KSPSetOptionsPrefix()`, `KSPAppendOptionsPrefix()`, `KSPSetUseFischerGuess()`, `KSPSetGuess()`, `KSPGetGuess()`, `KSPGuess`

## Level
advanced

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


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