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# KSPGuessFischerSetModel
Use the Paul Fischer algorithm or its variants to compute the initial guess 
## Synopsis
```
#include "petscksp.h" 
PetscErrorCode KSPGuessFischerSetModel(KSPGuess guess, PetscInt model, PetscInt size)
```
Logically Collective


## Input Parameters

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





## See Also
 [](ch_ksp), `KSPGuess`, `KSPGuessCreate()`, `KSPSetUseFischerGuess()`, `KSPSetGuess()`, `KSPGetGuess()`, `KSP`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/guess/impls/fischer/fischer.c.html#KSPGuessFischerSetModel">src/ksp/ksp/guess/impls/fischer/fischer.c</A>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/guess/impls/fischer/fischer.c.html#KSPGuessFischerSetModel_Fischer">KSPGuessFischerSetModel_Fischer in src/ksp/ksp/guess/impls/fischer/fischer.c</A><BR>


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


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