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# KSPSetInitialGuessKnoll
Tells the iterative solver to use `PCApply()` to compute the initial guess (The Knoll trick) 
## Synopsis
```
#include "petscksp.h" 
#include "petscmat.h" 
PetscErrorCode KSPSetInitialGuessKnoll(KSP ksp, PetscBool flg)
```
Logically Collective


## Input Parameters

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





## Developer Note
The Knoll trick is not currently implemented using the `KSPGuess` class


## See Also
 [](ch_ksp), `KSPGetInitialGuessKnoll()`, `KSPSetInitialGuessNonzero()`, `KSPGetInitialGuessNonzero()`, `KSP`

## Level
advanced

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


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