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# SNESFASGalerkinFunctionDefault
Computes the Galerkin FAS function 
## Synopsis
```
#include "petscsnes.h"  
PetscErrorCode SNESFASGalerkinFunctionDefault(SNES snes, Vec X, Vec F, void *ctx)
```
Collective


## Input Parameters

- ***snes -*** the `SNESFAS` nonlinear solver context
- ***X -*** input vector
- ***ctx -*** the application context



## Output Parameter

- ***F -*** output vector





## Note
The Galerkin FAS function evaluation is defined as
```none
F^l(x^l) = I^l_0 F^0(P^0_l x^l)
```


## See Also
 `SNESFAS`, `SNESFASGetGalerkin()`, `SNESFASSetGalerkin()`

## Level
developer

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/impls/fas/fasgalerkin.c.html#SNESFASGalerkinFunctionDefault">src/snes/impls/fas/fasgalerkin.c</A>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/snes/impls/fas/fasgalerkin.c)


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