# PCSPAISetEpsilon
Set the tolerance for the `PCSPAI` preconditioner 
## Synopsis
```
#include "petscpc.h" 
PetscErrorCode PCSPAISetEpsilon(PC pc, PetscReal epsilon1)
```

## Input Parameters

- ***pc -*** the preconditioner
- ***eps -*** epsilon (default .4)



## Note
Espilon must be between 0 and 1. It controls the
quality of the approximation of M to the inverse of
A. Higher values of epsilon lead to more work, more
fill, and usually better preconditioners. In many
cases the best choice of epsilon is the one that
divides the total solution time equally between the
preconditioner and the solver.




## See Also
 `PCSPAI`, `PCSetType()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/spai/ispai.c.html#PCSPAISetEpsilon">src/ksp/pc/impls/spai/ispai.c</A>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/spai/ispai.c.html#PCSPAISetEpsilon_SPAI">PCSPAISetEpsilon_SPAI in src/ksp/pc/impls/spai/ispai.c</A><BR>


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


[Index of all PC routines](index.md)  
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