:orphan:
# KSPGMRESCGSRefinementType
How the classical (unmodified) Gram-Schmidt is performed in the GMRES solvers 
## Synopsis
```
typedef enum {
  KSP_GMRES_CGS_REFINE_NEVER,
  KSP_GMRES_CGS_REFINE_IFNEEDED,
  KSP_GMRES_CGS_REFINE_ALWAYS
} KSPGMRESCGSRefinementType;
```

## Values

- ***`KSP_GMRES_CGS_REFINE_NEVER` -*** one step of classical Gram-Schmidt
- ***`KSP_GMRES_CGS_REFINE_IFNEEDED` -*** a second step is performed if the first step does not satisfy some criteria
- ***`KSP_GMRES_CGS_REFINE_ALWAYS` -*** always perform two steps





## See Also
 [](ch_ksp), `KSP`, `KSPGMRESClassicalGramSchmidtOrthogonalization()`, `KSPGMRESSetOrthogonalization()`,
`KSPGMRESGetOrthogonalization()`,
`KSPGMRESSetCGSRefinementType()`, `KSPGMRESGetCGSRefinementType()`, `KSPGMRESModifiedGramSchmidtOrthogonalization()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/include/petscksp.h.html#KSPGMRESCGSRefinementType">include/petscksp.h</A>


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