# PCEisenstatSetNoDiagonalScaling
Causes the Eisenstat preconditioner, `PCEISENSTAT` not to do additional diagonal preconditioning. For matrices with a constant along the diagonal, this may save a small amount of work. 
## Synopsis
```
#include "petscpc.h" 
PetscErrorCode PCEisenstatSetNoDiagonalScaling(PC pc, PetscBool flg)
```
Logically Collective on pc


## Input Parameters

- ***pc -*** the preconditioner context
- ***flg -*** `PETSC_TRUE` turns off diagonal scaling inside the algorithm



## Options Database Key

- ***-pc_eisenstat_no_diagonal_scaling -*** Activates `PCEisenstatSetNoDiagonalScaling()`





## Note
If you use the `KSPSetDiagonalScaling()` or -ksp_diagonal_scale option then you will
likely want to use this routine since it will save you some unneeded flops.


## See Also
 `PCEisenstatSetOmega()`, `PCEISENSTAT`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/eisens/eisen.c.html#PCEisenstatSetNoDiagonalScaling">src/ksp/pc/impls/eisens/eisen.c</A>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/eisens/eisen.c.html#PCEisenstatSetNoDiagonalScaling_Eisenstat">PCEisenstatSetNoDiagonalScaling_Eisenstat in src/ksp/pc/impls/eisens/eisen.c</A><BR>


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


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