PETSc version 3.17.4
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# PCEisenstatSetNoDiagonalScaling

Causes the Eisenstat preconditioner 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()

### Level

intermediate

### Location

src/ksp/pc/impls/eisens/eisen.c

### Implementations

PCEisenstatSetNoDiagonalScaling_Eisenstat in src/ksp/pc/impls/eisens/eisen.c
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