PETSc version 3.17.0
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# KSPGCRSetModifyPC

Sets the routine used by GCR to modify the preconditioner.

### Synopsis

    #include "petscksp.h"
    PetscErrorCode  KSPGCRSetModifyPC(KSP ksp,PetscErrorCode (*function)(KSP,PetscInt,PetscReal,void*),void *data,PetscErrorCode (*destroy)(void*))

Logically Collective on ksp

### Input Parameters

+ ksp - iterative context obtained from KSPCreate() . function - user defined function to modify the preconditioner . ctx - user provided context for the modify preconditioner function - destroy - the function to use to destroy the user provided application context.

### Calling Sequence of function

PetscErrorCode function (KSP ksp, PetscInt n, PetscReal rnorm, void *ctx)

ksp - iterative context n - the total number of GCR iterations that have occurred rnorm - 2-norm residual value ctx - the user provided application context

### Notes

The default modifypc routine is KSPGCRModifyPCNoChange()

.seealso: KSPGCRModifyPCNoChange()

### Level

intermediate

### Location

src/ksp/ksp/impls/gcr/gcr.c

### Implementations

KSPGCRSetModifyPC_GCR in src/ksp/ksp/impls/gcr/gcr.c
Index of all KSP routines
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