petsc-3.14.5 2021-03-03
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# KSPPIPEFGMRESSetShift

Set the shift parameter for the flexible, pipelined GMRES solver.

### Synopsis

    #include "petscksp.h"
    PetscErrorCode KSPPIPEFGMRESSetShift(KSP ksp,PetscScalar shift)

A heuristic is to set this to be comparable to the largest eigenvalue of the preconditioned operator. This can be acheived with PETSc itself by using a few iterations of a Krylov method. See KSPComputeEigenvalues (and note the caveats there).

Logically Collective on ksp

### Input Parameters

| ksp | - the Krylov space context
| shift | - the shift

### Options Database

| -ksp_pipefgmres_shift <shift>

### See Also

KSPComputeEigenvalues()

### Level

intermediate

### Location

src/ksp/ksp/impls/gmres/pipefgmres/pipefgmres.c
Index of all KSP routines
Table of Contents for all manual pages
Index of all manual pages