slepc-3.22.2 2024-12-02
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# NEPNArnoldiSetLagPreconditioner

Determines when the preconditioner is rebuilt in the nonlinear solve.

### Synopsis

    #include "slepcnep.h"
    PetscErrorCode NEPNArnoldiSetLagPreconditioner(NEP nep,PetscInt lag)

Logically Collective

### Input Parameters

| nep | - nonlinear eigenvalue solver
| lag | - 0 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within the nonlinear iteration, 2 means every second time the Jacobian is built, etc.

### Options Database Keys

| -nep_narnoldi_lag_preconditioner <lag> | - the lag value

### Notes

The default is 1. The preconditioner is ALWAYS built in the first iteration of a nonlinear solve.

### See Also

NEPNArnoldiGetLagPreconditioner()

### Level

intermediate

### Location

src/nep/impls/narnoldi/narnoldi.c
Index of all NEP routines
Table of Contents for all manual pages
Index of all manual pages