petsc-3.14.5 2021-03-03
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# SNESSetLagJacobianPersists

Set whether or not the Jacobian lagging persists through multiple solves

### Synopsis

    #include "petscsnes.h"
    PetscErrorCode  SNESSetLagJacobianPersists(SNES snes,PetscBool flg)

Logically collective on SNES

### Input Parameter

| snes | - the SNES context
| flg | - jacobian lagging persists if true

### Options Database Keys

| -snes_lag_jacobian_persists <true,false> | - sets the persistence
| -snes_lag_jacobian < | - 2,1,2,...> - sets the lag
| -snes_lag_preconditioner_persists <true,false> | - sets the persistence
| -snes_lag_preconditioner < | - 2,1,2,...> - sets the lag

### Notes

This is useful both for nonlinear preconditioning, where it's appropriate to have the Jacobian be stale by several solves, and for implicit time-stepping, where Jacobian lagging in the inner nonlinear solve over several timesteps may present huge efficiency gains.

### See Also

SNESSetLagPreconditionerPersists(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESGetNPC(), SNESSetLagJacobianPersists()

### Level

developer

### Location

src/snes/interface/snes.c
Index of all SNES routines
Table of Contents for all manual pages
Index of all manual pages