petsc-3.14.6 2021-03-30

SNESSetLagJacobian

Determines when the Jacobian is rebuilt in the nonlinear solve. See SNESSetLagPreconditioner() for determining how often the preconditioner is rebuilt.

Synopsis

#include "petscsnes.h"  
PetscErrorCode  SNESSetLagJacobian(SNES snes,PetscInt lag)

Logically Collective on SNES

Input Parameters

	snes	- the SNES context
	lag	- -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time the Jacobian is built etc. -2 means rebuild at next chance but then never again

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

The default is 1 The Jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 If -1 is used before the very first nonlinear solve the CODE WILL FAIL! because no Jacobian is used, use -2 to indicate you want it recomputed at the next Newton step but never again (unless it is reset to another value)

Level

intermediate

Location

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