SNESNoLineSearchNoNorms

This routine is not a line search at all; it simply uses the full Newton step. This version does not even compute the norm of the function or search direction; this is intended only when you know the full step is fine and are not checking for convergence of the nonlinear iteration (for example, you are running always for a fixed number of Newton steps).

Synopsis

int SNESNoLineSearchNoNorms(SNES snes,void *lsctx,Vec x,Vec f,Vec g,Vec y,Vec w,PetscReal fnorm,PetscReal *ynorm,PetscReal *gnorm,int *flag)

Collective on SNES and Vec

Input Parameters

	snes	- nonlinear context
	lsctx	- optional context for line search (not used here)
	x	- current iterate
	f	- residual evaluated at x
	y	- search direction (contains new iterate on output)
	w	- work vector
	fnorm	- 2-norm of f

Output Parameters

	g	- residual evaluated at new iterate y
	gnorm	- not changed
	ynorm	- not changed
	flag	- set to 0, indicating a successful line search

Options Database Key

-snes_ls basicnonorms -Activates SNESNoLineSearchNoNorms()

Notes

SNESNoLineSearchNoNorms() must be used in conjunction with either the options

    -snes_no_convergence_test -snes_max_it <its>

or alternatively a user-defined custom test set via SNESSetConvergenceTest(); or a -snes_max_it of 1, otherwise, the SNES solver will generate an error.

During the final iteration this will not evaluate the function at the solution point. This is to save a function evaluation while using pseudo-timestepping.

The residual norms printed by monitoring routines such as SNESDefaultMonitor() (as activated via -snes_monitor) will not be correct, since they are not computed.

Keywords

SNES, nonlinear, line search, cubic