petsc-3.8.4 2018-03-24

SNESLineSearchApply

Computes the line-search update.

Synopsis

#include "petscsnes.h" 
PetscErrorCode SNESLineSearchApply(SNESLineSearch linesearch, Vec X, Vec F, PetscReal * fnorm, Vec Y)

Collective on SNESLineSearch

Input Parameters

	linesearch	- The linesearch context
	X	- The current solution
	F	- The current function
	fnorm	- The current norm
	Y	- The search direction

Output Parameters

	X	- The new solution
	F	- The new function
	fnorm	- The new function norm

Options Database Keys

	-snes_linesearch_type	- basic, bt, l2, cp, nleqerr, shell
	-snes_linesearch_monitor [:filename]	- Print progress of line searches
	-snes_linesearch_damping	- The linesearch damping parameter, default is 1.0 (no damping)
	-snes_linesearch_norms	- Turn on/off the linesearch norms computation (SNESLineSearchSetComputeNorms())
	-snes_linesearch_keeplambda	- Keep the previous search length as the initial guess
	-snes_linesearch_max_it	- The number of iterations for iterative line searches

Notes

This is typically called from within a SNESSolve() implementation in order to help with convergence of the nonlinear method. Various SNES types use line searches in different ways, but the overarching theme is that a line search is used to determine an optimal damping parameter of a step at each iteration of the method. Each application of the line search may invoke SNESComputeFunction several times, and therefore may be fairly expensive.

Keywords

SNESLineSearch, Create