petsc-3.4.2 2013-07-02

# 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, shell
| -snes_linesearch_monitor | - Print progress of line searches
| -snes_linesearch_damping | - The linesearch damping parameter
| -snes_linesearch_norms | - Turn on/off the linesearch norms
| -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

### See Also

SNESLineSearchCreate(), SNESLineSearchPreCheck(), SNESLineSearchPostCheck(), SNESSolve(), SNESComputeFunction()

Level:Intermediate
Location: src/snes/linesearch/interface/linesearch.c
Index of all SNES routines
Table of Contents for all manual pages
Index of all manual pages