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<div id="version" align=right><b>petsc-3.7.5 2017-01-01</b></div>
<div id="bugreport" align=right><a href="mailto:petsc-maint@mcs.anl.gov?subject=Typo or Error in Documentation &body=Please describe the typo or error in the documentation: petsc-3.7.5 v3.7.5 docs/manualpages/SNES/SNESLineSearchApply.html "><small>Report Typos and Errors</small></a></div>
<A NAME="SNESLineSearchApply"><H1>SNESLineSearchApply</H1></A>
Computes the line-search update.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscsnes.h"
PetscErrorCode SNESLineSearchApply(SNESLineSearch linesearch, Vec X, Vec F, PetscReal * fnorm, Vec Y)
</PRE>
Collective on <A HREF="../SNES/SNESLineSearch.html#SNESLineSearch">SNESLineSearch</A>
<P>
<H3><FONT COLOR="#CC3333">Input Parameters</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>linesearch </B></TD><TD>- The linesearch context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>X </B></TD><TD>- The current solution
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>F </B></TD><TD>- The current function
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>fnorm </B></TD><TD>- The current norm
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>Y </B></TD><TD>- The search direction
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Output Parameters</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>X </B></TD><TD>- The new solution
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>F </B></TD><TD>- The new function
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>fnorm </B></TD><TD>- The new function norm
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Options Database Keys</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_linesearch_type </B></TD><TD>- basic, bt, l2, cp, nleqerr, shell
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_linesearch_monitor [:filename] </B></TD><TD>- Print progress of line searches
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_linesearch_damping </B></TD><TD>- The linesearch damping parameter
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_linesearch_norms </B></TD><TD>- Turn on/off the linesearch norms
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_linesearch_keeplambda </B></TD><TD>- Keep the previous search length as the initial guess
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_linesearch_max_it </B></TD><TD>- The number of iterations for iterative line searches
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
This is typically called from within a <A HREF="../SNES/SNESSolve.html#SNESSolve">SNESSolve</A>() implementation in order to
help with convergence of the nonlinear method. Various <A HREF="../SNES/SNES.html#SNES">SNES</A> 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 <A HREF="../SNES/SNESComputeFunction.html#SNESComputeFunction">SNESComputeFunction</A> several times, and
therefore may be fairly expensive.
<P>
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../SNES/SNESLineSearch.html#SNESLineSearch">SNESLineSearch</A>, Create
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../SNES/SNESLineSearchCreate.html#SNESLineSearchCreate">SNESLineSearchCreate</A>(), <A HREF="../SNES/SNESLineSearchPreCheck.html#SNESLineSearchPreCheck">SNESLineSearchPreCheck</A>(), <A HREF="../SNES/SNESLineSearchPostCheck.html#SNESLineSearchPostCheck">SNESLineSearchPostCheck</A>(), <A HREF="../SNES/SNESSolve.html#SNESSolve">SNESSolve</A>(), <A HREF="../SNES/SNESComputeFunction.html#SNESComputeFunction">SNESComputeFunction</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>Intermediate
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/snes/linesearch/interface/linesearch.c.html#SNESLineSearchApply">src/snes/linesearch/interface/linesearch.c</A>
<BR><A HREF="./index.html">Index of all SNES routines</A>
<BR><A HREF="../../index.html">Table of Contents for all manual pages</A>
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