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<div id="version" align=right><b>petsc-3.4.2 2013-07-02</b></div>
<A NAME="SNESLineSearchPreCheckPicard"><H1>SNESLineSearchPreCheckPicard</H1></A>
Implements a correction that is sometimes useful to improve the convergence rate of Picard iteration
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscsnes.h"
PetscErrorCode SNESLineSearchPreCheckPicard(SNESLineSearch linesearch,Vec X,Vec Y,PetscBool *changed,void *ctx)
</PRE>
Logically Collective on <A HREF="../SNES/SNESLineSearch.html#SNESLineSearch">SNESLineSearch</A>
<P>
<H3><FONT COLOR="#CC3333">Input Arguments</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>linesearch </B></TD><TD>- linesearch context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>X </B></TD><TD>- base state for this step
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>Y </B></TD><TD>- initial correction
</TD></TR>
<P>
<H3><FONT COLOR="#CC3333">Output Arguments</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>Y </B></TD><TD>- correction, possibly modified
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>changed </B></TD><TD>- flag indicating that Y was modified
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Options Database Key</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_linesearch_precheck_picard </B></TD><TD>- activate this routine
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_linesearch_precheck_picard_angle </B></TD><TD>- angle
</TD></TR></TABLE>
<P>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
This function should be passed to <A HREF="../SNES/SNESLineSearchSetPreCheck.html#SNESLineSearchSetPreCheck">SNESLineSearchSetPreCheck</A>()
<P>
The justification for this method involves the linear convergence of a Picard iteration
so the Picard linearization should be provided in place of the "Jacobian". This correction
is generally not useful when using a Newton linearization.
<P>
<H3><FONT COLOR="#CC3333">Reference</FONT></H3>
Hindmarsh and Payne (1996) Time step limits for stable solutions of the ice sheet equation, Annals of Glaciology.
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../SNES/SNESLineSearchSetPreCheck.html#SNESLineSearchSetPreCheck">SNESLineSearchSetPreCheck</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>advanced
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/snes/linesearch/interface/linesearch.c.html#SNESLineSearchPreCheckPicard">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>
<BR><A HREF="../singleindex.html">Index of all manual pages</A>
<P><H3><FONT COLOR="#CC3333">Examples</FONT></H3>
<A HREF="../../../src/snes/examples/tutorials/ex15.c.html">src/snes/examples/tutorials/ex15.c.html</A><BR>
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