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<TITLE>SNESLineSearchGetParams</TITLE>
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<A NAME="SNESLineSearchGetParams"><H1>SNESLineSearchGetParams</H1></A>
Gets the parameters associated with the line search routine in the Newton-based method <A HREF="../SNES/SNESLS.html#SNESLS">SNESLS</A>.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscsnes.h"
PetscErrorCode PETSCSNES_DLLEXPORT SNESLineSearchGetParams(SNES snes,PetscReal *alpha,PetscReal *maxstep,PetscReal *steptol)
</PRE>
Not collective, but any processor will return the same values
<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>snes </B></TD><TD>- The nonlinear context obtained from <A HREF="../SNES/SNESCreate.html#SNESCreate">SNESCreate</A>()
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>alpha </B></TD><TD>- The scalar such that .5*f_{n+1} . f_{n+1} <= .5*f_n . f_n - alpha |f_n . J . f_n|
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>maxstep </B></TD><TD>- The maximum norm of the update vector
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>steptol </B></TD><TD>- The minimum norm fraction of the original step after scaling
</TD></TR></TABLE>
<P>
<P>
<H3><FONT COLOR="#CC3333">Note</FONT></H3>
To not get a certain parameter, pass in <A HREF="../Sys/PETSC_NULL.html#PETSC_NULL">PETSC_NULL</A>
<P>
We are finding the zero of f() so the one dimensional minimization problem we are
solving in the line search is minimize .5*f(x_n + lambda*step_direction) . f(x_n + lambda*step_direction)
<P>
Contributed by: Mathew Knepley
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../SNES/SNES.html#SNES">SNES</A>, nonlinear, set, line search parameters
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../SNES/SNESLineSearchSetParams.html#SNESLineSearchSetParams">SNESLineSearchSetParams</A>(), <A HREF="../SNES/SNESLineSearchSet.html#SNESLineSearchSet">SNESLineSearchSet</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>intermediate
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/snes/impls/ls/lsparams.c.html#SNESLineSearchGetParams">src/snes/impls/ls/lsparams.c</A>
<BR><A HREF="./index.html">Index of all SNES routines</A>
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