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<div id="version" align=right><b>petsc-3.7.5 2017-01-01</b></div>
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<A NAME="SNESKSPSetUseEW"><H1>SNESKSPSetUseEW</H1></A>
Sets <A HREF="../SNES/SNES.html#SNES">SNES</A> use Eisenstat-Walker method for computing relative tolerance for linear solvers within an inexact Newton method.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscsnes.h"
PetscErrorCode SNESKSPSetUseEW(SNES snes,PetscBool flag)
</PRE>
Logically Collective on <A HREF="../SNES/SNES.html#SNES">SNES</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>snes </B></TD><TD>- <A HREF="../SNES/SNES.html#SNES">SNES</A> context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>flag </B></TD><TD>- <A HREF="../Sys/PETSC_TRUE.html#PETSC_TRUE">PETSC_TRUE</A> or <A HREF="../Sys/PETSC_FALSE.html#PETSC_FALSE">PETSC_FALSE</A>
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Options Database</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_ksp_ew </B></TD><TD>- use Eisenstat-Walker method for determining linear system convergence
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_ksp_ew_version ver </B></TD><TD>- version of Eisenstat-Walker method
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_ksp_ew_rtol0 <rtol0> </B></TD><TD>- Sets rtol0
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_ksp_ew_rtolmax <rtolmax> </B></TD><TD>- Sets rtolmax
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_ksp_ew_gamma <gamma> </B></TD><TD>- Sets gamma
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_ksp_ew_alpha <alpha> </B></TD><TD>- Sets alpha
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_ksp_ew_alpha2 <alpha2> </B></TD><TD>- Sets alpha2
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_ksp_ew_threshold <threshold> </B></TD><TD>- Sets threshold
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
Currently, the default is to use a constant relative tolerance for
the inner linear solvers. Alternatively, one can use the
Eisenstat-Walker method, where the relative convergence tolerance
is reset at each Newton iteration according progress of the nonlinear
solver.
<P>
<P>
<H3><FONT COLOR="#CC3333">Reference</FONT></H3>
S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
inexact Newton method", SISC 17 (1), pp.16-32, 1996.
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../SNES/SNES.html#SNES">SNES</A>, <A HREF="../KSP/KSP.html#KSP">KSP</A>, Eisenstat, Walker, convergence, test, inexact, Newton
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../SNES/SNESKSPGetUseEW.html#SNESKSPGetUseEW">SNESKSPGetUseEW</A>(), <A HREF="../SNES/SNESKSPGetParametersEW.html#SNESKSPGetParametersEW">SNESKSPGetParametersEW</A>(), <A HREF="../SNES/SNESKSPSetParametersEW.html#SNESKSPSetParametersEW">SNESKSPSetParametersEW</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>advanced
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/snes/interface/snes.c.html#SNESKSPSetUseEW">src/snes/interface/snes.c</A>
<BR><A HREF="./index.html">Index of all SNES routines</A>
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