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<div id="version" align=right><b>petsc-3.4.2 2013-07-02</b></div>
<A NAME="PCSORSetSymmetric"><H1>PCSORSetSymmetric</H1></A>
Sets the SOR preconditioner to use symmetric (SSOR), backward, or forward relaxation. The local variants perform SOR on each processor. By default forward relaxation is used.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscpc.h"
PetscErrorCode PCSORSetSymmetric(PC pc,MatSORType flag)
</PRE>
Logically Collective on <A HREF="../PC/PC.html#PC">PC</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>pc </B></TD><TD>- the preconditioner context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>flag </B></TD><TD>- one of the following
</TD></TR></TABLE>
<PRE>
SOR_FORWARD_SWEEP
SOR_BACKWARD_SWEEP
SOR_SYMMETRIC_SWEEP
SOR_LOCAL_FORWARD_SWEEP
SOR_LOCAL_BACKWARD_SWEEP
SOR_LOCAL_SYMMETRIC_SWEEP
</PRE>
<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>-pc_sor_symmetric </B></TD><TD>- Activates symmetric version
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_sor_backward </B></TD><TD>- Activates backward version
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_sor_local_forward </B></TD><TD>- Activates local forward version
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_sor_local_symmetric </B></TD><TD>- Activates local symmetric version
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_sor_local_backward </B></TD><TD>- Activates local backward version
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
To use the Eisenstat trick with SSOR, employ the <A HREF="../PC/PCEISENSTAT.html#PCEISENSTAT">PCEISENSTAT</A> preconditioner,
which can be chosen with the option
<DT><B>-pc_type eisenstat </B> -Activates Eisenstat trick
<br>
<P>
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../PC/PC.html#PC">PC</A>, SOR, SSOR, set, relaxation, sweep, forward, backward, symmetric
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../PC/PCEisenstatSetOmega.html#PCEisenstatSetOmega">PCEisenstatSetOmega</A>(), <A HREF="../PC/PCSORSetIterations.html#PCSORSetIterations">PCSORSetIterations</A>(), <A HREF="../PC/PCSORSetOmega.html#PCSORSetOmega">PCSORSetOmega</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>intermediate
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/ksp/pc/impls/sor/sor.c.html#PCSORSetSymmetric">src/ksp/pc/impls/sor/sor.c</A>
<BR><A HREF="./index.html">Index of all PC 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/ksp/ksp/examples/tutorials/ex21f.F.html">src/ksp/ksp/examples/tutorials/ex21f.F.html</A><BR>
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