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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML3.2 EN">
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<TITLE>KSPSetOptionsPrefix</TITLE>
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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/KSP/KSPSetOptionsPrefix.html "><small>Report Typos and Errors</small></a></div>
<A NAME="KSPSetOptionsPrefix"><H1>KSPSetOptionsPrefix</H1></A>
Sets the prefix used for searching for all <A HREF="../KSP/KSP.html#KSP">KSP</A> options in the database.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscksp.h"
PetscErrorCode KSPSetOptionsPrefix(KSP ksp,const char prefix[])
</PRE>
Logically Collective on <A HREF="../KSP/KSP.html#KSP">KSP</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>ksp </B></TD><TD>- the Krylov context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>prefix </B></TD><TD>- the prefix string to prepend to all <A HREF="../KSP/KSP.html#KSP">KSP</A> option requests
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
A hyphen (-) must NOT be given at the beginning of the prefix name.
The first character of all runtime options is AUTOMATICALLY the
hyphen.
<P>
For example, to distinguish between the runtime options for two
different <A HREF="../KSP/KSP.html#KSP">KSP</A> contexts, one could call
<PRE>
<A HREF="../KSP/KSPSetOptionsPrefix.html#KSPSetOptionsPrefix">KSPSetOptionsPrefix</A>(ksp1,"sys1_")
<A HREF="../KSP/KSPSetOptionsPrefix.html#KSPSetOptionsPrefix">KSPSetOptionsPrefix</A>(ksp2,"sys2_")
</PRE>
<P>
This would enable use of different options for each system, such as
<PRE>
-sys1_ksp_type gmres -sys1_ksp_rtol 1.e-3
-sys2_ksp_type bcgs -sys2_ksp_rtol 1.e-4
</PRE>
<P>
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../KSP/KSP.html#KSP">KSP</A>, set, options, prefix, database
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../KSP/KSPAppendOptionsPrefix.html#KSPAppendOptionsPrefix">KSPAppendOptionsPrefix</A>(), <A HREF="../KSP/KSPGetOptionsPrefix.html#KSPGetOptionsPrefix">KSPGetOptionsPrefix</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>advanced
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/ksp/ksp/interface/itcl.c.html#KSPSetOptionsPrefix">src/ksp/ksp/interface/itcl.c</A>
<BR><A HREF="./index.html">Index of all KSP 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/ex42.c.html">src/ksp/ksp/examples/tutorials/ex42.c.html</A><BR>
<A HREF="../../../src/ksp/ksp/examples/tutorials/ex43.c.html">src/ksp/ksp/examples/tutorials/ex43.c.html</A><BR>
<A HREF="../../../src/ksp/ksp/examples/tutorials/ex49.c.html">src/ksp/ksp/examples/tutorials/ex49.c.html</A><BR>
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