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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/KSPSetNormType.html "><small>Report Typos and Errors</small></a></div>
<A NAME="KSPSetNormType"><H1>KSPSetNormType</H1></A>
Sets the norm that is used for convergence testing.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscksp.h"
PetscErrorCode KSPSetNormType(KSP ksp,KSPNormType normtype)
</PRE>
Logically Collective on <A HREF="../KSP/KSP.html#KSP">KSP</A>
<P>
<H3><FONT COLOR="#CC3333">Input Parameter</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>ksp </B></TD><TD>- Krylov solver context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>normtype </B></TD><TD>- one of
</TD></TR></TABLE>
<pre>
<A HREF="../KSP/KSP_NORM_NONE.html#KSP_NORM_NONE">KSP_NORM_NONE</A> - skips computing the norm, this should only be used if you are using
</pre>
<pre>
the Krylov method as a smoother with a fixed small number of iterations.
</pre>
<pre>
Implicitly sets <A HREF="../KSP/KSPConvergedSkip.html#KSPConvergedSkip">KSPConvergedSkip</A> as <A HREF="../KSP/KSP.html#KSP">KSP</A> convergence test.
</pre>
<pre>
<A HREF="../KSP/KSP_NORM_PRECONDITIONED.html#KSP_NORM_PRECONDITIONED">KSP_NORM_PRECONDITIONED</A> - the default for left preconditioned solves, uses the l2 norm
</pre>
<pre>
of the preconditioned residual P^{-1}(b - A x)
</pre>
<pre>
<A HREF="../KSP/KSP_NORM_UNPRECONDITIONED.html#KSP_NORM_UNPRECONDITIONED">KSP_NORM_UNPRECONDITIONED</A> - uses the l2 norm of the true b - Ax residual.
</pre>
<pre>
<A HREF="../KSP/KSP_NORM_NATURAL.html#KSP_NORM_NATURAL">KSP_NORM_NATURAL</A> - supported by <A HREF="../KSP/KSPCG.html#KSPCG">KSPCG</A>, <A HREF="../KSP/KSPCR.html#KSPCR">KSPCR</A>, <A HREF="../KSP/KSPCGNE.html#KSPCGNE">KSPCGNE</A>, <A HREF="../KSP/KSPCGS.html#KSPCGS">KSPCGS</A>
</pre>
<P>
<P>
<H3><FONT COLOR="#CC3333">Options Database Key</FONT></H3>
<DT><B>-ksp_norm_type <none,preconditioned,unpreconditioned,natural></B> -
Notes:
Not all combinations of preconditioner side (see <A HREF="../KSP/KSPSetPCSide.html#KSPSetPCSide">KSPSetPCSide</A>()) and norm type are supported by all Krylov methods.
If only one is set, PETSc tries to automatically change the other to find a compatible pair. If no such combination
is supported, PETSc will generate an error.
<br>
<P>
<H3><FONT COLOR="#CC3333">Developer Notes</FONT></H3>
Supported combinations of norm and preconditioner side are set using <A HREF="../KSP/KSPSetSupportedNorm.html#KSPSetSupportedNorm">KSPSetSupportedNorm</A>().
<P>
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../KSP/KSP.html#KSP">KSP</A>, create, context, norms
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../KSP/KSPSetUp.html#KSPSetUp">KSPSetUp</A>(), <A HREF="../KSP/KSPSolve.html#KSPSolve">KSPSolve</A>(), <A HREF="../KSP/KSPDestroy.html#KSPDestroy">KSPDestroy</A>(), <A HREF="../KSP/KSPConvergedSkip.html#KSPConvergedSkip">KSPConvergedSkip</A>(), <A HREF="../KSP/KSPSetCheckNormIteration.html#KSPSetCheckNormIteration">KSPSetCheckNormIteration</A>(), <A HREF="../KSP/KSPSetPCSide.html#KSPSetPCSide">KSPSetPCSide</A>(), <A HREF="../KSP/KSPGetPCSide.html#KSPGetPCSide">KSPGetPCSide</A>(), <A HREF="../KSP/KSPNormType.html#KSPNormType">KSPNormType</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/itcreate.c.html#KSPSetNormType">src/ksp/ksp/interface/itcreate.c</A>
<BR><A HREF="./index.html">Index of all KSP routines</A>
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