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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/KSPConvergedDefault.html "><small>Report Typos and Errors</small></a></div>
<A NAME="KSPConvergedDefault"><H1>KSPConvergedDefault</H1></A>
Determines convergence of the linear iterative solvers by default
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscksp.h"
PetscErrorCode KSPConvergedDefault(KSP ksp,PetscInt n,PetscReal rnorm,KSPConvergedReason *reason,void *ctx)
</PRE>
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>- iterative context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>n </B></TD><TD>- iteration number
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>rnorm </B></TD><TD>- residual norm (may be estimated, depending on the method may be the preconditioned residual norm)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>ctx </B></TD><TD>- convergence context which must be created by <A HREF="../KSP/KSPConvergedDefaultCreate.html#KSPConvergedDefaultCreate">KSPConvergedDefaultCreate</A>()
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Output Parameter</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>positive </B></TD><TD>- if the iteration has converged;
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>negative </B></TD><TD>- if residual norm exceeds divergence threshold;
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>0 </B></TD><TD>- otherwise.
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
<A HREF="../KSP/KSPConvergedDefault.html#KSPConvergedDefault">KSPConvergedDefault</A>() reaches convergence when rnorm < MAX (rtol * rnorm_0, abstol);
Divergence is detected if rnorm > dtol * rnorm_0,
<P>
<H3><FONT COLOR="#CC3333">where</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>rtol = relative tolerance,</B></TD><TD>- . abstol = absolute tolerance.
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>dtol = divergence tolerance,</B></TD><TD>- - rnorm_0 is the two norm of the right hand side. When initial guess is non-zero you
can call <A HREF="../KSP/KSPConvergedDefaultSetUIRNorm.html#KSPConvergedDefaultSetUIRNorm">KSPConvergedDefaultSetUIRNorm</A>() to use the norm of (b - A*(initial guess))
as the starting point for relative norm convergence testing, that is as rnorm_0
</TD></TR>
<P>
Use <A HREF="../KSP/KSPSetTolerances.html#KSPSetTolerances">KSPSetTolerances</A>() to alter the defaults for rtol, abstol, dtol.
<P>
Use <A HREF="../KSP/KSPSetNormType.html#KSPSetNormType">KSPSetNormType</A>() (or -ksp_norm_type <none,preconditioned,unpreconditioned,natural>) to change the norm used for computing rnorm
<P>
The precise values of reason are macros such as <A HREF="../KSP/KSP_CONVERGED_RTOL.html#KSP_CONVERGED_RTOL">KSP_CONVERGED_RTOL</A>, which are defined in petscksp.h.
<P>
This routine is used by <A HREF="../KSP/KSP.html#KSP">KSP</A> by default so the user generally never needs call it directly.
<P>
Use <A HREF="../KSP/KSPSetConvergenceTest.html#KSPSetConvergenceTest">KSPSetConvergenceTest</A>() to provide your own test instead of using this one.
<P>
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../KSP/KSP.html#KSP">KSP</A>, default, convergence, residual
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../KSP/KSPSetConvergenceTest.html#KSPSetConvergenceTest">KSPSetConvergenceTest</A>(), <A HREF="../KSP/KSPSetTolerances.html#KSPSetTolerances">KSPSetTolerances</A>(), <A HREF="../KSP/KSPConvergedSkip.html#KSPConvergedSkip">KSPConvergedSkip</A>(), <A HREF="../KSP/KSPConvergedReason.html#KSPConvergedReason">KSPConvergedReason</A>, <A HREF="../KSP/KSPGetConvergedReason.html#KSPGetConvergedReason">KSPGetConvergedReason</A>(),
<BR><A HREF="../KSP/KSPConvergedDefaultSetUIRNorm.html#KSPConvergedDefaultSetUIRNorm">KSPConvergedDefaultSetUIRNorm</A>(), <A HREF="../KSP/KSPConvergedDefaultSetUMIRNorm.html#KSPConvergedDefaultSetUMIRNorm">KSPConvergedDefaultSetUMIRNorm</A>(), <A HREF="../KSP/KSPConvergedDefaultCreate.html#KSPConvergedDefaultCreate">KSPConvergedDefaultCreate</A>(), <A HREF="../KSP/KSPConvergedDefaultDestroy.html#KSPConvergedDefaultDestroy">KSPConvergedDefaultDestroy</A>()
<P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>intermediate
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/ksp/ksp/interface/iterativ.c.html#KSPConvergedDefault">src/ksp/ksp/interface/iterativ.c</A>
<BR><A HREF="./index.html">Index of all KSP routines</A>
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