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<A NAME="KSPSetTolerances"><H1>KSPSetTolerances</H1></A>
Sets the relative, absolute, divergence, and maximum iteration tolerances used by the default <A HREF="../KSP/KSP.html#KSP">KSP</A> convergence testers.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscksp.h"
PetscErrorCode PETSCKSP_DLLEXPORT KSPSetTolerances(KSP ksp,PetscReal rtol,PetscReal abstol,PetscReal dtol,PetscInt maxits)
</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>- the Krylov subspace context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>rtol </B></TD><TD>- the relative convergence tolerance
(relative decrease in the residual norm)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>abstol </B></TD><TD>- the absolute convergence tolerance
(absolute <A HREF="../Sys/size.html#size">size</A> of the residual norm)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>dtol </B></TD><TD>- the divergence tolerance
(amount residual can increase before <A HREF="../KSP/KSPDefaultConverged.html#KSPDefaultConverged">KSPDefaultConverged</A>()
concludes that the method is diverging)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>maxits </B></TD><TD>- maximum number of iterations to use
</TD></TR></TABLE>
<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>-ksp_atol <abstol> </B></TD><TD>- Sets abstol
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-ksp_rtol <rtol> </B></TD><TD>- Sets rtol
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-ksp_divtol <dtol> </B></TD><TD>- Sets dtol
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-ksp_max_it <maxits> </B></TD><TD>- Sets maxits
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
Use <A HREF="../Sys/PETSC_DEFAULT.html#PETSC_DEFAULT">PETSC_DEFAULT</A> to retain the default value of any of the tolerances.
<P>
See <A HREF="../KSP/KSPDefaultConverged.html#KSPDefaultConverged">KSPDefaultConverged</A>() for details on the use of these parameters
in the default convergence test. See also <A HREF="../KSP/KSPSetConvergenceTest.html#KSPSetConvergenceTest">KSPSetConvergenceTest</A>()
for setting user-defined stopping criteria.
<P>
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
<A HREF="../KSP/KSP.html#KSP">KSP</A>, set, tolerance, absolute, relative, divergence,
<BR>convergence, maximum, iterations
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../KSP/KSPGetTolerances.html#KSPGetTolerances">KSPGetTolerances</A>(), <A HREF="../KSP/KSPDefaultConverged.html#KSPDefaultConverged">KSPDefaultConverged</A>(), <A HREF="../KSP/KSPSetConvergenceTest.html#KSPSetConvergenceTest">KSPSetConvergenceTest</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>intermediate
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/ksp/ksp/interface/itfunc.c.html#KSPSetTolerances">src/ksp/ksp/interface/itfunc.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/ex1.c.html">src/ksp/ksp/examples/tutorials/ex1.c.html</A><BR>
<A HREF="../../../src/ksp/ksp/examples/tutorials/ex2.c.html">src/ksp/ksp/examples/tutorials/ex2.c.html</A><BR>
<A HREF="../../../src/ksp/ksp/examples/tutorials/ex7.c.html">src/ksp/ksp/examples/tutorials/ex7.c.html</A><BR>
<A HREF="../../../src/ksp/ksp/examples/tutorials/ex8.c.html">src/ksp/ksp/examples/tutorials/ex8.c.html</A><BR>
<A HREF="../../../src/ksp/ksp/examples/tutorials/ex15.c.html">src/ksp/ksp/examples/tutorials/ex15.c.html</A><BR>
<A HREF="../../../src/ksp/ksp/examples/tutorials/ex23.c.html">src/ksp/ksp/examples/tutorials/ex23.c.html</A><BR>
<A HREF="../../../src/ksp/ksp/examples/tutorials/ex1f.F.html">src/ksp/ksp/examples/tutorials/ex1f.F.html</A><BR>
<A HREF="../../../src/ksp/ksp/examples/tutorials/ex2f.F.html">src/ksp/ksp/examples/tutorials/ex2f.F.html</A><BR>
<A HREF="../../../src/ksp/ksp/examples/tutorials/ex15f.F.html">src/ksp/ksp/examples/tutorials/ex15f.F.html</A><BR>
<A HREF="../../../src/ksp/ksp/examples/tutorials/ex21f.F.html">src/ksp/ksp/examples/tutorials/ex21f.F.html</A><BR>
<A HREF="../../../src/snes/examples/tutorials/ex1.c.html">src/snes/examples/tutorials/ex1.c.html</A><BR>
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