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<A NAME="PCMG"><H1>PCMG</H1></A>
Use multigrid preconditioning. This preconditioner requires you provide additional information about the coarser grid matrices and restriction/interpolation operators.
<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_mg_levels <nlevels> </B></TD><TD>- number of levels including finest
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_mg_cycles v or w</B></TD><TD>- . -pc_mg_smoothup <n> - number of smoothing steps after interpolation
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_mg_smoothdown <n> </B></TD><TD>- number of smoothing steps before applying restriction operator
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_mg_type <additive,multiplicative,full,cascade> </B></TD><TD>- multiplicative is the default
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_mg_log </B></TD><TD>- log information about time spent on each level of the solver
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_mg_monitor </B></TD><TD>- print information on the multigrid convergence
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_mg_galerkin </B></TD><TD>- use Galerkin process to compute coarser operators
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-pc_mg_dump_matlab </B></TD><TD>- dumps the matrices for each level and the restriction/interpolation matrices
to the Socket viewer for reading from MATLAB.
</TD></TR></TABLE>
<P>
Notes: By default this uses GMRES on the fine grid smoother so this should be used with <A HREF="../KSP/KSPFGMRES.html#KSPFGMRES">KSPFGMRES</A> or the smoother changed to not use GMRES
<P>
<P>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../PC/PCCreate.html#PCCreate">PCCreate</A>(), <A HREF="../PC/PCSetType.html#PCSetType">PCSetType</A>(), <A HREF="../PC/PCType.html#PCType">PCType</A> (for list of available types), <A HREF="../PC/PC.html#PC">PC</A>, <A HREF="../PC/PCMGType.html#PCMGType">PCMGType</A>, <A HREF="../PC/PCEXOTIC.html#PCEXOTIC">PCEXOTIC</A>
<BR><A HREF="../PC/PCMGSetLevels.html#PCMGSetLevels">PCMGSetLevels</A>(), <A HREF="../PC/PCMGGetLevels.html#PCMGGetLevels">PCMGGetLevels</A>(), <A HREF="../PC/PCMGSetType.html#PCMGSetType">PCMGSetType</A>(), <A HREF="../PC/PCMGSetCycleType.html#PCMGSetCycleType">PCMGSetCycleType</A>(), <A HREF="../PC/PCMGSetNumberSmoothDown.html#PCMGSetNumberSmoothDown">PCMGSetNumberSmoothDown</A>(),
<A HREF="../PC/PCMGSetNumberSmoothUp.html#PCMGSetNumberSmoothUp">PCMGSetNumberSmoothUp</A>(), <A HREF="../PC/PCMGGetCoarseSolve.html#PCMGGetCoarseSolve">PCMGGetCoarseSolve</A>(), <A HREF="../PC/PCMGSetResidual.html#PCMGSetResidual">PCMGSetResidual</A>(), <A HREF="../PC/PCMGSetInterpolation.html#PCMGSetInterpolation">PCMGSetInterpolation</A>(),
<A HREF="../PC/PCMGSetRestriction.html#PCMGSetRestriction">PCMGSetRestriction</A>(), <A HREF="../PC/PCMGGetSmoother.html#PCMGGetSmoother">PCMGGetSmoother</A>(), <A HREF="../PC/PCMGGetSmootherUp.html#PCMGGetSmootherUp">PCMGGetSmootherUp</A>(), <A HREF="../PC/PCMGGetSmootherDown.html#PCMGGetSmootherDown">PCMGGetSmootherDown</A>(),
PCMGSetCycleTypeOnLevel(), <A HREF="../PC/PCMGSetRhs.html#PCMGSetRhs">PCMGSetRhs</A>(), <A HREF="../PC/PCMGSetX.html#PCMGSetX">PCMGSetX</A>(), <A HREF="../PC/PCMGSetR.html#PCMGSetR">PCMGSetR</A>()
<P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>intermediate
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/ksp/pc/impls/mg/mg.c.html#PCMG">src/ksp/pc/impls/mg/mg.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/ex42.c.html">src/ksp/ksp/examples/tutorials/ex42.c.html</A><BR>
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