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<div id="version" align=right><b>petsc-3.7.5 2017-01-01</b></div>
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<A NAME="SNESFAS"><H1>SNESFAS</H1></A>
Full Approximation Scheme nonlinear multigrid solver. The nonlinear problem is solved by correction using coarse versions
of the nonlinear problem. This problem is perturbed so that a projected
solution of the fine problem elicits no correction from the coarse problem.
<P>
<H3><FONT COLOR="#CC3333">Options Database</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_fas_levels </B></TD><TD>- The number of levels
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_fas_cycles<1> </B></TD><TD>- The number of cycles -- 1 for V, 2 for W
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_fas_type<additive,multiplicative,full,kaskade> </B></TD><TD>- Additive or multiplicative cycle
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_fas_galerkin<<A HREF="../Sys/PETSC_FALSE.html#PETSC_FALSE">PETSC_FALSE</A>> </B></TD><TD>- Form coarse problems by projection back upon the fine problem
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_fas_smoothup<1> </B></TD><TD>- The number of iterations of the post-smoother
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_fas_smoothdown<1> </B></TD><TD>- The number of iterations of the pre-smoother
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_fas_monitor </B></TD><TD>- Monitor progress of all of the levels
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-snes_fas_full_downsweep<<A HREF="../Sys/PETSC_FALSE.html#PETSC_FALSE">PETSC_FALSE</A>> </B></TD><TD>- call the downsmooth on the initial downsweep of full FAS
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-fas_levels_snes_ </B></TD><TD>- <A HREF="../SNES/SNES.html#SNES">SNES</A> options for all smoothers
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-fas_levels_cycle_snes_ </B></TD><TD>- <A HREF="../SNES/SNES.html#SNES">SNES</A> options for all cycles
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-fas_levels_i_snes_ </B></TD><TD>- <A HREF="../SNES/SNES.html#SNES">SNES</A> options for the smoothers on level i
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-fas_levels_i_cycle_snes_ </B></TD><TD>- <A HREF="../SNES/SNES.html#SNES">SNES</A> options for the cycle on level i
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-fas_coarse_snes_ </B></TD><TD>- <A HREF="../SNES/SNES.html#SNES">SNES</A> options for the coarsest smoother
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
The organization of the FAS solver is slightly different from the organization of <A HREF="../PC/PCMG.html#PCMG">PCMG</A>
As each level has smoother <A HREF="../SNES/SNES.html#SNES">SNES</A> instances(down and potentially up) and a cycle <A HREF="../SNES/SNES.html#SNES">SNES</A> instance.
The cycle <A HREF="../SNES/SNES.html#SNES">SNES</A> instance may be used for monitoring convergence on a particular level.
<P>
<P>
<H3><FONT COLOR="#CC3333">References</FONT></H3>
<DT><B>1. </B> -Peter R. Brune, Matthew G. Knepley, Barry F. Smith, and Xuemin Tu, "Composing Scalable Nonlinear Algebraic Solvers",
SIAM Review, 57(4), 2015
<br>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../PC/PCMG.html#PCMG">PCMG</A>, <A HREF="../SNES/SNESCreate.html#SNESCreate">SNESCreate</A>(), <A HREF="../SNES/SNES.html#SNES">SNES</A>, <A HREF="../SNES/SNESSetType.html#SNESSetType">SNESSetType</A>(), <A HREF="../SNES/SNESType.html#SNESType">SNESType</A> (for list of available types)
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>beginner
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/snes/impls/fas/fas.c.html#SNESFAS">src/snes/impls/fas/fas.c</A>
<BR><A HREF="./index.html">Index of all SNES 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/snes/examples/tutorials/ex12.c.html">src/snes/examples/tutorials/ex12.c.html</A><BR>
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