<div class="gmail_quote">On Fri, Dec 3, 2010 at 06:02, Vijay S. Mahadevan <span dir="ltr"><<a href="mailto:vijay.m@gmail.com">vijay.m@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div id=":3dg">I was wondering whether the MG preconditioner object is generic enough<br>
to work out of the box like say ILU or SOR. To elaborate on this, if<br>
I can provide the number of levels, restriction and prolongation<br>
operators for each level and the system operators along with vectors<br>
allocated for solution and rhs, would it work as a preconditioner for<br>
my given problem and a prescribed rhs at the finest level of PCMG. Or<br>
does it need some knowledge of the fine and coarser meshes to perform<br>
the MG operations correctly ?</div></blockquote></div><br><div>PCMG is purely algebraic so it does not need knowledge about the mesh, just interpolation/restriction. However, if you want to use non-Galerkin coarse operators, then you will need a coarse mesh (this is something that DMMG facilitates). Look at section 4.4.7 of the users manual for explanation of using PCMG. There don't seem to be any well-documented examples using PCMG directly, but you might want to look at src/ksp/examples/tests/ex19.c or src/snes/examples/tests/ex11.c.</div>
<div><br></div><div>Jed</div>