[petsc-users] Is PCMG a generic PC object ?

[Jed Brown]

On Fri, Dec 3, 2010 at 06:02, Vijay S. Mahadevan <vijay.m at gmail.com> wrote:

> I was wondering whether the MG preconditioner object is generic enough
> to work out of the box like say ILU or SOR.  To elaborate on this, if
> I can provide the number of levels, restriction and prolongation
> operators for each level and the system operators along with vectors
> allocated for solution and rhs, would it work as a preconditioner for
> my given problem and a prescribed rhs at the finest level of PCMG. Or
> does it need some knowledge of the fine and coarser meshes to perform
> the MG operations correctly ?
>

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.

Jed
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