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

[Jed Brown]

On Fri, Dec 3, 2010 at 19:29, Vijay S. Mahadevan <vijay.m at gmail.com> wrote:

> Jed and Dave, thanks for the explanation. Now I do understand that the
> MG PC is generic if I have restriction/prolongation operators for
> every level. But I do not have the fine grid operator on hand
> explicitly (only a shell matrix with MatMult) and technically all my
> coarser grid operators will also be matrix-free. I was originally
> planning to hand these shell matrices to petsc as the coarse
> operators but can petsc do this by itself with only access to the fine
> grid operator ?
>

PETSc cannot magically create intermediate-level shell operators.  If you
want to do everything matrix-free, then you have to provide everything that
needs to be "smart": restriction/interpolation, smoothers, and residuals.

Jed
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