[Libmesh-devel] Implementing multigrid style projections through GenericProjector interface

[Boris B. <bor...@bu...>]

Hello all,

I've been spending some time thinking about how to neatly implement
multigrid projections through the existing  GenericProjector interface and
would like some input on the following points.

- In order to properly insert local projection matrices into the global
projection I need some additional information in the ProjectionAction
parameter of the GenericProjector. Specifically, I need access to the old
dof information (as well as the existing new dof info) as this dictates
where the local projection matrix gets inserted into the global one. While
it seemed originally that I could hijack the Fvalue parameter information
and squeeze old dof info in there, now this appears to be a problem since
Fvalue is also used in Fe all throughout the Ke/Fe solves.

- Additionally, it seems like we may need to update the ProjectionAction
interface to take in Ke and Fe as well. This would be needed in order to
accommodate non-nodal dofs. Ke^{-1} would for example be needed to insert
into projection matrix for non nodal dofs, and likely even for Q2 space as
well.

If this line of thinking is on the right track I would appreciate any
feedback regarding how best to deal with these issues, or any tips on how I
could avoid these problems in the first place.

Thanks in advance,
Boris Boutkov