[Libmesh-devel] Multigrid Projection Matrixes with Periodic Boundaries

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

Hello again - Ive been doing further work on the multigrid projection
matrix front and things are starting to look fairly stable overall!

The main issue that has resurfaced is the treatment of the boundary
conditions. Though it seems that for most cases convergence rates are as
expected, there clearly still remains a problem with the periodic cases in
even the simplest 1D/2D test problems. I think that the natural way forward
is that we need to constrain the element matrixes as we are building up the
projection matrixes, the first place that comes to mind would be right
after we have set the target_matrix dof information inside the
MatrixFillAction component of the GenericProjector. The issue then is that
the usual  DofMap::constrain_element_matrix implementations only have
DenseMatrix versions whereas here it seems we would need Sparse ones in the
projection matrix situation.

In essence I'd like to verify that creating these analagous DofMap calls is
the right track to follow as Im still a bit shakey with the BC and DSNA
components of the library - so I'd appreciate any input as to the viability
of this gameplan or if an altogether different course of action is needed.


Thanks in advance for the input,
Boris