vdim not considered when sizing element assembly data in EABilinearFormExtension::Assemble

[lindsayad]

I'm looking into writing some AssemblyLevel::FULL code for vector integrators. When doing that I noticed that the element assembly data does not consider vdim in its sizing

mfem/fem/bilinearform_ext.cpp

Line 898 in 4a17243

ea_data.SetSize(ne*elemDofs*elemDofs);

Is there a reason vdim is not considered here or is this something I can help develop?

[v-dobrev]

It is probably not taken into account because we don't have any vector (i.e. for vdim > 1) integrators that support EA. At least I don't see any. If you can work on adding support for this, that will be great!

Depending on the specific integrator, the local matrices can be full, vdim*elemDofs x vdim*elemDofs, or block-diagonal with reduced storage requirement. As a first step, we can just assume the local matrices are always full if that is what you need for your case. If you have block-diagonal structure, this information will probably need to be made available in some way to EABilinearFormExtension, so it can be used where needed, e.g. when performing the action of the form.

[lindsayad]

That makes sense to me. Thanks @v-dobrev !

[rcarson3]

I should probably upstream this at some point.... but this isn't hard to support as I've done in my own branch for the NonlinearForm: https://github.com/rcarson3/mfem/blob/exaconstit-dev/fem/nonlinearform_ext.cpp#L143-L241

[rcarson3]

I will note though if you look at the full assembly logic in that same file that if memory serves me correctly either the FillSparseMatrix or FillJAndData logic for the full assembly just assumes VDIM = 1 which I never had to chase down the fix for years ago...