exterior facet integral is not capable to integrate on actual exterior facets of restricted domain

[Martin Eigel]

The example in this discussion should solve a DG discretised problem on a nodal patch (i.e. all elements which contain a certain vertex). For this, Restriction was employed to obtain a restricted function space. However, it turns out that the exterior facet integrals can not be restricted accordingly with the current implementation.

[Jan Blechta]

Duplicate of #190.

[Martin Sandve Alnæs]

Jan Blechta: I don't see the relation between this and #190.

[Jan Blechta]

@martinal

Issue #190:

Make elements, geometric quantities, expressions, measures, integrals, forms, and form data aware of domains.

This issue happens because ds measure is not aware of restriction and it does not redefine the meaning of "exterior".

I believed that Restriction and ufl.Domain are going to be closely related. Am I wrong?

[Martin Sandve Alnæs]

At least in this iteration, ufl.Domain represents a Mesh only, and issue #190 is about merging of an existing body of work and not open for additional features. It may be a piece of the work needed for #137 but it doesn't solve it so it's not a duplication.

In the bigger picture, I'm leaning towards not mirroring Restriction in ufl and generated code at all and handling that purely in dolfin. I'm open to being wrong about that if someone demonstrates the need later.

[Prof Garth Wells]

Will be addressed in future MeshView class and associated machinery.