Enable DUNE grid tests

[SoilRos]

For this to work it is additionally needed that

• Entities return the "correct"¹ number of faces (to count intersections in the tests).
• The refinement does not throw. Instead, it returns false when it cannot make a refinement.
• DUNE is at least version 2.10 due to https://gitlab.dune-project.org/core/dune-grid/-/merge_requests/734

Footnotes

1. "Correct" here means with respect to the topology of a cube which is what the number of corners says. This is not correct for deformed entities though. Hence, this goes from wrong-wrong, to simply wrong. ↩

[SoilRos]

jenkins build this serial please

[SoilRos]

jenkins build this serial please

[SoilRos]

The CI does not seem to have DUNE 2.10, hence, this cannot be tested there. For now, I only can assure that this works locally, but it would be nice to have an automated test so that we can see if the test from DUNE are broken.

[blattms]

We clearly indicate in our capabilities that we do not support entities with these co-dimensions.
Shouldn't the check in DUNE honor that?

Even if we add this, then these numbers would not refelect any collapsed entities.

[SoilRos]

To run the test yes. If I remember correctly, the test checks that the number of intersections is higher than the number of subentites of codimension 1. As I wrote in the footnote of the PR description, this just matches what we already say with the geometry type.

From my understanding, this function is just the short-hand of calling referenceElement<double,dimension>(type()).size(codim). IMO, the current behavior, which is returning 0, is a bug. This is independent on whether the types for entities of lower codimension can be instantiated or not.

[SoilRos]

As discussed privately, you are right in the sense that dune should not require this information if the grid does not have entities of that codimension enabled. I am thus proposing a check that confirms that entities and reference element counts coincide, and a fix that makes dune use the reference element instead of the entity information.

Naturally, this would be wrong one we try more degenerate code. But I think this is a good first step.

I added you as a reviewer in the dune side: See https://gitlab.dune-project.org/core/dune-grid/-/merge_requests/794.

[SoilRos]

I convert this PR to be a draft because dune 2.11 requires the grid to fulfill the grid concept check. And this will not work until

• the geometry type is returned as a value Return geometry by value (alternative 1) #885,
• the instantiations of template Codim<2>::Entity are disabled (see dune-grid!778), and
• the grid correctly handles the entities that cannot be handled (this original PR has some things missing for the tests to pass). See Make entity marking dune conformant #947.