Change sharedtria dof distribution to match distributed tria

[tcclevenger]

This was discussed here: #3078 (comment)
Talking with @tjhei, we felt it best to change from "coin flip" assignment to "smallest subdomain" assignment for those active dofs on the interface between two subdomains of a p::shared::T so that we match the distribution in p::distributed::T (this is also how we chose to distribute mg dofs for p::shared::T).
Note:

• There are 4 different tests (16 total runs) that we expect to fail with this change. This is due to the fact that each of these test output n_locally_owned_dofs. This value will obviously change when we change the way in which we break ties along the interface.
• I have added two tests, i) testing against a p4est mesh for accuracy against p::distributed::T and ii) creating an adaptive mesh and outputting the owned dofs for each subdomain and dof numbering for each cell.
• I changed some filenames from tests I wrote for a previous pull request. Just a wording change.

[davydden]

/run-tests

[tjhei]

you need to put p4est into the filename

[agrayver]

For the record: DoFTools::subdomain_wise (or, more specifically, DoFTools::get_subdomain_association) also uses the coin flip strategy and this patch does not change it (either intentionally or not).

[tjhei]

(either intentionally or not).

Yes. I was thinking about this yesterday. Those functions can go away. I will make a PR that deprecates them.

[bangerth]

This would deserve a changelog entry in the "incompatibilities" section.

[tcclevenger]

I'm a bit curious as to why the checks actually passed considering I have not yet fixed the test which fail to pass on my computer due to the change. Looking at the build details it doesn't appear to have run any sharedtria tests. I just still go back and update these, correct?

[bangerth]

Yes, you need to update these anyway. The tester only runs a subset of the sequential tests because running the entire test suite would take too long.

[davydden]

I have not yet fixed the test which fail to pass on my computer due to the change

let us know when you check locally that all relevant tests pass with this PR. I put a WIP tag for now...

[tcclevenger]

All tests for sharedtria now pass.

[tcclevenger]

I've added the changelog entry and all relevant test have passed. Let me know if there are any other changes needed, if not everything should be good to go. Thanks!

[jppelteret]

@tjhei @davydden @kronbichler Can this be merged?

[davydden]

I have no further comments, ok to merge as far as I am concerned.

[tjhei]

I will go ahead and press "merge" then.