[Libmesh-devel] EquationSystem Reinit with Refinement

[Tim A. <tra...@bu...>]

I have been looking into refactoring EquationSystem::reinit() with the
original motivation of preserving refinement flags for apps (such as GRINS)
that call refine_and_coarsen() and then es->reinit().
refine/coarsen_elements() end up getting called twice (once outside reinit,
and then again inside), and the second calls clear out the JUST_REFINED and
JUST_COARSENED flags, breaking some of my GRINS QoI code.

I created 2 simple unit tests in libMesh to check refinement flags both
when the user calls refine_and_coarsen_elements() and then es->reinit()
(refine-then-reinit), as well as when the user just sets the refinement
flags and calls es->reinit() to do the actual refinement
(reinit-and-refine). These 2 tests can be found here
<https://github.com/tradowsk/libmesh/commit/a3bdd55d24a4f7cad16efd0041caa9934fb6117f#diff-b37b7959e5e90cfb6e8e35e3cf832cd5R121>
.

However, I believe I have discovered an issue with the current
implementation of ES::reinit(). In the reinit-and-refine case (my
testReinitRefinePreserveFlags test), an assert gets tripped here
<https://github.com/libMesh/libmesh/blob/master/include/base/dof_object.h#L807>.
Additionally, I modified the GRINS AMR code to do reinit-and-refine and
tripped the same assert on the first adaptive refinement of a QoI
calculation.

I was able to find a fix for the refine-then-reinit case, which will pass
my testRefineThenReinitPreserveFlags libMesh test, as well as a few tests I
have in GRINS.

But I have been unable to find a fix for the reinit-and-refine case. I have
tried:

1) testing for dof_constraints_created==true on equation_systems.C lines
246 & 270 (passed libMesh make check, but failed a GRINS regression and AMR
test)

2) Using refine_and_coarsen_elements() instead of the current 2-step
coarsen then refine (made no difference)

3) Moving the coarsen/refine_elements() calls to the beginning of reinit()
before the new systems are added, and left distribute_dofs(),
reinit_constraints(), and get_system(i)->reinit() to the very end (fails
several libmesh tests: incorrect results on split_mesh and NULL_PTR error
in another test)

Does anyone else use the reinit-and-refine case, and if so, how did you get
it working?
I'm not very familiar with this part of the libMesh code, and I would
appreciate any feedback as to whether I am missing something or any
suggestions from more knowledgeable devs.

Thanks!

-- 
*~Tim Adowski*