[Libmesh-devel] Mesh Corruption In XDA Format

[Derek G. <ga...@mi...>]

(Note: this is cross-posted between MOOSE and libMesh devel lists because
it's interesting to both!)

I had a user here at MIT bring me this interesting problem.  She developed
her code last year and got good results (i.e.: it worked last year).  She
did an internship for 6 months and came back to the code only recently came
back to the code and her same stuff doesn't work anymore.

What she is doing is writing out XDA format meshes from one simulation and
reading them into the next simulation.  What's happening is that the XDA
format meshes are "corrupt" for some reason.  We finally tracked it down to
happening when her mesh gets really fine due to adaptivity.  I've been able
to replicate this in a small MOOSE input file (runs with moose_test) that I
have attached.

The original mesh looks like this:

[image: initial_mesh.png]

After 5 adaptivity steps it looks like this:

[image: corruption.png]

To generate that I outputted the file in XDA format and then just read it
in and converted it to Exodus.

The really weird thing about this problem is that it runs just fine... and
the Exodus output looks just fine:

[image: solution.png]

So the mesh is NOT actually corrupt in memory.  In addition, earlier XDA
files look just fine.  Here it is after 4 adaptivity steps:

[image: four.png]

Anyone have an idea of what's going on?

Derek