[MOAB-dev] DMMoabLoadFromFile() - parallel performance issue

[WARNER, JAMES E. (LARC-D309)]

Hi Vijay & Iulian,

Hope you are doing well! I have a question regarding some strange behavior we’re seeing with the DMMoabLoadFromFile() function…

After doing some recent profiling of our MOAB-based finite element code, we noticed that we are spending a disproportionate amount of CPU time within the DMMoabLoadFromFile() function, which gets slower / remains constant as we increase the number of processors. We also recently attempted a scalability test with ~30M FEM nodes  on 500 processors which hung in DMMoabLoadFromFile() for about 45 minutes before we killed the job. We then re-ran the test on one processor and it made it through successfully in several seconds.

To reproduce the problem we’re seeing, we wrote a test case (attached here) that simply loads a smaller mesh with approximately 16K nodes and prints the run time. When I run the code on an increasing number of processors, I get something like:

NP=1: Time to read file: 0.0416839 [sec.]
NP=2: Time to read file: 1.42497 [sec.]
NP=4: Time to read file: 1.13678 [sec.]
NP=8: Time to read file: 1.0475 [sec.]
…

If it is relevant/helpful – we are using the mbpart tool to partition the mesh.  Do you have any ideas why we are not seeing scalability here? Any thoughts/tips would be appreciated! Let me know if you would like any more information.

Thanks,
Jim



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/moab-dev/attachments/20151214/5a08d61f/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: moab_test.tgz
Type: application/octet-stream
Size: 1448543 bytes
Desc: moab_test.tgz
URL: <http://lists.mcs.anl.gov/pipermail/moab-dev/attachments/20151214/5a08d61f/attachment-0001.obj>