[Nek5000-users] Simulation hanging at 'mapping elements to processors'

[nek5000-users at lists.mcs.anl.gov]

Hi Marco,


I'm not 100 % about the hanging point, but I suggest - especially for larger problems like this - running on a power of 2 processors (i.e., 1024 in your case).


This is particularly critical for performance when the XXT (default) coarse grid solver is used.  Less so, perhaps, for the AMG coarse solver...I'm assuming you're using the XXT one - but not certain.


Best,


Paul


________________________________
From: Nek5000-users <nek5000-users-bounces at lists.mcs.anl.gov> on behalf of nek5000-users at lists.mcs.anl.gov <nek5000-users at lists.mcs.anl.gov>
Sent: Thursday, September 21, 2017 3:37:55 PM
To: Nek5000-users at lists.mcs.anl.gov
Subject: [Nek5000-users] Simulation hanging at 'mapping elements to processors'

Hello,

I am trying to run a simulation that has ~500,000 elements on 1280 processors with lx1=4 for debugging purposes. My simulation hangs after outputting 'mapping elements to processors’. I generated the mesh with Cubit and then used the exo2nek script to get the re2 file. Genmap runs fine on the re2 file.

I was wondering if this problem has been encountered in the past, and what I could do to fix it.

Thanks,
Marco

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