[Nek5000-users] problem with running nek5000 on supercomputers

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

Hi Ami,

When you increase the processor count, you can recompile with a smaller lelt.

Suppose you have lelt=1000 and you go from P=64 to P=128.  Then set lelt=500 and
recompile.

Make certain lelg >= 500*P and lp >= 128.

I would suggest lelg="big enough" (and an even number) and lp=32768.

Paul

________________________________
From: nek5000-users-bounces at lists.mcs.anl.gov [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: Monday, November 10, 2014 5:05 AM
To: nek5000-users at lists.mcs.anl.gov
Subject: [Nek5000-users] problem with running nek5000 on supercomputers

Hi Neks,

I am trying to run my simulation with nek5000 on supercomputers, the size of the problem is something like:

 text      data     bss     dec     hex filename
2233955  187412 2554984280      2557405647      986ee9cf        nek5000

I don't have any problem when I use 32~64 CPUs to run parallel on supercomputers, but once I go for more than 64 CPUs, I always get "allocation failed" error. I have tried to run on different supercomputer like as Gordon SDSC, OSC, TACC, but I got the same type of error each time. I have checked the active memories, it seems for each of them memories have large unused portion. Does any one have any idea why when I increase the number of CPUs I get this allocation error?!

Thank you,
Ami
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