[Beowulf] hang-up of HPC Challenge
kus at free.net
Tue Aug 19 16:45:43 PDT 2008
For some localization of possible problem reason, I ran pure HPL test
instead of HPCC. HPL performs direct output to screen instead of
writing to the file.
Using MPICH w/np=8 I obtained normal HPL result for N=35000 -
3 "PASSED" strings for ||Ax-b|| calculations. BUT ! Linux hang-ups
immediately after output of this strings.
In message from "Mikhail Kuzminsky" <kus at free.net> (Mon, 18 Aug 2008
>I ran a set of HPC Challenge benchmarks on ONE dual socket quad-core
>Opteron2350 (Rev. B3) based server (8 logical CPUs).
>RAM size is 16 Gbytes. The tests performed were under SuSE
>10.3/x86-64, for LAM MPI 7.1.4 and MPICH 1.2.7 from SuSE
>distribution, using Atlas 3.9. Unfortunately there is only one such
>cluster node, and I can't reproduce the run on another node :-(
>For N (matrix size) up to 10000 all looks OK. But for more large N
>(15000/20000/...) hpcc execution (mpirun -np 8 hpcc) leads to Linux
>In the "top" output I see 8 hpcc examplars each eating about 100% of
>CPU, and reasonable amounts of virtual and RSS memory per hpcc
>process, and the absense of swap using. Usually there is no PTRANS
>results in hpccoutf.txt results file, but in a few cases (when I
>"activelly looked" to hpcc execution by means of ps/top issuing) I
>see reasonable PTRANS results but absense of HPLinpack results. One
>time I obtained PTRANS, HPL and DGEMM results for N=20000, but hangup
>later - on STREAM tests. May be it's simple because of absense (at
>hangup) of final writing of output buffer to output file on HDD.
>One of possible reasons of hang-ups is memory hardware problem, but
>what is about possible software reasons of hangups ?
>The hpcc executable is 64-bit dynamically linked.
>/etc/security/limits.conf is empty. stacksize limit (for user issuing
>mpirun) is "unlimited", main memory limit - about 14 GB, virtual
>memory limit - about 30 GB. Atlas was compiled for 32-bit integers,
>but it's enough for such N values. Even /proc/sys/kernel/shmmax is
>What else may be the reason of hangup ?
>Computer Assistance to Chemical Research Center
>Zelinsky Institute of Organic Chemistry
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