Fwd: [gmx-users] Performance problems with more than one node

vivek sharma viveksharma.iitb at gmail.com
Fri Sep 26 09:22:47 CEST 2008


Hi Carsten and Justin,
I am interrupting here as I tried with the option u suggested..
I tried cut-off instead of PME as coulombtype option it is running well for
24 processor, then I tried with 60 processor , following is the result I am
getting

Result1: When tried for 50 ps of run on 24 processors, with PME took 12:29
in comparison to 7:54 with cut-off

Result2: When tried for 500 ps of run on 60 processors, with PME it is
giving same segmentation fault again and with cut-off it is giving LINCS
warning and exiting with writing the intermediate step.pdb

Can you suggest some more option that I can try for scaling experiment...
Also I tried with shuffle and sort option it didn't worked for me as my
system is simply one protein molecule in a ater box (around 45000 no. of
atoms)
connected Gromacs version I am using is 3.3.3 and the hardware is like all
nodes contain quad-core 3.0 GHz Intel Xeon processors connected via
infiniband.

With Thanks,
Vivek

2008/9/26 Carsten Kutzner <ckutzne at gwdg.de>

> Hi Tiago,
>
> if you swith off PME and suddenly your system scales, then the
> problems are likely to result from bad MPI_Alltoall performance. Maybe
> this is worth a check. If this is the case, there's a lot more information
> about this in the paper "Speeding up parallel GROMACS on high-
> latency networks" from 2007 to which you will also find link on the
> gromacs webpage.
>
> What you can also do to track down the problem is to compile gromacs with
> MPE logging, for which you have to enable the #define USE_MPE macro at the
> begin of mpelogging.h (you will have to use gmx version 4, though). You
> will get a logfile which you can view with jumpshot then. The MPE tools
> come with the MPICH MPI distribution.
>
> Carsten
>
>
> Tiago Marques wrote:
>
>> We currently have no funds available to migrate to infiniband but we will
>> in the future.
>>
>> I thought on doing interface bonding but I really think that isn't really
>> the problem here, there must be something I'm missing, since most
>> applications scale well to 32 cores on GbE. I can't scale any application to
>> more than 8 though.
>>
>> Best regards,
>>                           Tiago Marques
>>
>>
>> On Tue, Sep 23, 2008 at 6:30 PM, Diego Enry <diego.enry at gmail.com<mailto:
>> diego.enry at gmail.com>> wrote:
>>
>>    Tiago you can try merging two network interfaces with "channel
>>    bonding" it's native on all new (2.6.x) linux kernels. You only need
>>    two network adapters (most dual socket boards come with then), two
>>    network switches ( or two VPN on the same switch).
>>
>>    To tell you the truth, you will not much improvement even with the
>>    latest gromacs version (4beta). However other software that may be
>>    used by your group like NAMD, GAMESS, will benefit a lot from this
>>    approach. (it almost doubles network bandwidth)
>>
>>    The best solution for gromacs is to migrate to infiniband. Go for it,
>>    it is not super expensive anymore.
>>
>>
>>    On Tue, Sep 23, 2008 at 1:48 PM, Jochen Hub <jhub at gwdg.de
>>    <mailto:jhub at gwdg.de>> wrote:
>>     > Tiago Marques wrote:
>>     >> I don't know how large the system is. I'm the cluster's system
>>    administrator
>>     >> and don't understand much of what's going on. The test was given
>>    to me by a
>>     >> person who works with it. I can ask him or look at it, if you
>>    can point me
>>     >> how to do it.
>>     >
>>     > Hi,
>>     >
>>     > you can count the nr of atoms in the structure:
>>     >
>>     > grep -c ATOM protein.pdb
>>     >
>>     > Jochen
>>     >
>>     >>
>>     >> Thanks, I will look at some of his posts.
>>     >>
>>     >> Best regards,
>>     >>
>>     >>                         Tiago Marques
>>     >>
>>     >>
>>     >> On Tue, Sep 23, 2008 at 4:03 PM, Jochen Hub <jhub at gwdg.de
>>    <mailto:jhub at gwdg.de>> wrote:
>>     >> Tiago Marques wrote:
>>     >>> Hi!
>>     >>>
>>     >>> I've been using Gromacs on dual-socket quad-core Xeons with
>>    8GiB of RAM,
>>     >>> connected with Gigabit Ethernet and I always seem to have
>>    problems scaling
>>     >>> to more than a node.
>>     >>>
>>     >>> When I run a test on 16 cores, it does run but the result is
>>    often slower
>>     >>> than when running on only 8 cores on the same machine. The best
>>    result
>>     >> I've
>>     >>> managed is not being slower than 8 cores on 16.
>>     >>>
>>     >>> What am I missing here, or are the tests inappropriate to run
>>    over more
>>     >> than
>>     >>> one machine?
>>     >>
>>     >> How large is your system? Which gromacs version are you using?
>>     >>
>>     >> And have a look at the messages by Carsten Kutzner in this list, he
>>     >> wrote a lot on gromacs scaling.
>>     >>
>>     >> Jochen
>>     >>
>>     >>> Best regards,
>>     >>>
>>     >>> Tiago Marques
>>     >>>
>>     >>>
>>     >>>
>>     >>>
>>
>>  ------------------------------------------------------------------------
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>>     >> ************************************************
>>     >> Dr. Jochen Hub
>>     >> Max Planck Institute for Biophysical Chemistry
>>     >> Computational biomolecular dynamics group
>>     >> Am Fassberg 11
>>     >> D-37077 Goettingen, Germany
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>>     > --
>>     > ************************************************
>>     > Dr. Jochen Hub
>>     > Max Planck Institute for Biophysical Chemistry
>>     > Computational biomolecular dynamics group
>>     > Am Fassberg 11
>>     > D-37077 Goettingen, Germany
>>     > Email: jhub[at]gwdg.de <http://gwdg.de>
>>     > Tel.: +49 (0)551 201-2312
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>>
>>
>>    --
>>    Diego Enry B. Gomes
>>    Laboratório de Modelagem e Dinamica Molecular
>>    Universidade Federal do Rio de Janeiro - Brasil.
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>
> --
> Dr. Carsten Kutzner
> Max Planck Institute for Biophysical Chemistry
> Theoretical and Computational Biophysics Department
> Am Fassberg 11
> 37077 Goettingen, Germany
> Tel. +49-551-2012313, Fax: +49-551-2012302
> www.mpibpc.mpg.de/home/grubmueller/
> www.mpibpc.mpg.de/home/grubmueller/ihp/ckutzne/
>
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