I feel hierarchical collectives are slower compare to tuned one. I
had done some benchmark in the past specific to collectives, and this is
what i feel based on my observation.
Neeraj Chourasia (MTS)
Computational Research Laboratories Ltd.
(A wholly Owned Subsidiary of TATA SONS Ltd)
B-101, ICC Trade Towers, Senapati Bapat Road
Pune 411016 (Mah) INDIA
(O) +91-20-6620 9863 (Fax) +91-20-6620 9862
Terry Dontje <Terry.Dontje_at_[hidden]>
Sent by: users-bounces_at_[hidden]
08/07/2009 04:35 PM
Please respond to
Open MPI Users <users_at_[hidden]>
Re: [OMPI users] Performance question about OpenMPI and MVAPICH2 on
Did your affinity script bind the processes per socket or linearly to
cores. If the former you'll want to look at using rankfiles and place the
ranks based on sockets. TWe have found this especially useful if you are
not running fully subscribed on your machines.
Also, if you think the main issue is collectives performance you may want
to try using the hierarchical and SM collectives. However, be forewarned
we are right now trying to pound out some errors with these modules. To
enable them you add the following parameters "--mca coll_hierarch_priority
100 --mca coll_sm_priority 100". We would be very interested in any
results you get (failures, improvements, non-improvements).
> Message: 4
> Date: Thu, 06 Aug 2009 17:03:08 -0600
> From: Craig Tierney <Craig.Tierney_at_[hidden]>
> Subject: Re: [OMPI users] Performance question about OpenMPI and
> MVAPICH2 on IB
> To: Open MPI Users <users_at_[hidden]>
> Message-ID: <4A7B612C.8070501_at_[hidden]>
> Content-Type: text/plain; charset=ISO-8859-1
> A followup....
> Part of problem was affinity. I had written a script to do processor
> and memory affinity (which works fine with MVAPICH2). It is an
> idea that I got from TACC. However, the script didn't seem to
> work correctly with OpenMPI (or I still have bugs).
> Setting --mca mpi_paffinity_alone 1 made things better. However,
> the performance is still not as good:
> Cores Mvapich2 Openmpi
> 8 17.3 17.3
> 16 31.7 31.5
> 32 62.9 62.8
> 64 110.8 108.0
> 128 219.2 201.4
> 256 384.5 342.7
> 512 687.2 537.6
> The performance number is GFlops (so larger is better).
> The first few numbers show that the executable is the right
> speed. I verified that IB is being used by using OMB and
> checking latency and bandwidth. Those numbers are what I
> expect (3GB/s, 1.5mu/s for QDR).
> However, the Openmpi version is not scaling as well. Any
> ideas on why that might be the case?
users mailing list
Notice: The information contained in this e-mail
message and/or attachments to it may contain
confidential or privileged information. If you are
not the intended recipient, any dissemination, use,
review, distribution, printing or copying of the
information contained in this e-mail message
and/or attachments to it are strictly prohibited. If
you have received this communication in error,
please notify us by reply e-mail or telephone and
immediately and permanently delete the message
and any attachments.
Internet communications cannot be guaranteed to be timely,
secure, error or virus-free. The sender does not accept liability
for any errors or omissions.Thank you