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Subject: Re: [OMPI users] Performance difference on OpenMPI, IntelMPI and ScaliMPI
From: Torgny Faxen (faxen_at_[hidden])
Date: 2009-08-06 08:48:49

se attached file.

I have traced how MPI_IPROBE is called and also managed to significantly
reduce the number of calls to MPI_IPROBE. Unfortunately this only
resulted in the program spending time in other routines. Basically the
code runs through a number of timesteps and after each timestep all
slave nodes wait for the master to give go ahead for the next step and
this is were a lot of time is being spent. Either a load inbalance or
just waiting for all MPI_BSEND:s to complete or something else.

I am kind of stuck right now and will have to do some more
investigations . Strange that this works so much better using Scali MPI.

Regards / Torgny

Pavel Shamis (Pasha) wrote:
>> However, setting:
>> -mca btl_openib_eager_limit 65536
>> gave a 15% improvement so OpenMPI is now down to 326 (from previous
>> 376 seconds). Still a lot more than ScaliMPI with 214 seconds.
> Can you please run ibv_devinfo on one of compute nodes ? It is
> interesting to know what kind of IB HW you have on our cluster.
> Pasha
> _______________________________________________
> users mailing list
> users_at_[hidden]

   Torgny Faxén		
   National Supercomputer Center
   Linköping University	
   S-581 83 Linköping
   Telephone: +46 13 285798 (office) +46 13 282535  (fax)

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