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Subject: Re: [OMPI users] EXTERNAL: Re: Best way to map MPI processes to sockets?
From: Blosch, Edwin L (edwin.l.blosch_at_[hidden])
Date: 2012-11-08 12:31:25

Thanks, that's what I'm looking for.

My first look for documentation is always the FAQ, not the man pages. I found no mention of -npersocket in the FAQ but there it is very clear in the man page. Boy do I feel dumb.

Anyway, thanks a lot.

From: users-bounces_at_[hidden] [mailto:users-bounces_at_[hidden]] On Behalf Of Ralph Castain
Sent: Thursday, November 08, 2012 10:08 AM
To: Open MPI Users
Subject: Re: [OMPI users] EXTERNAL: Re: Best way to map MPI processes to sockets?

I gather from your other emails you are using 1.4.3, yes? I believe that has npersocket as an option. If so, you could do:

mpirun -npersocket 2 -bind-to-socket ...

That would put two processes in each socket, bind them to that socket, and rank them in series. So ranks 0-1 would be bound to the first socket, ranks 2-3 to the second.


On Thu, Nov 8, 2012 at 6:52 AM, Blosch, Edwin L <edwin.l.blosch_at_[hidden]<mailto:edwin.l.blosch_at_[hidden]>> wrote:
Yes it is a Westmere system.

Socket L#0 (P#0 CPUModel="Intel(R) Xeon(R) CPU E7- 8870 @ 2.40GHz" CPUType=x86_64)
      L3Cache L#0 (size=30720KB linesize=64 ways=24)
        L2Cache L#0 (size=256KB linesize=64 ways=8)
          L1dCache L#0 (size=32KB linesize=64 ways=8)
            L1iCache L#0 (size=32KB linesize=64 ways=4)
              Core L#0 (P#0)
                PU L#0 (P#0)
        L2Cache L#1 (size=256KB linesize=64 ways=8)
          L1dCache L#1 (size=32KB linesize=64 ways=8)
            L1iCache L#1 (size=32KB linesize=64 ways=4)
              Core L#1 (P#1)
                PU L#1 (P#1)

So I guess each core has its own L1 and L2 caches. Maybe I shouldn't care where or if the MPI processes are bound within a socket; if I can test it, that will be good enough for me.

So my initial question is now changed to:

What is the best/easiest way to get this mapping? Rankfile?, --cpus-per-proc 2 --bind-to-socket, or something else?

0 0 unspecified
1 0 unspecified
2 1 unspecified
3 1 unspecified


-----Original Message-----
From: users-bounces_at_[hidden]<mailto:users-bounces_at_[hidden]> [mailto:users-bounces_at_[hidden]<mailto:users-bounces_at_[hidden]>] On Behalf Of Brice Goglin
Sent: Wednesday, November 07, 2012 6:17 PM
To: users_at_[hidden]<mailto:users_at_[hidden]>
Subject: EXTERNAL: Re: [OMPI users] Best way to map MPI processes to sockets?

What processor and kernel is this? (see /proc/cpuinfo, or run "lstopo -v" and look for attributes on the Socket line) You're hwloc output looks like an Intel Xeon Westmere-EX (E7-48xx or E7-88xx).
The likwid output is likely wrong (maybe confused by the fact that hardware threads are disabled).


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