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Subject: Re: [OMPI devel] Any plans to support Intel MIC (Xeon Phi) in Open-MPI?
From: Jeff Squyres (jsquyres) (jsquyres_at_[hidden])
Date: 2013-05-02 21:28:16


I know the MPICH guys did a bunch of work to support the Phi's. I don't know exactly what that means (I haven't read their docs about this stuff), but I suspect that it's more than just launching MPI processes on them...

On May 2, 2013, at 8:54 PM, Paul Hargrove <phhargrove_at_[hidden]> wrote:

> Ralph,
>
> I am not an expert, by any means, but based on a presentation I heard 4 hours ago:
>
> The Xeon and Phi instruction sets have a large intersection, but neither is a subset of the other.
> In particular, Phi has its own SIMD instructions *instead* of Xeon's MMX, SSEn, etc.
> There is also on CMPXCHG16B instruction on Phi, among others.
> So, there will need to be different binaries, or "fat" binaries that branch based on CPU type.
>
> -Paul
>
>
> On Thu, May 2, 2013 at 5:47 PM, Ralph Castain <rhc_at_[hidden]> wrote:
>
> On May 2, 2013, at 5:12 PM, Christopher Samuel <samuel_at_[hidden]> wrote:
>
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > Hi folks,
> >
> > The new system we're bringing up has 10 nodes with dual Xeon Phi MIC
> > cards, are there any plans to support them by launching MPI tasks
> > directly on the Phis themselves (rather than just as offload devices
> > for code on the hosts)?
>
> We had something similar at one time - I developed it for the Roadrunner cluster so you could run MPI tasks on the GPUs. Worked well, but eventually fell into disrepair due to lack of use.
>
> In this case, I suspect it will be much easier to do as the Phis appear to be a lot more visible to the host than the GPU did on RR. Looking at the documentation, the Phis just sit directly on the PCIe bus, so they should look just like any other processor, and they are Xeon binary compatible - so there is no issue with tracking which binary to run on which processor.
>
> Brice: do the Phis appear in the hwloc topology object?
>
> Chris: can you run lstopo on one of the nodes and send me the output (off-list)?
>
>
> >
> > All the best,
> > Chris
> > - --
> > Christopher Samuel Senior Systems Administrator
> > VLSCI - Victorian Life Sciences Computation Initiative
> > Email: samuel_at_[hidden] Phone: +61 (0)3 903 55545
> > http://www.vlsci.org.au/ http://twitter.com/vlsci
> >
> > -----BEGIN PGP SIGNATURE-----
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> > Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/
> >
> > iEYEARECAAYFAlGDAPYACgkQO2KABBYQAh+y9ACfZ0SdqDuV7Euq3B0ANtxPhH1D
> > 3h4An1Zlhu2Ut+OFvbTa9xbLBkspwwPY
> > =TbIy
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>
> --
> Paul H. Hargrove PHHargrove_at_[hidden]
> Future Technologies Group
> Computer and Data Sciences Department Tel: +1-510-495-2352
> Lawrence Berkeley National Laboratory Fax: +1-510-486-6900
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-- 
Jeff Squyres
jsquyres_at_[hidden]
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