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Subject: Re: [OMPI devel] Any plans to support Intel MIC (Xeon Phi) in Open-MPI?
From: Paul Hargrove (phhargrove_at_[hidden])
Date: 2013-05-02 20:54:51


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
> >
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> >
> > iEYEARECAAYFAlGDAPYACgkQO2KABBYQAh+y9ACfZ0SdqDuV7Euq3B0ANtxPhH1D
> > 3h4An1Zlhu2Ut+OFvbTa9xbLBkspwwPY
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>
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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