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 <phhargr...@lbl.gov> 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 <r...@open-mpi.org> wrote:
> 
> On May 2, 2013, at 5:12 PM, Christopher Samuel <sam...@unimelb.edu.au> 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: sam...@unimelb.edu.au Phone: +61 (0)3 903 55545
> > http://www.vlsci.org.au/      http://twitter.com/vlsci
> >
> > -----BEGIN PGP SIGNATURE-----
> > Version: GnuPG v1.4.11 (GNU/Linux)
> > Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/
> >
> > iEYEARECAAYFAlGDAPYACgkQO2KABBYQAh+y9ACfZ0SdqDuV7Euq3B0ANtxPhH1D
> > 3h4An1Zlhu2Ut+OFvbTa9xbLBkspwwPY
> > =TbIy
> > -----END PGP SIGNATURE-----
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> 
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> 
> -- 
> Paul H. Hargrove                          phhargr...@lbl.gov
> 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
jsquy...@cisco.com
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