Re: [bgl-discuss] Fwd: [bgl-support #302] May I ask you two questions?

[Paul Fischer <fischer@xxxxxxxxxxx>]

Andrew,

I got the impression (perhaps I misunderstood) from Ray Bair
that any of the viable subsets (i.e., 2^k node partitions)
gave was reconfigured to a torus??

Paul


On Wed, 7 Feb 2007, Andrew Cherry wrote:

> To answer (2), the minimum partition that can give you a torus is 512
> nodes.
>
> -Andrew
>
> On Feb 7, 2007, at 3:57 PM, Yongzhi Chen wrote:
>
> > Hi Kamil,
> >
> > Thank you for your response.
> >
> > (1) So in you opinion, a 2% fluctuation is normal. I really want to
> > make
> > sure it.
> >
> > (2) Can you please tell me the minimum partition that can guarantee
> > me a
> > torus machine, 256 or above? Thanks a lot.
> >
> > Best,
> > -Yongzhi
> >
> > -----Original Message-----
> > From: Kamil Iskra [mailto:iskra@xxxxxxxxxxx]
> > Sent: Wednesday, February 07, 2007 12:18 PM
> > To: Yongzhi Chen
> > Cc: discuss@xxxxxxxxxxxxxxx; BG/L Support
> > Subject: Re: [bgl-discuss] Fwd: [bgl-support #302] May I ask you two
> > questions?
> >
> > So you get a distribution of some... 2% ?  That doesn't sound too bad.
> > Then again, I'm doing file I/O performance testing, so I'm used to
> > much
> > larger distributions.
> >
> > Your way of measuring time looks OK, BTW.
> >
> >
> > Perhaps the links utilized by process pairs in your test happened
> > to be
> > non-overlapping?  How did you run this experiment?  Which pairs did
> > you
> > test (surely not all 120 at the same time)?  Did you use a custom
> > BGLMPI_MAPPING?
> >
> > Bacground info:
> >
> > Each node on BG/L has 6 torus connections to its nearest neighbors,
> > each
> > one with a bandwidth of around 150 MB/s.  With small partitions
> > like the
> > one you used, it's actually not a torus, but a mesh, and nodes use
> > between
> > 3 and 5 links.  There is a number of ways that lets you find the
> > location
> > of any particular process within the torus topology:
> >
> > MPI_Get_processor_name() function puts it in the returned string,
> > so you
> > can just print it out,
> >
> > rts_coordinatesForRank(getpid(), &x, &y, &z, &t) (include <rts.h>;
> > it's in
> > /bgl/BlueLight/ppcfloor/bglsys/include),
> >
> > rts_get_personality(), followed by BGLPersonality_xCoord(),
> > BGLPersonality_yCoord(), etc.
> >
> > Kamil
> >
> > --
> > Kamil Iskra, PhD
> > Argonne National Laboratory, Mathematics and Computer Science Division
> > 9700 South Cass Avenue, Building 221, Argonne, IL 60439, USA
> > phone: +1-630-252-7197  fax: +1-630-252-5986
> >
> >
>
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>

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