[Beowulf] Home beowulf - NIC latencies

Nicolas Jungers nj at hemeris.com
Fri Feb 4 12:21:24 EST 2005


On Thu, 2005-02-03 at 04:53 +0100, Vincent Diepeveen wrote:
> Good morning!
> 
> With the intention to run my chessprogram on a beowulf to be
> constructed
> here (starting with 2 dual-k7 machines here) i better get some good
> advice
> on which network to buy. Only interesting thing is how fast each node
> can
> read out 64 bytes randomly from RAM of some remote cpu. All nodes do
> that
> simultaneously.
> 
> The faster this can be done the better the algorithmic speedup for
> parallel
> search in a chess program (property of YBW, see publications in
> journal of
> icga: www.icga.org). This speedup is exponential (or better you get
> punished exponential compared to single cpu performance).
> 
> Which network cards considering my small budget are having lowest
> latencies
> can be used?
> 
> quadrics/dolphin seems bit out of pricerange. Myrinet is like 684 euro
> per
> card when i altavista'ed online and i wonder how to get more than 2
> nodes
> to work without switch. Perhaps there is low cost switches with
> reasonable
> low latency?
> 
> Please note MPI is probably what i'll use, though i keep finding
> online
> information about 'gamma'. Is that faster latency than MPI
> implementations?

gamma bypass tcp/ip, then shaving most of the latency. Unfortunately
it's not very actively developed, though they "recently" (last year)
updated their stack to the e1000 (intel Giga ethernet) NIC. I know that
(some at) the CERN use they own communication stack on e1000 similar to
gamma, with impressive results. I dunno if it's widely available.

Nicolas

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