[Beowulf] evaluating FLOPS capacity of our cluster

Mark Hahn hahn at mcmaster.ca
Mon May 11 14:30:31 EDT 2009


>> Excellent. Thanks Gus. That sort of estimate is exactly what I needed.
>> I do have AMD Athelons.

right - for PHB's, peak theoretical throughput is a reasonable approach,
especially since it doesn't require any real work on your part.  the only
real magic is to find the flops-per-cycle multiplier for your cpus.
basically, anything introduced since core2 has been 4 f/c (incl core2). 
before that, only ia64 was 4 f/c.  as others have mentioned, the ">= core2
generation" includes AMD barcelona/shanghai/etc versions (server and
desktop), as well as nehalem on the intel side.

> Typical Rmax/Rpeak ratios in Top500 are around the 80% ballpark.

80 is fairly high, and generally requires a high-bw, low-lat net.
gigabit, for instance, is normally noticably lower, often not much 
better than 50%.  but yes, top500 linpack is basically just
interconnect factor * peak, and so unlike real programs...
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