top500 list (was: opteron VS Itanium 2)
Keith D. Underwood
kdunder at sandia.gov
Mon Nov 17 11:56:51 EST 2003
> > Lightning (LANL Opteron) (2816 CPUs) - 8.1 TFlops
> yield is 72%.
BTW, 60% of 8 GF == 4.8 GF per processor. 72% of 4 GF == 2.88. If you
use LINPACK as a metric, why do you think the latter wins? (note the
if. I'm not suggesting LINPACK is the right benchmark.)
> for the billionth time: rmax is just a matter of how much money
> you have. rmax/rpeak is the only part of top500 that matters.
You have to include cost. Otherwise, if I could buy a 1 PetaFLOP system
that yielded 10% efficiency for the same price as a 100 TeraFLOP system
that yielded 75% efficiency, I should buy the latter? Or, put another
way, a vendor would be better off building a slower processor with a
modern memory system that achieved 95% of peak. You can always put more
of them together with more money, right? (I'm not sure if I know of any
networks that scale to 100,000 processors).
rmax/rpeak is just as bad (or worse) of a metric as rmax if it is the
only metric. It's not like LINPACk is terribly communication bound or
anything (in which case, rmax/rpeak might mean something).
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