Author: Robert Hyatt
Date: 20:35:30 07/15/03
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On July 15, 2003 at 23:05:37, Vincent Diepeveen wrote: > > >Now i can disproof again the 130ns figure that Bob keeps giving here for dual >machines and something even faster than that for single cpu (up to 60ns or >something). Then i'm sure he'll be modifying soon his statement something like >to "that it is not interesting to know the time of a hashtable lookup, because >that is not interesting to know; instead the only scientific intersting thing is >to know is how much bandwidth a machine can actually achieve". > What is _interesting_ is the fact that you are incapable of even recalling the numbers I posted. to wit: dual xeon 2.8ghz, 400mhz FSB. 149ns latency PIII/750 laptop, SDRAM. 125ns. Aaron posted the 60+ ns numbers for his overclocked athlon. I assume his numbers are as accurate as mine since he _did_ run lm_bench, rather than something with potential bugs. I can post bandwidth numbers if you want, but that has nothing to do with latency, as those of us understanding architecture already know. >That's what i'm after of course. > >Apart from a bug in the RNG i need to point that RAM factors could also play a >role here. Like the distance signals need to carry in the RAM. If that's not the >problem but the RNG is the problem then definitely it is the case that i would >encourage you to find a better RNG or a modification to this RNG so that it >works better for small hashsizes. > >For now i just conclude that it is a fact that the 130 ns figures is *not* even >close to the times that we need to do a lookup in the hashtable at a dual Xeon >133Mhz DDR ram which bob has. It's quite a bit closer to 400ns in fact :) It is _exactly_ 150ns +/- 1ns. No more, no less.
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