Author: Robert Hyatt
Date: 11:03:50 12/09/03
Go up one level in this thread
On December 09, 2003 at 13:48:43, J. Wesley Cleveland wrote: >On December 09, 2003 at 13:33:41, Robert Hyatt wrote: > >>On December 09, 2003 at 13:30:11, Slater Wold wrote: >> >>>On December 09, 2003 at 13:17:55, Robert Hyatt wrote: >>> >>>>On December 09, 2003 at 13:04:01, Slater Wold wrote: >>>> >>>>>On December 09, 2003 at 12:49:17, Robert Hyatt wrote: >>>>> >>>>>>On December 09, 2003 at 12:33:20, Slater Wold wrote: >>>>>> >>>>>>>On December 09, 2003 at 11:49:19, Mathieu Pagé wrote: >>>>>>> >>>>>>>>On December 09, 2003 at 11:16:02, stuart taylor wrote: >>>>>>>> >>>>>>>>>Is 2.2 Ghz. of a 64-bit computer a similar speed for chess as is 4.4 is it were >>>>>>>>>a 32-bit one? >>>>>>>>>If not, what? >>>>>>>>>S.Taylor >>>>>>>> >>>>>>>>Hi! >>>>>>>> >>>>>>>>No, it is not. >>>>>>>> >>>>>>>>64-bit computer are not twice as fast as 32-bit ones. The number of bit >>>>>>>>represent the natural lenght of an number on a cpu. Since chess engines use lot >>>>>>>>of 64 bits numbers they will run faster on 64 bits machines because on 32-bit >>>>>>>>machines they have to do some trick to do 64 bits maths that are natural on a 64 >>>>>>>>bit cpu. >>>>>>>> >>>>>>>>I dont think the improvement will be in the range of 2x speed up. Anyway it will >>>>>>>>vary from diffrents engines. >>>>>>>> >>>>>>>>Mathieu >>>>>>> >>>>>>>GCP reported 70% with Sjeng. >>>>>>> >>>>>>>Bob has reported about 50% with Crafty. >>>>>> >>>>>>Not exactly. I reported 1.0M with a 2.8ghz xeon, vs 1.6M with a 1.8ghz >>>>>>opteron. If you factor in a clock speed equalization, the xeon slows to >>>>>>1.8ghz and would produce about 650K nodes per second and the opteron would >>>>>>be more than 2x faster. >>>>>> >>>>>>I have not done a direct comparison of 32 bit code vs 64 bit code on the >>>>>>opteron as I have no 32 bit compiler available there. If I get to do that >>>>>>at some point it time, it would be interesting. It would be more interesting >>>>>>to be able to say "use only 32 bit ops, but use all 16 registers" to get a >>>>>>_real_ feel for what 64 bits offers over 32 bits, but that looks even >>>>>>harder to test. >>>>> >>>>>Well, we can always deduct. :) >>>>> >>>>>An opteron 144 (1.8Ghz) running SuSe and gcc33, using -m32 to produce 32 bit >>>>>code, got these results on 186.crafty: >>>> >>>>We can't compare with that at all. That is a _way_ old version, obviously. >>>> >>>>I can't do -m32 on this machine, as the libraries are all -m64 and they >>>>become incompatible (I have already tried this a few days back in fact.) >>>> >>>> >>>>> >>>>>90.1 1109 >>>>> >>>>>The fastest 2.8Ghz Xeon on SPEC's website does: >>>>> >>>>>92.0 1087 (2k AS IC++ 7.0 compiler) >>>>> >>>>> >>>>>For all practical purposes, we can say that a O144 a P4 2.8Ghz Xeon are >>>>>'comparible'. >>>> >>>>OK. Can't argue there with no data of my own to rely on.. >>>> >>>> >>>> >>>>> >>>>>1.0M to 1.6M = 60% speedup >>>> >>>>Not directly attributable to 64 bit however. -m32 restricts you to 8 >>>>registers, while -m64 adds the other 8. That also factors in and makes >>>>this less clear. >>> >>>Like I said, it was just a 'deduction'. I know you're pretty scientific, but >>>this was just a rough comparison. >>> >>>I'd be confident in this statement however: "64-bits, depending on application, >>>can speedup a typical chess program from 40% to 70%." >>> >>>Which is nice, considering it is practically 'free'. >> >> >>the only unknown is the 40%. IE out of my 60% boost, what part comes >>from 16 vs 8 registers as opposed to 64 bit vs 32 bit registers? I'll >>answer that precisely one day, I hope. > >If you look at the specint results for the opteron with 64 bit gcc, crafty is >the only test that gains significantly over opteron with 32 bit Intel. >This suggests that the extra 8 registers are not contributing much to the other >tests, so probably don't to crafty either. That's a reasonable assumption, of course. But I've been bitten too many times to make many "assumptions" without seeing the real stuff for myself.
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