Author: Bas Hamstra
Date: 01:17:12 06/05/02
Go up one level in this thread
On June 04, 2002 at 20:31:41, Robert Hyatt wrote: >On June 04, 2002 at 18:01:03, Gian-Carlo Pascutto wrote: > >>On June 04, 2002 at 17:52:47, Dann Corbit wrote: >> >>>On June 04, 2002 at 16:28:39, Gian-Carlo Pascutto wrote: >>> >>>>On June 04, 2002 at 16:18:55, Gian-Carlo Pascutto wrote: >>>> >>>>>Because you are using a processor that is clocked at twice the clock >>>>>frequency? Why compare a 1ghz processor to a (nearly) 2ghz processor >>>>>and conclude anything about efficiency there? Is there anything that >>>>>suggests that the alpha is simply more "efficient"? To justify that >>>>>clock frequency disparity? >>>>> >>>>>A machine twice as fast (clock freq) _should_ perform just as well as >>>>>a 64 bit machine at 1/2 the frequency... Less would suggest that the >>>>>32 bit machine simply sucks badly. >>>> >>>>I don't agree with the validity of a clock-for-clock comparison, >>>>but if you want to do it anyway, I'll again point to Vincent's >>>>numbers: >>>> >>>>At the same clockspeed, Crafty only gets 33% faster on the 64-bits >>>>machine. >>>> >>>>When you read this, keep in mind that most applications get _more_ >>>>than 33% faster on the 64-bits machine. >>> >>>All the new 64 bit chips in the discussion are pretty much beta stage right >>>now. >> >>Not true for the Alpha. > >Depends on the alpha being discussed. DEC had processors beyond the 21264 >running. Although the 21264 was pretty good. Dann was a bit off on the >performance as Tim Mann was running a 21264 at 600mhz and getting right at >1M nodes per second. Mckinley is getting 1.5M at 1000mhz, so the alpha might >have a bit of an advantage still. but it is pretty small... > >Mckinley is only available to a select few. 21264's are fairly common. >Anything beyond that is not readily available... > > >> >>>So, I think that architecturally, it makes good sense to design for a 64 bit >>>system right now. >> >>That makes sense, if the 64 bit design is actually faster than the corresponding >>32 bit design (even on 64 bit hardware if you wish). >> >>The case for bitboards is not clear on that matter. Certainly, if >>the speedup over nonbitboards is only 33% they will have a hard time >>convincingly beating alternative appraoches even on 64 bit hardware. >> >>-- >>GCP > >You are assuming that bitboards are _slower_ than non-bitboard programs on >32 bit machines. I haven't seen this demonstrated yet. We can always do some >sort of a test. IE since the most common move generator issue is "generate all >captures" we can try that with bitboard and non-bitboard approaches to see if >one is really much better than the other on 32 bit machines. I don't think so >myself. I think they are pretty equal due to the multiple pipe issue. > >But a test could be done to see, since this is the most common thing needed >in a chess engine. That's not a fair test, I think. IMO the most heavily used routines are: - See() - GenCaps() - SquareAttacked() - Make/Unmake() You just pick the one in which bitboards is good. In fact it is nearly impossible to figure out what's best overall by comparing only parts. What you could do though, is generate "profile data" about a search in average middlegame positions, and see how many times each of the above functions is being called. Then we could turn this into a sort of benchmark: 10.000 * a() 8.000 * b() 3.000 * d() 5000 * c() and compare times for bitboards and 0x88 to do this. This would at least tell us if bitboards is faster *for Crafty*. Best regards, Bas.
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