Author: Eugene Nalimov
Date: 12:15:01 11/21/98
Go up one level in this thread
On November 21, 1998 at 13:03:07, Robert Hyatt wrote: >On November 21, 1998 at 11:55:18, Amir Ban wrote: > >>On November 21, 1998 at 10:34:55, Robert Hyatt wrote: >> >>>On November 20, 1998 at 23:25:37, James Robertson wrote: >>> >> >>>> >>>>Deep blue was searching 250,000,000 nps right? Would it take roughly 160 seconds >>>>(40,000,000,000 / 250,000,000) for Deep Blue to search the same number of nodes? >>>> >> >>You have to divide the Deep Blue NPS by some factor due to the unavoidable loss >>when doing parallel search. This factor depends on the number of processors and >>the efficiency of the algorithm. I think we can safely assume a factor of 5, at >>least. > >It's not that bad. Hsu reported roughly 30% loss... ie if he searches 250M >nodes per second, that is something close to a single processor searching >about 170M nodes per second. I see similar numbers in crafty between 1-8 >processors and also saw similar (actually maybe a little better) numbers >with Cray Blitz... I beleive that Murray Campbell said that their "effective" node rate is about 25-30% of "nominal" because of parallel overhead. They have not 8 or 16 processors, but hundreds... Eugene > >> >> >>> >>>just don't overlook the *huge* difference in the "shape" of the trees. The >>>tree by dark thought is basically shallow and wide, when compared to deep >>>blue. Because at this point Dark Thought has searched 20 plies, about >>>*double" the depth of Deep Blue... Yet apparently DB went far deeper along >>>the critical lines (seems singular extensions and other things they do work >>>very well here)... >>> >> >>It's true that Deep Blue did brute force (no forward pruning like null move), >>but you expect a 20-ply null-move search to find what an (incomplete) 11-ply >>full-width search supposedly found. >> >>One way to compare DB to other search engines is to consider the following: DB >>gets fail-high on Qb6 after 1 sec., and this resolves after 5 sec. >> >>Amir > > >I think their search is difficult to understand. IE I'll point back to the >position I posted last year on r.g.c.c about the c5 move in a game against >Cray Blitz, in Orlando at the 88 or 89 ACM event. They played c5 after >failing high to +2.x, the game went *10* full moves further before *we* >failed low to -2.x... I was looking right at their output and they had >this incredibly long PV showing that the bishop was going to be lost. They >saw it 20 full plies before we did. Lots of micros tried this position last >year, and almost all would play c5 (as we expected that reply ourselves in >the real game). But *none* had any clue that it was winning material.. even >when they went far into the variation... > >The stuff they do with singular extensions and threats really shines in some >positions... and probably costs them dearly in others... But they have the >horsepower to pay the price when it doesn't work, and then they kill us when >it does.. > >In Cape May (94 ACM) we ran with the full singular-extension algorithm >enabled and promptly lost the first game we played, because we searched out >the bottom of our 60 ply limit, and we didn't detect that...
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