Author: Gian-Carlo Pascutto
Date: 08:15:03 01/30/02
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On January 30, 2002 at 11:04:18, Vincent Diepeveen wrote: >On January 30, 2002 at 10:12:25, Gian-Carlo Pascutto wrote: > >>Why are you blindly assuming that their effective branching factor >>is 40, just because that is the average number of legal chess >>moves? You should know better. And I know you do. > >branching factor is not the issue here GCP and you know it. >the total number of nodes needed when assuming a theoretical >minimum here is more important. > >Please get your college book again and see that this is about >the squareroot of the number of legal moves. The formula is: nodes = (branching factor)^floor(depth/2) + (branching factor)^ceil(depth/2) -1 Your formula is an approximation. >The average number of legal moves, not counting checking positions as >those get extended, it is 40. > >so squareroot(40) is what you need for nodes. For an alphabeta with perfect move ordering and NO enhancements whatsoever, yes. But that is not what Deep Blue is. I tested a comparable version of Sjeng. I got the number 10-20 out of experimentation, rather than out of my a**. >>They used PVS. Aspiration windows. Hashtables for the first TWELVE >>plies. Even futility pruning. > >In 1998 and 1999 it was mentionned by direct postings from Hsu >and others that they only did a fullwidth search not a single form >of pruning as they disbelieved this, Bob has quoted that zillions of >times in these years. Bob'll have to be the reference on this, but I always understood they didn't use any form of pruning except for quiescent futility pruning, which is what I tested with. >>The _worst_ I saw was around 20, on _average_ it was only about 10 or >>even less. > >that would make it 18^20 then in your case = 9^400, >where i used 18^squareroot(40) = 9^40, get the point? Your maths is wrong. So wrong, I suspect you and Bob attended the same school :) -- GCP
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