Author: Andrew Dados
Date: 19:41:48 12/05/01
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On December 05, 2001 at 18:09:48, Ricardo Gibert wrote: >On December 05, 2001 at 15:41:12, Bruce Moreland wrote: > >>On December 05, 2001 at 08:22:40, Gerd Isenberg wrote: >> >>>About the pawn hash key discussions: Why using Zobrist keys for pawn hashing at >>>all, at least in BitBoard programs? Isn't it smarter to use a unique 46 Bit >>>(Rank2-7) Difference of two colored Pawn-BitBoards instead of zobrist keys for >>>pawns? No key collisions and key and index (key mod nEntries) calculation on the >>>fly. >>> >>>Gerd >> >>Even if you could generate a Godel number for each pawn structure, there would >>still be some problems. Zobrist keys are wildly different even with small >>changes in pawn structure, so the keys tend to disperse well in the table. >>Depending upon how you generate the Godel number, things might not disperse as >>well. This could be solved by applying a function to the Godel number that >>translated it to another unique number that was not particularly like the >>original number, but this sounds like a challenge in a few different ways. >> >>Please pardon logic errors in the above, I spent too much time doing research >>for this answer and now I'm late to go do something. >> >>I calculated 2^85 different pawn structures, but I believe this is somewhat >>wrong. > >You only need a 48 bit bitmap for the location for all pawns, then since there >are only 16 pawns, you only need an additional 16 bits for color for 64 bits >total. You can do better than 64 bits with Rube Goldberg like tricks, but it is >not worth the trouble. > >> >>bruce 15 bits for color. Which makes 2^63 max pawn positions
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