Author: Robert Hyatt
Date: 21:26:03 05/11/02
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On May 11, 2002 at 21:12:35, David Dory wrote: > >Vince wrote: >>>Bitboards is a tradeoff. You put less information into >>>a single 64 bits word. So you can use instructions like AND and OR >>>more easily. > >>>Gnuchess is putting more information into a single word for each >>>square. The advantage is you can faster work with complex knowledge. > >You wrote: >>So in short it means, bitboard helps put more information (==more knowledge)in >>single square (64 bits?), if that is what I understand. > > >You have it exactly backward. Bitboards put less info than the design used by >Gnuchess 4, but they are faster, and you have the opportunity to be quite >creative with their use, without a big penalty in speed. Actually Vincent has it backward. Bitmaps are "dense" in terms of information. For example, in the opening position, 1/2 the bits are 1's and 1/2 are 0's. That seems to suggest 50% density but that is _wrong_. The zero bits also have significant meaning (squares that are empty). Bitmaps are by far the best way to represent a chess board when you have a 64 bit machine. Just compare a 32 bit program to a bitmapper on a 64 bit machine to see why. Every internal instruction moves 64 bits around, and 1/2 of the bits are totally useless on a 32 bit program. On a bitmapper, _every_ bit counts... > >Dave
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