Author: Tord Romstad
Date: 12:01:55 10/08/03
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On October 08, 2003 at 09:18:51, Sune Fischer wrote: >On October 08, 2003 at 08:17:17, Tord Romstad wrote: > >>I don't know much about the "many advantages". My main reason for this >>board representation is that it is extremely simple to use, and that >>the code is clear and easy to understand. > >Heh, that would be my reason to use bitboards :) > >The good thing about bitboards IMO, is that all the complexity is located in the >initializing of the attack boards (if you use rotated). The problem is that you have to do lots of low-level stuff before you even get off the ground. I detest low-level programming, and try to avoid it whenever possible. >The parts one needs to work with a lot is kept clean and simple instead of being >littered with loops everywhere. People keeps claiming that, but all the bitboard code I have seen includes lots of loops (mostly loops through all the 1s in a bitboard). >Oh well, individual taste can't be debated I guess. We can agree about that. And as I have said repeatedly, it is entirely possible that I will try bitboards myself in the not too distant future (when I get a PowerMac G5). >There is just one thing about the geometrical relations I don't understand. > >Suppose you do >dir = sq1-sq2+128 (in 0x88) > >then dir is going to be some multiply of the direction and not (usually) the >step size needed for the board scan in the direction of dir. > >So if one needs a table lookup in any cas, what's the great advantage over the >smaller 64 sized board? Geometrical relations are not only useful for generating attack information, but also in the evaluation, like when evaluating the king's position relatively to passed pawns and other pieces in the endgame. I don't claim that the advantage is very great, but it's there. Tord
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