Author: Alessandro Damiani
Date: 12:23:55 11/21/02
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On November 21, 2002 at 06:47:24, Steffan Westcott wrote: >On November 21, 2002 at 05:55:59, Alessandro Damiani wrote: > >>And for sliding pieces? The distance between the from- and the to-square is not >>fixed. In the worst case, for each to-square there are 7 from-squares for one >>direction. Do you keep one bitboard for each distance in one direction, ordered >>from 1 to 7? Just my first thought. > >No, just one bitboard is used to store all possible destination squares for, >say, upward rook moves. Look for my example routines FillUpOccluded(), >FillRightOccluded(), etc in the CCC archives (when they get updated, eventually >:-< ) for a suggestion on how to calculate this type of bitboard quickly. > I already understood the concept with "one bitboard for each direction". Let's take a look at the example position I gave in a previous post (here again): [D]4r1k1/2q2pp1/p1p4p/Pp1b4/1P6/2N1PN2/4QPPP/3R2K1 w - - 0 1 The bitboard for *all bishops right-down* is: :::::::: :::::::: :::::::: :::::::: ::::#::: :::::#:: :::::::: :::::::: As you said, each time a move is searched, its to-square is removed from the bitboard. We look at the bitboard above as a generic state in the generation process (part of the invariant). By knowing the direction "right-down" we start at the left-up most bit set to 1, right? Do you keep an additional invariant related to the from-square? Or do I like the from-square far too much?? *g* I wrote my own method for attack detection two years ago. It is not Rotated Bitboards. I call it Rotated Indices. Bob Hyatt reported that my method is a little bit faster than his on 32bit machines, while on 64bit it is not clear. The chess-specific improvements I added later were not used in the tests. My method is free and can be downloaded from my homepage. So, for the time being I don't need a new attack detection. I may change to your flooded bitboards when they are faster than mine on a 64bit monster. ;) But I already flooded all the weak pawns and squares. hehe Thanks! Alessandro
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