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Subject: Re: Notion: shrunken bitboards

Author: James Robertson

Date: 19:33:56 04/27/01

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On April 27, 2001 at 21:46:26, Dann Corbit wrote:

>Since bishops can only touch 32 squares of a chess board, has anyone bothered to
>write a system using 32 bit bitboards for bishops?  About like a rotated
>bitboard, but shrunk by half.

This would be possible, but you would need the all-pieces, just black pieces and
just white pieces bitboards also 32 bits (so you can and/or/xor with our bishop
board). Since this is not possible (there are 64 squares), you would need two of
each of these boards, one on just the light squares (for one bishop) and one on
just the dark squares (for the other bishop). These 6 additional bitmaps can't
be used anywhere else (except queen diagonal moves). This is a lot to update
each move, and outweighs the benefits of the smaller, "32-bit processor
friendly" representation.

James

>
>Also, knights can only cover a 5x5 area (with only 8 spots attacked or defended)
>and so it seems that knights might also use a compressed scheme (though not
>nearly so obvious as bishops).



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