Author: José Carlos
Date: 14:44:36 08/26/05
Go up one level in this thread
On August 26, 2005 at 15:04:55, Robert Hyatt wrote: >I'm fixing to change the way I number bits to make bit 0 the LSB (as the BSF/BSR >instructions count on the X86) rather than the MSB as the leading zero >instruction counts on the Cray-1 architecture. > >I have four choices for which square bit 0 represents (four logical choices, >anyway, I guess one could number bits randomly should they choose). > >A1 = 0 >H1 = 0 >A8 = 0 >H8 = 0 > >For those of you using bitboards, which did you use? Since it doesn't matter to >me at all, since I am having to rewrite a bunch of stuff to make this work, I >thought I would try to match the most common layout which will make the programs >more compatible if we share any ideas. > >I am leaning toward H1 = 0, H2 = 8, ..., H8 = 56 and A8 = 63, but I've not made >any decision yet... The reason for this is that it is easier to visualize if >you think of the chess board as being composed of the 1 rank and the rightmost 8 >bits of the bitboard, the 2nd rank is the next 8 bits, etc. > >The alternative is H8=0, etc, so that the last rank is the rightmost bits, the >seventh rank is the next 8 bits, etc. Anything else requires "mentally >mirroring" so that if A1 or A8 is bit zero, the bits are backward, since A8 is >the left end of a rank, and bit 0 is the right end of a set of 8 bits... In Anubis (non rotated bitboards) I have H1 = 0 so that I can visualize the board easily and have some pstables like this: static const SINT8 as8psCaballo[] = { -25,-15,-15,-10,-10,-15,-15,-25, -10, -4, -2, 0, 0, -2, -4,-10, -4, 0, 5, 3, 3, 5, 0, -4, -2, 1, 5, 8, 8, 6, 1, -2, -2, 1, 5, 8, 8, 6, 1, -2, -4, 1, 6, 3, 3, 6, 1, -4, -6, -1, -1, 0, 0, -1, -1, -6, -20,-10, -4, -2, -2, -4,-10,-20 }; It is knight eval. I also have a translate-to-black table like this: static const SINT8 as8Negras[] = // Tabla para traducir coordenadas y reducir espacio { 56,57,58,59,60,61,62,63, 48,49,50,51,52,53,54,55, 40,41,42,43,44,45,46,47, 32,33,34,35,36,37,38,39, 24,25,26,27,28,29,30,31, 16,17,18,19,20,21,22,23, 8, 9,10,11,12,13,14,15, 0, 1, 2, 3, 4, 5, 6, 7 }; Seems to me the more natural way to represent the board. José C.
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