Author: Frederik Tack
Date: 09:41:43 12/23/05
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On December 23, 2005 at 12:15:31, Gerd Isenberg wrote: >>>I see - but if i like to introduce color dependent routines for bitboard >>>traversal, i would make them rank-symmetric but not file-symmetric - so that >>>black-white mirrored (including side to move changed) positions are exactly >>>searched in the same manner as the original position. >> >>That's exactly what these functions do, they are rank-symmetric. > >Yes, but a kind of file-symmetry as well. > > a8 h8==MSB >8 0 b 0 0 b 0 0 0 >7 0 0 0 0 0 0 0 0 >6 0 0 0 0 0 0 0 0 >5 0 0 0 0 0 0 0 0 >4 0 0 0 0 0 0 0 0 >3 0 0 0 0 0 0 0 0 >2 0 0 0 0 0 0 0 0 >1 0 w 0 0 w 0 0 0 > a b c d e f g h > a1==LSB h1 > >For white, using bsf you get b1, and then e1 from q-wing to k-wing. >For Black, using bsr you get e8 before b8 - but i like to get b8 before e8. >Or did i miss something? > >Gerd I see what you mean. Next to the two functions i mentioned, i also have a BitscanForwardWhite and a BitscanReverseBlack function. If i need file symmetry, i use the two BSF or the two BSR functions. However, in that case i don't have rank symmetry. If i wanna use the BSF and BSR instructions, i will never have the perfect symmetry, but i don't really need that. Fred
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