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Subject: Re: just another reverse bitscan

Author: Gerd Isenberg

Date: 09:15:31 12/23/05

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>>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



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