Author: Reinhard Scharnagl
Date: 02:55:41 12/24/03
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On December 24, 2003 at 01:06:30, Russell Reagan wrote: >If you were able to get rid of the castling rights by the method I mentioned in >my other post, you could do this (I think): > >1. filling matrix: 62 bit (one bit for each square 0...63, excluding kings) >2. white king's position: 6 bit (coordinate 0...63, castling rights included >here) >3. black king's position: 6 bit (coordinate 0...63, castling rights included >here) >4. active color: 1 bit >5. e.p. flag: 1 bit >6. e.p. column of pawn (if need be): 3 bit (column 0...7) >7. left pieces: 2...4 bit (from filling matrix, except K, castling R and P), no >more than 81 bits > >This would require 160-bits at most. Surely further improvements are possible. >One I can think of is that if the e.p. flag is 0, then we can use the other >3-bits for something (or get rid of them). If the e.p. flag is 1, then we can >locate both the pawn that can be captured by the column, requiring the 3-bits >you have already accounted for, and we can also know the location of the >capturing pawn with 1-bit (left or right of the threatened pawn). In either >case, you can save at least one bit, so we should be down to 159-bits. An e.p.-situation can have two threatening pawns, so there saving one bit is not as easy as described. Reinhard.
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