Author: Russell Reagan
Date: 22:06:30 12/23/03
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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.
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