Author: Russell Reagan
Date: 00:14:14 12/24/03
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On December 24, 2003 at 01:52:18, KarinsDad wrote: >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. > > >Except if the rooks do not castle, they could be anywhere. If the rook has moved there is no castling right, so what is the problem? >Standard encoding for a position with no captures yet yields: > >62 bit piece/pawn location >12 bit kings and castling info This portion below can be encoded using no more than 88-bits, assuming no captures or promotions (even with some odd promotions I tried, it still equals 88-bits, since there must be a capture in order for there to be a promotion). That would give us a total of 166 bits. Somehow Reinhard is able to do this in 81-bits. If that is correct, then we should be able to represent the position in 159 bits. >30 bits (max) piece or pawn >16 bits (max) pawn color >48 bits (max) piece type and color
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