Author: KarinsDad
Date: 22:52:18 12/23/03
Go up one level in this thread
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. Standard encoding for a position with no captures yet yields: 62 bit piece/pawn location 12 bit kings and castling info 30 bits (max) piece or pawn 16 bits (max) pawn color 48 bits (max) piece type and color 1 bit side to move 3 bits e.p. (if necessary, the other e.p. bit isn't needed) So, we are at 172 bits max for the normal encoding. Capturing a pawn with another pawn drops a pawn color bit and a piece/pawn bit, but there are now 3 remaining pawns that could promote and change to pieces for a net gain of 4 more bits (+6 - 2), etc. There are ways to decrease this, but they are tricky.
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.