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Subject: Re: Storing a position

Author: Russell Reagan

Date: 12:17:53 05/04/04

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On May 04, 2004 at 14:07:55, Chris Hull wrote:

>Does anyone know of a way to store any legal chess position in 160 bits?
>
>I am only concerned with those position that can be legally reach within
>a game. It must include ways to store some wacky but legal positions like
>10 rooks or 10 bishops or 9 queens or no pawn but 28 combined pieces on
>both sides, plus all the more regular looking ones.
>
>Thanks.
>
>Chris

Here is another thread to look at.

http://chessprogramming.org/cccsearch/ccc.php?find_thread=338187

The basic idea discussed there was this:

* 64 bit bitboard representing the state of each square (occupied/empty)
* 80+ bits of Huffman encoded piece values (varies depending upon promotions
  and captures)
* 1 bit side to move
* 4 bits for castling rights
* 4 bits for en passant square

I don't remember what the final conclusion was, but it was right around 160
bits, or slighty lower.

Does anyone know what the current minimum number of bits is? I read 157 or 155
in the other links posted in this thread.



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