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Subject: Re: Is this where the 174 bit minimal figure comes from?

Author: KarinsDad

Date: 19:56:18 05/17/99

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On May 17, 1999 at 21:15:59, Dann Corbit wrote:

>From:
>http://www.xs4all.nl/~verhelst/chess/representations.html
>
>We have this:
>
>"Minimal coding
>When using 4 bits per square, an array representation will have a total size of
>256 bits. It is possible to squeeze a chess position in less bits by using
>Huffman coding techniques. For example (C is colour of the piece):
>
>Empty square: 0
>Pawn: 10C
>Bishop: 1100C
>Knight: 1101C
>Rook: 1110C
>Queen: 11110C
>King: 11111C
>This gives a total size of 32 + 48 + 20 + 20 + 20 + 12 + 12 = 164 bits. Some
>additional bits will be necessary to indicate castle status and side to move."
>
>You would also need to store e.p. square, if any, I think. Ten bits more
>[5ep+4castle+1stm]gives 174 bits.

This 174 does not include promotions.

Actually, the 174 bits in the other posts came from a different scheme:

100 bits 30 pieces and pawns packed
12 bits kings and castling
61 bits (62 remaining squares bitboard - last one not needed)
1 bit side to move

or something to this affect (but I do not know where ep fits into this, maybe
into the kings structure).

KarinsDad :)



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