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Subject: Re: Question about Bit storage

Author: Dann Corbit

Date: 15:08:18 01/28/02

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On January 28, 2002 at 17:55:24, Scott Gasch wrote:

>On January 28, 2002 at 17:48:48, Les Fernandez wrote:
>
>>Just curious to know what is the best being done now for storing a chess
>>position.  In the worse case scenario (castling right exists) it takes me 162
>>bits to store 32 pieces, color, location, side to move, castling, enpassant,
>>promotion, ce and pv.  Now if castling rights do not exist then the worse case
>>scenario for the above is 81 bits.  Much further reduction in bits/position is
>>possible but at the moment I am interested in the above.
>>
>>Thanks in advance,
>>
>>Les
>
>How can you have a 162 bit requirement with castling rights and a 81 bit
>requirement without castling rights?  You're telling me you need 81 bits to
>store castling information?  Here's a breakthrough for you:
>
>0000 = no castling possible
>0001 = white can castle short
>0010 = white can castle long
>0100 = black can castle short
>1000 = black can castle long
>1111 = all castling possible

As Professor Clouseau once said, "And the mystery, she is solved":
ftp://cap.connx.com/pub/les/cp.doc

It's a word document.  Might get some revisions in the near future, but it
explains it well enough.

Here's another breakthrough which will reduce the 162 bits back to 81:
Have 6 files, one for each castling status.  Then, you need no bits, because the
castling status is implicit.



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