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Subject: Re: Question about Bit storage

Author: Uri Blass

Date: 07:23:58 01/29/02

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On January 29, 2002 at 09:57:30, Robert Hyatt 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 store a complete chess position without castling rights in 81
>bits?  castling rights are certainly not 81 bits of information to get you
>up to 162.
>
>Something is wrong.

His post is clearly misleading.

I guess that he meant the following:

1)Every position when there is no castling rights is practically 4 positions
2)it is possible to use 324 bits to store it(note that it is possible to use
clearly less than it)

3)324/4=81 so it is possible to store 4 positions when castling is impossible by
81 bits per position

4)if castling is possible every position is only 2 positions so he can use only
an average of 324/2=162


Uri



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