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Subject: Re: Min # of bits needed to store a chess position

Author: Alessandro Scotti

Date: 04:31:30 04/21/00

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On April 21, 2000 at 02:03:53, Dann Corbit wrote:

>On April 21, 2000 at 01:44:07, Tom Kerrigan wrote:
>>On April 20, 2000 at 11:58:55, KarinsDad wrote:
>>>On April 20, 2000 at 04:21:58, James Robertson wrote:
>>>
>>>>What is the current minumum number of bits required to store a chess position?
>>>>If somebody could send me instructions on how to encode a chess position in as
>>>>few bits as possible, I would be very happy.
>>>>
>>>>Thanks,
>>>>James
>>>>jrobertson@newmail.net
>>>
>>>
>>>I think the answer is around 155 or so bits with a enumeration algorithm, but
>>>I'm not sure if anyone has actually written one and proved it. The reason is
>>>that it would be a bit of a bear to write (but doable).
>>>
>>>My best is 162 bits with the algorithm I put together. It also has not been
>>>written. However, it would be quicker to calculate than an enumeration
>>>algorithm.
>>>
>>>A good algorithm is the one used in EDP. It requires 192 bits, but is extremely
>>>simple to code up. Something like:
>>>
>>> 64   64 bits bitboard
>>>128   4 bits per piece times 32 pieces
>>
>>Hmm. I wonder if some sort of Huffman encoding would be useful for the bitboard.
>>Of course, then you get positions that are variable bit lengths, but if that's
>>not a requirement...
>
>that is an excellent idea for average length reduction, but I think it will
>actually expand the worst case length by a few bits.

Well, at most it will expand the length by one bit, used to indicate that we're
*not* using Huffman for this position...



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