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

Author: Dann Corbit

Date: 23:03:53 04/20/00

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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.



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