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Subject: Re: It may be impossible to represent all board positions with 160 bits

Author: Dann Corbit

Date: 14:09:41 05/27/99

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On May 27, 1999 at 16:56:22, KarinsDad wrote:
[snip]
>2) Due to the "tricks" being used to decrease the number of bits, the actual
>number of legal positions may be greater than 2^x where x = minimum number of
>bits it can be fit into. For example, if I had a 4x4 chess board and only one
>piece to place on it, it is obvious that there would be 16 possibilities or 4
>bits required to represent it normally (assuming the piece had to be on the
>board). If I could then use some compression trick to drop it down to 3 bits, it
>would not mean that the number of possibilities dropped from 16 to 8, it would
>just mean that I was clever.
If you have some mapping from a large set of bits to a smaller one, then it does
completely number the possibilities or you have an error.  I am assuming that a
binary string of n bits can be translated to a unique board position.  If this
is true, and all board positions can be generated using *whatever* function you
wish to apply to the bit string, then the count of bits will absolutely be a way
to determine the limit of legal board positions.

I won't be hasty to dismiss his methodology until I have seen it in total.
The work of J. Niervegelt does, indeed, indicate that there may be only about
100 bits of information in a chess position.  However, I don't think any 18
queen positions were tried, so I'll withhold judgement on that one.  At any
rate, a correct and compact coding will have important theoretical value.



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