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

Author: Heiner Marxen

Date: 14:41:35 04/22/00

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On April 22, 2000 at 14:47:08, Tom Kerrigan wrote:

>On April 22, 2000 at 13:28:39, KarinsDad wrote:
>
>>On April 22, 2000 at 13:25:03, Tom Kerrigan wrote:
>>
>>[snip]
>>>
>>>Notice my idea was to use Huffman encoding for the bitboard, and not the pieces.
>>>
>>>-Tom
>>
>>
>>How so? Please elaborate.
>>
>>KarinsDad :)
>
>I doubt it would be possible to do a very good job compressing the pieces (4
>bits ea.) themselves, but I think the bitboard should be fairly compressable. I
>suspect that most bitboards have strings of 0's scattered throughout them.

If you mean that bitboard which distinguishes empty from nonempty positions,
then no: try to do the math yourself (at first I did not believe it myself):
there are at least 2 and at most 32 of the 64 bits set to "non-empty".
Sum choose(2,64) upto choose(32,64) and compare to 2^64, and you will see,
that you need a little bit more than 63 bits to code all possibilities,
regardless of how clever you do it.

Heiner

>-Tom



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