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Subject: Re: Counting & Encoding Any Chess Position in 157 bits

Author: Ratko V Tomic

Date: 00:25:28 11/10/99

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Errata:

>
>    3.6 Castle state was not included in the count, but it was estimated
>        that it would add less than 0.13 bits to the position code, in
>        the worst case (check earlier discussion on king pair + castle
>        status encoding in 12 bits). The ep status also wasn't encoded,
>        but since there could be at most 4 ep capture targets (white
>                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>        assumed to move, thus 4 targets are black pawns on the 5-th rank),
>                              ^^^^^^^^^
>        the ep would add at most log2(5)=2.32 bits
                                  ^^^^^^^^^^^^

This should say: "at most 5 ep capture targets" (e.g. the 5th rank could
be: pPppPppP with 5 black potential targets & 3 white pawns capable of
capturing any of the 5). Thus the code addition is log2(6)=2.58 bits.
This addition of 0.26 bits still doesn't bring the full position code
above the 157 bits.





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