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

Author: Les Fernandez

Date: 23:32:49 11/10/99

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On November 10, 1999 at 03:25:28, Ratko V Tomic wrote:

>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.

Hello Ratko,

Listen I have been following this very interesting thread since it started and
am involved in another thread which has also generated some interest.  Appears
to be some different ideas then what I have seen here.  One of the gentlemne is
interested in max of promoted pieces.  ie I remembered seeing the thread that
you can have 8 queens of one color and 4 of the other.  Can someone tell me what
the max #'s are for rooks, knights and bishops. Thanks.  BTW if anyone out here
is interested in the other thread discussing other suggestions let me know and I
will post it.

Les



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