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

Author: blass uri

Date: 00:47:19 11/11/99

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On November 11, 1999 at 02:32:49, Les Fernandez wrote:

>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.

The max number of promoted pieces is 8 for both sides(queens,rooks,bishops or
knights)

Every capture of a piece can generate 2 passed pawns(1 white and 1 black) and
there are 14 pieces in the initial positions except kings(7 white and 7 black)
so it is not a problen to capture 8 of them.

Uri

 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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