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Subject: Re: Tablebase format

Author: Steven J. Edwards

Date: 12:42:36 08/29/98

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On August 29, 1998 at 04:42:55, Dan Newman wrote:

>On August 28, 1998 at 19:19:28, Larry Coon wrote:
>
>>On August 28, 1998 at 14:12:57, Dan Newman wrote:
>>
>>
>>>Yes, I think that's it.  (But, what if there are two pawns;
>>>which gets the "qsf" index?  My vote is: the last one.)
>>>
>>>-Dan.
>>
>>I may be missing the obvious, but does it matter?
>>Pick -either- pawn and force it to the queenside,
>>and let the other be an "all", and I think it'll
>>work the same whichever one you pick.
>>
>>Larry Coon
>
>Hmm.  You're right--that it doesn't matter which pawn on the
>board is chosen to be the one--but it does matter which index
>gets to be the "qsf" index.  For example KRKPP could have the
>signature "qsf all all all all" or "all qsf all all all"
>which makes a difference in how you calculate the offset into
>the file.  The "qsf" coordinate has to be remapped from the
>range [0-63] to [0-31] and the other coordinates transformed
>depending on whether the qsf-pawn flipped sides or not.  I
>guess the trouble is that we don't know for sure which SJE
>has chosen--it merely seems reasonable to me that he'd choose
>the last pawn.  (For that matter, I don't see why it would
>have to be a pawn that gets the "qsf" index--I'm
>extrapolating from the KPK case I guess...)
>
>-Dan.


If there is at least one pawn, then the last pawn in the class name
gets the queenside mapping and all other men in the class get the 64
square mapping.

If there are no pawns, then the last man in the class name (always a
black man) gets the a1-d1-d4 triangle mapping; all the other men in
the class get the 64 square mapping.

-- Steven (sje@mv.mv.com)





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