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Subject: Re: Tablebase format

Author: Dan Newman

Date: 11:12:57 08/28/98

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On August 28, 1998 at 13:44:01, Larry Coon wrote:

>On August 28, 1998 at 05:35:47, Dan Newman wrote:
>
>>>1. Is it safe to assume that "qsf" (queenside)and "tri"
>>>   (a1-d1-d4 triangle) indexing are never used in the
>>>   same tablebase file?
>>
>>Yes, that's my understanding too.  When there are only pieces on
>>the board there are more symmetries to play around with than when
>>there are pawns, so we can use the "tri" indexing for one of the
>>pieces.  Since pawns are highly directional you lose a lot of the
>>symmetry and must go to "qsf" indexing--which gives less than
>>a third of the "compression" that "tri" gives.
>
>Makes sense.  So the general rule would be:
>   -- If there are -any- pawns, there will be one "qsf" (on
>      a pawn) and the rest will be "all."
>   -- If there are -no- pawns, there will be one "tri" (on
>      the last black piece) and the rest will be "all."
>Sound better?
>

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.



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