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Subject: Re: Practical Tablebases (much smaller) ?

Author: Miguel A. Ballicora

Date: 10:40:53 11/13/01

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On November 13, 2001 at 13:23:12, Robert Hyatt wrote:

>On November 13, 2001 at 12:03:31, Uri Blass wrote:
>
>>On November 13, 2001 at 10:09:30, Robert Hyatt wrote:
>>
>>>On November 13, 2001 at 08:31:09, William Penn wrote:
>>>
>>>>I suspect this has been discussed before but I didn't pay attention, so please
>>>>pardon my redundancy. If you could just point me in the right direction, much
>>>>appreciated...
>>>>
>>>>Can't we make some assumptions without compromising very much practical playing
>>>>strength and significantly reduce the size of the endgame tablebases? For
>>>>example it seems a waste to generate separate positions for "white to move" and
>>>>"black to move".
>>>
>>>How would you handle all the common zugzwang positions?  black king at e6,
>>>white king at e4, white pawn at e3.  White to move draws.  Black to move
>>>loses.
>>
>>There is a solution for it.
>>You probe the tablebases only when the right side is to move.
>>
>>I understand that calculating the moves when you are in a tablebases position
>>becomes more comlicated but it can be solved by 2 ply search.
>>
>>Uri
>
>
>This implies you _only_ stop the search when a specific side is on move.
>This will break the basic idea of minimax to a degree, because some positions
>will be searched one ply deeper than they should be, and that means comparing
>apples and oranges in the evaluations those two searches return.

Everytime you find a tablebase position, you ask if white is on the move.
If it is, you do a 1 ply search from here that will return the same result
as if you have both tablebases and you probe immediately.

Regards,
Miguel




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