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Subject: Re: TB's Basic Question

Author: Robert Hyatt

Date: 21:45:13 01/25/00

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On January 25, 2000 at 13:07:38, Dave Gomboc wrote:

>On January 24, 2000 at 09:09:50, Steve Coladonato wrote:
>
>>On January 23, 2000 at 17:06:14, José de Jesús García Ruvalcaba wrote:
>>
>>>On January 23, 2000 at 11:45:29, Steve Coladonato wrote:
>>>
>>
>><snip>
>>
>>>>
>>>>From this and Michel's response, is it not true then that the "best move" is
>>>>stored in the tablebases and if so why have the program run thru the legal moves
>>>>and probe the tablebases for each one?  If you're concerned about legal moves,
>>>>pick the best move as noted in the tablebase and then check to see if it's legal
>>>>(in case of some error in the tablebase).  I realize the CPU time here is
>>>>minimal and I'm just trying to get the logic behind the use of tablebases.
>>>>
>>>>Thanks again.
>>>>
>>>>Steve
>>>
>>>	Tablebases do not store moves (not even the "best" move). They only store
>>>scores for positions.
>>>	(Assuming the root position is in tablebases and that there are no tablebases
>>>missing) the program has to search all the legal ply-one moves, and probe for
>>>every resulting position. This returns a score for each one, and the highest
>>>scoring one is chosen.
>>>José.
>>
>>Jose,
>>
>>After I sent the response I realized that the program would have to generate a
>>move and then find that position in the tablebase.  The table Michel included
>>was really only a representation of the tablebase, not the structure of the
>>tablebase.  So the (init+move) would have to found again using the hash lookup
>>and the scores for all (init+move)'s would be evaluated to determine the best
>>one.
>>
>>Thanks.
>>
>>Steve
>
>Sounds like you've got it all.
>
>Dave


Except there is no "hash lookup".  It is an exact probe into the table made
possible by computing a very precise table index that is unique for each
possible configuration of pieces on the board.



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