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Subject: Re: Crafty question for Dr. Hyatt

Author: Robert Hyatt

Date: 05:40:47 03/09/00

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On March 09, 2000 at 00:05:03, Jeremiah Penery wrote:

>On March 08, 2000 at 22:57:08, Sanjiv Karnataki wrote:
>
>>Hi,
>>
>>I noticed that in crafty all moves except the first move in the root move list
>>are sorted by the node count so that after the best move from the previous
>>iteration all other moves are in a descending order of node count searched in
>>the previous iteration?
>>
>>Am i correct in reading the code? and what is the advantage of doing this?
>>
>>Currently in my program, I keep the root move sorted based on the score returned
>>for each move from the previous iteration. highest score to lowest score. what
>>are the pros/cons of this method vs. crafty's?
>
>Alpha-Beta doesn't return scores for any move except the 'best' move.  At least
>they're not _real_ scores, in the sense that if you search those moves
>separately it's likely that you won't get the same score.
>
>If you sort moves by nodes, then moves which start looking better as you go
>deeper go closer to the top of the list.  So if you have move 'x' as the best,
>and it takes a million nodes to prove that 'y' is worse than x, and all other
>moves only take 1000 nodes, there's probably some reason it takes so long to
>prove move 'y' inferior.  It's more likely that this move can become the 'best'
>move in a subsequent iteration than it is for the other moves.


should have read your answer before responding myself.  Yours was even clearer.

:)



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