Author: Robert Hyatt
Date: 10:32:36 03/16/03
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On March 16, 2003 at 06:30:19, Martin Bauer wrote: >Hi, > >how can I see, if one move in a position ist much better, then all others? I >think AlphaBeta gives me only for the best move an exact value. So may be the >second best value is only slightly under the best value, but in fact is is much >worse. > >So what is the common way to detect if i should do an singular extension? Or did >I missunderstand something in AlphaBeta? > >Regards > >Martin Search the first move with the window alpha,beta. Search the remainder of the moves with alpha-X, beta-X. If all moves fail low there, while the first move did not fail low on the original alpha/beta window, you know the first move is > alpha, and the rest of the moves are <= alpha-X, where "X" is the singular margin. That's the trick. It isn't quite as simple in reality, as the first move might produce a score > alpha, and then another move fails high on alpha-X,beta-X, so now you have two moves that seem to be better than the rest. You have to re-search both of them to see if one is "X" better than the other (IE the second move could be the real best move and it could be singular.) It gets technically messy... but it is doable.
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