Author: Peter Fendrich
Date: 11:46:42 02/06/99
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On February 06, 1999 at 11:02:59, William Bryant wrote: >After a depth of 4, I tried using the alpha and beta returned from the >previous iteration as the initial alpha and beta for the next depth search > >This generated a speed increase (I assume for generating early cutoffs). > >Is this wise or are there pitfalls I haven't seen yet. > >Would it be better to widen the search window by a pawn or so by subtracting >100 from alpha and adding 100 to beta before the next iteration? > >Is there a better (read safter and/or more efficient) way of doing this? > >Thank you in advance. > >William >wbryant@ix.netcom.com In principle I think it's a good idea but it can be done with variations. I do it like this, in the beginning of each new iteration: alfa = eval - alfaMargin; beta = eval + betaMargin; alfaMargin and betaMargin, depending on various factors, are set to about 40 where pawn is 100. If the search returns a value outside alpha/beta, I have to re-search with a wider interval. Even here I take a chance with a window narower than the maximal window with risk for one more re-search. If it's the first move in the iteration, in some situations, I don't re-search that move if it's below alpha. Insead I hope for the next move to match the alpha/beta window. The risk, of cource is more re-search... I think it all depends of your program behaviour so the only way to know is to test... //Peter
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