Author: Inmann Werner
Date: 09:53:12 08/14/98
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On August 14, 1998 at 10:33:05, Dan Homan wrote: >On August 14, 1998 at 10:08:23, Inmann Werner wrote: > >>Question about aspiration window. >> >>I use Aspiration alpha-beta. >>For the first searched move on a ply in deeper depth, I set alpha=oldbestvalue-x >>and beta=oldbestvalue+x >>Nothing unnormal. >> >>Now I found some positions, where my program lowers the evaluation of this first >>move of a ply (till now the best!) always with x. (see above) >>If I change x, it is the same until x gets really high, and i get a "true" >>value. >> >>The disturbing thing on it is, that one ply deeper, the program should recognice >>how bad this move really is, but it does not make a fail low! (If I get a fail >>low, I research with open window) ----- >I am going to guess here. Your search cannot return a score less than >alpha-x, so if you define a fail low as (score < alpha-x), you will never >fail low (like you describe). If you define a fail low as (score <= alpha-x), >then everything should be ok. > > - Dan > Can i really not get a score less than alpha? When I will use score<=alpha-x, this would only be good for the search on the first move!? All other moves are searched with a close window. So, i think, i always would get a fail low. Am I right? P.S: I looked at Minimax (some reference for me), and Minimax uses score<alpha-x for a fail low detection. Is this a bug in Minimax? Werner
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