Author: Ulrich Tuerke
Date: 07:22:59 08/13/99
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On August 13, 1999 at 02:19:30, Scott Gasch wrote: >Hey, > >I have a (stupid?) question about aspiration search. I understand the concept >is to atrificially limit the search window in an effort to prune faster. >However, a value returned from Search(pos, a, b) will always be within the a-b >window. I.e. a <= value <= b. How, then, does one tell if the value returned >is bogus and needs to be re-Searched or whether it is good? Which does a value >== a or value == b mean? > >Thanks, >Scott Usually, the search window is defined without the boundary, i.e. a < value < b is an exact score; a = value or b = value means that you have to proceed a verification search. BTW, the alpha beta search of my program returns also values far outside the alpha-beta region; these can be taken as bounds for the verification search. I think that I remember vaguely that there are 2 kinds of alpha-beta implementations: "fail soft" and "fail hard". I think that "fail soft" always returns a value a <= value <= b ? It seems that you are using "fail soft" whereas I use "fail hard". I am sure that Bob Hyatt can help. Regards, Uli
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