Author: Dan Homan
Date: 07:33:05 08/14/98
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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 > >I removed hashing and null-move, but it is the same. >If i search the first move of a ply with a full window, everything gets ok, but >slow! > >I am sure, it is a failure in my thinking of aspiration alpha beta. >Has anybody an idea, what could be wrong, where I could search the failure? > >Werner
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