Author: José Carlos
Date: 12:10:21 05/25/02
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On May 25, 2002 at 07:29:30, Ulrich Tuerke wrote: >On May 24, 2002 at 19:41:52, José Carlos wrote: > >>On May 24, 2002 at 18:14:57, J. Wesley Cleveland wrote: >> >>> I was looking at the source of crafty and saw that on a fail low, the value >>>returned is alpha, rather than Max of all the values from the level below. Is >>>there some disadvantage in returning the real upper bound? I think it causes >>>some problems in Crafty making it much slower resolving fail-highs and fail-lows >>>at the root as these branches all need to be re-searched. >> >> I use fail soft because I think (not tested) that it generates smaller trees >>generally. >> The drawback is that what you call "real upper bound" is no always so. Null >>move and hashing make the search return "not totally correct bounds" some times. > >What do you mean by "not totally correct bound" ? >I don't care for truth or correctness in my chess program; the aim is just to >find a good move. In case my fail high verification search is failing low, I >just stick to the alpha of the verification search and go on searching the >remaining moves. I think, that's not really a problem. No it isn't if you take care of it. But what I meant with "not totally correct bound" is that, sometimes, the search says "this move is better than 0.54" and, if you research with an open window you find that the move is worth 0.51. I was trying to answer the original question saying that the "possible problems" fail soft can have come from this unexpected behaviour. Regards, José C.
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