Author: Vincent Diepeveen
Date: 20:12:18 01/26/01
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On January 26, 2001 at 12:03:53, Christophe Theron wrote: >On January 26, 2001 at 05:32:26, Steffen Jakob wrote: > >>On January 25, 2001 at 14:11:36, Peter McKenzie wrote: >> >>>On January 25, 2001 at 08:20:26, David Rasmussen wrote: >>> >>>>Howdy. >>>> >>>>Inspired by the thread on extensions, I was wondering whether the idea of >>>>negative extensions or reductions could be a good one. >>>> >>>>I mean, maybe many of the "unsound" pruning methods would be sounder if, instead >>>>of just pruning, they just adjusted the resulting depth down. In that way, a >>>>line would still be examined, only later. >>> >>>Hi, in the past I have thought of negative extensions too although I haven't >>>tried implementing them yet. I wouldn't consider nullmove to be a negative >>>extension, its not really in the spirit of an extension - I'd just call it a >>>pruning method. >>> >>>In my mind, extensions are usually a move based thing. By this I mean that we >>>can see some property of the move we have just played (or are just about to >>>play, depending on exactly how you implement the extension) which indicates that >>>we should extend. Obvious examples are >>>- check extension >>>- recapture extension >>>- single response extension >>>- passed pawn push extension >>> >>>So the question is, what sort of moves could be candidates for a negative >>>extension? >> >>Some underpromotions. >> >>Greetings, >>Steffen. > > > >I seem to remember that you have suggested this some months ago. > >I have tried and found that it was doing exactly nothing to the playing >strength. So the idea does not look bad, but it does not help at all. > > > > Christophe A possible explanation of that can be: most underpromotions which are useless are directly captured. About any chess programs ordering picks those moves usually as first so you get a repetition from hashtable then which is nearly for free and of course is not hurting overhead.
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