Author: Richard Pijl
Date: 08:51:02 11/27/02
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On November 27, 2002 at 11:12:28, David Rasmussen wrote: >On November 27, 2002 at 10:49:00, Richard Pijl wrote: > >>On November 27, 2002 at 10:01:02, David Rasmussen wrote: >> >>>Some time ago, along the lines of these thoughts, I proposed "negative >>>extensions". That is, if you can somehow classify a move as "probably not >>>interesting", you can "extend" the depth by -1 or -0.75 or whatever seems >>>reasonable. Exactly as you do with normal extensions. The good thing about this >>>is that nothing gets pruned for good, everything will eventually get searched >>>with iterative deepening, but you search what you think is interesting first. >> >>Isn't this just razoring? >> >>IIRC Beowulf is using this instead of futility pruning ... >> > >Well, I would say that razoring is a special case of negative extensions. >Razoring normally only happens near the frontier nodes. What I am talking about >can be applied anywhere in the tree. And also, razoring specifically deals with >the futility of getting the score up near alpha again. I am talking about all >sorts of "futile" moves. I.e. a move that moves a rook off the only open file, >is probably not good. That doesn't mean that we don't want to search this move >to some specified depth, in time. But it means that we might put off searching >it till later, by "extending" it negatively. > Won't analyzing this kill your search speed? I mean, you will have to apply a lot of patterns to really make a difference in decreasing the size of the tree, but that will cost performance. And bad moves should have more beta cutoffs in the subtree anyway, so the subtree is probably already quite small. >/David
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