Author: Robert Hyatt
Date: 10:23:31 11/03/98
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On November 03, 1998 at 07:15:57, Inmann Werner wrote: >>>********* >>>I tried something with null move. >>> >>>Problem: you can make a mate with the next move, but the opponent checks you as >>>long as it goes beyond the horizon. >>>I now only talk about this specific problem. I think, it often occurs and know, >>>that a "solution" for this problem does not stop horizon effect all. >>> >>>My thought: When the opponent is on move, I do a null move and one own move and >>>then quiet search. If a mate occurs here, I remember it, and pass it to the next >>>alpha_beta recursion which is my move. Only if a am checked at this time, I >>>extend 2 moves (not only one for the check) as long as extensions are allowed. >>>(Max Extensions...) >>>So I only extend if I can mate in one and the opponent slides out with a check! >>>There are also some limitations when doing the special null move, but there I am >>>experimating. >>> >>>My position above then gets solved at ply 6!!!!! >>>I tried some other positions with heavy threats and checks, where no real mate >>>can be made (worse for my algoritm). There it slows down about 10%, because it >>>looks deeper in maybe interesting things which in this case do not work. >>> >>>I must say, that I implemented above 3 hours ago, and 3 hours testing is not >>>much, but it is worth to think about. >>> >>>Werner >> >> >>my advice is "caution" doing this. IE Crafty finds this at depth=10, about >>10 seconds or so on my ALR. It's not hard to make it find it at depth=6 or >>7. But would it play better in games? No... it is *easy* to over-extend and >>find wonderful tactics but get killed positionally... > >But that would be a principle problem of extensions. If I do not extend in any >case, I can fasten up my program extremly, getting 1 ply deeper. >The question is, when to extend. >Many say, at checks and beats on the same field, because here it gets >interesting. >I do so, and the search slows down. Gets the program then a worse play? >Same I thought about mate threats and extensions. Aren´t they worth an >extension? > >Werner Here's my "stock answer" to that question: Doing the *right* extensions is critical. Doing extensions in the wrong places is futile. You simply try to shift the balance toward doing them in the "right places" only... if you do a few extra, it only costs you time. If you miss a "right place" it can cost you the game. And finally, if you do too many in the wrong place, that can *also* cost you the game... sort of like Goldilocks and the three bears... it has to be done "just right" to make everyone happy.. :)
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