Author: Mike S.
Date: 15:37:14 12/06/02
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On December 06, 2002 at 15:34:58, Bob Durrett wrote: >On December 06, 2002 at 13:18:31, Mike S. wrote: >(...) >>I thought, if the positional ideas are related to a *sacrifice*, these could be >>especially suitable as computer test positions, because they may have the >>necessary "testing character" of the solution move. >A true positional sacrifice [a sacrifice intended only to obtain positional >advantage] is a very interesting special case. True sacrifices to obtain >non-positional advantages, i.e. tactical, might also be considered a special >case, too. How chess engines handle positions involving either kind of true >sacrifice is a very interesting question. What is needed is a quantitative >measurement of the performance of the top chess engines when faced with such >positions. (...) Actually most "modern" test suites should contain such positions, IOW things are a bit easier than you seem to suppose. "True" sacs are pretty normal nowadays. There's no other problem than to find good test positions (and that has been done many time already, so there's no demand for any new especially sophisticated approaches IMO). Just find good test positons, and that' it... >>I'm afraid I can't explain >>that properly... but I'm convinced that "normal" moves are not good for test >>positions, neither for tactics nor for positional tests. > >Why not good? The non-sacrificial positions need not be positions having >several equally good moves. I suspect that positions of this type could be >found, where one move was much better than the rest. The criteria that there's only one best move, is *not sufficient*. It has to be a move which tells "by itself" that the engine has spotted something special. A sacrifice (simply a blunder if there wouldn't be the special pointe) can provide that. That's what I mean by "testing character". With "normal" moves, which don't sac anything or don't refute material offered, it's very difficult to tell if the engine has chosen this move for the intended reason or by luck. This is the point. An engine won't sac a queen without very good reasons, but a normal silent move like can remain doubtfull (in terms of testing clarity). >Note that I am thinking that design of engines to do well with positional >positions would *primarily* be a problem for design of the "position evaluation >software," as opposed to the "searching software." That may not be a valid >assumption. I don't know. Positional evaluation is part of computer chess since Shannon's papers (= ever since); there is no basic problem or demand for anything new about that. Every engine does it somehow (of course the quality and number of factors evaulated differs). The following position is one of the best examples I know (although I'm not 100% sure if Black can't *delay* the idea; in-between-moves can be a big problem for positional tests): [D]1r1r2k1/2b1qp1p/b1p3p1/p1p1p3/2P1P3/1PN1BP2/P1Q3PP/R2R2K1 b - - 0 1 From Liublinsky - Botvinnik, Moskva 1943 Some engines will find 1...Rd4!, transforming the doubled c-pawn into an protected passer (if White accepts; it's typical that engines which are planning Rd4, don't expect White to take the rook). Regards, M.Scheidl
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