Author: Dann Corbit
Date: 14:22:45 07/30/99
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On July 30, 1999 at 16:44:47, Ian Osgood wrote: >On July 29, 1999 at 20:47:14, Dann Corbit wrote: > >>On July 29, 1999 at 18:58:12, Ian Osgood wrote: >>>Do other program authors curtail the search when there is a forced move at the >>>root? >>Crafty does. It causes havoc with the Chess Analysis Project. Fortunately, >>Hiarcs will actually process such a position if I ask it to. >> >>>How do you detect that a root move may be forced? >>Umm.. You have no other choices but one? >> >>>Could you compare the values of the best and second-best root moves after a >>>search iteration to detect a forced root move? (Granted, the second-best score >>>won't be accurate due to alpha-beta, but I figure that if the difference was >>>greater than a queen's value, you could still conclude that the best move was >>>forced.) >>Here is how I would detect it: >>0. Am I in check? >>1. Is there only one way to get out of check? >>If so, then the move is forced. Otherwise, the move is not forced. > >I was thinking of a looser definition of "forced" (which subsumes one legal >move, of course). Obvious recaptures would be included, more along the lines of >crafty's "easy" moves with 1/3 search time. After I thought about it a bit, I could see that my definition was wrong anyway. For instance, you might have a bare king who is not in check with one legal move that does not place him into check. That (and any like it) is a forced move, despite his not being in check. The other branches of the thread already define it better than I ever could anyway, so I was hoping to silently skulk away without my ignorance showing. ;-)
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