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Article #434Re: "Solvability" (long & pedantic)
From: David Gudeman
Date: Wed, 30 Sep 1992 18:41
Date: Wed, 30 Sep 1992 18:41
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1668 bytes
In article <1992Sep30.013941.1664@cis.uab.edu> Robert Hyatt writes: ]In article <22964@optima.cs.arizona.edu> gudeman@cs.arizona.edu (David Gudeman) writes: ]>It's been some time since I looked at this stuff, but as I recall, Then don't post without refereshing your memory. ]>search strategies that are still guaranteed to find the optimal ]>solution cannot be asymptotically better than breadth-first search ]>with the same cost function. So alpha-beta pruning will do no better ]>than remove a polynomial number states from an exponential search ]>space. Breadth-first search doesn't even use cost functions, you dimwit. Don't post before your morning caffeine fix either. ]Alpha-beta with good move ordering reduces the size of the minimax ]tree to nearly the square root of the size of the minimax tree... Still, that doesn't reduce the complexity of an _exponential_ function. So if the size of the tree is intractable, it will remain intractable after pruning those nodes. I think what I was getting at (although I'm posting pre-caffeine again) is that an NP-hard search space cannot be made subexponential though clever search strategies (unless P = NP). But since (to my knowledge) chess has not been proven NP-hard, my whole point was rather pointless. So never mind. -- David Gudeman gudeman@cs.arizona.edu
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Path: arc1-ca.pugleaf.net!sparky!uunet!destroyer!ncar!noao!arizona!gudeman From: gudeman@cs.arizona.edu (David Gudeman) Newsgroups: sci.logic Subject: Re: "Solvability" (long & pedantic) Message-ID: <23072@optima.cs.arizona.edu> Date: 30 Sep 92 18:41:49 GMT Organization: U of Arizona CS Dept, Tucson Lines: 31