Author: Dave Gomboc
Date: 14:47:10 08/16/99
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On August 16, 1999 at 10:22:14, Bas Hamstra wrote: >What good is razoring? How safe is it? Pros en cons? It prunes at depths 1 to n-1 instead of from depths 2 to n, so it speeds things up a lot. It isn't a safe heuristic like alpha-beta. It will blow up in zugzwang positions, just like null-move. Dave >In August 16, 1999 at 03:44:38, Dave Gomboc wrote >>On August 16, 1999 at 00:17:39, Scott Gasch wrote: >> >>> >>>Would someone please explain the concept of razoring or point me to a reference? >>> >>>Thanks, >>>Scott >> >>You could consult section 4.1 of Computer Chess Compendium, Levy (ed.), >>Springer-Verlag, 1988. This book has some cool stuff in it, and is IMO well >>worth tracking down at your local university's library. >> >>It is actually a reprint of "Tree-Searching and Tree-Pruning Techniques", John >>Birmingham and Peter Kent, in Advances in Computer Chess 1 (Clarke, ed.), >>Edinburgh University Press, 1977, pp. 89-97. >> >>The quick low-down: >>when max-ing >> if static_eval(node) < backed_up_eval(some sibling node, depth) prune node >> >>[for min-ing, flip the compare.] >> >>That sounds a little insane. Probably it has something to do with their example >>being for a 4-ply search. :-) Maybe give >> >>(when max-ing) >> if backed_up_eval(node, depth-1) < backed_up_eval(some sibling node, depth) >> then prune >> >>a look-see. What ends up happening with the latter translation of their >>description is that branches that look sucky will get searched one ply less >>deeply. Of course, it would be possible to perform razoring recursively too. >> >>Dave
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