Author: Rémi Coulom
Date: 07:40:05 06/13/04
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On June 13, 2004 at 10:09:59, S J J wrote: > > I've read that the use of Alpha Beta searches can double the >number of ply a program is evaluating. > On the surface, it looks like both a MinMax and AlphaBeta searches >evaluate the same set of moves that have been generated (Alpha Beta >being able to avoid searching select branches). > To look twice the number of ply deeper, those positions would first >need to be generated. I'd expect generation of the 2X ply to take a >great amount of time compared to the time saved by Alpha Beta. > > I suspect that "somehow" Alpha Beta enables one to not only avoid >evaluating certain branches, but, also avoid the need to generate them >in the first place. Yes alpha-beta cuts-off big parts of the tree that do not have to be generated. For instance, if the first move that you search at the root returns a positive score, and the second move at the root is refuted by one move of the opponent, then it is not necessary to search more refutations. For more details, take a look at Bruce's site: http://www.brucemo.com/compchess/programming/index.htm Rémi > > In my program, the amount of time needed to generate the moves is >several times what it takes to evaluate those moves, so I'm assuming >to get the deepest search, Alpha Beta helps trim the number of branches >that generate moves. > > Any clarification would be appreciated.
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