Author: Robert Hyatt
Date: 19:30:15 04/27/04
Go up one level in this thread
On April 27, 2004 at 12:40:21, J. Wesley Cleveland wrote: >On April 26, 2004 at 12:14:33, José Carlos wrote: > >>On April 26, 2004 at 11:57:43, Vincent Diepeveen wrote: >> >[snip] >>>In *all* experiments i did with nullmove and a program not using *any* forward >>>pruning other than nullmove, the best thing was to *always* nullmove. >> >> >> Yes, that's what other programmers also said (including me) in the thread we >>had last week. That's pretty intuitive. With not any other forward pruning (or >>very little) but null move, the cost of not trying a null move that would have >>produced a cutoff it terrible compared to the benefit of saving an useless null >>move try. So avoid null move, in this case, must be only in a very few cases >>where you're 99.99% certain you'll fail low... if any. > >This seems way too conservative. With R=3 and a branching factor of 4, a null >move should use 1/64 the nodes of a full width search, so if you are 99% >confident you'll fail low, avoid the null move. That math can't be right. at best it saves 1/16th the nodes, because not _every_ ply is full-width. > Fortunately, null move questions >are easy to test. When you would avoid a null move (or skip a full search), set >a flag, make the null move (or full search) anyway, and increment one of two >counters depending on whether the result is the one you expect.
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