Author: J. Wesley Cleveland
Date: 09:40:21 04/27/04
Go up one level in this thread
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. 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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