Author: Vasik Rajlich
Date: 03:33:20 07/16/04
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On July 16, 2004 at 03:35:37, Tord Romstad wrote: >On July 16, 2004 at 02:02:10, Dann Corbit wrote: > >>What are the tricks necessary to get NULL MOVE successfully integrated into an >>MTD(f) search? >> >>Is there anything special that needs to happen? > >In theory, there is a problem with search inconsitencies. In practise, I've >found >that it isn't that bad. I don't use any tricks at all. A standard recursive >null >move search works fine. > >Tord There is one interesting caveat in comparison to PVS. A PVS engine has the choice to treat null move as any normal move, or to require that the null move fails high. (ie within bounds, but not fail high, is not enough) The latter is somewhat logical, and IIRC this is what Crafty does. An MTD (f) engine must treat a null move as a normal move. I couldn't come up with a way to circumvent this restriction. It seems to be an inherent restriction of the MTD (f) search. Another way to look at this: an MTD (f) engine must accept null moves along the "pv", where "pv" is defined as following the fail-high moves, and highest-scoring fail-low moves. Vas
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