Author: Robert Hyatt
Date: 05:39:14 02/29/00
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On February 29, 2000 at 03:19:00, Bas Hamstra wrote: >On February 29, 2000 at 01:34:48, Sanjiv Karnataki wrote: > >>Hi All, >> >>I just finished reading Ernest Heinz's article on the subject and I had a >>question about the code sample. It uses a routine called "try_null" that is not >>given in the article and the only thing the article says is "tries to avoid >>superfluous null-move searches that do not really promise to cut off as decided >>by the function try_null" >> >>Does anyone know how that decision could be made? I was thinking of trying it in >>my program. >> >>Thank you >> >>Sanjiv. > >For instance if material is more than PawnValue below Alpha,chances are there >will be no cutoff. Not perferct of course. Also the hash table trick (used in crafty and many other null-move programs) can be used. If you get a hit on the hash table, but the depth is not deep enough to let you take the true score of cutoff score, it still might be good enough to prove that a null-move search won't fail high (see search.c in Crafty source, look for "avoid_null". Then look at hash.c to see how this gets set to disable a null move at this position.)
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