Author: Ricardo Gibert
Date: 13:35:53 01/20/00
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On January 20, 2000 at 15:06:36, J. Wesley Cleveland wrote: >On January 19, 2000 at 21:01:47, Robert Hyatt wrote: > >>On January 19, 2000 at 19:24:37, Ricardo Gibert wrote: >> >>>[snip] > > >>Feel free to refute this... but please do so with data rather than opinion. >>It is easy to produce... > >It is also easy to hack crafty to check for null move failures. At the point in >the code where you exit on null move cutoff, just set a flag and continue. Then, >after you do the full search, if the null move would have produced a cutoff, and > the full search did not, you have a null move failure. You don't need to do this. You can save yourself the trouble by noting that in say for example in a particular game, null move is effective up to about move 60 by going 10 ply, then you would expect null move to be effective up to about move 55 by going 20 ply instead. Null move loses its effectiveness for about 8% of those 60 moves. You don't need to consider the fact you are searching with incrementally increasing depth, since the searches at lower depths are a drop in the bucket compared to 20 ply search. So it is reasonable to surmise that with an increase in search depth of 10 to 20, null move will lose its effectiveness for a small, but significant percentage of the positions encountered in a game. Any test you do will probably reflect something like this, so why bother?
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