Author: Ricardo Gibert
Date: 06:36:04 01/07/06
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On January 07, 2006 at 09:14:03, Michael Neish wrote: > >I hope this doesn't come across as too much of a beginner's question. > >Is it beyond question that null move improves search? If yours is a fairly conventional program, then it is as you say, "...beyond question..." Null move is acknowledged as a big win for the vast majority of programs when implemented correctly. > >The reason I ask is that I recently dusted off my old program, and ran a few >tests on it, and was dismayed to discover that I seem to be getting very little >benefit from using it. This is trying out different parameters (R-2, R-3, at >depth >2, >3, etc.). > >I thought the whole idea of using null was that you could get a swifter cut-off >and hence reduce the number of nodes searched to reach a given depth, but I'm >getting little or no reduction at all, and in some cases even an increase. > >Depending on the position, and the parameters used, about 40-60% of null moves >performed fail high and return immediately. The remainder move on to a normal >search. So I thought that, in my program's case, perhaps the nodes wasted on >null move searches that don't fail high is almost the same as those saved by >null move searches that do fail high. Does this make sense? > >Is a cut-off rate of about 40-60% to be expected, or should it be higher? > >For what it's worth, around 80% of nodes in the tree are in Quiesce(). Could >this have something to do with it? > >So barring an error in my implementation, can anyone comment on why null move is >giving me virtually null benefit? > >Thanks in advance to anyone who takes the time to reply. > >Regards, > >Mike.
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