Author: Uri Blass
Date: 01:18:34 02/13/04
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On February 13, 2004 at 01:47:40, Tord Romstad wrote: >On February 12, 2004 at 22:17:46, Anthony Cozzie wrote: > >>Nullmove may be the best thing to happen to computer chess ever, but its not >>perfect. > >I'm beginning to get a nagging feeling that recursive null move pruning (at >least the conventional kind) is possibly the *worst* thing to happen to computer >chess ever. There has to be a better way to reduce the size of the tree, but >I have no clue how to find it. :-( > >The zugzwang problem is not too serious, of course, and if you really care >about it it is not hard to solve. The real problem with recursive null move >pruning is that it performs horribly at finding long non-forcing lines. For >instance, a human player could take a quick look at a position and see that >black needs to exchange off white's strong knight on c4, and notice that this >could be achieved by the maneuvre f7-f6 followed by Bh7-g6-e8-d7-c8-a6xc4. >A recursive null move searcher needs a huge search depth to find such plans. > >Tactically, recursive null move pruning performs really well. Strategically, >it's horrendous. > >Tord I believe that chess is mainly about tactics and you can decide about rules when not to use null move pruning(if it seems that the moves are a plan). I do not do it but it is one of the things that I should try and the problem is to have a function to decide if some moves are a plan. In most practical cases at least part of the moves of the plan threat something so you do not need a huge depth. Uri
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