Author: Andrew Dados
Date: 11:27:12 01/18/00
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On January 18, 2000 at 13:57:54, Dann Corbit wrote: >On January 18, 2000 at 12:49:38, Bruce Moreland wrote: >[snip] >>>Opinions? Am I all wet? >> >>Yes, you are all wet. I will resist the temptation to use a drug metaphor since >>people seem to be a little cranky about that today. >> >>I don't see any reason to suppose that you can't use induction to predict the >>characteristics of a 25-ply search by examining the characteristics of a 15-ply >>search. > >I know you know a lot more about it than I do, and everyone is in agreement that >I am wrong. But I still don't understand why. From the plethora of posts I >have seen here where a program fails to find a move in a test position and it is >found that it is zugzwang, I presume that it is not terribly rare. Now, >ignoring NULL moves makes you run so much faster that it almost always a good >idea. You get a full ply more -- sometimes two (if I understand correctly). >But it seems to me that NULL move is dodging bullets in the sense that you >almost never get bitten. But if you ignore thousands of them, maybe one of them >was dangerous. And if you ignore one million of them, it could be even worse. > >On the other hand, I also recognize that there are more than one good pathway >from most board positions. So perhaps even when it does go wrong, NULL move >pruning may still pick out a good path most of the time. > >I am sure that my supposition is wrong, since so many others think that it is. >But I still don't understand why. Problem you signal exists, but it's extremaly rare.. for starters - I think zugzwang positions are not 1/10000 of all, but way less common. Then it's same type as hash collision problem: it _may_ occure, but even then it does not have to affect root score. Seem impossible to experiment its relevance. -Andrew-
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