Author: Ricardo Gibert
Date: 22:25:19 01/18/00
Go up one level in this thread
On January 18, 2000 at 23:20:29, Robert Hyatt wrote: >On January 18, 2000 at 18:54:46, Ricardo Gibert wrote: > >>On January 18, 2000 at 18:35:52, Robert Hyatt wrote: >> >>>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. >>> >>> >>>Here is a "hint"> :) >>> >>>what makes you think that in a 10 ply search, where there are N zug positions, >>>that in a search space 10 times bigger there are more than 10*N zug positions? >>> >>>That is point 1. Point 2... there _are_ more zug positions overall. But there >>>are also more non-zug positions. And for a zug position to screw up and then >>>cause a key score to change is no more probable in a tree with M positions and N >>>zug positions than it is in a tree with 100M positions and 100N zug positions... >>> >>>Everything grows at the same exponential rate... and stay exactly proportional >>>to each other... >> >>I don't necessarily agree with Dan, but there's a fly in your ointment. >>Everything does not stay proportional. The deeper you search, the more >>simplified the position is. The more simplified the position gets, the more >>likely it may be zugzwang. > > > >That isn't necessarily true. I have seen 100 move games with queens and rooks >still on the board. And (at least in my case) we can take evasive action to >recognize some zug positions and not let them become a problem... > > > >> The character of the search and the topology of the >>tree does change the deeper you go. The branching factor of the tree changes as >>the position gets more simplified. The relative value of the pieces changes as >>the position becomes more open. The King becomes more of an asset than a >>liability, etc. > > >However, I read his question as from position N, do a 10 ply search and then a >20 ply search, and the 20 ply search should have more serious null-move >problems. I don't agree. 10 more plies does not appreciably simplify the >position in the majority of the pathways.. Perhaps, but it breaks your argument all the same.
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