Author: Robert Hyatt
Date: 20:20:29 01/18/00
Go up one level in this thread
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..
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