Author: Ricardo Gibert
Date: 11:16:52 01/19/00
Go up one level in this thread
On January 19, 2000 at 09:58:32, Robert Hyatt wrote: >On January 19, 2000 at 01:25:19, Ricardo Gibert wrote: > >>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. > > >ANd how would that be? From the opening position, I have _no_ chance to reach >a pieceless ending in 10 or 20 plies. Until at _least_ 1/2 of the total >material on the board is gone, I don't reach 5 piece endings and do EGTB probes. >It is also unlikely that I reach a significant number of zug positions either, >at least a number large enough to affect the root score, which was the original >premise of this... This is the first mention of an "opening position" in this thread. I agree you you can save your argument by reinventing the premises until it works.
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