Author: Robert Hyatt
Date: 18:06:41 01/19/00
Go up one level in this thread
On January 19, 2000 at 18:42:18, Dan Newman wrote: >On January 19, 2000 at 17:55:50, Robert Hyatt wrote: > >>On January 19, 2000 at 14:26:25, Ricardo Gibert wrote: >> >>>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. >> >> >>OK... change that to "middlegame position". Same result. I don't reach >>endgame positions very often from middlegame positions. Usually not until >>around move 40 or so in a real game. That leaves 40 moves to search with >>no regard to null-move failures at all. And if the program is smart enough to >>switch null-move off when it is not appropriate, rather than just turning it off >>at the root, this is a total non-issue... for _any_ position you care to name... >> >>So my original statement remains accurate... A bigger tree is _not_ more >>prone to null-move failures than a smaller one... > >In fact it's really the other way 'round. Null-move doesn't work very well >if you only do a shallow search. It really needs a good deep search to avoid >another sort of failure... > >-Dan. That is another good point of course...
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