Author: Robert Hyatt
Date: 14:55:50 01/19/00
Go up one level in this thread
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...
This page took 0.01 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.