Author: José Carlos
Date: 00:07:25 07/09/02
Go up one level in this thread
On July 09, 2002 at 01:56:15, Uri Blass wrote: >On July 08, 2002 at 23:34:52, Robert Hyatt wrote: > >>On July 08, 2002 at 15:00:46, Uri Blass wrote: >> >>>On July 08, 2002 at 13:30:33, Robert Hyatt wrote: >>> >>>>On July 08, 2002 at 12:29:17, Uri Blass wrote: >>>> >>>>>On July 08, 2002 at 11:39:40, Robert Hyatt wrote: >>>>> >>>>>>On July 08, 2002 at 00:21:23, Christophe Theron wrote: >>>>>> >>>>>>>On July 07, 2002 at 23:53:16, Robert Hyatt wrote: >>>>>>> >>>>>>>>On July 07, 2002 at 23:42:03, Omid David wrote: >>>>>>>> >>>>>>>>>On July 07, 2002 at 21:43:47, Robert Hyatt wrote: >>>>>>>>> >>>>>>>>>>On July 07, 2002 at 16:47:33, Omid David wrote: >>>>>>>>>> >>>>>>>>>>>On July 07, 2002 at 16:36:57, Robert Hyatt wrote: >>>>>>>>>>> >>>>>>>>>>>>On July 07, 2002 at 11:48:27, Omid David wrote: >>>>>>>>>>>> >>>>>>>>>>>>>On July 06, 2002 at 23:23:28, Robert Hyatt wrote: >>>>>>>>>>>>> >>>>>>>>>>>>>>On July 06, 2002 at 22:29:44, Omid David wrote: >>>>>>>>>>>>>> >>>>>>>>>>>>>>>On July 06, 2002 at 10:20:17, Robert Hyatt wrote: >>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>On July 06, 2002 at 01:07:36, Ricardo Gibert wrote: >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>Okay, but so what? >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>So perhaps the idea of "forward pruning" is foreign to us as well... >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>I see no logical difference between deciding which moves are interesting and >>>>>>>>>>>>>>>>>worth looking at and deciding which moves are not interesting and not worth >>>>>>>>>>>>>>>>>looking at. It looks to me like 2 sides of the same coin, so your speculation >>>>>>>>>>>>>>>>>that "perhaps the idea of "forward pruning" is foreign to us as well..." does >>>>>>>>>>>>>>>>>not seem to be of any consequence. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>However, that has been _the point_ of this entire thread: Is DB's search >>>>>>>>>>>>>>>>inferior because it does lots of extensions, but no forward pruning. I >>>>>>>>>>>>>>>>simply said "no, the two can be 100% equivalent". >>>>>>>>>>>>>>> >>>>>>>>>>>>>>>Just a quick point: The last winner of WCCC which *didn't* use forward pruning >>>>>>>>>>>>>>>was Deep Thought in 1989. Since then, forward pruning programs won all WCCC >>>>>>>>>>>>>>>championships... >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>>In 1992 no "supercomputer" played. In 1995 deep thought had bad luck and lost >>>>>>>>>>>>>>a game it probably wouldn't have lost had it been replayed 20 times. No >>>>>>>>>>>>>>"supercomputer" (those are the programs that likely relied more on extensions >>>>>>>>>>>>>>than on forward pruning due to the hardware horsepower they had) has played >>>>>>>>>>>>>>since 1995... >>>>>>>>>>>>>> >>>>>>>>>>>>>>I'm not sure that means a lot, however. IE I don't think that in 1995 fritz >>>>>>>>>>>>>>was a wild forward pruner either unless you include null move. Then you >>>>>>>>>>>>>>would have to include a bunch of supercomputer programs including Cray Blitz >>>>>>>>>>>>>>as almost all of us used null-move... >>>>>>>>>>>>> >>>>>>>>>>>>>I personally consider null-move pruning a form of forward pruning, at least with >>>>>>>>>>>>>R > 1. I believe Cray Blitz used R = 1 at that time, right? >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>I believe that at that point (1989) everybody was using null-move with R=1. >>>>>>>>>>>>It is certainly a form of forward pruning, by effect. >>>>>>>>>>> >>>>>>>>>>>Yes, and today most programs use at least R=2... The fact is that new ideas in >>>>>>>>>>>null-move pruning didn't cause this change of attitude, just programmers >>>>>>>>>>>accepted taking more risks! >>>>>>>>>> >>>>>>>>>> >>>>>>>>>>I think it is more hardware related. Murray Campbell mentioned R=2 in the >>>>>>>>>>first null-move paper I ever read. He tested with R=1, but mentioned that >>>>>>>>>>R=2 "needs to be tested". I think R=2 at 1980's speeds would absolutely >>>>>>>>>>kill micros. It might even kill some supercomputers. Once the raw depth >>>>>>>>>>with R=2 hits 11-12 plies minimum, the errors begin to disappear and it starts >>>>>>>>>>to play reasonably. But at 5-6-7 plies, forget about it. >>>>>>>>> >>>>>>>>>So using a fixed R=3 seems to be possible in near future with faster hardware, >>>>>>>>>doesn't it? >>>>>>>> >>>>>>>> >>>>>>>>Very possibly. Or perhaps going from 2~3 as I do now to 3~4 or even 4~5 for >>>>>>>>all I know... I should say that going from 2 to 3 is not a huge change. Bruce >>>>>>>>and I ran a match a few years ago with him using Ferret vs Crafty with Ferret >>>>>>>>using pure R=2, and then pure R=3. We didn't notice any particular difference >>>>>>>>at that time. It played about the same, searched about the same depth, etc... >>>>>>> >>>>>>> >>>>>>>Increasing R is pointless after 3. >>>>>>> >>>>>>>Because instead of having a null move search using 5% of your time (just an >>>>>>>example, I do not know the exact value), it will use only 2% or 3%. >>>>>>> >>>>>>>The speed increase is ridiculous, and the risks are getting huge. >>>>>>> >>>>>>>The only thing you can get by increasing R after that is having a percentage of >>>>>>>search spent in null move close to 0. So a potential of 2% or 3% increase in >>>>>>>speed. >>>>>>> >>>>>>>And an big potential to overlook easy combinations everywhere in the tree. >>>>>>> >>>>>>>That's why I believe that working on R>3 is a waste of time. >>>>>>> >>>>>>> >>>>>>> Christophe >>>>>> >>>>>> >>>>>>You are overlooking _the_ point here. At present, doing 12-14 ply searches, >>>>>>R>3 doesn't make a lot of difference. But in the future, when doing (say) >>>>>>18 ply searches, R=4 will offer a lot more in terms of performance. Same as >>>>>>R=3 did when we got to 12-14 plies... _then_ it might make sense to up R >>>>>>once again. >>>>> >>>>>I do not know. >>>>>I did not investigated different R's but I suspect that constant R may be a bad >>>>>idea and R should be function of the position. >>>>> >>>>>I do not see a reason to use R=4 in the future and not to use it today at the >>>>>same conditions. >>>>> >>>>>Uri >>>> >>>> >>>>I adjust R between 2 and 3 already. >>>> >>>>The reason to use R=4 in the future is easy: Which would you rather do to >>>>reject a move at the current ply... (a) a search to depth D, or (b) a search >>>>to depth D-3, or (c) a search to depth D-4? That is what the R value is all >>>>about. And it makes a significant difference at deeper depths. >>> >>>Everything that can be used in the future can be used also today. >>> >>>If you talk about deep depth you can also today use a rule to search to depth >>>D-4 and not D-3 if D is big enough. >>> >>>I see no reason to wait to the future. >>> >>>Uri >> >> >>Two reasons... >> >>1. R=4 doesn't make a huge difference because the current hardware is not >>fast enough to drive the search deep enough to make it matter. >> >>2. R=4 will produce tactical oversights at today's depths, while R=3 produces >>fewer of these. >> >>I personally think that as depth goes up, so can R, with relative safety. This >>based on 8 years of testing this in Crafty... > >I see no reason to wait for the future. >If R=4 is good only for depth>15 then people can use it also today only when the >remaining depth is bigger than 15. > >Uri Which is the same as not using it at all in normal time controls, unless in far endgame, where null move can be too dangerous due to zugzwang. But if you make 20h a move games you can try R=4 and see if it makes a difference at big depths. José C.
This page took 0 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.