Author: Robert Hyatt
Date: 16:30:00 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 Of course, if we _never_ reach that then it becomes pointless to have the test in the program. But not in a couple of years.
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