Author: Robert Hyatt
Date: 10:30:33 07/08/02
Go up one level in this thread
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.
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