Author: Vincent Diepeveen
Date: 17:41:01 04/27/04
Go up one level in this thread
On April 26, 2004 at 19:30:40, Omid David Tabibi wrote: >On April 26, 2004 at 13:41:53, Vincent Diepeveen wrote: > >>On April 26, 2004 at 12:14:33, José Carlos wrote: >> >>>On April 26, 2004 at 11:57:43, Vincent Diepeveen wrote: >>> >>>>On April 26, 2004 at 11:48:35, José Carlos wrote: >>>> >>>>>On April 26, 2004 at 11:32:26, Tord Romstad wrote: >>>>> >>>>>>On April 26, 2004 at 10:39:42, José Carlos wrote: >>>>>> >>>>>>> An interesting experiment, of course. But I think your conditions are rather >>>>>>>different from 'most' programs. I mean: >>>>>>> - You allow any number of null moves in a row (most programs don't do even >>>>>>>two) >>>>>> >>>>>>This has no importance, I think. My experience is that I almost always get the >>>>>>same score and PV when I enable/disable several null moves in a row, and that >>>>>>the difference in number of moves searched is *very* tiny. >>>>> >>>>> >>>>> You're probably right, as you've tested and I speak from intuition, but at >>>>>first sight, it seems that the fact that you allow several null moves in a row >>>>>will increase your percentage of null-moves-tries/total-nodes-searched, and thus >>>>>that avoiding unnecessary null moves will be a good idea. >>>> >>>>In *all* experiments i did with nullmove and a program not using *any* forward >>>>pruning other than nullmove, the best thing was to *always* nullmove. >>> >>> >>> Yes, that's what other programmers also said (including me) in the thread we >>>had last week. That's pretty intuitive. With not any other forward pruning (or >>>very little) but null move, the cost of not trying a null move that would have >>>produced a cutoff it terrible compared to the benefit of saving an useless null >>>move try. So avoid null move, in this case, must be only in a very few cases >>>where you're 99.99% certain you'll fail low... if any. >> >>99.99% means 1 in 10k nodes. >> >>So doing nullmove always is cheaper, because in a lot of cases >>transpositiontable is doing its good job and in other cases you search more than >>10k nodes which you avoid searching now. >> >>> Gothmog is very different from that 'paradigm' (he does a lot of forward >>>prunning and applies many ideas he has commented here), hence it works pretty >>>well for him. >> >>I get impression evaluation function plays a major role in when something is >>useful or when it isn't. >> >>Checks in qsearch is also a typical example of this. >> >>> >>>>Double nullmove i invented to proof nullmove gives the same results like a >>>>normal fullwidth search for depth n which i may pick, and i use it as it finds >>>>zugzwangs and i am sure that is very helpful, because the weakest chain counts. >>>> >>>>So double nullmove always completely outgunned doing a single nullmove then >>>>disallowing a nullmove and then allowing the next one. >>> >>> I tried double null move some time ago, and it didn't work for me. Probably I >>>did something wrong, but I recall an old post (see the archives) from C. Theron >>>where he gave some points why double null move should not work. I, myself, >>>didn't invest too much time though as I had much weaker points to fix in my >>>program before. >> >>Christophe didn't post it doesn't work AFAIK. >> >>Further i must remind you that majority of commercial programmers posting here >>is not busy letting you know what works for them or doesn't work for them. >> >>To quote Johan: "don't inform the amateurs". >> >>I remember that Christophe also posted that evaluation function is not so >>important. >> >>His latest postings here made more sense however than the crap posted before >>that. >> >>>>The quickest way to of course get a cutoff in a tree is by a nullmove. >>> >>> >>> Ed gives some clues about static forward pruning in his page. It must be >>>doable as Rebel is, and has always been, one of the top, but it's very difficult >>>to fine tune. >> >>If anything on Ed's homepage works for you, then you are a lot behind the 'top >>programs' (i hate to write it down like that but my english is not sufficient to >>give a more political description than that). >> >>>>So always allowing a nullmove is also intuitive the best thing to do. >>>> >>>>Any forward pruning or weak qsearch you might use can however change that of >>>>course. >>> >>> >>> Hard to say how qsearch can affect that, but forward pruning definetly makes a >>>difference in the current topic. >> >>I feel the qsearch plays a more important role. >> >>Considering the number of games he played he probably has played blitz level >>matches. So small search depths. So tactics dominated. >> >>If you nullmove more then qsearch plays a bigger role. If it plays a bigger role >>and is not so very good then you will conclude not nullmoving is better. >> >>'verified nullmove' uses the same buggy principle. > >In Falcon I use many checks in quiescence, and verified null-move works better >than ever :) You mean you forward prune that much in falcon that you need to force it to search a ply near the leafs to avoid extreme supernullmove forward pruning :) > > >> >>> José C. >>> >>> >>>>>>> - You do pruning and reductions that are not public domain >>>>>>> This is important because your results mean: 'in a non-standard null move >>>>>>>implementation (where you try more null move searches than most others) and with >>>>>>>a lot of heavy pruning and reductions (I assume they're heavy according to your >>>>>>>posts here and the high depths Gothmog gets) and in a MTD(f) root search, >>>>>>>limiting null move application seems to benefit". This conclusion is, apart from >>>>>>>interesting of course, very intuitive. >>>>>> >>>>>>This is a very good point. During our discussion last week, several people >>>>>>claimed that checking the static eval before doing a null move search wasn't >>>>>>really necessary, because the cost of a null move search would be tiny >>>>>compared to the cost of searching the moves anyway. This isn't really >>>>>>true for Gothmog, because most of the moves are usually not searched to >>>>>>full depth. >>>>>> >>>>>>I am not sure it is fair to describe my pruning and reductions as "not >>>>>>public domain", though. It is true that I haven't published any paper >>>>>>and that my engine is not open source (at least not yet), but I am happy >>>>>>to describe the tricks I use to anybody who wants to listen. :-) >>>>> >>>>> >>>>> True. I dind't mean they're a secret, but they're not implemented in most >>>>>chess programs. Expressing correctly in english is not easy for me... >>>> >>>>that's the case for all of us. >>>> >>>>> >>>>>>Whether the use of MTD(f) is important is hard to say, but my guess is >>>>>>that it isn't. >>>>> >>>>> >>>>> Probably not. I mentioned it just to underline that your program is different >>>>>from the average, though it's true that MTF(f) is more popular now than a few >>>>>years ago. >>>>> >>>>> José C. >>>>> >>>>> >>>>>>> Thanks for the data. You sure inspired many others to do similar tests (I'll >>>>>>>do when I have time). >>>>>> >>>>>>Yes, it would be interesting to see the results of similar experiments for >>>>>>other engines. It seems like a sure bet that this is a YMMV issue. :-) >>>>>> >>>>>>Tord
This page took 0.01 seconds to execute
Last modified: Thu, 07 Jul 11 08:48:38 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.