Author: Christophe Theron
Date: 18:15:31 04/29/04
Go up one level in this thread
On April 28, 2004 at 14:49:47, Uri Blass wrote: >On April 28, 2004 at 10:50:35, Vincent Diepeveen wrote: > >>On April 28, 2004 at 06:39:30, Uri Blass wrote: >> >>>On April 28, 2004 at 06:06:37, Vasik Rajlich wrote: >>> >>>>On April 27, 2004 at 21:05:11, Vincent Diepeveen wrote: >>>> >>>>>On April 27, 2004 at 17:10:16, Dann Corbit wrote: >>>>> >>>>>>On April 27, 2004 at 06:10:04, Vasik Rajlich wrote: >>>>>> >>>>>>>On April 27, 2004 at 01:38:49, Uri Blass wrote: >>>>>>> >>>>>>>>On April 27, 2004 at 00:44:34, rasjid chan wrote: >>>>>>>> >>>>>>>>>On April 26, 2004 at 20:07:00, Uri Blass 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. >>>>>>>>>> >>>>>>>>>>No >>>>>>>>>> >>>>>>>>>>You can be 99.99% sure about fail low more often than 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". >>>>>>>>>> >>>>>>>>>>What reason do you have to tell other what works for you and what does not work >>>>>>>>>>for you? >>>>>>>>>> >>>>>>>>>>You do not plan to inform the amateurs about better code for tablebases than the >>>>>>>>>>nalimov tablebases so I do not see you as a person who try to help 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. >>>>>>>>>> >>>>>>>>> >>>>>>>>>>I understand that you claim that basically Christophe's claim that most of the >>>>>>>>>>improvement in tiger came from better search and not from better evaluation was >>>>>>>>>>disinformation. >>>>>>>>> >>>>>>>>>Firstly there is not that BIG a stake for disinformation and posting >>>>>>>>>here is also just normal human behaviour that does not require >>>>>>>>>asking "....why do I post ? ". Then also ask why do I talk. >>>>>>>>> >>>>>>>>>I think Christophe was quite clear about the reasons why chess programming >>>>>>>>>is NOT about evaluation(not dumb evaluation). After pawn structures, passed >>>>>>>>>pawns etc, it is very difficult to try to improve on it. The curve for >>>>>>>>>evaluation is logarithmic for elo-increase/code-increase + huge overhead, >>>>>>>>>the very reverse of exponential.Search almost have no trend patterns and >>>>>>>>>search improvements usually have no overhead, you just need to be smarter >>>>>>>>>then the rest. Assume your opponent searches on average 3 plys ahead. >>>>>>>>>How do you do a good evaluation that can see 3 plys ahead? Evaluation is horizon >>>>>>>>>dumb. >>>>>>>>> >>>>>>>>>Rasjid >>>>>>>> >>>>>>>>I did not claim that christophe claimed wrong things. >>>>>>>>It is Vincent who claimed it. >>>>>>>> >>>>>>>>I prefer not to talk about the top programs. >>>>>>>>I can only say that it is clear for me that I can get much by search >>>>>>>>improvements. >>>>>>>> >>>>>>>>Certainly searching 3 plies forward or doing something equivalent can help >>>>>>>>significantly but the problem is how to do it. >>>>>>>>If you are optimistic about doing it with no price by intelligent extensions and >>>>>>>>reductions >>>>>>>>and better order of moves then it is clear that going for search is the right >>>>>>>>direction. >>>>>>>> >>>>>>>>If you are not optimistic even about getting something equivalent to 1 ply >>>>>>>>forward then evaluation is the right direction. >>>>>>>> >>>>>>>>Uri >>>>>>> >>>>>>>I don't think you need objective answers to these questions. >>>>>>> >>>>>>>You just need a game plan. >>>>>>> >>>>>>>A plain, reasonably tuned eval combined with a state of the art selective search >>>>>>>seems like a perfectly reasonable game plan to me. >>>>>>> >>>>>>>Ditto for plain search combined with a state-of-the art evaluation. >>>>>> >>>>>>Bruce Moreland (who's program Ferret was at one time among the top two or three >>>>>>in the world) found a great annoyance when as he improved his evaluation: he >>>>>>discovered that he was then being outsearched. >>>>>> >>>>>>I think the lesson is simple: >>>>>>If your new smarter eval makes the program stronger, then keep the new >>>>>>evaluation terms. If not, rip them out. >>>>> >>>>>I feel search is overrated too much. It's so so hard to make a good eval, only >>>>>when you have a real well tested and tuned eval making a good search is >>>>>important. >>>>> >>>>>Even searching fullwidth i can beat Crafty. >>>>> >>>>>In fact i saw diep at a P4 2.8Ghz in blitz beat crafty at its dual Xeon lately >>>>>at icc. I was pretty amazed because i always say that you need at least 12-14 >>>>>ply to search outside tactical barrier. >>>>> >>>>>Perhaps i'll change that back to 10 ply one day :) >>>> >>>>Eval is hard, true. So is selective search. >>>> >>>>Moreland's approach is definitely not the way to end up with a great eval. When >>>>your eval is cheap, you can't just add one expensive thing to it and expect it >>>>to pay off. One expensive idea might cost you 20% of your nodes. With this >>>>approach, if you're testing honestly, you'll always end up throwing out the >>>>expensive stuff. >>> >>>This was also my thinking in the past but I doubt it. >>>If you have big stuff everything that you add cost you more than in case that >>>you have small stuff. >>> >>>If you have small stuff then the program can use the fast memory when you add >>>something. >>> >>>If you have big stuff it needs to use the slow memory so the theory that if you >>>have a lot of knowledge you can add things with smaller price may be wrong. >>> >>>> >>>>If you want a program with a great eval, you have to commit to it, let >>>>everything slow down, and go from there. >>>> >>>>Another thing to keep in mind: a few years ago, it might well be the case that >>>>allowing onesself to be outsearched was a death wish. This may be changing now. >>>> >>>>Chess Genius dominated computer chess with a very unusual selective algorithm >>>>that worked great at low depths. Eventually, it became irrelevant. >>> >>>I think that the top programs simply got better and can beat chess genius even >>>if you give them the hardware that genius used to top the ssdf list. >> >>>Chess Genius today is not the best also with 386 hardware. >> >>386 hardware hello? >> >>Genius basically has been put onto 680x0 dedicated machines. Millions sold from >>them. The genius in software was a joke compared to that. >> >>How are you *ever* going to beat genius with a program of today compiled for a >>64KB ram + 512KB rom 68x motorola cpu 10Mhz with genius assembly optimized for >>it. Well I happen to have done exactly that, so maybe I can comment. Chess Tiger for 68K-based PalmOS devices is stronger than the version of Genius you are talking about. Genius had been designed for this processor (Motorola 68000), when Chess Tiger for Palm is just a port of the PC version of the Chess Tiger engine (not even written in assembly, it's 100% pure C). You can do the same experiment on 386 and you will see that Tiger beats Genius on 386. If you want to get a feel of this, just check the P90 SSDF list. They do not have a 386 list with Tiger, but I have tried it myself. The P90 list gives a very good indication of what happens. So I do not know exactly what was you point, but you are definitely wrong. ...as usual. Sigh. Christophe >>Or even worse: 4KB ram and 64KB rom. Note you also must make interface within >>that memory. >> >>Compilers have problems working within that. >> >>In short you'll search 4 ply with movei onto that, versus 10 ply assembly >>optimized genius. >> >>Who wins? >> >>I bet genius with 100-0. > >I did not talk about movei and I did not talk about older hardware than 1990. >It is possible that Genius is better with inferior hardware than 386 but Genius >was clearly the best for 386 and 486 when today there are better programs for >that hardware. > >Uri
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