Author: José Carlos
Date: 08:48:35 04/26/04
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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. >> - 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... >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
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