Author: Vincent Diepeveen
Date: 05:44:36 10/13/03
Go up one level in this thread
On October 12, 2003 at 12:16:42, Omid David Tabibi wrote: if you search 14 ply with just 8 plies of mainline at a P3-733 then everyone can understand you forward prune, assuming a normal evaluation. the positions used for your ICGA article were all mating positions, now you suddenly use other positions????????? if so why? >On October 12, 2003 at 11:57:02, Vincent Diepeveen wrote: > >>On October 12, 2003 at 10:23:35, Omid David Tabibi wrote: >> >>>On October 12, 2003 at 09:27:09, Tord Romstad wrote: >>> >>>>On October 12, 2003 at 06:32:25, Omid David Tabibi wrote: >>>> >>>>>Recently I conducted some extensive experiments with two versions of Falcon, one >>>>>with checks in quiescence and one without. Falcon already has lots of >>>>>extensions, but adding checks in quiescence resulted in a significant boost for >>>>>tactical strength. >>>>> >>>>>I tested the following options: >>>>> >>>>>a) checks everywhere in quiescence >>>>>b) checks only in the first ply of quiescence >>>>>c) no checks in quiescence >>>>> >>>>>Option 'a' was ruled out after some testing, as it resulted in a total explosion >>>>>of quiescence search. I tried controlling it in some ways, but still the >>>>>overhead was considerably more than the benefit. It seems that The King and >>>>>HIARCS are the only engines using this method. >>>> >>>>These are not the only ones. I am fairly sure Diep searches checks everywhere >>>>in the >>>>qsearch, and Gothmog (my engine) also does. >>> >>>True, I referred to commercial engines. HIARCS and King definitely do checks >>>everywhere in quiescence (with certain limitations of course), but I'm not >>>completely sure about Fritz, Shredder, and Tiger (Junior seems not to have a >>>quiescence at all, but it has a large set of extensions). >>> >>> >>>> >>>>>Option 'b' produces almost the same tactical strength as option 'a', with a >>>>>considerably lower overhead. >>>> >>>>Interesting. I have only tried options 'a' and 'c' myself, and always found >>>>option >>>>'a' to be significantly better (in games as well as test suites). I should >>>>probably >>>>do some experiments with option 'b' as well. >>>> >>>>>Only using checks in the first ply of quiescence, Falcon managed to solve almost >>>>>all tactical positions of LCTII in less than 1 second, >>>> >>>>Very impressive. Gothmog (on an Athlon XP 2.4 GHz) solves the first 8 positions >>>>in >>>>less than a second, but needs 1:18 for number 9, >>> >>>[D]6k1/5p2/3P2p1/7n/3QPP2/7q/r2N3P/6RK b - - 0 1 >>> >>>If you do checks everywhere in quiescence, you should see this immediately. >>>After 1...Rxd2 2.Qxd2 all the rest of the moves are checks until you detect draw >>>by threefold repetition (maybe you've turned off repetition detection in >>>quiescence? or your max extensions limit is too shallow...). HIARCS finds the >>>move at the first iteration! >>> >>>The following is Falcon's analysis (with checks enabled only at the first ply of >>>quiescence): >>> >>>Falcon 0.0.3.5 running on GenuineIntel 733MHz 256MB: >>>depth time nodes nps score variation >>> 6/10 0.16 16k 103k 3.22 1...h5f4 >>> 6/12 0.29 30k 104k 8.55 1...f7f5 1.d6d7 a2a8 2.d4d5 >>> 6/12 0.31 32k 106k 3.47 1...h5f4 1.d6d7 f4e6 2.d7d8q e6d >>> 3.d4d8 g8h7 >>> 8/14 0.43 47k 109k 3.61 1...h5f4 1.d6d7 f4e6 2.d7d8q e6d >>> 3.d4d8 g8h7 4.d8d4 >>> 8/17 0.89 99k 111k 3.50 1...a2d2 1.d4d2 h3f3 2.d2g2 f3f4 >>> 3.d6d7 f4d6 >>>10/19 0.97 108k 111k 3.17 1...a2d2 >>>10/19 11.42 1275k 111k 0.00 1...a2d2 1.d4d2 h3f3 2.g1g2 f3f1 >>> 3.g2g1 f1f3 >>>12/21 11.54 1292k 112k 0.00 1...a2d2 1.d4d2 h3f3 2.g1g2 f3f1 >>> 3.g2g1 f1f3 >>>14/23 12.04 1374k 114k 0.00 1...a2d2 1.d4d2 h3f3 2.g1g2 f3f1 >>> 3.g2g1 f1f3 >>>16/25 14.07 1722k 122k 0.00 1...a2d2 1.d4d2 h3f3 2.g1g2 f3f1 >>> 3.g2g1 f1f3 >>> >>> >>> >>>>25 seconds for number 10, 25 >>>>seconds >>>>for number 11, and doesn't solve number 12 at all (at least not within a few >>>>hours). >>> >>>Falcon doesn't manage to solve number 12 either. >>> >>> >>>>Earlier >>>>versions solved number 9 instantly, but the quick solution turned out to be >>>>caused by >>>>a bug: I had accidentally changed my single-reply-to-check extension to a >>>>two-replies-to-check extension. >>>> >>>>>outperforming the normal >>>>>version (no checks in quiescence). But adding checks in quiescence (although >>>>>only at its first ply) significantly slowed down the engine (from average of >>>>>350kNPS to 150kNPS on my PIII/733MHz) and resulted in a worse branching factor. >>>> >>>>You must have a very inefficient way of generating checks, I think. >>> >>>That's true. Only recently I added checks in quiescence to the engine, and so >>>still haven't written a gen_checks() functions. However, the kind of attack >>>tables I use result in a very speedy generation of captures, which results in a >>>very optimized captures only quiescence. Adding checking moves will slow down >>>the engine considerably anyway, even if I write a good gen_checks()... >>> >>>One thing I have to mention is that in the normal version I never check for >>>check evasions in quiescence. If the side to move is in check and doesn't have >>>any legal non-losing capture, I just return eval(). That's another reason why >>>the normal quiescence is so fast. >>> >>> >>>>I haven't >>>>spent a >>>>lot of time optimising check generation myself, and in my program the NPS drops >>>>by >>>>only about 15%. It would probably be possible to push it below 5% with some >>>>effort. >>>> >>>>>So, it seems that adding checks in quiescence is great for solving tactical test >>>>>suites, but not so for actual game play. The same goes for some of the >>>>>aggressive extensions I tried; great for tactics, poor in games. >>>>> >>>>>I'd be interested to hear others' thoughts on this issue. >>>> >>>>It seems like checks in the qsearch is one of those things that works well in >>>>some >>>>programs, and not in others. Crafty, for instance, seems to do very well >>>>without >>>>any checks whatsoever, >>> >>>I wouldn't say so from a tactical point of view. Whenever the game turned >>>tactical, Crafty didn't have any chance against Falcon with checks in >>>quiescence. But Crafty did search deeper and played a better positional game. I >>>must also add that Falcon uses a huge number of different extensions (I think >>>only HIARCS has more extensions), and so maybe adding checks in quiescence on >>>top of them all isn't such a good idea... >>> >>> >>>>but for me the results without checks are clearly worse. >>>> >>>>Other ideas that I have never been able to make work are recapture extensions >>>>and >>>>all sorts of nullmove pruning except plain R=3 (R=2, R=2.5, adaptive pruning and >>>>verified >>>>nullmove pruning are all clearly worse for me). >>> >>>In Falcon I conducted all the experiments I conducted on Genesis for the paper >>>verified null-move pruning, and got the same results. Plain R=3 was too risky >>>neglecting many tactical shots. I now use a modified version of verified >>>null-move pruning. >> >>This simply is a matter of bad experimentation from your side. >> >>When you do check first ply in qsearch and no dubious forward pruning last ply >>(your search depths are *very* big considering hardware) then at your 'testset' >>that version will outperform any other version trivially with R=3, because it's >>nearly all mating problems. > >You have said this again and again but that doesn't make it true. In my >"testset" there are 138 Neishtadt positions, 879 ECM positions, 1001 WCS >positions, and only 434 "mate in 4" and 353 "mate in 5" positions. Is this what >you call "nearly all mating problems"? > > >> >>>But maybe plain R=3 didn't work for me because I didn't have checks in >>>quiescence, and so it resulted in a very inaccurate search. The only program >>>I've heard which uses plain R=3 is DIEP, which does conduct checks everywhere in >>>quiescence. >> >>You should test R=3/2 too when you forward prune that much. > >How do you know that I forward prune "that much"? > > >> >>> >>>> >>>>>I also considered using some form of static mate threat detection, independent >>>>>of null-move search, but haven't found any interesting way to do so yet. >>>> >>>>I have also experimented with static mate threat detection in the evaluation >>>>function, >>>>but it is very tricky to get it right. Also, all minor bugs are likely to have >>>>catastrophic >>>>consequences (at least if you allow the evaluation function to return a mate >>>>score when >>>>the static mate finder reports a mate in n for the side to move). >>>> >>>>Tord
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