Author: Vincent Diepeveen
Date: 06:21:15 10/13/03
Go up one level in this thread
On October 13, 2003 at 09:00:43, Omid David Tabibi wrote: >On October 13, 2003 at 08:44:36, Vincent Diepeveen wrote: > >>On October 12, 2003 at 12:16:42, Omid David Tabibi wrote: >> >>if you search 14 ply > >You count plies one way, Junior count's them another way, and Falcon counts them >in its own way. > > > >>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, > >LOL! You again show that you never read that ICGA article! > >In that article I used exactly the positions I mentioned here: > >138 Neishtadt positions, 879 ECM positions, 1001 WCS positions, and 434 "mate in >4" and 353 "mate in 5" positions. So kind of a 1000 mating positions. that proofs my point convincingly. >:) > > >>now you suddenly use other positions????????? > >No, they are the very same 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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