Author: Omid David Tabibi
Date: 06:00:43 10/13/03
Go up one level in this thread
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. :) >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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