Author: Uri Blass
Date: 05:26:54 10/12/03
Go up one level in this thread
On October 12, 2003 at 08:21:35, Uri Blass wrote: >On October 12, 2003 at 07:35:57, Omid David Tabibi wrote: > >>On October 12, 2003 at 07:24:51, Uri Blass 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. >>>> >>>>Option 'b' produces almost the same tactical strength as option 'a', with a >>>>considerably lower overhead. The most significant contribution of checks in the >>>>first ply of quiescence seems to be in conjuction with null-move pruning near >>>>leaf nodes: >>>> >>>>For example at depth = 3, using R = 2, the null-move search will be called with >>>>a depth of 0, i.e., direct call to quiescence search. Here the presence of >>>>checks in the first ply can return a checkmate value which will result in an >>>>extension to main search (mate threat extension). >>>> >>>>Only using checks in the first ply of quiescence, Falcon managed to solve almost >>>>all tactical positions of LCTII in less than 1 second, 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. >>>> >>>>Next I conducted some self-play matches between the two versions, and also some >>>>matches versus other engines. >>>> >>>>The results of the matches were quite interesting. The version with checks in >>>>quiescence not only didn't outperform the normal version in actual games, but >>>>produced slightly inferior games in general. I especially conducted a few tens >>>>of matches for each version against Crafty. The normal version beat Crafty by >>>>something like 60%-40%. The version with checks in quiescence scored 50%. >>>>Whenever the game turned tactical it literally butchered Crafty, but on normal >>>>quiet positions Crafty once and again made a mincemeat of it by simply searching >>>>deeper, which resulted in a better positional play. >>>> >>>>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. >>>> >>>>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. Also, >>>>Falcon does not detect checkmates statically in eval(), but only when one side >>>>doesn't have any legal moves, i.e., it needs an additional ply to see the >>>>checkmate. But I don't think the latter is any important, since when the other >>>>side is checked, a check extension is already done, which will result in the >>>>detection of the checkmate. >>> >>>How can checks only in the first ply of the quiescence >>>do your program more than twice slower in nodes per second? >>> >>>Did you profile your program to see what parts it waste more time on them? >> >>Falcon's quiescence uses SEE to prune losing captures. Also its gen_captures() >>function is very fast because of the attack tables. But adding checks requires >>generation of all moves (a costly operation), and doing a makemove() for each of >>them to see whether they check the opponent (makemove is the most expensive >>function in the program, since the attack tables are dynamically updated there). > > >My attack tables are also dynamically updated in makemove but >when I generate checks I do not make moves that are not checks and I use the >from and to square to define if the move is a check. > >If you do makemove for moves that are not checks only to see if they check the >opponent(this is what I understand from your post) it seems that you spend a lot >of time on unnecessary moves. > >You should check if they check the opponent without makemove or have a special >function to generate only checks like you suggest later. > >I do not see why it is not going to reduce most of your slow down in nodes per >second. > >Uri unless you already count the quiet moves that you make in the qsearch only to verify that they are not checks as nodes and in this case I do not understand why do you get significant slow down in nodes per second. Uri
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