Author: Tony Werten
Date: 02:01:32 09/18/04
Go up one level in this thread
On September 18, 2004 at 03:56:48, Uri Blass wrote: >On September 18, 2004 at 03:22:25, Tony Werten wrote: > >>On September 17, 2004 at 11:50:41, Robert Hyatt wrote: >> >>>On September 17, 2004 at 08:15:41, Tony Werten wrote: >>> >>>>On September 16, 2004 at 11:21:32, Robert Hyatt wrote: >>>> >>>>>On September 16, 2004 at 10:06:46, martin fierz wrote: >>>>> >>>>>>On September 16, 2004 at 09:53:14, Robert Hyatt wrote: >>>>>> >>>>>>[snip] >>>>>> >>>>>>ok,ok, i believe you. i just never saw anybody here saying it worked for them, >>>>>>but i distinctly remembered people saying it didn't work for them. >>>>> >>>>>Correct both ways for me. I reported more than once that it looked >>>>>significantly better in Cray Blitz, but that tests with Crafty never produced >>>>>results that looked better than crafty without SE. I don't know whether the >>>>>null-move R=3 stuff hurt the SE detection code or not, although I did speculate >>>>>that it was possible since CB used null-move R=1, non-recursive, rather than the >>>>>aggressive way we do it today... >>>>> >>>>> >>>>>> >>>>>>>Bruce has reported _lots_ of test data here in CCC. Including ECM results with >>>>>>>and without, etc... >>>>>> >>>>>>but... do you really believe a tactical test set like ECM is the right way to >>>>>>test SE? and what about the question pham already posted: >>>>> >>>>>That wasn't the only tests. Bruce mentioned several times that he noticed that >>>>>with SE, the program played a bit more "steadily" in tactical positions, and >>>>>that against programs without SE, he would usually be going along when "BAM" >>>>>(his words) SE would find a deep tactic and end the game... >>>>> >>>>>He once said "this is a stupendous extension" although I believe that later he >>>>>became "less than stupendous" when looking at real games rather than tactical >>>>>test positions. But he did use real game data, and went so far as to play lots >>>>>of Crafty vs Ferret games where I turned book learning off and set the width to >>>>>1 so he could play crafty the same opening with and without SE... >>>>> >>>>> >>>>>> >>>>>>in http://www.brucemo.com/compchess/programming/extensions.htm#singular >>>>>>bruce wrote the stuff below in 2001 - not very enthusiastic about SE if you ask >>>>>>me! i probably based my anti-SE-bias in part on this without remembering where i >>>>>>had it from, i read bruce's pages a long time ago. >>>>>> >>>>>>cheers >>>>>> martin >>>>>> >>>>>> >>>>>>"Singular extension >>>>>>This extension is the search heuristic centerpiece of Deep Thought, the >>>>>>strongest computer chess player of the 1980's, and precursor to Deep Blue. >>>>>> >>>>>>The idea is that if one move is significantly better than all of the other moves >>>>>>(a singular move), it should be extended. >>>>>> >>>>>>This can be interpreted as a more general case of the recapture and single >>>>>>response extensions. It encompasses these, but also can be used in cases where >>>>>>the singular move is not a recapture and where the side making the move isn't in >>>>>>check. >>>>>> >>>>>>I don't know why it worked in DT, but it seems to me that this is a loss-seeking >>>>>>extension. >>>>> >>>>>The question is, did he write that before or after _he_ chose to implement the >>>>>"cheapo version" and then actually keep it in his program because it seemed to >>>> >>>>I'm not so sure the version Bruce is using is much different from the Deep Blue >>>>version. >>>> >>>>In one of their papers they describe the parameters they sent to the hardware >>>>search. One of them is "depth offset for singularity tests" >>>> >>>>That does sound like what Bruce described ( unless I'm missing something) It >>>>also seems to indicate that DB didn't use them the last x ply (where x would be >>>>6 in a few minutes search) wich makes sense from my own testing where testing to >>>>close to horizon would blow up the search. >>> >>>It really is way different. IE for PV-singular their test is much stronger than >>>what Bruce and I were doing. We did a very shallow search at the start of any >>>new node, to see if one of the first moves tried would fail high. If so, we >>>searched the rest of the moves with a offset (lower) window to see if any of >>>them would fail high. This is weaker than the DB PV-singular test, similar to >>>the DB FH-singular test. But then there are issues like the sticky transposition >>>table, and all the work they did to exclude obvious singluar moves that don't >>>deserve extensions in the "trivial" part of the search. IE if I play BxN, >>>re-capturing is pointless to extend, even though it is the only good move to >>>play, in many circumstances. >>> >>>I implemented the full SE approach in Cray Blitz. It took a _long_ time to get >>>it right. In fact, I reported in 1993 at the ACM event that I had a serious SE >>>bug that could over-extend and run out the end of the search arrays. The code >>>that Bruce/I were using was very simple to write compared to the SE >>>implementation I did for CB, following their paper very carefully. >>> >>>> >>>>I used to have the same version of SE. It didn't cost much, but didn't gain much >>>>either, except for a very few times. I always left it in, hoping for it to make >>>>a difference in an important game and at least once it did. >>>> >>> >>> >>> >>>"same version" == what? IE for the DB approach it cost me about 2 plies of >>>overall depth. They reported something similar. The version Bruce and I were >>>playing with cost us about the same thing. 2 plies lopped off the search to see >>>deeper tactics. It didn't pay off very well for me, but seemed to be a little >>>better than break-even for Bruce... >>> >>>The version Bruce/I were using added maybe 200 lines of code total. The SE code >>>in Cray Blitz was closer to 2500 lines of code total. >> >>I'm definately talking about a 200 lines version. With special care for pv >>nodes, since they tend to blow up the search. The dualcredit system from DB >>seems to take care of that quite nicely, reducing the extensions with an average >>of 30%. >> >>My offset searches are not really shallow, just depth-2ply. Seems costly, but is >>nescessairy for some addition. Only after this addition it seemed to slightly >>more than break even for me. > >I wonder if you have a stable version at 40/40 time control. >Xinix of 21.08.2004 was taken out of WBEC because of crashing again and again. Nope. I was develloping on 2 computers. One win98 with Delphi 5, one winxp Delphi 7. Somewhere it went seriously wrong. I couldn't be bothered with searching for a correct version ( things already went wrong before the crashing) and redo all my work since I thought it was time for a rewrite anyway. Tony > >Uri
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