Author: Uri Blass
Date: 00:56:48 09/18/04
Go up one level in this thread
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. Uri
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