Author: Robert Hyatt
Date: 08:07:15 04/30/04
Go up one level in this thread
On April 30, 2004 at 02:00:57, Ed Schröder wrote: >On April 29, 2004 at 23:25:59, Robert Hyatt wrote: > >>On April 29, 2004 at 16:17:34, Ed Schröder wrote: >> >>>On April 29, 2004 at 14:44:47, Robert Hyatt wrote: >>> >>>>On April 29, 2004 at 09:28:53, Ed Schröder wrote: >>>> >>>>>On April 29, 2004 at 07:37:23, Vincent Diepeveen wrote: >>>>> >>>>>[ snips ] >>>>> >>>>>>>This is all very poor Vince, I assume you don't play much with nowadays top >>>>>>>programs. From 1982 to 2001 Rebel won its games by positional understanding and >>>>>>>not by search and Rebel lost its games because it was outsearched. Today Rebel >>>>>>>isn't outsearched at all, it now loses its games because the current top >>>>>>>programs have a better positional understanding than Rebel. >>>>>>> >>>>>>>You should have a good look at the current tops, the positional progress has >>>>>>>been great the last years. To me it all seems to indicate (provided your search >>>>>>>is okay) the only way to make progress is to improve on chess knowledge. But >>>>>>>what's new, I already came to that conclusion in 1986 after some intensive talks >>>>>>>with Hans Berliner. >>>>> >>>>>>What i mean is Ed, is that you would not have accomplished the great results >>>>>>with Rebel which you managed, had you just searched with a fullwidth search + >>>>>>bunch of checks in qsearch. >>>>> >>>>>No of course not, brute force is silly, Rebel since day 1 has been a selective >>>>>program. But I am getting your point, in the days before the nullmove was >>>>>discovered Genius and Rebel had the best (static) selective search, a dominant >>>>>factor in their successes, is that what you meant to say? If so, it is true. >>>>> >>>>>If only Frans had kept his mouth shut to Chrilly (Chrilly leaking nullmove in >>>>>the ICCA journal) it is very likely Fritz would been the next Richard Lang still >>>>>dominating all the rating lists and WCC's for the last decade. But Frans didn't >>>>>and then all bets were off. >>> >>> >>>>Chrilly wasn't the one that started the null-move search stuff. Don Beal was >>>>the first I recall reading although Murray Campbell also wrote a paper on the >>>>idea. I will try to flip through the surviving Cray Blitz source listing to see >>>>exactly when null-move was added to it. All I remember is Burton Wendroff >>>>(Lachex) sending me a copy of Murray's paper and saying "try this". (this >>>>happened while I was preparing for an ACM or WCCC event). Of course I am >>>>talking about R=1, non-recursive, as it was defined "in the good old days".. :) >>> >>>Actually Don Beal told Frans about nullmove in Cologne 1986, Don at that time >>>only used nullmove in QS. Don did not use nullmove as we know it today, that >>>came after Chrilly's article. >>> >>>Ed > > >>Yes, but Campbell defined "the null-move observation" exactly as it is used >>today (no move played, reduce depth, if it fails high, then let the search fail >>high with no more searching.) He even suggested that R=2 needs serious testing. > >Did Campbell mention recursive nullmove too? Because that's where the real >strength of the algorithm comes from. They discussed it and dismissed it as too risky at the search depths of that time... Remember that non-supercomputer programs were hitting 5-6- plies generally... > > >>Chrilly's main advancement was using the null-move observation to detect threats >>and extend the search when the condition was met. I don't know of anyone that >>really does this today. I did it back around version 9, but stopped due to the >>high cost and low return... > >As far as I can remember the article was about detecting mate-threats only, I >could be wrong. I use it, when the first nullmove returns a mate-value I extend >one ply. > >My best, > Chrilly's idea was this: when a normal move fails high, but a null-move fails low (on a lowered window) then the fail-high move is likely holding off some sort of threat that the null-move search sees quickly. Extend. I think this was explained in the section "The program that knew too much" but remember that this is from memory of a paper written/published 10+ years ago... I used this idea in Crafty for a year or so, around version 9 or so it was removed due to excessive overhead... I think many do the mate score extension. Bruce Moreland was the first I ever recall mentioning that idea. I got it from him several years ago. >Ed
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