Author: Dann Corbit
Date: 23:28:59 10/04/01
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On October 05, 2001 at 02:10:32, Christophe Theron wrote: [snip] >Yes it's the classical explanation of this theory of "search vs knowledge", but >as far as I know you do not need an enormous k2 and k3 to get the best branching >factor that can be achieved nowadays. > >And if you have a huge k2, I can predict that your program is going to be >criticized for being a root processor! :) > >It might happen some day that we find some expensive way of achieving better >branching factors, but at this time we do not need to slow down the nps rate >(even in a very fast searcher) in order to get state-of-the-art branching >factors. How do you know that Stefan Meyer-Kahlen has not achieved this in Shredder (IOW: maybe he _has_ achieved a branching factor better than anyone else by ludicrous gobs of knowledge). >I would also like to point out that if you find some extremely expensive way of >getting a better branching factor, you can keep your nps very high and still get >the benefits of your better BF by applying your system on the first plies only >and letting the last plies running at full speed. You do not have to have a run >time of k2+k3*exp(k4*depth). > >Further, the formula has nothing to do with my idea of dimishing returns from >knowledge (exactly like dimishing returns from search depth), which was what I >was trying to stress out. Actually, I think I did understand you. All chess programs are going to "hit the wall" because of the exponential nature of chess. Once you get to (for instance) 17 plies in ten minutes, ply 18 is going to be hecka-hard (maybe taking days). But a smaller branching factor (of say 20%) can accomplish something phenomenal in that regard. Sort of like what NULL move accomplished. Shave the tree way down so you only search the fat branches and suddenly you're zooming. Of course, it's *still* an exponenatial search. But I would hate to compete with someone who did trim the tree and I achieved no trimming at all. Pure alpha-beta will get slaughtered by a null-move alpha beta. If a similar reduction is gained through other means [e.g. I believe that Rebel does not use null-move but achieves the reduction in other ways] then you will have to be millions of times faster to achieve the same depth. Reducing the branching factor is where it's at. As soon as we reduce it to 1, chess will be solved.[1] ;-) [1] Assuming that the trimming is perfectly accurate.
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