Author: Tord Romstad
Date: 00:02:04 03/26/04
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On March 26, 2004 at 02:39:29, Johan de Koning wrote: >>I thought so, too, but after watching the first two games of a blitz match >>between the normal version of my engine and an identical version with the >>null move disabled I am already beginning to doubt it. The non-nullmove >>version is leading by 2-0. > >IIRC it was only 2 days ago Will Singleton posted a funny remark about >discarding null moves after 10 games. :-) Yes, I remember. :-) I wasn't really close to discarding null moves, of course, but I was surprised that the version without null move had any chance at all, and that the difference in search depth was not greater. I expect the null move version to win by a clear margin when enough games are played, but it will be interesting to see how big the difference is. After 8 games, it's 4-4. >>The difference in search depth isn't as big as I expected. In the middle >>game, the null move version typically reaches about 12 plies, while the >>version without null move reaches 11 plies. > >Hmmm... that sounds pretty incredible. >We're not talking about 11 ply full-width here, are we? No, I do lots of pruning besides null-move, and reach rather high search depths even without it. Here are the number of nodes I need to search n plies (n from 1 to 13) with and without null move from the opening position: Plies Nodes (null move off) Nodes (null move on) 1 55 55 2 228 261 3 965 439 4 3,741 2,318 5 13,213 6,638 6 35,056 18,964 7 37,398 36,095 8 77,226 60,240 9 117,274 109,939 10 239,355 237,775 11 555,661 412,969 12 1,942,523 1,084,089 13 12,060,312 3,531,279 I have no good explanation for the bizarrely irregular effective branching factor of my non-nullmove search here. I wonder how it is possible that hardly any nodes are needed in the 7th iteration. Tord
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