Author: Uri Blass
Date: 02:10:00 09/29/03
Go up one level in this thread
On September 29, 2003 at 03:13:13, Johan de Koning wrote: >On September 28, 2003 at 16:00:43, Tim Foden wrote: > >>On September 26, 2003 at 18:26:17, Johan de Koning wrote: > >>>1. d4? d5? 2.g4 wins (see the earlier d4d5 run) >>>1. d4? b5! draws (see D29) >>>1. c4 mate in 19 or 18 >>>1. b4 mate in 18 >>>Assuming no bugs of course. >>> >>>... Johan >> >>:) > >That wasn't intended to be funny! Shortly after my post I did discover a bug. >Similar to yours, in the "ancient" first optimization heuristic. >/**/ if( OppoReachedRank7() ) return -MATE(d + 2); >/**/ if( OnlyMeStalemate() ) return -MATE(d ); >The first if can return a score that should be treated as an upper bound until >the stale is resolved and possibly returned a worse score. Of course it won't >affect the outcome of the game, and of course the first line became redundant >after the more aggressive full passer heuristic. > >BTW, I also tried a-h mirroring in the TT (yes, including move and ep :-). >On d4d5 and 7-7 the difference was below noise level, as expected. >On the initial position the total time improved from 1.27 to 1 day, with the >node counts of course improving a few % more. > >Not very impressive. And that's because (I guess) mirrored positions are miles >apart in the search tree and don't live long enough in the always-replace fork >of the TT. The depth-preferred fork did a good job however: the occasionally >observed current lines never started with e,f,g,h. > >Anyway, I think I'll skip the experiment with fully normalized TT entries. >(That's with inactive files removed, and the remaining files flipped/sorted >into canonical form). That would be good for a complete retrograde analysis, >but it won't beat alpha-beta on a fixed starting position. I do not see a reason that it won't beat alpha beta because it does not mean not using alpha beta. If you do normalized TT entries then you need to change your TT to include numbers instead of moves and when you try hash move first you may calculate the move based on the number. killer moves and history tables if you use them for order of moves do not need to be changed. Uri
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