Author: Uri Blass
Date: 12:38:01 01/20/01
Go up one level in this thread
On January 20, 2001 at 13:30:15, Ulrich Tuerke wrote: >On January 20, 2001 at 09:56:57, Uri Blass wrote: > >>On January 20, 2001 at 06:24:19, Thorsten Czub wrote: >> >>> >>>[Event "Odyssee2001-Tournament"] >>>[Site "k6-400, 40/120"] >>>[Date "2001.01.20"] >>>[Round "1"] >>>[White "Shredder4 Chessbits-style"] >>>[Black "Comet B27"] >>>[ECO "C99"] >>>[Result "*"] >>> >>>1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7 6. Re1 >>>b5 7. Bb3 d6 8. c3 O-O 9. h3 Na5 10. Bc2 c5 11. d4 Qc7 >>>12. Nbd2 cxd4 13. cxd4 Nc6 14. Nb3 a5 15. Be3 a4 16. Nbd2 >>>Bd7 17. Nf1 Rfe8 18. Rc1 Qb7 19. Ng3 a3 20. b3 Rac8 21. Qd2 >>>exd4 22. Nxd4 d5 23. Nxc6 Bxc6 24. e5 Ne4 25. Bxe4 dxe4 >>>26. Nf5 Bf8 27. Nd6 Bxd6 28. exd6 Re6 29. Bf4 Rg6 30. Re3 >>>h6 31. Rec3 * >>> >>>after Rec3 shredder4 got a fail-low and comet first considered >>>about Rxg2 with positive score for black, but now has changed >>>mind and says 0.47 for white when playing Rxg2+. now comet >>>says +0.74 for white. >>> >>>anyway - interesting game too. >> >>I see that CometB27 had a lot of fail low by 0.27 at iteration 11. >> >>I think that the decision about this constant number is not a good decision and >>it is better to increase the number after failing low. >> >>Comet needs a long time to find e3 at depth 11 because of this decision and had >>not enough time at tournament time control when other programs have no problem >>to find e3 at tournament time control. >> >>Maybe Uli can change the 0.27 design decision for the next rounds and to use >>bigger numbers after failing low without solving the fail low problem. >> >>Uri > >If I got this right Uri, you are referring to the aspiration window treatment of >Comet. It uses a very small window, basically of constant width, which will be >just shifted in case of a verification search. >This way, one sometimes needs a lot of verification searches in fail low/high >cases. >I think that this is what you are referring to ? Yes > >However, the advantage is that this method speeds up the search im more quiet >positions. >I think that I will still stick to this - at least for a while. I think that the window should not be of constant width. There is no problem with a small window in the first fail low but I think that after failing low and not finding a better move it is better to increase the width of the window. I think that a rule to double the size of the window after failing low without finding a better move may be better. You can also use the previous changes in the evaluation to decide about the size of the window(if there were big changes then it suggest that the position is tactical and it is better to use a bigger window. In the relevant position Comet has a lot of fail low at depth 11 and not only 1,2 or 3 Here is the relevant position: [D]2r3k1/1q3pp1/2bP2rp/1p6/4pB2/pPR4P/P2Q1PP1/2R3K1 b - - 0 1 Comet needed a lot of iterations to get from +1 for black(at the end of iteration 10) to a better move at depth 11. The scores at depth 11 from white point of view -0.86,-0.59,-0.32,-0.05,+0.22,+0.49,+0.76,+1.03 before finding a better move. I am not sure about the +1.03 but I remember that after the +0.76 it failed low the last time and changed its mind to e3. It is better if it can get the following scores -0.86,-0.59,-0.05,+1.03 so it can changes its mind in 4 iterations instead of 8 iterations. Uri
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