Author: Robert Hyatt
Date: 12:47:36 01/20/01
Go up one level in this thread
On January 20, 2001 at 15:38:01, Uri Blass wrote:
>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
Here I actually don't think it matters. Black seems to be losing, period.
Here is what Crafty sees on my PII/400 notebook:
8-> 3.68 0.56 1. ... Rxg2+ 2. Kf1 e3 3. Qxe3 Re8
4. Qd4 Bf3 5. d7 Rd8 6. Rc7
9 5.69 -- 1. ... Rxg2+
9 13.24 3.19 1. ... Rxg2+ 2. Kf1 e3 3. Bxe3 Rg6
4. Rxc6 Rxc6 5. Rxc6 Qxc6 6. d7 Rd6
7. d8=Q+ Rxd8 8. Qxd8+
9 14.53 ++ 1. ... e3!!
(2) 9-> 26.99 2.80 1. ... e36
10 29.07 ++ 1. ... e3!!
10 48.52 1.99 1. ... e3 2. fxe3 Rxg2+ 3. Qxg2 Bxg2
4. Rxc8+ Kh7 5. R8c7 Qd5 6. Kh2 Qd2
7. R1c2
10-> 58.84 1.99 1. ... e3 2. fxe3 Rxg2+ 3. Qxg2 Bxg2
4. Rxc8+ Kh7 5. R8c7 Qd5 6. Kh2 Qd2
7. R1c2
11 1:05 1.93 1. ... e3 2. fxe3 Rxg2+ 3. Qxg2 Bxg2
4. Rxc8+ Kh7 5. Kh2 Qf3 6. d7 Qxh3+
7. Kg1 Qxd7 8. Kxg2 Qd2+ 9. Kf3 Qxa2
(2) 11-> 1:28 1.93 1. ... e3 2. fxe3 Rxg2+ 3. Qxg2 Bxg2
4. Rxc8+ Kh7 5. Kh2 Qf3 6. d7 Qxh3+
7. Kg1 Qxd7 8. Kxg2 Qd2+ 9. Kf3 Qxa2
12 2:05 1.77 1. ... e3 2. fxe3 Rxg2+ 3. Qxg2 Bxg2
4. Rxc8+ Kh7 5. R8c7 Qf3 6. h4 Bh3
7. R1c2 Bf5 8. R2c6
(note + scores are good for white)
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