Author: Anthony Cozzie
Date: 11:45:42 11/11/03
Go up one level in this thread
On November 11, 2003 at 01:00:14, John Stanback wrote:
>As others have noted, this is an interesting position since the tree
>becomes so much smaller after the capture such that it's easy
>to enough search depth to see the impact of Qxf3.
>I made a simple modification that lets Zarkov find Qxf3 in
>under a minute (or less depending on the threshold). This also helps
>on lots of other sacrifice positions, but I don't know
>if overall it helps more than it hurts since I just implemented
>it 15 minutes ago.
>The extra code is only applied at the root and looks like this:
>
>MakeMove();
>d = depth;
>while (1)
> {
> score = -Search(side,ply,d,-beta,-alpha);
> if (!capture || nodes_just_searched > threshold)) break;
> ++d;
> }
>UnmakeMove();
>
>Where threshold is some fraction of the total nodes searched
>during the previous iteration, say nodes/32 or nodes/16.
>
>This allows the program to search captures at the root to
>arbitrary depth. In this position for example, it searches
>Qxf3 to more than 20 ply during iteration 11!
>
>It doesn't seem to cause much slowdown on about 20 other positions
>I tried. I think this might cause some strangeness with the hashtable.
>It may make sense to try some variant of this at ply=2 also.
>
>
>John
>
>
>
>On November 10, 2003 at 03:37:58, Eduard Nemeth wrote:
>
>>[Event "4NCL West Bromwich ENG"]
>>[Site "?"]
>>[Date "2003.??.??"]
>>[Round "2"]
>>[White "McDonald, N."]
>>[Black "Turner, M."]
>>[Result "0-1"]
>>[ECO "C47"]
>>[WhiteElo "2380"]
>>[BlackElo "2505"]
>>[PlyCount "104"]
>>[EventDate "2003.??.??"]
>>
>>1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. d4 exd4 5. Nxd4 Bb4 6. Nxc6 bxc6 7. Bd3 d5 8.
>>exd5 cxd5 9. O-O O-O 10. Bg5 c6 11. Ne2 Bg4 12. c3 Be7 13. Qc2 h6 14. Bh4 Nh5
>>15. Bxe7 Qxe7 16. Ng3 Nf4 17. Rae1 Qg5 18. Bf5 Rae8 19. Re3 Bxf5 20. Qxf5 Ne2+
>>21. Rxe2 Qxf5 22. Rxe8 Qg4 23. Re7 h5 24. Rfe1 h4 25. h3 Qa4 26. Nf5 g6 27. Nd4
>>c5 28. Nf3 Qxa2 29. Rb7 d4 30. cxd4 cxd4 31. Nxd4 Qd5 32. Rb4 Qa5 33. Nc6 Qc5
>>34. Ne7+ Kg7 35. Rb7 Rd8 36. b4 Qc3 37. Rf1 a6 38. b5 axb5 39. Rxb5 Rd7 40.
>>Nf5+ gxf5 41. Rxf5 Qd2 42. Rf3 Rd6 43. Kh1 Qe2 44. Rc1 Kg6 45. Ra1 Rd1+ 46.
>>Rxd1 Qxd1+ 47. Kh2 Qxf3 48. gxf3 Kf5 49. Kh1 Kf4 50. Kg2 f6 51. Kg1 Kxf3 52.
>>Kf1 f5 0-1
>>
>>After move 47 (white):
>>
>>McDonald,N - Turner,M
>>
>>[D]8/5p2/6k1/8/7p/5R1P/5PPK/3q4 b - - 0 1
>>
>>Interesting win is now Qxf3! (see game).
>>
>>Can your program this move find?
>>
>>Eduard
One of the suggestions on Ed Schroeder's webpage: Since K-P endings are very
easy to search, extend by 3 ply when we reach a K-P ending.
anthony
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