Author: José Carlos
Date: 23:45:28 11/10/03
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
Interesting idea. What about real games? In games, I don't clear the hash
table between moves, so if I did this (haven't tried 'cause I'm at work now) I
guess I'd have extrange behaviour when I'd cuoff by hash hit in the first
iterations. I mean, if I search up to depth 12, in the next move I go to depth
10 almost instantly due to hash hits in ply 2.
Do you preserve the hash table between moves? Have you tried games to see how
your idea affects?
José C.
>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
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.