Author: David Rasmussen
Date: 18:48:28 11/26/02
Go up one level in this thread
I found the bug...
time nodes depth score pv
00:00:00.00 984n 01/02/17 -0.321 19. Nxf6+ Nxf6
00:00:00.03 1063n 01/02/17 ---------------------------------------------------
00:00:00.06 1962n 02/03/12 -1.418 19. Nxf6+ Nxf6 20. Nd2 Nxg4
21. Bxg4 Bxg4
00:00:00.06 2302n 02/03/16 -1.231 19. cxd5 axb3 20. dxc6 bxc2
21. cxd7 Nxd7
00:00:00.08 2493n 02/03/16 ---------------------------------------------------
00:00:00.09 3774n 03/04/19 -1.231 19. cxd5 axb3 20. dxc6 bxc2
21. cxd7 Nxd7
00:00:00.12 5599n 03/04/19 ---------------------------------------------------
00:00:00.12 8727n 04/05/19 -1.231 19. cxd5 axb3 20. dxc6 bxc2
21. cxd7 Nxd7
00:00:00.17 16kn 04/06/19 ---------------------------------------------------
00:00:00.19 23kn 05/07/19 -1.231 19. cxd5 axb3 20. dxc6 bxc2
21. cxd7 Nxd7
00:00:00.22 34kn 05/07/19 -0.898 19. Nxf6+!
00:00:00.25 45kn 05/08/18 +0.010 19. Nxf6+ gxf6 20. Nd2 h5
21. cxd5 Qxd5
00:00:00.29 55kn 05/08/20 ---------------------------------------------------
00:00:00.39 94kn 06/09/20 -0.049 19. Nxf6+ Nxf6 20. Nxc5 d4
21. Nxe6 Qxe6 22. Bf4 Nxg4
23. Bxg4 Qxg4+
00:00:00.56 146kn 06/09/23 ---------------------------------------------------
00:00:00.72 216kn 07/11/23 +0.084 19. Nxf6+ Nxf6 20. Nxc5 d4
21. Bxd4 Bxc5 22. Bg2 Qc8
23. Bxc5 Qxc5 24. Bxb7
00:00:01.03 326kn 07/11/23 ---------------------------------------------------
00:00:01.37 480kn 08/14/23 +0.084 19. Nxf6+ Nxf6 20. Nxc5 d4
21. Bxd4 Bxc5 22. Bg2 Qc8
23. Bxc5 Qxc5 24. Bxb7
00:00:01.65 581kn 08/14/23 ---------------------------------------------------
00:00:02.39 941kn 09/16/24 +0.084 19. Nxf6+ Nxf6 20. Nxc5 d4
21. Bxd4 Bxc5 22. Bg2 Qb6
23. Bxc5 Qxc5 24. Bxb7
00:00:03.11 1235kn 09/16/24 ---------------------------------------------------
00:00:05.78 2495kn 10/16/24 -0.032 19. Nxf6+ Nxf6 20. Nxc5 dxc4
21. Nxe6 Qxe6 22. Qxc4 Bxe3
23. Qxe6 Bxf2+ 24. Kxf2 fxe6
00:00:07.03 3025kn 10/16/25 ---------------------------------------------------
00:00:12.70 5776kn 11/21/26 -0.018 19. Nxf6+ Nxf6 20. Nxc5 Nxg4
21. cxd5 Qxd5 22. Bxg4 Bxg4
23. Rfc1 Bf5 24. Qc3 Rae8
00:00:15.69 6991kn 11/21/26 ---------------------------------------------------
00:00:24.62 11Mn 12/22/29 -0.122 19. Nxf6+ Nxf6 20. Nxc5 Nxg4
21. cxd5 Qxd5 22. Bxg4 Bxg4
23. Ne4 Bd4 24. Bxd4 Qxd4
25. Rae1 Rae8
00:00:29.94 13Mn 12/22/29 17/42 19. Nd6
Time used: 00:00:30.00
nps: 456882 nodes: 13711044 Q-nodes: 5348044 (39%)
move order: 88%
hash probes: 2528374 hash hits: 735380 (29%) hash usage: 97%
pawn hash probes: 10680903 pawn hash hits: 10472532 (98%)
EGTB probes: 0 EGTB hits: 0 (0%)
I bet you're curious to know what the bug was :)
I can't explain it exactly, because that would require that you have detailed
knowledge about the way my functions work. But there was a _huge_ bug in the way
that qsearch looped through moves. Basically, in certain situations, if there
were n captures generated, qsearch could end up trying only the expected best
one of them, n times! That is, doing the exact same search n times!
What I don't understand is how Chezzz was at all able to play chess with this
sort of bug, let alone get a decent rating on ICC. I guess it shows that qsearch
can be pretty inaccurate or even buggy, and still "work".
Wow...
There's noting better than when you've just fixed a bug :)
/David
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