Author: Severi Salminen
Date: 05:16:44 01/08/01
Hi!
This position from a Kramnik-Leko game was posted recently here by Eduard
Nemeth. I tried it with my program and found odd behaviour. (See below)
[D]2br1r2/1pR1Rp2/1p3k2/1B1p1Pp1/PP1P2P1/K7/8/8 w - -
This is the output of my engine if null moves are disabled (you won't see
end-of-ply statistics except at the end of search. A info line is printed when
PV changes):
--------------------------
Time Depth Score Nodes PV
0.00 1 0.39 7 a5
0.00 1 0.53 9 Bf1
0.00 1 0.59 11 Be2
0.00 1 0.63 13 Bd3
0.00 1 0.66 25 Re5
0.00 2 0.53 68 Re5 Rh8
0.00 3 0.58 233 Re5 Rh8 Kb3
0.00 3 0.60 1065 Kb2 Rd6 Re5
0.00 3 0.61 1256 Kb3 Rd6 Re5
0.06 4 0.58 1694 Kb3 Rd6 Be8 Rd8
0.17 5 0.68 7665 Kb3 Kg7 Kc3 Rd6 Re5
0.44 6 0.56 28541 Kb3 Kg7 Re5 Rh8 Bd3 Rd6
2.37 7 0.66 149581 Kb3 Kg7 Kc2 Kf6 Kd3 Rd6 Re5
11.10 8 1.16 672797 Kb3
(++)
14.72 8 1.29 858649 Kb3 Kg7 Bd7 Bxd7 Rxd7 Rxd7 Rxd7 b5
44.88 9 1.29 2557418 Kb3 Kg7 Bd7 Bxd7 Rxd7 Rxd7 Rxd7 b5 Rxd5
Eval: 1.29, nodes: 3007933, qnodes: 4116797, time: 117.60, nps: 81456
Futile moves: 12023153, order: 99.0%
------------
And this is with null moves:
-----------
Time Depth Score Nodes PV
0.00 1 0.39 7 a5
0.00 1 0.53 9 Bf1
0.00 1 0.59 11 Be2
0.00 1 0.63 13 Bd3
0.00 1 0.66 25 Re5
0.00 2 0.53 69 Re5 Rh8
0.00 3 0.58 277 Re5 Rh8 Kb3
0.05 3 0.60 1149 Kb2 Rd6 Re5
0.05 3 0.61 1358 Kb3 Rd6 Re5
0.05 4 0.48 1662 Kb3 Rd6 Re5 Rh8
0.22 5 0.65 7311 Kb3 Rd6 Kc2 Kg7 Re5
0.38 6 0.58 18869 Kb3 Rd6 Re3 Rd8 Re5 Rh8
0.99 7 0.66 65854 Kb3 Kg7 Kc2 Kf6 Kd3 Rd6 Re5
2.19 8 1.16 156746 Kb3
(++)
2.80 8 1.29 210619 Kb3 Kg7 Bd7 Bxd7 Rxd7 Rxd7 Rxd7 b5
(--)
5.65 9 1.29 456674 Kb3 Kg7 Bd7 Bxd7 Rxd7 Rxd7 Rxd7 b5 Rxd5
Eval: 1.29, nodes: 199941, qnodes: 301868, time: 6.15, nps: 81594
Futile moves: 498682, order: 94.7%
-------
So both versions fail high at d=8 trying Kb3, but why does the null move version
fail low at d=9 but research with infinite window results the same score? The
PVs (and scores) are the same so I think everything is working right. Is this
kind of behaviour "normal" when using null moves or do I have a bug? Can
aspiration search and null moves cause these articats?
Severi
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