Eelco de Groot wrote:
I could not find an obvious Zugzwang in the position from the Stockfish game that could have caused the problems for some programs. I took some positions along the PV after f5, changed the side to move so White could have "passed" but the Black pieces still win easily.
Hi Eelco!
That's what I did, changing sides after 1...f5 makes white loose at once, this isn't zugzwang, which doesn't mean there isn't such later in the tree but what I saw about nullmove and other pruning techniques, is that forward and history pruning switched off at some engines brings the solution much more quickly, which isn't found by default so soon.
Besides Toga, this is so with Glaurung 2.2 too:
5k2/5p2/2b1p1pN/1p2P1P1/5Q1p/1Pb4P/4KP2/1q1B4 b - - 0 1
Analysis by Glaurung 2.2 JA:
1...Le8 2.De3 b4 3.Dd3 Db2+ 4.Lc2 Lxe5
-+ (-2.21) Tiefe: 6 00:00:00 21kN
1...Le8 2.De3 b4 3.f4 Lb5+ 4.Kf2 Dxd1 5.Dc5+ Kg7 6.Dxb5 Dxb3
-+ (-2.01) Tiefe: 7 00:00:00 28kN
1...Le8 2.Sg4 Da1 3.Df6 Dc1 4.Dh8+ Ke7 5.Se3 Dd2+ 6.Kf1 Lc6
-+ (-1.76) Tiefe: 8 00:00:00 51kN
1...Le8 2.Sg4 Da1 3.Df6 b4 4.Dh8+ Ke7 5.Df6+ Kd7 6.Df3 Kc7 7.Kf1 Lxe5 8.Sxe5 Dxe5
-+ (-1.86) Tiefe: 9 00:00:00 90kN
1...Le8 2.Sg4 Da1 3.Df6 b4 4.Dh8+ Ke7 5.Df6+ Kd7 6.Df3 Kc7 7.Kf1 Lxe5 8.Sxe5 Dxe5
-+ (-1.86) Tiefe: 10 00:00:00 143kN
1...Le8 2.Sg4 Db2+ 3.Kf1 Da1 4.Se3 Lc6 5.Dxh4 Lxe5 6.Db4+ Kg8 7.f4 Ld4
-+ (-1.74) Tiefe: 11 00:00:01 355kN
1...Le8 2.Sg4 Db2+ 3.Kf1 Da1 4.Se3 Lc6 5.Dxh4 Lxe5 6.Db4+ Kg8 7.Dd2 Lf3 8.Dd8+ Kh7
-+ (-1.76) Tiefe: 12 00:00:01 518kN
1...Le8 2.Sg4 Db2+ 3.Kf1 Da1 4.Se3 Lc6 5.Dxh4 Lxe5 6.Db4+ Kg8 7.Dd2 Lf3 8.Dd8+ Kh7 9.b4
-+ (-1.78) Tiefe: 13 00:00:01 903kN
1...Le8 2.Sg4 Db2+ 3.Kf1 Da1 4.Df3 b4 5.Kg2 Dc1 6.Le2 Dxg5 7.De4 Ld2 8.Db7 Df4
-+ (-1.92) Tiefe: 14 00:00:01 1712kN
1...Le8 2.Sg4 Db2+ 3.Kf1 Da1 4.Df3 b4 5.Dd3 Ld4 6.Kg2 Dc3 7.Lc2 Lc6+ 8.f3 Kg7 9.Lb1 Lxe5 10.Sxe5 Dxe5
-+ (-1.84) Tiefe: 15 00:00:02 3234kN
1...Le8 2.Sg4 Db2+ 3.Kf1 Da1 4.Df3 b4 5.Kg2 Dc1 6.Le2 Dxg5 7.De4 Kg7 8.f4 Df5 9.Dxf5 gxf5 10.Sf6 Lc6+ 11.Kf2
-+ (-1.68) Tiefe: 16 00:00:02 5489kN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.De4 Kg8 5.Sc4 Lb5 6.Db7 Lxc4+ 7.bxc4 Db2+ 8.Kf3 Lxe5 9.De4 Dc3+ 10.Kg2 Kg7 11.Dxh4 b3 12.Dh6+ Kg8
-+ (-1.86) Tiefe: 17 00:00:05 15840kN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.Dxh4 Lb5+ 5.Kf3 Lc6+ 6.Ke2 Da6+ 7.Sc4 Lxe5 8.Dg4 Lc3 9.Df4 Lg2 10.Dd6+ Dxd6 11.Sxd6 Lxh3 12.Kd3 Ke7
-+ (-2.00) Tiefe: 18 00:00:08 25346kN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.Dxh4 Lb5+ 5.Kf3 Lc6+ 6.Ke2 Da6+ 7.Sc4 Lxe5 8.Dg4 Lc3 9.Dg3 Da2+ 10.Kf1 Kg7 11.Db8 Ld4 12.Se3 Dd2
-+ (-1.80) Tiefe: 19 00:00:12 40801kN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.Dxh4 Lb5+ 5.Kf3 Lc6+ 6.Ke2 Da6+ 7.Sc4 Lxe5 8.Dg4 Lc3 9.Dg3 Da2+ 10.Kf1 Ld5 11.Df4 Kg8 12.Se5 Da7 13.Kg1
-+ (-1.80) Tiefe: 20 00:00:19 66933kN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.Dxh4 Lb5+ 5.Kf3 Lc6+ 6.Ke2 Da6+ 7.Sc4 Lxe5 8.Dg4 Lc3 9.Dg3 Da2+ 10.Kf1 Kg7 11.Kg1 Db1 12.Dg4 Dd3 13.Le2 Dd5
-+ (-1.96) Tiefe: 21 00:00:32 114mN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.Dxh4 Lb5+ 5.Kf3 Lc6+ 6.Ke2 Da6+ 7.Sc4 Lxe5 8.Dg4 Lc3 9.Kf1 Db5 10.Df4 Dd5 11.Dd6+ Dxd6 12.Sxd6 Ke7 13.Sc4 Ld4 14.Ke2 Ld5
-+ (-1.86) Tiefe: 22 00:00:56 203mN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.Dxh4 Lb5+ 5.Kf3 Lc6+ 6.Ke2 Da6+ 7.Sc4 Lxe5 8.Dg4 Lb5 9.Kf1 Da1 10.Kg2 Lc7 11.Df3 Dc1 12.h4 Lxc4 13.bxc4 Dxc4 14.h5 gxh5 15.Dxh5
-+ (-1.76) Tiefe: 23 00:01:58 433mN
1...f5 2.exf6 e5 3.Dg4 Lb7 4.Sg8 Db2+ 5.Kf1 Dd2 6.De2 Kxg8 7.Dxd2 Lxd2 8.Lg4 Kf7 9.Ld7 b4 10.Ke2 Lxg5 11.Kd3 Ld5 12.Lb5 Lxf6 13.Lc4 e4+ 14.Kc2 Lxc4 15.bxc4 Ke6
-+ (-6.07) Tiefe: 23 00:13:06 2837mN
And now have a look, what Glaurung does, pruning in main search and in quiescence search is turned off:
5k2/5p2/2b1p1pN/1p2P1P1/5Q1p/1Pb4P/4KP2/1q1B4 b - - 0 1
Analysis by Glaurung 2.2 JA00:
1...Le8 2.De3 b4 3.Dd3 Db2+ 4.Lc2 Lxe5
-+ (-2.21) Tiefe: 6 00:00:00 17kN
1...Le8 2.De3 b4 3.Dd3 Db2+ 4.Lc2 Lxe5 5.Dc4
-+ (-2.15) Tiefe: 7 00:00:00 27kN
1...Le8 2.De3 b4 3.Dd3 Db2+ 4.Lc2 Lxe5 5.Dc4 Dd4 6.Dxd4 Lxd4
-+ (-2.33) Tiefe: 8 00:00:00 51kN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.De4 Kg8 5.Kf1 Lb5+ 6.Kg1 Lxe5 7.Dxh4
-+ (-1.78) Tiefe: 9 00:00:00 174kN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.Kf1 Ld2 5.Dg4 Lb5+ 6.Kg1 Dxe5 7.Dxh4 Lxe3 8.fxe3 Dxe3+ 9.Kg2
-+ (-1.88) Tiefe: 10 00:00:00 274kN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.De4 Kg8 5.Kf1 Ld4 6.Dg4 Lb5+ 7.Kg1 Lxe3 8.fxe3 Dxe5 9.Dxh4 Dxe3+ 10.Kg2
-+ (-1.80) Tiefe: 11 00:00:01 476kN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.De4 Da6+ 5.Sc4 Lc6 6.Dxh4 Lxe5 7.Kf1 Lc3
-+ (-1.82) Tiefe: 12 00:00:01 904kN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.Dxh4 Lb5+ 5.Kf3 Lc6+ 6.Ke2 Da6+ 7.Sc4 Lxe5 8.Lc2 Lc3 9.Dh7
-+ (-1.76) Tiefe: 13 00:00:01 1810kN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.Dxh4 Lb5+ 5.Kf3 Lc6+ 6.Ke2 Da6+ 7.Sc4 Lxe5 8.Lc2 Lc3 9.Dh6+ Ke8 10.f3
-+ (-1.76) Tiefe: 14 00:00:01 2993kN
1...Le8 2.Sg4 Db2+ 3.Kf1 Da1 4.Df3 b4 5.Dd3 Ld4 6.Sf6 Lc6 7.f4 Db2 8.Dc2 Dc3 9.Dxc3 bxc3
-+ (-1.88) Tiefe: 15 00:00:02 7050kN
1...Le8 2.Sg4 Db2+ 3.Kf1 Da1 4.Df3 b4 5.Kg2 Ld2 6.Sf6 Dxe5 7.Sxe8 Dxg5+ 8.Dg4 Dd8 9.Sc7 Dxc7 10.Dxh4 Lf4
-+ (-1.88) Tiefe: 16 00:00:04 10770kN
1...Le8 2.Sg4 Db2+ 3.Kf1 Da1 4.Df3 b4 5.Kg2 Ld2 6.Sf6 Dxe5 7.Sxe8 Dxg5+ 8.Dg4 Dd8 9.Sc7 Dxc7 10.Dxh4 Lf4 11.Lf3
-+ (-1.76) Tiefe: 17 00:00:05 17646kN
1...Le8 2.Sg4 Db2+ 3.Kf1 Da1 4.Df3 b4 5.Kg2 Ld2 6.Sf6 Dxe5 7.Sxe8 Dxg5+ 8.Dg4 Dd8 9.Sc7 Dxc7 10.Dxh4 Lf4 11.Lf3 De5
-+ (-1.74) Tiefe: 18 00:00:10 36798kN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.Dc4 Da5 5.De4 Dc5 6.Sc4 Lb5 7.Lc2 Lxe5 8.Dxh4 Ld4 9.Dg3 Lxc4+ 10.bxc4 Dxc4+ 11.Dd3 Dd5 12.Db3
-+ (-1.92) Tiefe: 19 00:00:23 87418kN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.Dc4 Da5 5.De4 Dc5 6.Sc4 Lb5 7.Lc2 Lxe5 8.Dxh4 Ld4 9.Dg3 Lxc4+ 10.bxc4 Dxc4+ 11.Dd3 Dd5 12.Db3 De5+ 13.Kd1
-+ (-1.92) Tiefe: 20 00:00:32 124mN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.Dc4 Da5 5.De4 Dc5 6.Sc4 Lb5 7.Lc2 Lxe5 8.Dxh4 Lc3 9.Df4 Le5 10.De4 Ld4 11.Da8+ Kg7 12.Dg2 Lxc4+ 13.bxc4 Dxc4+ 14.Kd2
-+ (-1.92) Tiefe: 21 00:00:49 193mN
1...Le8 2.Sg4 b4 3.Se3 Da1 4.Dxh4 Lb5+ 5.Kf3 Lc6+ 6.Ke2 Da6+ 7.Sc4 Lxe5 8.Dg4 Lc3 9.Kf1 Db5 10.Df4 Dd5 11.Dd6+ Dxd6 12.Sxd6 Ke7 13.Sc4 Ld4 14.Ke2 Ld5
-+ (-1.86) Tiefe: 22 00:01:41 406mN
1...f5 2.exf6 e5 3.Dg4 Lb7 4.Sf5 Le4 5.Kf1 Lxf5 6.Df3 Dd3+ 7.Dxd3 Lxd3+ 8.Le2 e4 9.f3 Ld2 10.fxe4 Lxe4 11.Lxb5 Lxg5 12.Ke2 Lf5 13.Ld3 Lxh3 14.Kf3
-+ (-4.82) Tiefe: 22 00:04:34 1073mN
1...f5 2.exf6 e5 3.Dg4 Lb7 4.Sf5 Le4 5.Kf1 Lxf5 6.Df3 Dd3+ 7.Dxd3 Lxd3+ 8.Le2 e4 9.f3 Ld2 10.fxe4 Lxe4 11.Lxb5 Lxg5 12.b4 Lf5 13.Kg2 Le4+ 14.Kf1 Ld2 15.Ke2 Lxb4
-+ (-4.88) Tiefe: 23 00:05:42 1336mN
Ten minutes and one depth earlier, and this is the worst of my MP- trials, I saw it arising even at once, too.
All that on 4x2,5Ghz, 1536 Mb hash.
Thanks a lot for your work and explanation!
All the best for Ancalagon!
Peter.