A study by Troitsky

[Andrew]

[D]8/5p2/1Q6/p2pppq1/8/3k4/p7/3K2B1 w - - 0 0

After 1. Qb5+ Kc3 2. Qc5+ Kb2 3. Qc2+ Ka1

white wins after
4. Qc1+ QxQ 5. Kxc1

Most engines can see a mate score quickly after Qc1+

However, take them to the position after Ka1

[D]8/5p2/8/p2pppq1/8/8/p1Q5/k2K2B1 w - - 0 3

and they won't play Qc1 but instead like Qc3+ with a draw.
Is a problem with null move, pruning or something else?

(this is position 32 from his book 360 Briliant and instructive endgames)

Andrew

[Martin]

The mate is still quite deep when the Queens are exchanged. With the Queens on the board most engines will need a lot of time to reach that depth.

It's probably not a nullmove issue, unless the engine also nullmoves when it has only pawns, which is unusual, as far as I know (in any case, my engine doesn't do it).
So black can't do 'nothing' when the Queens are off the board, he has to move his pawns till finally a hole appears and the white B can mate.
Nice study!

[AdminX]

Rybka 2.3.2a using the Deep Analysis feature in the Aquarium GUI finds it.

[Dr.Wael Deeb]

Rybka 2.3.2a using the Deep Analysis feature in the Aquarium GUI finds it.

Hey Ted,you are playing with our nerves,we won't hold on much longer

[AdminX]

Hey Ted,you are playing with our nerves,we won't hold on much longer

If you liked that then ...

It took about 12 minutes to find the 1st position as Mate in 18 at (d=23) using the same feature

[d]8/5p2/1Q6/p2pppq1/8/3k4/p7/3K2B1 w - - 0 0

1. Qb5 Kc3 2. Qxa5 Kb2 3. Qb4 Ka1 4. Qc3 Kb1 5. Qc2 Ka1 6. Qc1 Qxc1 7. Kxc1 d4 8. Bf2 f4 9. Be1 f3 10. Bf2 f6 11. Be1 e4 12. Bh4 f2 13. Bxf2 e3 14. Bh4 e2 15. Bf2 e1=Q 16. Bxe1 f5 17. Bf2 d3 18. Bd4#

[Ampzilla]

Aquarium where did you the GUI

[Andrew]

Thanks for running these Ted! The funny thing is that if you force Qc1
(in the second pos I posted) then
with black to move it sees it is lost in seconds:
This is not just Rybka, but also Hiarcs, Shredder and others.

Analysis by Rybka 2.3.2a 32-bit :

4...Qxc1+ 5.Kxc1 d4 6.Kc2 f4 7.Bf2 f3 8.Be1 a4 9.Kd3
-+ (-5.35) Depth: 5 00:00:00
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Kc2 f3 8.Kc1 a4 9.Kc2 f6
-+ (-5.60) Depth: 6 00:00:00 5kN
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Kc2 a4 8.Kc1 f3 9.Kc2 f5 10.Kd3
-+ (-5.30) Depth: 7 00:00:00 6kN
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Kc2 a4 9.Bg3 f6 10.Bf2 f5 11.Kd3 Kb2
-+ (-5.60) Depth: 8 00:00:00 8kN
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Be1 a4 9.Bf2 f6 10.Kc2 f5 11.Kc1 f4 12.Kd2
-+ (-5.23) Depth: 9 00:00:00 9kN
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Be1 a4 9.Kc2 f6 10.Bh4 f5 11.Bf2 f4 12.Kd3 Kb2
-+ (-5.51) Depth: 10 00:00:01 11kN
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Be1 a4 9.Kc2 f6 10.Bf2 f5 11.Kc1 f4 12.Kd2 Kb2
-+ (-5.51) Depth: 11 00:00:01 13kN
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Be1 a4 9.Kc2 f6 10.Bf2 f5 11.Kc1 f4 12.Kd2 Kb2
-+ (-5.42) Depth: 12 00:00:01 17kN
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Be1 f6 9.Bf2 a4 10.Bg3 e4 11.Bh4 f2 12.Bxf2 e3 13.Be1 f5 14.Kc2
-+ (-4.65) Depth: 13 00:00:01 22kN
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Be1 f6 9.Bf2 a4 10.Bg3 a3 11.Bh4 f5 12.Bf2 f4 13.Kc2 d3+ 14.Kc1
-+ (-4.40) Depth: 14 00:00:02 24kN
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Bg3 f6 9.Bf2 a4 10.Bg3 a3 11.Bf2 f5 12.Bh4 f4 13.Bf2 d3 14.Be1 d2+ 15.Bxd2
-+ (-4.08) Depth: 15 00:00:02 27kN
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Bg3 f6 9.Bf2 a4 10.Bg3 a3 11.Bf2 f5 12.Bh4 f2 13.Bxf2 f4 14.Kc2 f3 15.Kc1 d3 16.Be1
-+ (-4.22) Depth: 16 00:00:02 30kN
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Bg3 f6 9.Bf2 a4 10.Bg3 a3 11.Bf2 f5 12.Bh4 f2 13.Bxf2 f4 14.Kc2 f3 15.Kc1 d3 16.Be1
-+ (-4.22) Depth: 18 00:00:02 33kN
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Bg3 f6 9.Bf2 a4 10.Bg3 a3 11.Bf2 f5 12.Bh4 f2 13.Bxf2 f4 14.Kc2 f3 15.Bg3 d3+ 16.Kc1 d2+ 17.Kxd2 Kb1
-+ (-3.47) Depth: 18 00:00:02 38kN
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Bg3 f6 9.Bf2 f5 10.Bg3 f4 11.Bf2 a4 12.Bh4 f2 13.Bxf2 f3 14.Bg3 f2 15.Bxf2 a3 16.Bh4 d3 17.Bf6 d2+ 18.Kxd2 Kb1
-/+ (-1.33) Depth: 19 00:00:02 45kN, tb=1
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Bg3 f6 9.Bf2 f5 10.Bg3 f4 11.Bf2 a4 12.Bh4 f2 13.Bxf2 f3 14.Bg3 f2 15.Bxf2 a3 16.Bh4 d3 17.Be1 d2+ 18.Bxd2
+/- (1.17) Depth: 20 00:00:02 45kN, tb=2
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Bg3 f6 9.Bf2 f5 10.Bg3 f4 11.Bf2 a4 12.Bh4 f2 13.Bxf2 f3 14.Bg3 f2 15.Bxf2 a3 16.Bh4 d3 17.Be1 d2+ 18.Bxd2 e4 19.Bc3#
+- (#16) Depth: 20 00:00:03 49kN, tb=4
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Bg3 f6 9.Bf2 f5 10.Bg3 f4 11.Bf2 a4 12.Bh4 f2 13.Bxf2 f3 14.Bg3 f2 15.Bxf2 a3 16.Bh4 d3 17.Be1 d2+ 18.Bxd2 e4 19.Bc3#
+- (#16) Depth: 21 00:00:03 57kN, tb=7
4...Qxc1+ 5.Kxc1 d4 6.Bf2 f4 7.Bh4 f3 8.Bg3 f6 9.Bf2 f5 10.Bg3 f4 11.Bf2 a4 12.Bh4 f2 13.Bxf2 f3 14.Bg3 f2 15.Bxf2 a3 16.Bh4 d3 17.Be1 d2+ 18.Bxd2 e4 19.Bc3#
+- (#16) Depth: 22 00:00:03 72kN, tb=12

(, 03.05.2008)

[AdminX]

Aquarium where did you the GUI

I'm a beta tester for it. (Rybka Forum)

[Mike S.]

Rybka 2.3.2a 32 bit, single cpu finds it too, at the same depth (naturally after more time consumption):

Engine: Rybka 2.3.2a 32-bit
von Vasik Rajlich
16.01 0:01 0.00 1.Dc3+ Kb1 2.Dc2+ Ka1 (136.623) 100.5
(...)
29.01 22:12 0.00 1.Dc3+ Kb1 2.Dc2+ Ka1 (126.709.182) 97.3
29.04 23:26 +2.50 1.Dc1+ Dxc1+ 2.Kxc1 d4 3.Lf2 f4 4.Le1 f3 5.Lg3 f6 6.Lf2 a4 7.Lg3 e4 (136.091.521) 99.0

D=Q

But it did not find a mate until 47 minutes yet, on D945 3.4 GHz. After entering 1.Qc1, mate was announced immediatly.

27.00 0:01 -M15 1...Dxc1+ 2.Kxc1 d4 3.Lf2 f4 4.Le1 f3 5.Lg3 f6 6.Lf2 a4 7.Lg3 a3 8.Lf2 f5 9.Lh4 f2 10.Lxf2 f4 11.Le1 f3 12.Lf2 d3 13.Le1 d2+ 14.Lxd2 e4 (151.481) 132.2

[Ovyron]

Rybka 2.3.2a 32 bit, single cpu finds it too, at the same depth (naturally after more time consumption):

<snip>
29.04 23:26 +2.50 1.Dc1+ Dxc1+ 2.Kxc1 d4 3.Lf2 f4 4.Le1 f3 5.Lg3 f6 6.Lf2 a4 7.Lg3 e4 (136.091.521) 99.0

With Aquarium's Deep Analysis it takes 11:16 on my 1CPU 2.1 Ghz Athlon to find the mate with Qc1:



The strange thing is that it thinks that Qc3 transposes to the mate by Qc3 Kb1 Qc2 Ka1 Qc1! - Qc3 also mates!