Colossus of a mate in 7

[Spliffjiffer]

This is the hardest mateproblem in 7 moves i have ever seen so far.
The queen maneuver from g8 over g2 to a8 and back to her initial starting square with mate is just impressive.

Efim D. Bogoljubow


[D]R5QK/3p1p2/1pbPkB2/4Ppp1/2p4N/2p5/p2P1R1n/8 w - - 0 1



Im sure your engines will find it (at least chest does it very quickly).
Spend a little time on that problem...its really awesome IMO

[Dan Astrachan]

On my lowly computer at work:

Strelka_5.5x64 (128-Mb hash):

Code: Select all

  21	01:24	 140 609 981	1 670 567	+M7	d2-d3 c4xd3 Rf2-f4 g5xf4 Ra8-a4 Bc6xa4 Qg8-g2 a2-a1Q Nh4-g6 f7xg6 Qg2-a8 b6-b5 Qa8-g8+

[Ajedrecista]

Hello Peer:

This is the hardest mateproblem in 7 moves i have ever seen so far.
The queen maneuver from g8 over g2 to a8 and back to her initial starting square with mate is just impressive.

Efim D. Bogoljubow


[D]R5QK/3p1p2/1pbPkB2/4Ppp1/2p4N/2p5/p2P1R1n/8 w - - 0 1



Im sure your engines will find it (at least chest does it very quickly).
Spend a little time on that problem...its really awesome IMO

My PC is an Intel Pentium D930 (3GHz) with two cores and a 32-bit OS; I have proved a bunch of engines during a short period of time (a few minutes at maximum, each engine).

IIRC, Houdini 1.5a, Critter 1.6a and Komodo 3 get stuck with Rxa2, giving huge evals. Other engines think that Qxg5 is best:

· Cyclone xTreme II, Deep Rybka 4.1, SF 2.2.2 JA, Naum 4.2, Spark 1.0 and Zappa Mexico II think that Qxg5 is mate in eight.

· Deep Shredder 12 and Spike 1.2 think that Qxg5 is mate in nine.

But the first engine I proved is also the best: Chest UCI 5.2 (it is a single core mate solver):

Code: Select all

FEN: R5QK/3p1p2/1pbPkB2/4Ppp1/2p4N/2p5/p2P1R1n/8 w - - 0 1 

ChestUCI_52:
FEN: R5QK/3p1p2/1pbPkB2/4Ppp1/2p4N/2p5/p2P1R1n/8 w - -   (9+11)
Stellungs-Analyse:  C0/R0/K2/P8/X23   W:7/41
Parameter in Datenbank gefunden:  #7; 04:26-; 00:07 @ C2/R-2/K3/P9/X31;
Suche nach Spezial-Matt [C2/R-2/K3/P9/X31] in 7 ...  (Hash=64MB)
   7	00:01	           0	0	+M7	d2d3
Suche abgeschlossen ...  (Zeit=1.30s)
Matt in 7 gefunden !  (1 Lösung in 00:01)
  7/7	00:01	     371.051	286.304	+M7	d2d3 c4xd3 Rf2f4 g5xf4 Ra8a4 Bc6xa4 Qg8g2 c3c2 Nh4g6 f7xg6 Qg2a8 f4f3 Qa8g8+

Only around 1.3 seconds in my slow computer; final position:

[d]6QK/3p4/1p1PkBp1/4Pp2/b7/3p1p2/p1p4n/8 b - - 1 7

Please note that there are many possibilities for black since 4.- Qg2 (advance of different pawns, promotions or underpromotions and moves of bishop or knight).

Qg8# is not the only mating move: there are other mates in seven. For example: 1.- d3, cxd3; 2.- Rf4, gxf4; 3.- Ra4, Bxa4; Qg2, Bc6; 5.- Qxa2+, Bd5; 6.- Ng2, Bxa2; 7.- Nxf4#:

[d]7K/3p1p2/1p1PkB2/4Pp2/5N2/2pp4/b6n/8 b - - 0 7

Black is checkmated and does not have any legal moves. Again, black could do other moves instead 5.- ..., Bc6 or 6.- ..., Bxa2.

Regards from Spain.

Ajedrecista.

[Spliffjiffer]

Yes...after 4.Qg2 there are some lines which not end in the Qa8,Qg8# maneuver...ty for clarification.

The mainline of Bogoljubow's solution was: 1.d3 cd 2.Rf4 gf 3.Ra4 Bxa4 4.Qg2 a1Q 5.Ng6 fg 6.Qa8 and 7.Qg8#

From my human point of view this line is the most obvious (even so for strelka it seems )

The first two times this problem was published ( "Deutsche Schachzeitung"and then "The Problemist") it were not solved by anyone.
Only the third time there were two correct solutions.

For a human (well the humans i know) the 1.d3 move seems nearly unfindable...and even the engines have their problems to find it quickly (instead of matesolving software).

Btw....does anyone know a problem with mate in 7 moves without zugzwang-elements for which an engine (lets say houdini, critter, stockfish, rybka) takes longer than this one ?
...a hard task i think.

Regards from germany

[BBauer]

This one may take some time for some engines.
Kind regards

[D]8/8/p7/p7/b3Q3/K7/p1r5/rk6 w - -

[Spliffjiffer]

well i looked 1 sec on this and im sure there is some zugzwang involved...ill check it anyway....ty

[Spliffjiffer]

as i thought...but only one zugzwang... nice...

the solution:
1.Qh1 Rc1(well...only move) 2.Qh7 Rc2 3.Qe4! Bd7(Zugzwang which makes the b3 square available for the queen) 4.Qe1 Rc1 5.Qd2 Rc2 6.Qd1 Rc1 7.Qb3#

Btw...Zappa Mexico ll without nullmove detection finds it in 2 secs on a pentium e6600 @2,4 ghz

[Ajedrecista]

Hello Bernhard:

This one may take some time for some engines.
Kind regards

[D]8/8/p7/p7/b3Q3/K7/p1r5/rk6 w - -

Chest also solves this position, in even less time than the other! Around 343 ms were enough:

Code: Select all

FEN: 8/8/p7/p7/b3Q3/K7/p1r5/rk6 w - - 0 1 

ChestUCI_52:
FEN: 8/8/p7/p7/b3Q3/K7/p1r5/rk6 w - -   (2+7)
Stellungs-Analyse:  C0/R0/K2/P2/X6   W:2/27
Suche nach Matt in 10 ...  (Hash=64MB)
   7	00:00	           0	0	+M7	Qe4h1+
Suche abgeschlossen ...  (Zeit=0.34s)
Matt in 7 gefunden !  (1 Lösung in 00:00)
  7/7	00:00	      80.563	234.877	+M7	Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b5 Qe4e1+ Rc2c1 Qe1d2 Rc1c3+ Qd2xc3 a5a4 Qc3b2+

JetChess is a perft counter that also solves short checkmates. Analysis by JetChess 1.0.0.0 with 64 MB of hash:

Code: Select all

  1  Qe4-d5   0
  2  Qe4-c6   0
  3  Qe4-b7   0
  4  Qe4-a8   0
  5  Qe4-f5   0
  6  Qe4-g6   0
  7  Qe4-h7   0
  8  Qe4-f3   0
  9  Qe4-g2   0
 10  Qe4-h1   Mate
 11  Qe4-d3   0
 12  Qe4*c2   0
 13  Qe4-e5   0
 14  Qe4-e6   0
 15  Qe4-e7   0
 16  Qe4-e8   0
 17  Qe4-f4   0
 18  Qe4-g4   0
 19  Qe4-h4   0
 20  Qe4-d4   0
 21  Qe4-c4   0
 22  Qe4-b4   0
 23  Qe4*a4   0
 24  Qe4-e3   0
 25  Qe4-e2   0
 26  Qe4-e1   0
 27  Ka3*a4   0

Solution:  Qe4-h1  (mate in 7)

Time: 363 ms

Solving time of JetChess was similar to the spent time by Chest.

Cyclone is very good solving checkmates. Analysis by Cyclone xTreme II w32 (using two cores) in an Intel Pentium D930 (3 GHz), with 128 MB of hash, running under Arena 2.0.1 GUI:

FEN: 8/8/p7/p7/b3Q3/K7/p1r5/rk6 w - - 0 1

Cyclone xTreme II:
1/8 00:00 88 0 -12,24 Qe4xa4 Rc2c3+ Qa4b3+ Rc3xb3+ Ka3xb3 a5a4+ Kb3c3
1/8 00:00 200 0 -2,45 Ka3xa4 Kb1b2 Qe4b7+ Kb2c1 Qb7xa6
1/8 00:00 227 0 0,00 Qe4e1+ Rc2c1 Qe1e4+ Rc1c2
2/8 00:00 555 0 0,00 Qe4e1+ Rc2c1 Qe1e4+ Rc1c2
3/8 00:00 762 0 0,00 Qe4e1+ Rc2c1 Qe1e4+ Rc1c2
4/10 00:00 1.081 0 0,00 Qe4e1+ Rc2c1 Qe1e4+ Rc1c2
5/12 00:00 1.273 0 0,00 Qe4e1+ Rc2c1 Qe1e4+ Rc1c2
6/16 00:00 1.758 0 0,00 Qe4e1+ Rc2c1 Qe1e4+ Rc1c2
7/21 00:00 3.761 0 0,00 Qe4e1+ Rc2c1 Qe1e4+ Rc1c2
8/30 00:00 22.898 0 0,00 Qe4e1+ Rc2c1 Qe1e4+ Rc1c2
9/30 00:00 45.048 0 0,00 Qe4e1+ Rc2c1 Qe1e4+ Rc1c2
10/30 00:00 131.666 0 0,00 Qe4e1+ Rc2c1 Qe1e4+ Rc1c2
11/30 00:00 217.274 0 0,00 Qe4e1+ Rc2c1 Qe1e4+ Rc1c2
12/30 00:00 340.273 0 0,00 Qe4e1+ Rc2c1 Qe1e4+ Rc1c2
13/32 00:00 574.956 0 0,00 Qe4e1+ Rc2c1 Qe1e4+ Rc1c2
13/40 00:01 720.263 1.240.000 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 a5a4 Qc3b2+
14/40 00:01 900.170 1.316.904 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 a5a4 Qc3b2+
15/40 00:01 1.122.525 1.443.069 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 a5a4 Qc3b2+
16/40 00:01 1.397.646 1.579.120 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 a5a4 Qc3b2+
17/40 00:02 1.696.219 1.692.966 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 a5a4 Qc3b2+
18/40 00:02 1.999.049 1.801.253 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 a5a4 Qc3b2+
19/40 00:02 2.307.580 1.893.865 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 a5a4 Qc3b2+
20/40 00:02 2.621.366 1.974.608 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 a5a4 Qc3b2+
21/40 00:02 2.926.035 2.037.314 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 a5a4 Qc3b2+
22/40 00:03 3.239.293 2.085.765 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 a5a4 Qc3b2+
23/40 00:03 3.547.473 2.134.166 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 a5a4 Qc3b2+
24/40 00:03 3.864.393 2.171.779 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 a5a4 Qc3b2+
25/40 00:03 4.176.953 2.211.759 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 a5a4 Qc3b2+
26/40 00:04 4.485.085 2.244.897 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 a5a4 Qc3b2+

I stopped the analysis because it becomes evident that Cyclone succeed in this position.

Komodo 3 w32 (single core) surprised me!

FEN: 8/8/p7/p7/b3Q3/K7/p1r5/rk6 w - - 0 1

Komodo3-32:
1 00:00 120 7.680 -1,84 Ka3xa4 Kb1b2 Qe4b7+
2 00:00 399 25.536 -1,53 Ka3xa4 Kb1b2 Qe4d3
3 00:00 1.526 97.664 -1,69 Ka3xa4 Kb1c1 Qe4e3+ Kc1b1 Ka4xa5
4 00:00 1.834 117.376 -0,05 Ka3xa4 Kb1c1 Qe4e3+ Kc1b1 Qe3d3
5 00:00 2.051 131.264 -0,05 Ka3xa4 Kb1c1 Qe4e3+ Kc1b1 Qe3d3 Kb1c1 Qd3e3+
5 00:00 2.223 142.272 -0,05 Ka3xa4 Kb1c1 Qe4e3+ Kc1b1 Qe3d3 Kb1c1 Qd3e3+
6 00:00 2.906 185.984 -0,05 Ka3xa4 Kb1c1 Qe4e3+ Kc1b1 Qe3d3 Kb1c1 Qd3e3+
6 00:00 4.056 129.792 -0,05 Ka3xa4 Kb1c1 Qe4e3+ Kc1b1 Qe3d3 Kb1c1 Qd3e3+
7 00:00 5.645 180.640 -0,05 Ka3xa4 Kb1c1 Qe4e3+ Kc1b1 Qe3d3 Kb1c1 Qd3e3+
7 00:00 9.136 292.352 -0,05 Ka3xa4 Kb1c1 Qe4e3+ Kc1b1 Qe3d3 Kb1c1 Qd3e3+
8 00:00 13.609 290.325 0,00 Ka3xa4 Kb1c1 Qe4f4+ Kc1b1 Qf4f1+ Kb1b2 Qf1f6+ Rc2c3 Qf6f2+ Kb2c1 Qf2e1+ Kc1b2 Qe1d2+ Rc3c2 Qd2d4+
8 00:00 20.275 259.520 0,00 Ka3xa4 Kb1c1 Qe4f4+ Kc1b1 Qf4f1+ Kb1b2 Qf1f6+ Rc2c3 Qf6f2+ Kb2c1 Qf2e1+ Kc1b2 Qe1d2+ Rc3c2 Qd2d4+
9 00:00 27.830 296.853 -0,05 Ka3xa4 Kb1c1 Qe4f4+ Kc1b1 Qf4f1+ Kb1b2 Qf1f6+ Rc2c3 Qf6f2+ Kb2c1 Qf2e1+ Kc1b2 Qe1d2+ Rc3c2 Qd2d4+ Rc2c3 Qd4d2+
9 00:00 52.994 339.161 0,00 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4c6 Qe4xc2+ Kb1xc2
9 00:00 56.332 327.749 0,00 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4c6 Qe4xc2+ Kb1xc2
10 00:00 59.390 316.746 +0,16 Qe4h1+
10 00:00 60.793 324.229 +0,63 Qe4h1+
10 00:00 65.751 323.697 +M9 Qe4h1+
10 00:00 74.548 340.790 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4c6 Qe4e1+ Rc2c1 Qe1d2 Rc1c2 Qd2d1+ Rc2c1 Qd1b3+
10 00:00 90.792 341.805 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4c6 Qe4e1+ Rc2c1 Qe1d2 Rc1c2 Qd2d1+ Rc2c1 Qd1b3+

Good!

Spark is able to solve it too!

FEN: 8/8/p7/p7/b3Q3/K7/p1r5/rk6 w - - 0 1

Spark-1.0-win32-mp:
1 00:00 27 0 0,00 Qe4h1+ Rc2c1 Qh1e4+ Rc1c2
2/4 00:00 245 0 0,00 Qe4h1+ Rc2c1 Qh1e4+ Rc1c2
3/6 00:00 541 0 0,00 Qe4h1+ Rc2c1 Qh1e4+ Rc1c2
4/9 00:00 1.818 0 0,00 Qe4h1+ Rc2c1 Qh1e4+ Rc1c2
5/10 00:00 4.500 0 0,00 Qe4h1+ Rc2c1 Qh1e4+ Rc1c2
6/12 00:00 8.088 0 0,00 Qe4h1+ Rc2c1 Qh1e4+ Rc1c2
7/14 00:00 14.451 0 0,00 Qe4h1+ Rc2c1 Qh1e4+ Rc1c2
8/16 00:00 26.471 0 0,00 Qe4h1+ Rc2c1 Qh1e4+ Rc1c2
9/18 00:00 50.248 0 0,00 Qe4h1+ Rc2c1 Qh1e4+ Rc1c2
12/27 00:00 1.258.198 1.547.599 +0,11 Qe4e5 Rc2d2 Qe5e1+ Kb1c2 Qe1xa1 Ba4b5 Qa1xa2+ Kc2c3 Qa2a1+ Kc3d3 Qa1b1+ Kd3d4 Qb1g1+ Kd4c4 Qg1g4+ Rd2d4 Qg4c8+ Kc4d3 Qc8h3+ Kd3d2
13/27 00:01 1.570.672 1.521.968 +0,10 Qe4e5 Rc2d2 Qe5e1+ Kb1c2 Qe1xa1 Ba4b5 Qa1xa2+ Kc2d1 Qa2b1+ Kd1e2 Qb1e4+ Ke2f2 Qe4f4+ Kf2e2 Qf4g4+ Ke2f2 Qg4f5+ Kf2e1 Qf5e5+ Ke1d1 Qe5a1+ Kd1e2 Qa1f6 Rd2d3+ Ka3a2 a5a4
13/27+ 00:01 1.593.692 1.544.275 +0,81 Qe4h1+ Rc2c1
13/27+ 00:01 1.594.025 1.544.597 +M9 Qe4h1+ Rc2c1
13/27 00:01 1.671.366 1.527.756 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 Bc2d1 Qc3b2+
14/27 00:01 2.551.536 1.683.071 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 Bc2d1 Qc3b2+
15/27 00:01 2.953.748 1.733.420 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 Bc2d1 Qc3b2+
16/27 00:01 3.343.654 1.768.193 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 Bc2d1 Qc3b2+
17/27 00:02 3.763.796 1.810.387 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 Bc2d1 Qc3b2+
18/27 00:02 4.182.346 1.845.695 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 Bc2d1 Qc3b2+
19/27 00:02 4.606.781 1.865.848 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 Bc2d1 Qc3b2+
20/27 00:02 5.031.515 1.883.052 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 Bc2d1 Qc3b2+
21/27 00:02 5.455.819 1.907.629 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 Bc2d1 Qc3b2+
23/27 00:03 6.305.541 1.921.249 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 Bc2d1 Qc3b2+
26/27 00:03 7.580.080 1.956.149 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 Bc2d1 Qc3b2+
26/27 00:03 7.764.630 1.956.318 +M7 Qe4h1+ Rc2c1 Qh1h7+ Rc1c2 Qh7e4 Ba4b3 Qe4e1+ Rc2c1 Qe1d2 Bb3c2 Qd2c3 Bc2d1 Qc3b2+

Thinker is a WinBoard engine and does not show output moves in the analysis; I set a game in fifteen minutes and let it play: in 15 seconds (in spite of 16 shown), just do nodes/(nodes/sec.), it played Qh1+ giving a mate eval of +M106 (which means mate in seven):

Code: Select all

FEN: 8/8/p7/p7/b7/K7/p1r5/rk5Q b - - 1 1 

SP-x86-Inert---Thinker:
Qe4-h1
  63	00:16	  22.801.968	1.520.131	+M106	e4h1 c2c1 h1h2

Forcing each move, Thinker 5.4D Inert played 1.- Qh1+, Rc1; 2.- Qh7+, Rc2; 3.- Qe4, Bc6; 4.- Qe1+, Rc1; 5.- Qd2, Rc2; 6.- Qd1+, Rc1; 7.- Qb3#. As you see, each engine gives different continuations, all of them valid.

OTOH, I proved Thinker in the other position, and it failed under the same conditions (it spent more less 30.81 seconds in this move):

Code: Select all

FEN: 6QK/3p1p2/1pbPkB2/4Ppp1/2p4N/2p5/R2P1R1n/8 b - - 0 1 

SP-x86-Inert---Thinker:
Ra8xa2
  10	00:31	  17.945.773	582.465	+25,77	a8a2 g5h4 g8e8 e6d5 e8f7 d5d4

Regards from Spain.

Ajedrecista.

[Uri Blass]

Yes...after 4.Qg2 there are some lines which not end in the Qa8,Qg8# maneuver...ty for clarification.

The mainline of Bogoljubow's solution was: 1.d3 cd 2.Rf4 gf 3.Ra4 Bxa4 4.Qg2 a1Q 5.Ng6 fg 6.Qa8 and 7.Qg8#

From my human point of view this line is the most obvious (even so for strelka it seems )

The first two times this problem was published ( "Deutsche Schachzeitung"and then "The Problemist") it were not solved by anyone.
Only the third time there were two correct solutions.

For a human (well the humans i know) the 1.d3 move seems nearly unfindable...and even the engines have their problems to find it quickly (instead of matesolving software).

Btw....does anyone know a problem with mate in 7 moves without zugzwang-elements for which an engine (lets say houdini, critter, stockfish, rybka) takes longer than this one ?
...a hard task i think.

Regards from germany

I remember that leonid posted hard mates for chess engines.
Here is an example

This does not seem to be good enough but maybe another position if leonid is good enough(stockfish2.2.2 4 cpu could find the mate in 31 seconds) but maybe a different position of leonid is good enough.

http://www.stmintz.com/ccc/index.php?id=154354

[D]rQ1Q1rnk/q4qbp/3nQqbB/q1Q1NnNn/5QQ1/b2Q4/1QB3Q1/1K1R3R w - -

1.Ngxf7+ Nxf7 2.Nxg6+ hxg6 3.Bxg7+ Nfxg7 4.Qgxh5+ Nxh5 5.Qfxf6+ Ngxf6 6.Qdxf8+ Kh7 7.Qgxg6#

[JuLieN]

[D]R5QK/3p1p2/1pbPkB2/4Ppp1/2p4N/2p5/p2P1R1n/8 w - - 0 1

Funnily, Prédateur 2.2.1 finds a mate when reaching the 12th deepening: I saw no other engine finding a mate so early. But of course it takes Pred seven minutes to do so

Code: Select all

3 [+15.79]  1.Txh2 gxh4 2.De8+ Rd5 3.Txa2  (0.00)
 3 [+16.18]  1.Fxg5 Rxe5 2.Txh2  (0.00)
 4 [+16.75]  1.Txa2 Cg4 2.De8+ Rd5 3.Dxf7+ Rc5 4.d4+  (0.01)
 4 [+16.76]  1.Txh2 gxh4 2.De8+ Rd5 3.Dxf7+ Re4 4.Txa2  (0.01)
 4 [+17.84]  1.De8+ Rd5 2.Dxf7+ Rd4 3.Cxf5+ Re4 4.Txa2  (0.02)
 6 [+16.70]  1.Txa2 Cg4 2.Txf5 gxh4 3.Dxg4 cxd2  (0.19)
 6 [+16.88]  1.Txh2 gxh4 2.De8+ Rd5 3.Txa2 cxd2 4.Taxd2+ Re4 5.Txh4+ Re3  (0.25)
 6 [+17.35]  1.Fxg5 Fxa8 2.De8+ Rd5 3.Dxa8+ Rxe5 4.Te2+ Rd4 5.dxc3+ Rd3 6.Txh2  (0.30)
 7 [+17.34]  1.Fxg5 Fxa8 2.De8+ Rd5 3.Dxa8+ Rc5 4.Txh2 c2 5.d4+ Rxd4  (0.74)
 7 [+17.38]  1.Txh2 Fxa8 2.De8+ Rd5 3.Dxa8+ Re6 4.Dxa2 b5 5.Fxg5 cxd2  (0.97)
 9 [+17.81]  1.Txh2 c2 2.Cxf5 Rxf5 3.Dxg5+ Re6 4.Te8+ Rd5 5.e6+ Re4 6.exd7+ Rf3 7.Df5+ Rg3 8.De5+ Rg4  (7.20)
 9 [+18.83]  1.Txa2 Cg4 2.De8+ Rd5 3.Txf5 Re4 4.Txg5 Ch6 5.dxc3 Rd3 6.Cf5  (11.55)
 9 [+19.18]  1.Cxf5 Rd5 2.Txh2 c2 3.Ce3+ Rc5 4.Cxc2 Fxa8 5.Dxa8 b5  (17.80)
 9 [+326.12]  1.Dxg5 Rd5 2.e6 Rc5 3.Fd4+ Rb4 4.dxc3+ Rb3 5.Tb2+ Rxb2 6.Dd2+ Ra1  (22.14)
11 [+19.13]  1.Txh2 Fxa8 2.De8+ Rd5 3.Dxa8+ Rc5 4.Cxf5 c2 5.Da3+ Rc6 6.Cd4+ Rd5 7.Cxc2 Rc6  (124.89)
11 [+23.41]  1.Txf5 Cg4 2.Te8+ Rd5 3.e6+ Re4 4.exf7+ Rd3 5.Dg6 Rc2 6.Tf1+ Rb3 7.f8=D Cxf6 8.Dgxf6  (260.58)
12 [M9]  1.Dxg5 Fxa8 2.Dxf5+ Rd5 3.e6+ Rc6 4.exd7 Cg4 5.d8=D Ce5 6.Dxa8+ Rc5 7.Dxe5+ Rb4 8.dxc3+ Rb3 9.Dxa2#  (421.06)

It then finds a mate in 8 at depth 13, but I stopped the search as it seemed to need several hours to find the mate in 7...