Mate in 11 position for Amateurs

[KhepriChess]

Not entirely surprised, but Khepri fails to find it up to depth 20. Search actually seems to explode at depth 20 and just hangs trying to go any deeper. Interesting position though. I do notice that the other engines here (so far) immediately look at the Rook on c7, and make it the PV, but Khepri seems to discard that in favor of f1d1. Maybe I'll poke around and see if I can get it to do any better.

[Chessnut1071]

This is a fascinating position. It seems The King is still an order of magnitude faster than anyone else at solving these types of positions. Stockfish 15 takes 555k nodes and a depth of 18 to see mate — others I have tested are no better.

What is amazing is the path to mate is all checks from white. In other positions I had thought The King's secret sauce was handling forced threats but this position has few threat-based paths. Clearly The King does something "special" when analyzing positions that are in check which results in a sophisticated extension of certain moves. I suspect the threshold for extending is quite high, otherwise there would be a search explosion.

Anyone else have any ideas as to how The King is handling this type of position?

— Steve

This puzzle is a Shogi, an all check puzzle. These are the fastest puzzles with a White check only filter.

[Steve Maughan]

What do you mean that the puzzle is a Shogi?

Steve

[Chessnut1071]

What do you mean that the puzzle is a Shogi?

Steve

A Shogi is a Japanese term for a game in which every white move is a check and ends in checkmate. This game is not exactly a Shogi because there is a line where a move isn't a white check.

1. Rg7+ KxR
2. Pf6+ RxP 3. QxR+
2. Pf6+ Kh8 3. Ng6+
2. Pf6+ Kg8 3. Bh7+
2. Pf6+ Kh6 3. Ng4+ QxN 4. QxQ isn't a check but forces mate in 11.

[JVMerlino]

A Shogi is a Japanese term for a game in which every white move is a check and ends in checkmate. This game is not exactly a Shogi because there is a line where a move isn't a white check.

1. Rg7+ KxR
2. Pf6+ RxP 3. QxR+
2. Pf6+ Kh8 3. Ng6+
2. Pf6+ Kg8 3. Bh7+
2. Pf6+ Kh6 3. Ng4+ QxN 4. QxQ isn't a check but forces mate in 11.

After 3.Ng4, Qxg4 is sub-optimal. The full line with best play is:

28.Rg7+ Kxg7 29.f6+ Kh6 30.Ng4+ Kg5 (or Kh5) 31.Qf5+ Nxf5 32.Rxf5+ Kg6 33.Re5+ Rc2 34.Bxc2+ then the line splits:

34...Qd3 35.Bxd3+ Kf7 36.Re7+ Kg8 37.Nh6+ Kh8 38.Rh7#
or
34...Qe4 35.Bxe4 Kf7 36.Re7+ Kg8 37.Nh6+ Kh8 38.Rh7#

[Chessnut1071]

A Shogi is a Japanese term for a game in which every white move is a check and ends in checkmate. This game is not exactly a Shogi because there is a line where a move isn't a white check.

1. Rg7+ KxR
2. Pf6+ RxP 3. QxR+
2. Pf6+ Kh8 3. Ng6+
2. Pf6+ Kg8 3. Bh7+
2. Pf6+ Kh6 3. Ng4+ QxN 4. QxQ isn't a check but forces mate in 11.

After 3.Ng4, Qxg4 is sub-optimal. The full line with best play is:

28.Rg7+ Kxg7 29.f6+ Kh6 30.Ng4+ Kg5 (or Kh5) 31.Qf5+ Nxf5 32.Rxf5+ Kg6 33.Re5+ Rc2 34.Bxc2+ then the line splits:

34...Qd3 35.Bxd3+ Kf7 36.Re7+ Kg8 37.Nh6+ Kh8 38.Rh7#
or
34...Qe4 35.Bxe4 Kf7 36.Re7+ Kg8 37.Nh6+ Kh8 38.Rh7#

Agreed, however, since 3. NQ4+ QxN exits it's no a true Shogi.

[Steve Maughan]

Deep Rybka 4.1 seems to be the best. It's even faster than The King, solving in less than 3k nodes!

[fen]2r2rk1/ppR5/1n1n4/3PNP2/3q3p/5Qp1/P5PP/1B3R1K w - -[/fen]

Code: Select all

Engine: Deep Rybka 4.1 SSE42 x64 (4096 MB)
by Vasik Rajlich

1.00   0:00   +1.01++  1.Rxc8 Rxc8 2.Re1 Nxd5 3.f6 (281) 281 

1.00   0:00   +1.06    1.Rxc8 Rxc8 2.f6 Qxe5 3.Qg4+ Kf7 
                       4.Qg6+ Kf8 5.Qg7+ Ke8 6.f7+ Nxf7 
                       7.Qxf7+ Kd8 8.Bf5 Rc4 9.Be6 (285) 17 

1.00   0:00   +M80++   1.Rg7+ Kxg7 2.f6+ Kh6 3.Ng4+ Kh5 
                       4.Qf5+ Nxf5 5.Rxf5+ Kg6 6.Re5+ Rc2 
                       7.Bxc2+ Qe4 8.Bxe4+ Kf7 9.Re7+ Kg8 
                       10.Nh6+ Kh8 11.Rh7+ (303) 6 

1.00   0:00   +M80++   1.Rg7+ Kxg7 2.f6+ Kh6 3.Ng4+ Kh5 
                       4.Qf5+ Nxf5 5.Rxf5+ Kg6 6.Re5+ Rc2 
                       7.Bxc2+ Qe4 8.Bxe4+ Kf7 9.Re7+ Kg8 
                       10.Nh6+ Kh8 11.Rh7+ (314) 4 

1.00   0:00   +M80++   1.Rg7+ Kxg7 2.f6+ Kh6 3.Ng4+ Kh5 
                       4.Qf5+ Nxf5 5.Rxf5+ Kg6 6.Re5+ Rc2 
                       7.Bxc2+ Qe4 8.Bxe4+ Kf7 9.Re7+ Kg8 
                       10.Nh6+ Kh8 11.Rh7+ (325) 5 

1.00   0:00   +M80++   1.Rg7+ Kxg7 2.f6+ Kh6 3.Ng4+ Kh5 
                       4.Qf5+ Nxf5 5.Rxf5+ Kg6 6.Re5+ Rc2 
                       7.Bxc2+ Qe4 8.Bxe4+ Kf7 9.Re7+ Kg8 
                       10.Nh6+ Kh8 11.Rh7+ (336) 5 

1.00   0:00   +M80++   1.Rg7+ Kxg7 2.f6+ Kh6 3.Ng4+ Kh5 
                       4.Qf5+ Nxf5 5.Rxf5+ Kg6 6.Re5+ Rc2 
                       7.Bxc2+ Qe4 8.Bxe4+ Kf7 9.Re7+ Kg8 
                       10.Nh6+ Kh8 11.Rh7+ (347) 5 

1.00   0:00   +M80++   1.Rg7+ Kxg7 2.f6+ Kh6 3.Ng4+ Kh5 
                       4.Qf5+ Nxf5 5.Rxf5+ Kg6 6.Re5+ Rc2 
                       7.Bxc2+ Qe4 8.Bxe4+ Kf7 9.Re7+ Kg8 
                       10.Nh6+ Kh8 11.Rh7+ (358) 5 

1.00   0:00   +M80++   1.Rg7+ Kxg7 2.f6+ Kh6 3.Ng4+ Kh5 
                       4.Qf5+ Nxf5 5.Rxf5+ Kg6 6.Re5+ Rc2 
                       7.Bxc2+ Qe4 8.Bxe4+ Kf7 9.Re7+ Kg8 
                       10.Nh6+ Kh8 11.Rh7+ (369) 5 

1.00   0:00   +M80++   1.Rg7+ Kxg7 2.f6+ Kh6 3.Ng4+ Kh5 
                       4.Qf5+ Nxf5 5.Rxf5+ Kg6 6.Re5+ Rc2 
                       7.Bxc2+ Qe4 8.Bxe4+ Kf7 9.Re7+ Kg8 
                       10.Nh6+ Kh8 11.Rh7+ (380) 6 

1.00   0:00   +M80     1.Rg7+ Kxg7 2.f6+ Kh6 3.Ng4+ Kh5 
                       4.Qf5+ Nxf5 5.Rxf5+ Kg6 6.Re5+ Rc2 
                       7.Bxc2+ Qe4 8.Bxe4+ Kf7 9.Re7+ Kg8 
                       10.Nh6+ Kh8 11.Rh7+ (400) 6 

2.00   0:00   +M80     1.Rg7+ Kxg7 2.f6+ Kh6 3.Ng4+ Kh5 
                       4.Qf5+ Nxf5 5.Rxf5+ Kg6 6.Re5+ Rc2 
                       7.Bxc2+ Qe4 8.Bxe4+ Kf7 9.Re7+ Kg8 
                       10.Nh6+ Kh8 11.Rh7+ (473) 7 

3.00   0:00   +M80     1.Rg7+ Kxg7 2.f6+ Kh6 3.Ng4+ Kh5 
                       4.Qf5+ Nxf5 5.Rxf5+ Kg6 6.Re5+ Rc2 
                       7.Bxc2+ Qe4 8.Bxe4+ Kf7 9.Re7+ Kg8 
                       10.Nh6+ Kh8 11.Rh7+ (727) 11 

4.00   0:00   +M80     1.Rg7+ Kxg7 2.f6+ Kh6 3.Ng4+ Kh5 
                       4.Qf5+ Nxf5 5.Rxf5+ Kg6 6.Re5+ Rc2 
                       7.Bxc2+ Qe4 8.Bxe4+ Kf7 9.Re7+ Kg8 
                       10.Nh6+ Kh8 11.Rh7+ (1.172) 18 

5.00   0:00   +M80     1.Rg7+ Kxg7 2.f6+ Kh6 3.Ng4+ Kh5 
                       4.Qf5+ Nxf5 5.Rxf5+ Kg6 6.Re5+ Rc2 
                       7.Bxc2+ Qe4 8.Bxe4+ Kf7 9.Re7+ Kg8 
                       10.Nh6+ Kh8 11.Rh7+ (2.108) 33 

6.00   0:00   +M11     1.Rg7+ Kxg7 2.f6+ Kh6 3.Ng4+ Kh5 
                       4.Qf5+ Nxf5 5.Rxf5+ Kg6 6.Re5+ Rc2 
                       7.Bxc2+ Qe4 8.Bxe4+ Kf7 9.Re7+ Kg8 
                       10.Nh6+ Kh8 11.Rh7+ (2.965) 47 

[Jouni]

Rybka was famous for reporting false nodes to appear like smarter engine .

[Chessnut1071]

A Shogi is a Japanese term for a game in which every white move is a check and ends in checkmate. This game is not exactly a Shogi because there is a line where a move isn't a white check.

1. Rg7+ KxR
2. Pf6+ RxP 3. QxR+
2. Pf6+ Kh8 3. Ng6+
2. Pf6+ Kg8 3. Bh7+
2. Pf6+ Kh6 3. Ng4+ QxN 4. QxQ isn't a check but forces mate in 11.

After 3.Ng4, Qxg4 is sub-optimal. The full line with best play is:

28.Rg7+ Kxg7 29.f6+ Kh6 30.Ng4+ Kg5 (or Kh5) 31.Qf5+ Nxf5 32.Rxf5+ Kg6 33.Re5+ Rc2 34.Bxc2+ then the line splits:

34...Qd3 35.Bxd3+ Kf7 36.Re7+ Kg8 37.Nh6+ Kh8 38.Rh7#
or
34...Qe4 35.Bxe4 Kf7 36.Re7+ Kg8 37.Nh6+ Kh8 38.Rh7#

Agreed, however, since 3. NQ4+ QxN exits it's no a true Shogi.

Optimized Checkmate Evaluation for Shogi & near Shogi puzzles:

Time 0.2895 sec Nodes: 330,909; white 268,980; black 61,929; total engine calls 780,294

Evaluation function:

White
score = 100 *check move + 3 *(8 - distance to enemy king)
score = 50 * capture piece value > 3

Black
score = 270 * check + 37 * successful move + 10 * last success + 20 * capture move + 1 * ent passant -7.5 * P - 12 * N -30 * B + 1 * R + 14 * Q - 3 * K
= - 50 * (material loss 7,8,9) - 30 * (material loss 4,5,6) - 70 * (material loss 2,3) + 10 * (material gain 2,3) +121 * (material gain 4,5,6) + 43.5 * (Material gain 7,8,9)


The evaluation function for black was optimized over 90 checkmate puzzles 10 - 24 ply
The evaluation function for white was optimized for Shog1 and near shogi puzzles 18 - 22 ply

Shogi and near Shogi puzzles are not very useful to gauge the strength of forced checkmate algorithms. The above evaluation was a simple optimization which only included less than a dozen variables and less than 100 puzzles. In fact, a specific optimization for the 11-move mate puzzle can be done is a few 100 nodes if optimized specifically for the puzzle.

[JuLieN]

[fen]2r2rk1/ppR5/1n1n4/3PNP2/3q3p/5Qp1/P5PP/1B3R1K w - - 0 28[/fen]

The current dev version of Myrddin needs just under one second, and 2.26M nodes, to spot Mate in 11 at depth 12. But, as always, The King from CM9000 is insanely fast with positions like this. It spots the mate practically instantly (roughly 0.03s), needing only 46,266 nodes to announce it at depth 1/5.

Less than a second for my latest version of Prédateur.

Code: Select all

FEN: 2r2rk1/ppR5/1n1n4/3PNP2/3q3p/5Qp1/P5PP/1B3R1K w - - 0 28 

Prédateur:
  2/4	00:00	         518	518k	+0,83	Rc7xc8 Rf8xc8
  3/4	00:00	          3k	1.673k	+0,80	Rc7xc8 Rf8xc8 Ne5-g6
  4/7	00:00	         12k	1.971k	+0,79	Rc7xc8 Rf8xc8 Qf3-f4 Qd4xf4
  4/17	00:00	         32k	2.437k	+1,08	Rf1-d1 Qd4xd1+ Qf3xd1 Rc8xc7 Qd1-f3 Nd6xf5
  5/17	00:00	         46k	2.422k	+1,42	Rf1-d1 Qd4xd1+ Qf3xd1 Rc8xc7 Ne5-g6 Rf8xf5
  6/19	00:00	         93k	2.506k	+1,50	Rf1-d1 Qd4xd1+ Qf3xd1 Rc8xc7 Ne5-g6 Rf8xf5 Bb1xf5
  7/19	00:00	        260k	2.480k	+1,40	Rf1-d1 Qd4xd1+ Qf3xd1 Rc8xc7 Ne5-g6 Rf8xf5 Bb1xf5 Nd6xf5 Qd1-d3 h4xg3
  7/32	00:00	        532k	2.312k	+4,47	Rc7-g7+ Kg8xg7 f5-f6+ Kg7-h6 Ne5-g4+ Kh6-h5 Qf3-f5+ Nd6xf5 Rf1xf5+ Kh5-g6 Rf5-e5+ Rc8-c2 Bb1xc2+ Qd4-e4 Bc2xe4+ Kg6-f7 Re5-e7+
  8/28	00:00	        891k	2.297k	+4,58	Rc7-g7+ Kg8xg7 f5-f6+ Kg7-h6 Ne5-g4+ Kh6-h5 Qf3-f5+ Nd6xf5 Rf1xf5+ Kh5-g6 Rf5-e5+ Rc8-c2 Bb1xc2+ Qd4-d3 Bc2xd3+ Kg6-f7 Re5-e7+ Kf7-g8 Re7xb7
  9/24	00:01	      2.300k	2.530k	+M11	Rc7-g7+ Kg8xg7 f5-f6+ Kg7-h6 Ne5-g4+ Kh6-h5 Qf3-f5+ Nd6xf5 Rf1xf5+ Kh5-g6 Rf5-e5+ Rc8-c2 Bb1xc2+ Qd4-e4 Bc2xe4+ Kg6-f7 Re5-e7+ Kf7-g8 Ng4-h6+ Kg8-h8 Re7-h7+