Fun with mate study

[kiroje]

Hi

I was arranging mate/endgame study tournament in my local chessclub and had this one as one of the mate studies to solve

[pgn][Event "?"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "?"]
[Black "?"]
[Result "*"]
[FEN "2R5/1nP5/k3N3/8/K7/8/8/8 w - - 0 1"]
[SetUp "1"]

1.Ra8+ Kb6 2.Ra6+ Kxa6 3.c8=N Nc5+ 4.Nxc5# *

[/pgn]

Several engines have troubles with this one, some more than others ... Not so much to find a win, but finding the shortest win give several problems. Especially after whites 3. move there are some ...... blindness

Berserk 13
After whites 3. move - it gives this

Code: Select all

0:20/70, 1/4: 3...Nc5+, 35,6M nodes (1,7M nps), 8GB hash
0:08: 0.00/63 3...Nc5+ 4.Ka3 Kb7 5.Ne7 Kb6 6.Nd4 Nd7 7.Kb2 Ne5 8.Ka1 Kc5 9.Ndf5 Nd3 10.Ka2 Nc1+ 11.Kb1 Ne2 12.Nd6 Nc3+ 13.Ka1 Nd1 14.Ne4+ Kd4 15.Nf5+ Ke5 16.Ng7 Kf4 17.Ne6+ Kf5 18.Nd6+ Kg4 19.Ng5 Kf4 20.Nc4 Nf2 21.Kb1 Nd3 22.Ne6+ Ke4 23.Nd6+ Kd5 24.Ka1 Nb4 25.Nf5 Nc2+ 26.Kb2 Ne1 27.Nf4+ Kc6 28.Nd4+ Kc5 29.Nb3+ Kd6 30.Na5 Ke5 31.Ng6+ Kd6 32.Nb7+ Kd5 33.Nf4+ Kc4 34.Kb1
0:10: 0.00/64 3...Nc5+ 4.Ka3 Kb7 5.Ne7 Kb6 6.Nd4 Nd7 7.Kb2 Ne5 8.Ka1 Kc5 9.Ndf5 Nd3 10.Ka2 Nc1+ 11.Kb1 Ne2 12.Nd6 Nc3+ 13.Ka1 Nd1 14.Ne4+ Kd4 15.Nf5+ Ke5 16.Ng7 Kf4 17.Ne6+ Kf5 18.Nd6+ Kg4 19.Ng5 Kf4 20.Nc4 Nf2 21.Kb1 Nd3 22.Ne6+ Ke4 23.Nd6+ Kd5 24.Ka1 Nb4 25.Nf5 Nc2+ 26.Kb2 Ne1 27.Nf4+ Kc6 28.Nd4+ Kc5 29.Nb3+ Kd6 30.Na5 Ke5 31.Ng6+ Kd5 32.Ne5 Kc5 33.Nb3+ Kd6 34.Nd4 Kxe5
0:12: 0.00/65 3...Nc5+ 4.Ka3 Kb7 5.Ne7 Kb6 6.Nd4 Nd7 7.Kb2 Ne5 8.Ka1 Kc5 9.Ndf5 Nd3 10.Ka2 Nc1+ 11.Kb1 Ne2 12.Nd6 Nc3+ 13.Ka1 Nd1 14.Ne4+ Kd4 15.Nf5+ Ke5 16.Ng7 Kf4 17.Ne6+ Kf5 18.Nd6+ Kg4 19.Ng5 Kf4 20.Nc4 Nf2 21.Kb1 Nd3 22.Ne6+ Ke4 23.Nd6+ Kd5 24.Ka1 Nb4 25.Nf5 Nc2+ 26.Kb2 Ne1 27.Nf4+ Kc6 28.Nd4+ Kc5 29.Nb3+ Kd6 30.Na5 Ke5 31.Ng6+ Kd5 32.Ne5 Kc5 33.Nb3+ Kb4 34.Nd4 Kc5

Patricia 4
After whites 3. move - it gives this

Code: Select all

0:00/127-1: 3...Na5, 1K nodes (44,1K nps), 8GB hash, 8 threads
0:00: 0.00/125 3...Na5
0:00: 0.00/126 3...Na5
0:00: 0.00/127 3...Na5

PlentyChess 3.0.0
After whites 3. move - it gives this

Code: Select all

1:16/59-64: 3...Nc5+, 1G nodes (13,6M nps), 8GB hash
0:35: 0.00/56 3...Nc5+ 4.Kb4 Nxe6
0:35: 0.00/57 3...Nc5+ 4.Kb4 Nxe6
0:35: +0.01/58 3...Nc5+ 4.Kb4 Nxe6
1:16: +0.01/59 3...Nc5+ 4.Kb4 Ne4 5.Ne7 Kb6 6.Nd4 Kc7 7.Nb5+ Kd7 8.Ng6 Kc6 9.Nd4+ Kd5 10.Ne2 Nd2 11.Ne7+ Ke4 12.Ng3+ Ke5 13.Ng6+ Kd4 14.Nf5+ Kd5 15.Ne3+ Kd6 16.Nf4 Nf3 17.Nc4+ Kc6 18.Kb3 Ng5 19.Ne2 Kd5 20.Ne3+ Kd6 21.Kc3 Kc5 22.Ng1 Ne4+ 23.Kd3 Nf2+ 24.Kc2 Ng4 25.Nh3 Kd4 26.Ng5 Nxe3+

[Dann Corbit]

Additional information on this position:
[d]2R5/1nP5/k3N3/8/K7/8/8/8 w - - acd 999; bm Ra8+; ce 32760; dm 4; pm Ra8+; c0 "Pogosianz, E."; c3 "Ra8+"; c5 "http://lecoursdumaitre.e-monsite.com"; c6 "Gameknot.85465"; c7 "comment: BUS26 D13T E7a-B-S m"; pv Ra8+ Kb6 Ra6+ Kxa6 c8=N Nc5+ Nxc5#;
This was solved by Chest319 in batch mode (a mate prover).
You can find it on yacpdb as id 75464:
https://www.yacpdb.org/#search/MlI1MW5Q ... MS8xLzA=/1
You can also look it up on the PDB server:
https://pdb.dieschwalbe.de/search.jsp?e ... e6+wKa4%27
It is by a Ukranian composer:
https://www.arves.org/arves/index.php/e ... islav-1968

[Uri Blass]

Even when Berserk13 suggest the mating move in a position that I composed it has a big trouble to see that it is a mate.
[d]k7/2q5/K1N1N3/8/8/8/8/8 w - - 4 1

Berserk13:
time -1 start 303733687 alloc 0 max 2147483647 depth 200 timeset 0 searchmoves 0
1/1 00:00 268 268k 0.00 Ne6xc7+
2/2 00:00 2k 1,782k 0.00 Ne6xc7+
3/2 00:00 3k 3,203k 0.00 Ne6xc7+
4/2 00:00 5k 4,701k 0.00 Ne6xc7+
5/2 00:00 103k 6,423k 0.00 Ne6xc7+
6/2 00:00 135k 8,424k -0.01 Ne6xc7+
7/2 00:00 160k 10,019k 0.00 Ne6xc7+
8/2 00:00 162k 10,139k 0.00 Ne6xc7+
9/2 00:00 164k 10,265k -0.01 Ne6xc7+
10/2 00:00 166k 10,387k 0.00 Ne6xc7+
11/2 00:00 168k 10,501k 0.00 Ne6xc7+
12/2 00:00 170k 10,597k 0.00 Ne6xc7+
13/2 00:00 171k 10,712k 0.00 Ne6xc7+
14/2 00:00 173k 10,827k 0.00 Ne6xc7+
15/2 00:00 175k 10,952k 0.00 Ne6xc7+
16/2 00:00 177k 11,035k 0.00 Ne6xc7+
17/2 00:00 178k 11,106k 0.00 Ne6xc7+
18/2 00:00 179k 11,190k 0.00 Ne6xc7+
19/2 00:00 182k 11,347k -0.01 Ne6xc7+
20/2 00:00 183k 11,445k 0.00 Ne6xc7+
21/2 00:00 185k 11,538k -0.01 Ne6xc7+
22/2 00:00 187k 11,668k 0.00 Ne6xc7+
23/2 00:00 201k 12,553k -0.01 Ne6xc7+
24/2 00:00 203k 12,665k 0.00 Ne6xc7+
25/2 00:00 204k 12,753k 0.00 Ne6xc7+
26/2 00:00 206k 12,864k 0.00 Ne6xc7+
27/2 00:00 209k 13,044k -0.01 Ne6xc7+
28/2 00:00 211k 13,177k 0.00 Ne6xc7+
29/2 00:00 213k 13,305k 0.00 Ne6xc7+
30/2 00:00 214k 13,403k 0.00 Ne6xc7+
31/2 00:00 219k 13,707k -0.01 Ne6xc7+
32/2 00:00 224k 14,022k -0.01 Ne6xc7+
33/2 00:00 226k 7,295k 0.00 Ne6xc7+
34/2 00:00 228k 7,363k 0.00 Ne6xc7+
35/2 00:00 231k 7,441k 0.00 Ne6xc7+
36/2 00:00 232k 7,490k 0.00 Ne6xc7+
37/2 00:00 234k 7,548k 0.00 Ne6xc7+
38/2 00:00 236k 7,612k 0.00 Ne6xc7+
39/2 00:00 238k 7,683k 0.00 Ne6xc7+
40/2 00:00 240k 7,752k 0.00 Ne6xc7+
41/2 00:00 244k 7,862k 0.00 Ne6xc7+
42/2 00:00 245k 7,917k 0.00 Ne6xc7+
43/2 00:00 247k 7,975k 0.00 Ne6xc7+
44/2 00:00 251k 8,109k -0.01 Ne6xc7+
45/2 00:00 254k 8,178k 0.00 Ne6xc7+
46/2 00:00 256k 8,245k 0.00 Ne6xc7+
47/2 00:00 260k 8,398k -0.01 Ne6xc7+
48/2 00:00 262k 8,467k 0.00 Ne6xc7+
49/2 00:00 264k 8,509k 0.00 Ne6xc7+
50/2 00:00 267k 8,605k -0.01 Ne6xc7+
51/2 00:00 268k 8,649k 0.00 Ne6xc7+
52/2 00:00 275k 8,857k -0.01 Ne6xc7+
53/2 00:00 277k 8,926k 0.00 Ne6xc7+
54/2 00:00 284k 9,153k -0.01 Ne6xc7+
55/2 00:00 293k 9,446k 0.00 Ne6xc7+
56/2 00:00 670k 7,132k 0.00 Ne6xc7+
57/2 00:00 672k 7,144k 0.00 Ne6xc7+
58/2 00:00 672k 7,154k 0.00 Ne6xc7+
59/2 00:00 674k 7,166k 0.00 Ne6xc7+
60/2 00:00 700k 7,449k -0.01 Ne6xc7+
61/2 00:00 701k 7,461k 0.00 Ne6xc7+
62/2 00:00 706k 7,506k -0.01 Ne6xc7+
63/2 00:00 708k 7,531k 0.00 Ne6xc7+
64/2 00:00 726k 7,718k 0.00 Ne6xc7+
65/2 00:00 753k 8,005k 0.00 Ne6xc7+
66/2 00:00 924k 8,475k -0.01 Ne6xc7+
67/2 00:00 1,155k 8,189k 0.00 Ne6xc7+
68/2 00:00 1,427k 8,296k 0.00 Ne6xc7+
69/2 00:00 1,685k 8,302k -0.01 Ne6xc7+
70/2 00:00 1,773k 8,095k -0.01 Ne6xc7+
71/2 00:00 1,800k 8,218k 0.00 Ne6xc7+
72/2 00:00 2,197k 8,259k 0.00 Ne6xc7+
73/2 00:00 3,270k 8,363k 0.00 Ne6xc7+
74/2 00:00 3,929k 8,672k 0.00 Ne6xc7+
75/2 00:00 5,320k 8,956k 0.00 Ne6xc7+
76/2 00:00 7,554k 9,478k 0.00 Ne6xc7+
77/2 00:00 8,656k 9,554k 0.00 Ne6xc7+
78/2 00:00 8,994k 9,437k 0.00 Ne6xc7+
79/2 00:00 9,289k 9,440k 0.00 Ne6xc7+
80/2 00:01 15,668k 9,738k 0.00 Ne6xc7+
81/2 00:02 24,480k 10,444k 0.00 Ne6xc7+
82/2 00:04 55,353k 12,049k -0.01 Ne6xc7+

[Dann Corbit]

The tablebase version of Chest solves Uri's position in one node (not surprising)
G:\>chest324 -b -z26 --egtb-path=g:\nalimov uripos.epd > up-ch.epd

G:\>type up-ch.epd
% EGTB found tables for max 6 pieces
% EGTB uses 288083.1K memory internally
k7/2q5/K1N1N3/8/8/8/8/8 w - - acn 1; acs 5; bm Nxc7#; ce 32766; dm 1; pv Nxc7#;

The non-tablebase version also solves the problem in one node:
G:\>chest319 -b -M 8192 -z 26 uripos.epd > up2-ch.epd

G:\>type up2-ch.epd
k7/2q5/K1N1N3/8/8/8/8/8 w - - acn 1; acs 0; bm Nxc7#; ce 32766; dm 1; pv Nxc7#;

In this case the key move is very obvious, I think any human will do the same (queen is a powerful magnet for the knight, putting the enemy king in check. Other knight checks two other flight squares and king check the other! Checkmate.
So I guess that programs that fail to find the mate are going by the material assumption that two knights cannot mate (which is almost always true).

[kiroje]

So I guess that programs that fail to find the mate are going by the material assumption that two knights cannot mate (which is almost always true).

Hi Dann

I understand the idea of limiting certain very seldom encountered cases but I would rather have a bit less rating, for already incredibly strong progams, and the ability to solve these cases than not being able to see a mate in 1.

Stockfish 17 solves it from the startposition so it is possible at least

With regards

[chessica]

Even when Berserk13 suggest the mating move in a position that I composed it has a big trouble to see that it is a mate.
[d]k7/2q5/K1N1N3/8/8/8/8/8 w - - 4 1

Berserk13:
time -1 start 303733687 alloc 0 max 2147483647 depth 200 timeset 0 searchmoves 0
1/1 00:00 268 268k 0.00 Ne6xc7+
2/2 00:00 2k 1,782k 0.00 Ne6xc7+
3/2 00:00 3k 3,203k 0.00 Ne6xc7+
4/2 00:00 5k 4,701k 0.00 Ne6xc7+
5/2 00:00 103k 6,423k 0.00 Ne6xc7+
6/2 00:00 135k 8,424k -0.01 Ne6xc7+
7/2 00:00 160k 10,019k 0.00 Ne6xc7+
8/2 00:00 162k 10,139k 0.00 Ne6xc7+
9/2 00:00 164k 10,265k -0.01 Ne6xc7+
10/2 00:00 166k 10,387k 0.00 Ne6xc7+
11/2 00:00 168k 10,501k 0.00 Ne6xc7+
12/2 00:00 170k 10,597k 0.00 Ne6xc7+
13/2 00:00 171k 10,712k 0.00 Ne6xc7+
14/2 00:00 173k 10,827k 0.00 Ne6xc7+
15/2 00:00 175k 10,952k 0.00 Ne6xc7+
16/2 00:00 177k 11,035k 0.00 Ne6xc7+
17/2 00:00 178k 11,106k 0.00 Ne6xc7+
18/2 00:00 179k 11,190k 0.00 Ne6xc7+
19/2 00:00 182k 11,347k -0.01 Ne6xc7+
20/2 00:00 183k 11,445k 0.00 Ne6xc7+
21/2 00:00 185k 11,538k -0.01 Ne6xc7+
22/2 00:00 187k 11,668k 0.00 Ne6xc7+
23/2 00:00 201k 12,553k -0.01 Ne6xc7+
24/2 00:00 203k 12,665k 0.00 Ne6xc7+
25/2 00:00 204k 12,753k 0.00 Ne6xc7+
26/2 00:00 206k 12,864k 0.00 Ne6xc7+
27/2 00:00 209k 13,044k -0.01 Ne6xc7+
28/2 00:00 211k 13,177k 0.00 Ne6xc7+
29/2 00:00 213k 13,305k 0.00 Ne6xc7+
30/2 00:00 214k 13,403k 0.00 Ne6xc7+
31/2 00:00 219k 13,707k -0.01 Ne6xc7+
32/2 00:00 224k 14,022k -0.01 Ne6xc7+
33/2 00:00 226k 7,295k 0.00 Ne6xc7+
34/2 00:00 228k 7,363k 0.00 Ne6xc7+
35/2 00:00 231k 7,441k 0.00 Ne6xc7+
36/2 00:00 232k 7,490k 0.00 Ne6xc7+
37/2 00:00 234k 7,548k 0.00 Ne6xc7+
38/2 00:00 236k 7,612k 0.00 Ne6xc7+
39/2 00:00 238k 7,683k 0.00 Ne6xc7+
40/2 00:00 240k 7,752k 0.00 Ne6xc7+
41/2 00:00 244k 7,862k 0.00 Ne6xc7+
42/2 00:00 245k 7,917k 0.00 Ne6xc7+
43/2 00:00 247k 7,975k 0.00 Ne6xc7+
44/2 00:00 251k 8,109k -0.01 Ne6xc7+
45/2 00:00 254k 8,178k 0.00 Ne6xc7+
46/2 00:00 256k 8,245k 0.00 Ne6xc7+
47/2 00:00 260k 8,398k -0.01 Ne6xc7+
48/2 00:00 262k 8,467k 0.00 Ne6xc7+
49/2 00:00 264k 8,509k 0.00 Ne6xc7+
50/2 00:00 267k 8,605k -0.01 Ne6xc7+
51/2 00:00 268k 8,649k 0.00 Ne6xc7+
52/2 00:00 275k 8,857k -0.01 Ne6xc7+
53/2 00:00 277k 8,926k 0.00 Ne6xc7+
54/2 00:00 284k 9,153k -0.01 Ne6xc7+
55/2 00:00 293k 9,446k 0.00 Ne6xc7+
56/2 00:00 670k 7,132k 0.00 Ne6xc7+
57/2 00:00 672k 7,144k 0.00 Ne6xc7+
58/2 00:00 672k 7,154k 0.00 Ne6xc7+
59/2 00:00 674k 7,166k 0.00 Ne6xc7+
60/2 00:00 700k 7,449k -0.01 Ne6xc7+
61/2 00:00 701k 7,461k 0.00 Ne6xc7+
62/2 00:00 706k 7,506k -0.01 Ne6xc7+
63/2 00:00 708k 7,531k 0.00 Ne6xc7+
64/2 00:00 726k 7,718k 0.00 Ne6xc7+
65/2 00:00 753k 8,005k 0.00 Ne6xc7+
66/2 00:00 924k 8,475k -0.01 Ne6xc7+
67/2 00:00 1,155k 8,189k 0.00 Ne6xc7+
68/2 00:00 1,427k 8,296k 0.00 Ne6xc7+
69/2 00:00 1,685k 8,302k -0.01 Ne6xc7+
70/2 00:00 1,773k 8,095k -0.01 Ne6xc7+
71/2 00:00 1,800k 8,218k 0.00 Ne6xc7+
72/2 00:00 2,197k 8,259k 0.00 Ne6xc7+
73/2 00:00 3,270k 8,363k 0.00 Ne6xc7+
74/2 00:00 3,929k 8,672k 0.00 Ne6xc7+
75/2 00:00 5,320k 8,956k 0.00 Ne6xc7+
76/2 00:00 7,554k 9,478k 0.00 Ne6xc7+
77/2 00:00 8,656k 9,554k 0.00 Ne6xc7+
78/2 00:00 8,994k 9,437k 0.00 Ne6xc7+
79/2 00:00 9,289k 9,440k 0.00 Ne6xc7+
80/2 00:01 15,668k 9,738k 0.00 Ne6xc7+
81/2 00:02 24,480k 10,444k 0.00 Ne6xc7+
82/2 00:04 55,353k 12,049k -0.01 Ne6xc7+

FEN: k7/2q5/K1N1N3/8/8/8/8/8 w - - 4 1

Patricia 4.0 JA:

Code: Select all

 8/4	00:00,003	 409	136k	-0,25	Se6xc7+
 9/5	00:00,004	 552	138k	-0,25	Se6xc7+
 10/5	00:00,005	 718	144k	-0,26	Se6xc7+
 11/6	00:00,005	 840	168k	-0,25	Se6xc7+
 12/5	00:00,005	 971	194k	-0,26	Se6xc7+
 13/7	00:00,006	 1k	225k	-0,26	Se6xc7+
 14/8	00:00,007	 2k	257k	-0,26	Se6xc7+
 15/7	00:00,007	 2k	305k	-0,26	Se6xc7+
 16/6	00:00,008	 2k	307k	-0,25	Se6xc7+
 17/7	00:00,008	 3k	363k	-0,25	Se6xc7+
 18/7	00:00,009	 3k	380k	-0,25	Se6xc7+
 19/12	00:00,014	 6k	424k	-0,26	Se6xc7+
 20/11	00:00,016	 7k	427k	-0,26	Se6xc7+
 21/8	00:00,017	 7k	432k	-0,25	Se6xc7+
 22/12	00:00,021	 10k	485k	-0,26	Se6xc7+
 23/10	00:00,026	 14k	524k	-0,26	Se6xc7+
 24/10	00:00,028	 15k	539k	-0,26	Se6xc7+
 25/11	00:00,031	 17k	543k	-0,25	Se6xc7+
 26/15	00:00,050	 28k	557k	-0,26	Se6xc7+
 27/11	00:00,055	 30k	549k	-0,26	Se6xc7+
 28/14	00:00,063	 36k	568k	-0,26	Se6xc7+
 29/15	00:00,074	 42k	570k	-0,26	Se6xc7+
 30/12	00:00,079	 45k	571k	-0,25	Se6xc7+
 31/15	00:00,105	 62k	590k	-0,26	Se6xc7+
 32/18	00:00,130	 79k	608k	-0,25	Se6xc7+
 33/16	00:00,152	 93k	612k	-0,26	Se6xc7+
 34/14	00:00,156	 96k	615k	-0,26	Se6xc7+
 35/18	00:00,189	 120k	635k	-0,26	Se6xc7+
 36/16	00:00,205	 131k	640k	-0,25	Se6xc7+
 37/19	00:00,245	 164k	669k	-0,26	Se6xc7+
 38/22	00:00,302	 210k	695k	-0,26	Se6xc7+
 39/17	00:00,350	 251k	717k	-0,26	Se6xc7+
 40/18	00:00,377	 273k	724k	-0,26	Se6xc7+
 41/24	00:00,490	 362k	739k	-0,26	Se6xc7+
 42/18	00:00,503	 373k	741k	-0,25	Se6xc7+
 43/28	00:00,571	 427k	749k	-0,26	Se6xc7+
 44/17	00:00,588	 442k	751k	-0,25	Se6xc7+
 45/17	00:00,620	 467k	753k	-0,25	Se6xc7+
 46/24	00:00,952	 756k	794k	-0,26	Se6xc7+
 47/21	00:01,021	 821k	804k	-0,25	Se6xc7+
 48/21	00:01,086	 886k	816k	-0,26	Se6xc7+
 49/20	00:01,122	 920k	820k	-0,25	Se6xc7+
 50/21	00:01,242	 1.020k	821k	-0,26	Se6xc7+
 51/20	00:01,273	 1.048k	824k	-0,25	Se6xc7+
 52/24	00:01,680	 1.392k	828k	-0,26	Se6xc7+
 53/26	00:01,840	 1.541k	838k	-0,25	Se6xc7+
 54/28	00:02,058	 1.748k	849k	-0,26	Se6xc7+
 55/32	00:03,851	 3.314k	861k	-0,26	Se6xc7+
 56/19	00:03,909	 3.373k	863k	-0,25	Se6xc7+
 57/21	00:03,954	 3.417k	864k	-0,25	Se6xc7+
 58/30	00:05,104	 4.459k	874k	-0,26	Se6xc7+
 59/34	00:07,059	 6.408k	908k	-0,26	Se6xc7+
 60/33	00:08,311	 7.564k	910k	-0,26	Se6xc7+
 61/27	00:08,821	 8.083k	916k	-0,25	Se6xc7+
 62/32	00:09,282	 8.502k	916k	-0,25	Se6xc7+
 63/34	00:10,112	 9.397k	929k	-0,26	Se6xc7+
 64/26	00:10,389	 9.682k	932k	-0,25	Se6xc7+
 65/28	00:11,005	 10.329k	939k	-0,26	Se6xc7+
 66/24	00:11,122	 10.439k	939k	-0,25	Se6xc7+
 67/23	00:11,336	 10.664k	941k	-0,25	Se6xc7+
 68/33	00:15,135	 14.257k	942k	-0,26	Se6xc7+
 69/35	00:18,852	 17.577k	932k	-0,26	Se6xc7+
 70/25	00:19,079	 17.806k	933k	-0,25	Se6xc7+
 71/37	00:31,840	 30.893k	970k	-0,26	Se6xc7+
 72/22	00:31,921	 30.981k	971k	-0,25	Se6xc7+
 73/35	00:34,310	 33.404k	974k	-0,26	Se6xc7+
 74/26	00:34,360	 33.457k	974k	-0,26	Se6xc7+
 75/35	00:38,486	 37.313k	970k	-0,26	Se6xc7+
 76/25	00:38,781	 37.599k	970k	-0,25	Se6xc7+
 77/35	00:42,376	 40.922k	966k	-0,26	Se6xc7+
 78/30	00:43,114	 41.679k	967k	-0,25	Se6xc7+
 79/35	00:50,508	 49.045k	971k	-0,26	Se6xc7+
 80/32	00:52,056	 50.494k	970k	-0,25	Se6xc7+
 81/46	01:14,540	 70.162k	941k	-0,26	Se6xc7+
 82/24	01:14,950	 70.596k	942k	-0,25	Se6xc7+
 83/27	01:15,547	 71.148k	942k	-0,25	Se6xc7+
 84/34	01:16,472	 71.980k	941k	-0,26	Se6xc7+
 85/28	01:16,880	 72.392k	942k	-0,25	Se6xc7+
 86/43	01:47,377	 97.010k	903k	-0,26	Se6xc7+
 87/28	01:47,850	 97.436k	903k	-0,25	Se6xc7+
 88/32	01:49,414	 98.892k	904k	-0,25	Se6xc7+
 89/26	01:49,485	 98.963k	904k	-0,25	Se6xc7+
 90/28	01:50,016	 99.471k	904k	-0,25	Se6xc7+
 91/44	01:56,757	 105.187k	901k	-0,25	Se6xc7+
 92/22	01:56,848	 105.285k	901k	-0,25	Se6xc7+
 93/32	01:59,091	 107.246k	901k	-0,25	Se6xc7+
 94/32	01:59,926	 107.973k	900k	-0,25	Se6xc7+

[towforce]

Hi

I was arranging mate/endgame study tournament in my local chessclub and had this one as one of the mate studies to solve

[pgn][Event "?"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "?"]
[Black "?"]
[Result "*"]
[FEN "2R5/1nP5/k3N3/8/K7/8/8/8 w - - 0 1"]
[SetUp "1"]

1.Ra8+ Kb6 2.Ra6+ Kxa6 3.c8=N Nc5+ 4.Nxc5# *

[/pgn]

Chess.com's analysis engine gets this answer instantly!

[Dann Corbit]

Anything that uses 6 man files will solve it instantly if the files are available