I suspect mate in 9 is correct. Stockfish 7 found it after not too long.
A complicated position with lots of pieces and probably a high branching factor; Plus, many engines use fairly agressive branch pruning. It's no surprise that not every engine can find the shortest mate.
The Stockfish MateFinder found the mate even faster:
http://talkchess.com/forum/viewtopic.php?t=58597
Bright 0.5c found it in under 10 seconds.
Houdini 1.5a approx 12 sec.
Spark 1.0 approx 30 sec.
Apparently they prune 2...Bxg2
Engines don't look at all the moves, there are too many. Because they ignore many moves sometimes they get things wrong (like this).
The engine is just "too smart".
The only way that an engine can guarantee it won't miss the shortest mate is for the engine to offer a "brute force" option in which no pruning is done. SOS 5.1 for Arena has this option. Be warned, though - If there's any depth to the mate, the engine can take forever to find it.
BRUTE FORCE
sounds... a bit strange.
Slow blitz chess? Never heard of it.
Can I get a link?
http://www.3dkingdoms.com/chess/slow.htm
Just an aside note. Chessmaster 11 finds mate in 9 in 38 seconds.
Time Depth Score Positions Moves
0:38 1/11 -Mate09 12947055 1...‰e2+ 2.‹g3 †xg2 3.‰xg2 ‡h5+
4.‹h3 ‡xf4+ 5.‹g3 ‰xg2+ 6.‹xf4
ˆae8 7.ˆe1 ˆxe1 8.‹f5 ˆe5+ 9.‹f4
g5#
One would think that the stronger engines would eventually find mate in 9 but I guess that doesn't correlate with playing strength.
Strangely, Shredder 7 starts out finding mate in 13, goes up to mate in 15 and then goes back down to mate in 12 but doesn't get lower than that.
Engine: Shredder 7
by Stefan Meyer-Kahlen
Position: 1 1
10/29 0:02 +21.87 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Qe6+ 4.f5 Qxf5+ 5.g4 Nf4+ 6.Kh4 g5+ 7.Kg3 Qxg4+ 8.Kf2 Nh3+ 9.Ke1 Nxg1 10.Ne4 Bxh1 (2.399.628) 1067.9
11/32 0:03 +22.12++ 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Qe6+ 4.f5 Qxf5+ 5.g4 Nf4+ 6.Kh4 g5+ 7.Kg3 Qxg4+ 8.Kf2 Nh3+ 9.Ke1 Nxg1 10.Ne4 (3.629.672) 1071.9
11/32 0:03 +22.62++ 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Qe6+ 4.f5 Qxf5+ 5.g4 Nf4+ 6.Kh4 g5+ 7.Kg3 Qxg4+ 8.Kf2 Nh3+ 9.Ke1 Nxg1 10.Ne4 Bxh1 (3.644.055) 1071.4
11/34 0:06 +M13 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kh4 Qe7+ 5.Kg3 Nh5+ 6.Kh3 Bg4+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 Qe6+ (6.934.136) 1100.1
12/12 0:06 +M13 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kh4 Qe7+ 5.Kg3 Nh5+ 6.Kh3 Bg4+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 Qe6+ (7.472.552) 1093.5
13/13 0:06 +M13 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kh4 Qe7+ 5.Kg3 Nh5+ 6.Kh3 Bg4+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 Qe6+ (7.479.038) 1091.9
14/14 0:06 +M13 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kh4 Qe7+ 5.Kg3 Nh5+ 6.Kh3 Bg4+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 Qe6+ (7.479.082) 1091.9
15/30 0:07 +M13 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kh4 Qe7+ 5.Kg3 Nh5+ 6.Kh3 Bg4+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 Qe6+ (7.656.417) 1069.1
16/33 0:07 +M13 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kh4 Qe7+ 5.Kg3 Nh5+ 6.Kh3 Bg4+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 Qe6+ (8.167.461) 1038.7
17/24 0:08 +M13 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kh4 Qe7+ 5.Kg3 Nh5+ 6.Kh3 Bg4+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 Qe6+ (8.554.149) 1048.4
18/30 0:08 +M13 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kh4 Qe7+ 5.Kg3 Nh5+ 6.Kh3 Bg4+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 Qe6+ (9.306.790) 1065.3
19/32 0:09 +M13 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kh4 Qe7+ 5.Kg3 Nh5+ 6.Kh3 Bg4+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 Qe6+ (10.582.181) 1090.4
20/38 0:11 +M13 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kh4 Qe7+ 5.Kg3 Nh5+ 6.Kh3 Bg4+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 Qe6+ (12.962.894) 1152.4
21/41 0:14 +M13 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kh4 Qe7+ 5.Kg3 Nh5+ 6.Kh3 Bg4+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ (17.283.087) 1192.5
22/28 0:20 +M13 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kh4 Qe7+ 5.Kg3 Nh5+ 6.Kh3 Bg4+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 Qe6+ (26.200.313) 1300.9
23/28 0:36 +M15 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kg3 Nh5+ 5.Kh3 Bg4+ 6.Kh4 Qe7+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 Nf4+ (45.440.760) 1249.0
24/26 1:05 +M15 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kg3 Nh5+ 5.Kh3 Bg4+ 6.Kh4 Qe7+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 Ne4 (86.836.539) 1319.9
25/26 2:18 +M15 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kg3 Nh5+ 5.Kh3 Bg4+ 6.Kh4 Qe7+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 Ne4 (172.130.415) 1243.2
26/28 4:25 +M12 1...Qe2+ 2.Kg3 Nh5+ 3.Kh3 Nxf4+ 4.Kg3 Nh5+ 5.Kh3 Bg4+ 6.Kh4 Qe7+ 7.Kxg4 Ndf6+ 8.Kh4 g5+ 9.Kh3 g4+ (319.005.418) 1199.4
best move: Qe7-e2 time: 6:43.512 min n/s: 1.196.796 CPU 134.8% nodes: 482.884.435
