Gosu does not find the mate in 1....

[Dr. Axel Schumacher]

...200 times:

Here a test-game vs. Cerebro (Blitz):

Gosu 0.4 - Cerebro 1.21

1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Bxc6 dxc6 5.0-0 Bg4 6.d3 Nf6 7.h3 Bxf3 8.Qxf3 Be7 9.Qg3 Qd6 10.Na3 b5 11.Qxg7 Rg8 12.Qh6 Rg6 13.Qe3 Kf8 14.f4 Kg8 15.fxe5 Qxe5 16.Rf5 Qe6 17.c3 Rd8 18.Nc2 Qd7 19.Rf3 c5 20.Qf2 Qe8 21.Bd2 c4 22.e5 Nd7 23.d4 f6 24.e6 Nf8 25.Re1 Rd6 26.Rfe3 Qc8 27.Qf5 Rg5 28.Qf3 c6 29.h4 Rg6 30.h5 Rg7 31.Re4 f5 32.Qxf5 Rd5 33.Qf3 Kh8 34.Bh6 Rg8 35.Nb4 Rd6 36.Qf5 Qd8 37.Bf4 Rg7 38.Be5 Kg8 39.h6 Rxg2+ 40.Kxg2 Rxe6 41.Rg4+ Rg6 42.Rxg6+ Nxg6 43.Qe6+ Kf8 44.Nxc6 Ke8 45.Nxd8 Kxd8 46.Qd5+ Ke8 47.Qc6+ Kf7 48.Rf1+ Nf4+ 49.Rxf4+ Bf6 50.Rxf6+ Ke7 51.Qd6+ Ke8 52.Re6+ Kf7 53.Re7+ Kf8 54.Qf6+ Kg8 55.Qe6+ Kf8 56.Rf7+ Kg8 57.Rd7+ Kf8 58.Qe7+ Kg8 59.Qg5+ Kf8 60.Bd6+ Ke8 61.Re7+ Kd8 62.Rg7+ Kc8 63.Qf5+ Kd8 64.Qf6+ Kc8 65.Qe6+ Kd8 66.Rd7+ Kc8 67.Rf7+ Kd8 68.Qe7+ Kc8 69.Qb7+ Kd8 70.Qc7+ Ke8 71.Re7+ Kf8 72.Re5+ Kg8 73.Qc8+ Kf7 74.Qe8+ Kf6 75.Qe7+ Kg6 76.Qg5+ Kf7 77.Re7+ Kf8 78.Qf4+ Kg8 79.Qg3+ Kf8 80.Qf2+ Kg8 81.Qf7+ Kh8 82.Qf6+ Kg8 83.Qe6+ Kf8 84.Rf7+ Kg8 85.Rf2+ Kh8 86.Qe5+ Kg8 87.Rf5 b4 88.Rg5+ Kf7 89.Qf5+ Ke8 90.Qc8+ Kf7 91.Qd7+ Kf6 92.Be7+ Kf7 93.Bf6+ Kxf6 94.Qg7+ Ke6 95.Re5+ Kd6 96.Qe7+ Kc6 97.Qc5+ Kb7 98.Re7+ Kb8 99.Qd6+ Ka8 100.Qc6+ Kb8 101.Rb7+ Ka8 102.Rb5+ Ka7 103.Qb6+ Ka8 104.Qd8+ Ka7 105.Qd7+ Ka8 106.Qe8+ Ka7 107.Qf7+ Ka8 108.Qf8+ Ka7 109.Qc5+ Ka8 110.Qd5+ Ka7 111.Rb7+ Ka8 112.Rg7+ Kb8 113.Qd6+ Ka8 114.Qc6+ Kb8 115.Rg8+ Ka7 116.Qc5+ Kb7 117.Rg7+ Ka8 118.Ra7+ Kb8 119.Qb6+ Kc8 120.Rc7+ Kd8 121.Qd6+ Ke8 122.Re7+ Kf8 123.Rg7+ Ke8 124.Qd7+ Kf8 125.Qf5+ Ke8 126.Qe6+ Kd8 127.Qe7+ Kc8 128.Qd7+ Kb8 129.Qa7+ Kc8 130.Qb7+ Kd8 131.Qc7+ Ke8 132.Qf7+ Kd8 133.Qf6+ Kc8 134.Qxa6+ Kb8 135.Rb7+ Kc8 136.Ra7+ Kd8 137.Qd6+ Kc8 138.Rc7+ Kb8 139.Rd7+ Ka8 140.Rd8+ Ka7 141.Qe7+ Kb6 142.Qe6+ Ka7 143.Rd7+ Ka8 144.Qa6+ Kb8 145.Rd8+ Kc7 146.Qd6+ Kb7 147.Qd7+ Ka6 148.Qc6+ Ka5 149.Qc7+ Ka4 150.Qd7+ Ka5 151.Ra8+ Kb6 152.Rb8+ Ka5 153.Qd8+ Ka4 154.Ra8+ Kb5 155.Qe8+ Kb6 156.Qe6+ Kb7 157.Qc8+ Kb6 158.Qc5+ Kb7 159.Ra7+ Kb8 160.Qb6+ Kc8 161.Rc7+ Kd8 162.Qd6+ Ke8 163.Re7+ Kf8 164.Rg7+ Ke8 165.Qd7+ Kf8 166.Qf5+ Ke8 167.Qe6+ Kd8 168.Rd7+ Kc8 169.Qc6+ Kb8 170.Rd8+ Ka7 171.Qc7+ Ka6 172.Ra8+ Kb5 173.Rb8+ Ka4 174.Qc6+ Ka5 175.Rb5+ Ka4 176.Rxb4+ Ka5 177.Qd5+ Ka6 178.Qd6+ Ka7 179.Qb8+ Ka6 180.Qb7+ Ka5 181.Qc7+ Ka6 182.Qd7 Ka5 183.Qd8+ Ka6 184.Qe7 Ka5 185.Qg5+ Ka6 186.Qf6+ Ka7 187.Qb6+ Ka8 188.Qc6+ Ka7 189.Qd6 Ka8 190.Qd5+ Ka7 191.Qc5+ Ka6 192.Ra4+ Kb7 193.Ra5 Kb8 194.Rb5+ Ka8 195.Qc6+ Ka7 196.Rb7+ Ka8 197.Rd7+ Kb8 198.Rd8+ Ka7 199.Qd6 Kb7 200.Rb8+ Ka7 201.Qc7+ Ka6 202.Rb6+ Ka5 203.Rb7+ Ka4 204.Qd7+ Ka5 205.Qe6 Ka4 206.Rb4+ Ka5 207.Qf5+ Ka6 208.Qg5 Ka7 209.Qe7+ Ka6 210.Ra4+ Kb5 211.Qb4+ Kc6 212.Ra7 Kd5 213.Qb7+ Ke6 214.Qf7+ Kd6 215.Qf6+ Kd5 216.Qe5+ Kc6 217.Qe6+ Kb5 218.Qd5+ Kb6 219.Rb7+ Ka6 220.Qc6+ Ka5 221.Qd6 Ka4 222.Ra7+ Kb5 223.Qb8+ Kc6 224.Qb7+ Kd6 225.a4 Ke6 226.Qf7+ Kd6 227.Rd7+ Kc6 228.Qd5+ Kb6 229.Rb7+ Ka6 230.Qc6+ Ka5 231.Qc7+ Kxa4 232.Qxc4+ Ka5 233.Rb5+ Ka6 234.Rb8+ Ka7 235.Qc7+ Ka6 236.Rb6+ Ka5 237.Rf6+ Ka4 238.Qc4+ Ka5 239.Rf5+ Kb6 240.Qc5+ Kb7 241.Rf7+ Ka6 242.Rf6+ Kb7 243.Rb6+ Ka7 244.Rb5+ Ka6 245.Qc6+ Ka7 246.Qd5 Ka6 247.Ra5+ Kb6 248.Qc5+ Kb7 249.Qd6 Kc8 250.Rc5+ Kb7 251.Rc7+ Ka8 252.Qc6+ Kb8 253.Rb7+ Ka8 254.Rb5+ Ka7 255.Ra5+ Kb8 256.Qe8+ Kc7 and Gosu lost on time 0-1

That looks similar to the Smarthink bug, which does the same in similar positions. Well, nobody is perfect

[Arek Paterek]

...200 times:
...

Funny game
I know gosu has problems with giving mate. They are probably caused by pondering in connection with the hash table. It is my priority to find and fix this bug.
The "solution" in the actual version of gosu is to turn off the hash table when opponent has no pieces.
Generally I hope gosu's opponents have implemented the resign option