A Merry Christmas mate in 20

[kgburcham]

Posted at Chessbase
Study by P Benko

So far it seems to be a mate in 20.
kgburcham

[D] 8/r5k1/2p5/3PK2R/6p1/3q4/8/4Q3 w - -

[Aser Huerga]

Rybka 4.1 is very good yet finding mates, but only Mate in 21 after 36 minutes in my hardware:

i7-3930K 4.25Ghz
Rybka 4.1 MP

Code: Select all

[Mate in 21]  d=29  1.Rg5+ Kh8 2.Qh1+ Qh7 3.Rh5 cxd5 4.Qh4 Re7+ 5.Kd4 Rf7 6.Rxh7+ Rxh7 7.Qd8+ Kg7 8.Qg5+ Kf8 9.Qf5+ Kg8 10.Qe6+ Kf8 11.Qc8+ Kf7 12.Qd7+ Kg6 13.Qe6+ Kh5 14.Qxd5+ Kh6 15.Qd6+ Kg5 16.Qe5+ (0:36:12) 1991269kN
 [Mate in 21]  d=28  1.Rg5+ Kh8 2.Qh1+ Qh7 3.Rh5 cxd5 4.Qh4 Re7+ 5.Kd4 Rf7 6.Rxh7+ Rxh7 7.Qd8+ Kg7 8.Qg5+ Kf8 9.Qf5+ Kg8 10.Qe6+ Kf8 11.Qc8+ Kf7 12.Qd7+ Kg6 13.Qe6+ Kh5 14.Qxd5+ Kh6 15.Qd6+ Kg5 16.Qe5+ (0:22:00) 1202258kN
 [Mate in 21]  d=27  1.Rg5+ Kh8 2.Qh1+ Qh7 3.Rh5 cxd5 4.Qh4 Re7+ 5.Kd4 Rf7 6.Rxh7+ Rxh7 7.Qd8+ Kg7 8.Qg5+ Kf8 9.Qf5+ Kg8 10.Qe6+ Kf8 11.Qc8+ Kf7 12.Qd7+ Kg6 13.Qe6+ Kh5 14.Qxd5+ Kh6 15.Qd6+ Kg5 16.Qe5+ (0:13:06) 760807kN
 [Mate in 21]  d=26  1.Rg5+ Kh8 2.Qh1+ Qh7 3.Rh5 cxd5 4.Qh4 Re7+ 5.Kd4 Rf7 6.Rxh7+ Rxh7 7.Qd8+ Kg7 8.Qg5+ Kf8 9.Qf5+ Kg8 10.Qe6+ Kf8 11.Qc8+ Kf7 12.Qd7+ Kg6 13.Qe6+ Kh5 14.Qxd5+ Kh6 15.Qd6+ Kg5 16.Qe5+ (0:08:25) 502885kN
 [Mate in 21]  d=25  1.Rg5+ Kh8 2.Qh1+ Qh7 3.Rh5 cxd5 4.Qh4 Re7+ 5.Kd4 Rf7 6.Rxh7+ Rxh7 7.Qd8+ Kg7 8.Qg5+ Kf8 9.Qf5+ Kg8 10.Qe6+ Kf8 11.Qc8+ Kf7 12.Qd7+ Kg6 13.Qe6+ Kh5 14.Qxd5+ Kh6 15.Qd6+ Kg5 16.Qe5+ (0:05:32) 347555kN
 [Mate in 22]  d=24  1.Rg5+ Kh8 2.Qh1+ Qh7 3.Rh5 cxd5 4.Qh4 Re7+ 5.Kd4 Kg8 6.Rxh7 Rxh7 7.Qxg4+ Kf8 8.Kxd5 Rf7 9.Kd6 Rf6+ 10.Ke5 Kf7 (0:03:58) 257488kN
 [Mate in 21]  d=23  1.Rg5+ Kh8 2.Qh1+ Qh7 3.Rh5 cxd5 4.Qh4 Re7+ 5.Kd4 Rf7 6.Rxh7+ Rxh7 7.Qd8+ Kg7 8.Qg5+ Kf8 9.Qf5+ Kg8 10.Qc8+ Kf7 11.Qd7+ Kg6 12.Qxg4+ Kf6 13.Kxd5 Rb7 14.Qd4+ Kg5 (0:02:52) 186318kN
 [Mate in 23]  d=22  1.Rg5+ Kh8 2.Qh1+ Qh7 3.Rh5 cxd5 4.Qh4 Re7+ 5.Kd4 Rf7 6.Qg5 g3 7.Rxh7+ Rxh7 8.Qd8+ Kg7 9.Qc7+ Kh6 10.Qf4+ Kh5 11.Qf5+ Kh6 12.Ke5 Rc7 13.Qg4 Rg7 14.Qh3+ Kg5 15.Qxg3+ Kh6 16.Qh3+ (0:02:06) 134693kN
 [Mate in 22]  d=21  1.Rg5+ Kh8 2.Qh1+ Qh7 3.Rh5 cxd5 4.Kf4 Rf7+ 5.Kg3 Kg8 6.Rxh7 Rxh7 7.Qxd5+ Rf7 8.Kxg4 Kg7 (0:01:46) 111853kN
 [Mate in 25]  d=20  1.Rg5+ Kh8 2.Qh1+ Qh7 3.Rh5 cxd5 4.Qh4 Re7+ 5.Kd4 Rf7 6.Rxh7+ Rxh7 7.Qd8+ Kg7 8.Qg5+ Kf8 9.Qf6+ Kg8 10.Qe6+ Kf8 11.Qd6+ Ke8 12.Qf6 g3 13.Qg5 g2 14.Qg6+ Ke7 15.Qxh7+ Kf6 16.Qh8+ (0:01:28) 92225kN
 [Mate in 22]  d=19  1.Rg5+ Kh8 2.Qh1+ Qh7 3.Rh5 cxd5 4.Qh4 Re7+ 5.Kd4 Rf7 6.Rxh7+ Rxh7 7.Qd8+ Kg7 8.Qg5+ Kf8 9.Qf6+ Ke8 10.Qg6+ Rf7 11.Qh5 g3 12.Ke5 Kf8 13.Ke6 Re7+ 14.Kf6 Rg7 15.Qxd5 Ke8 16.Kxg7 (0:01:19) 81574kN
 [Mate in 26]  d=18  1.Rg5+ Kh8 2.Qh1+ Qh7 3.Rh5 cxd5 4.Kf4 Rf7+ 5.Kg3 Kg8 6.Rxh7 Rxh7 7.Qxd5+ Rf7 8.Kxg4 Kg7 9.Qd4+ Kh6 10.Qh8+ Kg6 11.Qh5+ Kf6 12.Qf5+ Kg7 13.Qg5+ Kh7 14.Qh4+ Kg8 15.Qd8+ Kh7 16.Qd3+ (0:01:06) 66474kN
 [Mate in 26]  d=17  1.Rg5+ Kh8 2.Qh1+ Qh7 3.Rh5 cxd5 4.Kf4 Rf7+ 5.Kxg4 Rg7+ 6.Kf4 Rf7+ 7.Kg3 Rg7+ 8.Kf2 Kg8 9.Rxh7 Rg5 10.Rh8+ Kf7 11.Qf3+ Kg6 12.Rg8+ Kh6 13.Qf6+ (0:01:04) 64208kN
 [Mate in 26]  d=16  1.Rg5+ Kh8 2.Qh1+ Rh7 3.Qa1 Rg7 4.Rh5+ Kg8 5.Qa8+ Kf7 6.Rf5+ Qxf5+ 7.Kxf5 g3 8.dxc6 g2 9.Qb7+ Kg8 10.Qb8+ Kf7 11.Qc7+ Kg8 12.Qd8+ Kh7 13.Qh4+ Kg8 14.c7 Rf7+ 15.Ke5 g1Q 16.c8Q+ (0:00:57) 56326kN
 [+53.04]  d=16  1.Rg5+ Kf8 2.Qb4+ Re7+ 3.Kf6 Qf3+ 4.Rf5 Qe4 5.Qb8+ Re8 6.Qc7 Re7 7.Qc8+ Re8 8.Kg6+ Kg8 9.Qc7 Re7 10.Qd8+ Re8 11.Qh4 Re7 12.Qf6 Qxf5+ 13.Qxf5 Rg7+ 14.Kh6 Rc7 15.d6 Rg7 16.d7 (0:00:50) 48258kN
 [+27.44]  d=16  1.Rg5+ Kf8 2.Qb4+ Re7+ 3.Kf6 Qe2 4.Rh5 Qf3+ 5.Rf5 Qe4 6.Qb8+ Re8 7.Qc7 Re7 8.Qc8+ Re8 9.Kg6+ Kg8 10.Qc7 Re7 11.Qd8+ Re8 12.Qh4 Re7 13.Qf6 Qxf5+ 14.Qxf5 Rg7+ 15.Kh6 Rc7 16.d6 (0:00:45) 43046kN
 [+14.64]  d=16  1.Rg5+ Kf8 2.Qb4+ Re7+ 3.Kf6 Qe2 4.Rh5 Qf3+ 5.Rf5 Qe4 6.Qb8+ Re8 7.Qc7 Re7 8.Qc8+ Re8 9.Kg6+ Kg8 10.Qc7 Re6+ 11.dxe6 Qxe6+ 12.Kg5 Qe3+ 13.Kxg4 Qe6 14.Kg5 Qe3+ 15.Kh5 Qe2+ 16.Kh4 (0:00:30) 24948kN
 [+8.24]  d=16  1.Rg5+ Kf8 2.Qb4+ Re7+ 3.Kf6 Qe2 4.Rh5 Qf3+ 5.Rf5 Qe4 6.Qb8+ Re8 7.Qc7 Re7 8.Qc8+ Re8 9.Kg6+ Kg8 10.Qc7 Re6+ 11.dxe6 Qxe6+ 12.Kg5 Qe3+ 13.Kxg4 Qe6 14.Kg5 Qe3+ 15.Kh4 Qh6+ 16.Kg4 (0:00:19) 12655kN
 [+5.04]  d=16  1.Rg5+ Kf8 2.Qb4+ Re7+ 3.Kf6 Qe2 4.Rh5 Qf3+ 5.Rf5 Qe4 6.Qb8+ Re8 7.Qc7 Re7 8.Qc8+ Re8 9.Kg6+ (0:00:12) 6900kN
 [+3.44]  d=16  1.Rg5+ Kf8 2.Qb4+ Re7+ 3.Kf6 Qe2 4.Rh5 Qf3+ 5.Rf5 Qe4 6.Qb8+ Re8 7.Qc7 Re7 8.Qc8+ Re8 9.Kg6+ Kg8 10.Qc7 Re7 11.Qd8+ Re8 12.Qh4 (0:00:08) 4698kN

[kgburcham]

Rybka 4.1 is very good yet finding mates, but only Mate in 21 after 36 minutes in my hardware:
i7-3930K 4.25Ghz
Rybka 4.1 MP

nice cpu and good overclock
mate in 21 might be correct, I don't trust the programs for some mates.
My Mate in 20 might be incorrect.
I don't care, programs are fun anyway.

Merry Christmas
kgburcham

[h1a8]

Why do programs increase the move to mate as time progresses? Shouldn't the distance to mate decrease or stay the same?
Is this a bug in chess programs?

[syzygy]

Why do programs increase the move to mate as time progresses? Shouldn't the distance to mate decrease or stay the same?
Is this a bug in chess programs?

This is usually the result of hashtable entries being overwritten.

[h1a8]

But why not overwrite them with lesser distance to mate? It makes the program look dumb when it announces a move to mate and then turn around and announce a higher move to mate.

[Spliffjiffer]

Rybka's PV is quite weird and its actually wrong...according to "Chest 5.2" there is no mate in 15 after 6...Rxh7 (wich would be a mate in 21) after a brute force search !

edit: stupid as i am i realized its a 6-men egtb and its a mate in 21 after 6...Rxh7 with 7. Qxg4

regards and happy new year