8 zugswangs

[David Dahlem]

[D]8/p5p1/1pP3p1/p5p1/k3p3/4p3/K7/8 w - - 0 1

I doubt if any engine will show a winning score for White, much less a mate score.

Code: Select all

White to play and win Novomesky and Siran 2002

1.c7 e2 2.c8Q e1Q With a Queen's ending of seven against zero pawns - the zero pawns win. 3.Qc4+ Qb4 4.Qc6+ Qb5 If b5, then 5.Qc2+ and mate. 5.Qxe4+ Qb4 6.Qd3! And for the first time, the crucial Zugzwang has arisen. Qb3 mate must remain guarded; Qb5 would be met by Qa3 mate, and b5 by Qc2+ and mate. Black can only make pawn moves. 6...a6 7.Qd7+ Qb5 8.Qd4+ Qb4 9.Qd3 But White can repeat the Zugzwang. 9...g4 And he can also repeat it now. The rest is evident. 10.Qd7+ Qb5 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qd4+ Qb4 14.Qd3 g5 15.Qd7+ Qb5 16.Qd4+ Qb4 17.Qd3 g6 18.Qd7+ Qb5 19.Qd4+ Qb4 20.Qd3 g4 21.Qd7+ Qb5 22.Qxg4+ Qb4 23.Qd7+ Qb5 24.Qd4+ Qb4 25.Qd3 g5 26.Qd7+ Qb5 27.Qd4+ Qb4 28.Qd3 g4 29.Qd7+ Qb5 30.Qxg4+ Qb4 31.Qd7+ Qb5 32.Qd4+ Qb4 33.Qd3 and after Zugzwang number 8, Black will finally be mated.

[Terry McCracken]

Hmmm...No one has answered so I suspect engines indeed miss the mate.

I'd test it but my system isn't setup at present. I moved recently.

[Edmund]

Glass is fully blind to Zugzwangs with queens on the board

[Adam Hair]

Every engine I tried, from Stockfish to Mephisto MMV, only saw the draw -
repeating Qe4+ and Qc4+. None saw Qd3.

[Ovyron]

Rybka's behavior on this line is really weird, starting from fresh hash she doesn't find anything even very late in the line, but if you make her analyze the positions one by one, she realizes white is winning since move 11.

I zoomed move by move, with infinite analysis ON, to this position:

[D]8/6p1/pp4p1/p5p1/kq6/3Q4/K7/8 w - -

Then, I just forced the moves one by one, here's the output:

Rybka 3 64bit 4CPU:

26.01 0:01 0.00 7.Qd7+ Qb5 8.Qg4+ Qb4 9.Qd7+ Qb5 10.Qg4+ Qb4 11.Qd7+ Qb5 12.Qg4+ Qb4 13.Qd7+ Qb5 14.Qg4+ Qb4 15.Qd7+ Qb5 16.Qg4+ Qb4 17.Qd7+ Qb5 18.Qg4+ Qb4 19.Qd7+ Qb5 20.Qg4+ (875.978) 470
27.01 0:10 0.00 7.Qd7+ Qb5 8.Qg4+ Qb4 9.Qd7+ Qb5 10.Qg4+ Qb4 11.Qd7+ Qb5 12.Qg4+ Qb4 13.Qd7+ Qb5 14.Qg4+ Qb4 15.Qd7+ Qb5 16.Qg4+ Qb4 17.Qd7+ Qb5 18.Qg4+ Qb4 19.Qd7+ Qb5 20.Qg4+ (4.938.038) 486 TB:3
28.01 0:20 0.00 7.Qd7+ Qb5 8.Qg4+ Qb4 9.Qd7+ Qb5 10.Qg4+ Qb4 11.Qd7+ Qb5 12.Qg4+ Qb4 13.Qd7+ Qb5 14.Qg4+ Qb4 15.Qd7+ Qb5 16.Qg4+ Qb4 17.Qd7+ Qb5 18.Qg4+ Qb4 19.Qd7+ Qb5 20.Qg4+ (9.578.419) 479 TB:8
29.01 0:37 0.00 7.Qd7+ Qb5 8.Qg4+ Qb4 9.Qd7+ Qb5 10.Qg4+ Qb4 11.Qd7+ Qb5 12.Qg4+ Qb4 13.Qd7+ Qb5 14.Qg4+ Qb4 15.Qd7+ Qb5 16.Qg4+ Qb4 17.Qd7+ Qb5 18.Qg4+ Qb4 19.Qd7+ Qb5 20.Qg4+ (17.603.477) 476 TB:27
30.01 1:05 0.00 7.Qd7+ Qb5 8.Qg4+ Qb4 9.Qd7+ Qb5 10.Qg4+ Qb4 11.Qd7+ Qb5 12.Qg4+ Qb4 13.Qd7+ Qb5 14.Qg4+ Qb4 15.Qd7+ Qb5 16.Qg4+ Qb4 17.Qd7+ Qb5 18.Qg4+ Qb4 19.Qd7+ Qb5 20.Qg4+ (30.653.406) 475 TB:59
31.01 1:50 0.00 7.Qd7+ Qb5 8.Qg4+ Qb4 9.Qd7+ Qb5 10.Qg4+ Qb4 11.Qd7+ Qb5 12.Qg4+ Qb4 13.Qd7+ Qb5 14.Qg4+ Qb4 15.Qd7+ Qb5 16.Qg4+ Qb4 17.Qd7+ Qb5 18.Qg4+ Qb4 19.Qd7+ Qb5 20.Qg4+ (51.460.115) 474 TB:141

*Qd7 forced*

31.00 0:00 0.00 7...Qb5 8.Qg4+ Qb4 9.Qd7+ Qb5 10.Qg4+ Qb4 11.Qd7+ Qb5 12.Qg4+ Qb4 13.Qd7+ Qb5 14.Qg4+ Qb4 15.Qd7+ Qb5 16.Qg4+ Qb4 17.Qd7+ Qb5 18.Qg4+ Qb4 19.Qd7+ Qb5 20.Qg4+ Qb4 (90) 5

*Qb5 forced*

31.00 0:46 0.00 8.Qg4+ Qb4 9.Qd7+ (21.382.134) 473 TB:86
32.01 2:46 0.00 8.Qg4+ Qb4 9.Qd7+ (76.958.206) 472 TB:369
33.01 5:16 0.00 8.Qg4+ Qb4 9.Qd7+ (141.866.018) 459 TB:859

*Qg4+ forced*

32.01 0:00 0.00 8...Qb4 (270.229) 477

*Qb4 forced*

33.00 0:00 0.00 9.Qd7+ (15.083) 321
34.01 0:49 0.00 9.Qd7+ (23.710.854) 488 TB:19
35.01 2:08 0.00 9.Qd7+ (61.814.964) 493 TB:275

*Qd7+ forced*

25.01 0:02 0.00 9...g4 (929.690) 420

*g4 forced*

29.01 0:02 0.00 10.Qd7+ Qb5 11.Qd4+ Qb4 (1.253.190) 477
30.01 0:36 0.00 10.Qd7+ Qb5 11.Qd4+ Qb4 12.Qd7+ Qb5 13.Qd4+ Qb4 14.Qd7+ Qb5 15.Qd4+ Qb4 16.Qd7+ Qb5 17.Qd4+ Qb4 18.Qd7+ Qb5 19.Qd4+ Qb4 20.Qd7+ Qb5 21.Qd4+ Qb4 22.Qd7+ Qb5 23.Qd4+ (16.375.571) 454 TB:53

*Qd7+ forced*

30.00 0:00 0.00 10...Qb5 11.Qd4+ Qb4 12.Qd7+ Qb5 13.Qd4+ Qb4 14.Qd7+ Qb5 15.Qd4+ Qb4 16.Qd7+ Qb5 17.Qd4+ Qb4 18.Qd7+ Qb5 19.Qd4+ Qb4 20.Qd7+ Qb5 21.Qd4+ Qb4 22.Qd7+ Qb5 23.Qd4+ Qb4 (87) 89

*Qb5 forced*

[D]8/3Q2p1/pp4p1/pq6/k5p1/8/K7/8 w - -

11.00 0:04 +7.43 11.Qxg4+ (2.891.998) 605
12.01 0:19 +6.90 11.Qxg4+ (12.159.628) 641
13.01 0:56 +8.21 11.Qxg4+ (35.077.780) 633 TB:3
14.01 4:53 +8.77 11.Qxg4+ (180.700.617) 629 TB:412

Now Rybka falls to the +5.12 bug and goes to slow motion.

But the last moments of analysis were really weird, no fail high or anything, just 0.00 one move, +7.43 the next, but it is entirely dependent of hash contents, for comparison here's Rybka on the last position with a clean hash:

19.01 0:01 0.00 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qg4+ Qb4 14.Qd7+ Qb5 15.Qg4+ Qb4 16.Qd7+ Qb5 17.Qg4+ Qb4 18.Qd7+ Qb5 19.Qg4+ Qb4 20.Qd7+ Qb5 21.Qg4+ Qb4 22.Qd7+ Qb5 23.Qg4+ Qb4 24.Qd7+ (755.723) 467
20.01 0:02 0.00 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qg4+ Qb4 14.Qd7+ Qb5 15.Qg4+ Qb4 16.Qd7+ Qb5 17.Qg4+ Qb4 18.Qd7+ Qb5 19.Qg4+ Qb4 20.Qd7+ Qb5 21.Qg4+ Qb4 22.Qd7+ Qb5 23.Qg4+ Qb4 24.Qd7+ (1.115.055) 477
21.01 0:03 0.00 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qg4+ Qb4 14.Qd7+ Qb5 15.Qg4+ Qb4 16.Qd7+ Qb5 17.Qg4+ Qb4 18.Qd7+ Qb5 19.Qg4+ Qb4 20.Qd7+ Qb5 21.Qg4+ Qb4 22.Qd7+ Qb5 23.Qg4+ Qb4 24.Qd7+ (1.600.949) 483
22.01 0:04 0.00 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qg4+ Qb4 14.Qd7+ Qb5 15.Qg4+ Qb4 16.Qd7+ Qb5 17.Qg4+ Qb4 18.Qd7+ Qb5 19.Qg4+ Qb4 20.Qd7+ Qb5 21.Qg4+ Qb4 22.Qd7+ Qb5 23.Qg4+ Qb4 24.Qd7+ (2.257.418) 483
23.01 0:07 0.00 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qg4+ Qb4 14.Qd7+ Qb5 15.Qg4+ Qb4 16.Qd7+ Qb5 17.Qg4+ Qb4 18.Qd7+ Qb5 19.Qg4+ Qb4 20.Qd7+ Qb5 21.Qg4+ Qb4 22.Qd7+ Qb5 23.Qg4+ Qb4 24.Qd7+ (3.314.369) 483 TB:1
24.01 0:10 0.00 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qg4+ Qb4 14.Qd7+ Qb5 15.Qg4+ Qb4 16.Qd7+ Qb5 17.Qg4+ Qb4 18.Qd7+ Qb5 19.Qg4+ Qb4 20.Qd7+ Qb5 21.Qg4+ Qb4 22.Qd7+ Qb5 23.Qg4+ Qb4 24.Qd7+ (4.744.132) 482 TB:4
25.01 0:14 0.00 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qg4+ Qb4 14.Qd7+ Qb5 15.Qg4+ Qb4 16.Qd7+ Qb5 17.Qg4+ Qb4 18.Qd7+ Qb5 19.Qg4+ Qb4 20.Qd7+ Qb5 21.Qg4+ Qb4 22.Qd7+ Qb5 23.Qg4+ Qb4 24.Qd7+ (6.832.356) 482 TB:10
26.01 0:21 0.00 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qg4+ Qb4 14.Qd7+ Qb5 15.Qg4+ Qb4 16.Qd7+ Qb5 17.Qg4+ Qb4 18.Qd7+ Qb5 19.Qg4+ Qb4 20.Qd7+ Qb5 21.Qg4+ Qb4 22.Qd7+ Qb5 23.Qg4+ Qb4 24.Qd7+ (10.054.506) 478 TB:23
27.01 0:31 0.00 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qg4+ Qb4 14.Qd7+ Qb5 15.Qg4+ Qb4 16.Qd7+ Qb5 17.Qg4+ Qb4 18.Qd7+ Qb5 19.Qg4+ Qb4 20.Qd7+ Qb5 21.Qg4+ Qb4 22.Qd7+ Qb5 23.Qg4+ Qb4 24.Qd7+ (14.795.006) 477 TB:38
28.01 0:47 0.00 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qg4+ Qb4 14.Qd7+ Qb5 15.Qg4+ Qb4 16.Qd7+ Qb5 17.Qg4+ Qb4 18.Qd7+ Qb5 19.Qg4+ Qb4 20.Qd7+ Qb5 21.Qg4+ Qb4 22.Qd7+ Qb5 23.Qg4+ Qb4 24.Qd7+ (22.162.892) 473 TB:75
29.01 1:24 0.00 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qg4+ Qb4 14.Qd7+ Qb5 15.Qg4+ Qb4 16.Qd7+ Qb5 17.Qg4+ Qb4 18.Qd7+ Qb5 19.Qg4+ Qb4 20.Qd7+ Qb5 21.Qg4+ Qb4 22.Qd7+ Qb5 23.Qg4+ Qb4 24.Qd7+ (38.671.831) 468 TB:244
30.01 2:11 0.00 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qg4+ Qb4 14.Qd7+ Qb5 15.Qg4+ Qb4 16.Qd7+ Qb5 17.Qg4+ Qb4 18.Qd7+ Qb5 19.Qg4+ Qb4 20.Qd7+ Qb5 21.Qg4+ Qb4 22.Qd7+ Qb5 23.Qg4+ Qb4 24.Qd7+ (60.245.195) 469 TB:378
31.01 3:27 0.00 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qg4+ Qb4 14.Qd7+ Qb5 15.Qg4+ Qb4 16.Qd7+ Qb5 17.Qg4+ Qb4 18.Qd7+ Qb5 19.Qg4+ Qb4 20.Qd7+ Qb5 21.Qg4+ Qb4 22.Qd7+ Qb5 23.Qg4+ Qb4 24.Qd7+ (94.341.137) 465 TB:877
32.01 5:29 0.00 11.Qxg4+ Qb4 12.Qd7+ Qb5 13.Qg4+ Qb4 14.Qd7+ Qb5 15.Qg4+ Qb4 16.Qd7+ Qb5 17.Qg4+ Qb4 18.Qd7+ Qb5 19.Qg4+ Qb4 20.Qd7+ Qb5 21.Qg4+ Qb4 22.Qd7+ Qb5 23.Qg4+ Qb4 24.Qd7+ (149.475.823) 465 TB:1.615

Does any other engine notice white is winning earlier than this?