test position: fortress

[jdart]

[D] 8/5q2/4kp1p/7R/6P1/5P2/6K1/8 w - - 0 79

This is from Salov-Korchnoi, Wijk aan Zee 1997. It is discussed in Mueller and Lambrecht's Fundamental Chess Endings.

Salov played Rb5 and a draw was soon agreed (Ra5 and Rc5 are ok, too). But White should not play Rxh6, and Kg3? leads to mate after Qxh5 gxh5 Kf5.

Commercial engines such as Fritz do not seem to have much trouble with this. Stockfish got it too after a short while. But generally speaking fortress draws are very difficult for programs.

--Jon

[ernest]

White should not play Rxh6

Takes Houdini only a few seconds (on dualcore) to avoid Rxh6 (but not with the right score...)

(1st try)
Analysis by Houdini 3 w32 Nlm:
1.Rxh6 Ke5 2.Kg3 Kd4 3.Rh1 Qc7+ 4.Kf2 Qc2+ 5.Kg3 Qc3 6.Rh8 Qc7+ 7.Kf2 Kd3 8.Kg2 Qe5 9.Kf2 Qe2+ 10.Kg3 Qe3 11.Rh5 Qg1+ 12.Kf4 Qd4+ 13.Kg3 Ke3 14.Rf5 Qa1 15.g5 Qg1+ 16.Kh4 Qh1+ 17.Kg4 Qg2+ 18.Kh5 fxg5 19.Rxg5 Qh3+ 20.Kg6 Qe6+ 21.Kh5 Kxf3 22.Ra5 Qg4+ 23.Kh6
-+ (-3.57) Depth: 23/45 00:00:07 25810kN, tb=28
1.Rxh6 Ke5
-+ (-3.72 --) Depth: 24/46 00:00:08 28632kN, tb=33
1.Rxh6 Ke5
-+ (-4.01 --) Depth: 24/51 00:00:09 32680kN, tb=49
1.Rxh6 Ke5 2.Kg3 Kd4 3.Rh1 Qc7+ 4.Kf2 Qc2+ 5.Kg3 Qc3 6.Rh7 Qc5 7.Rh1 Qb4 8.Rh8 Qe1+ 9.Kg2 Qe2+ 10.Kg3 Qe5+ 11.Kf2 Qe3+ 12.Kg3 Kd3 13.Rh5 Qg1+ 14.Kf4 Qf2 15.Rh3 Qc5 16.Rh5 Qc6 17.Rh3 Qe6 18.Rh5 Kd4 19.Kg3 Qe1+ 20.Kf4 Qe2 21.g5 Qe5+ 22.Kg4 f5+ 23.Kh3 Ke3 24.Kg2 Qb2+ 25.Kh3 Kxf3
-+ (-4.60) Depth: 24/65 00:00:18 67774kN, tb=203
1.Rc5 Qb7 2.Rh5 Qd7 3.Rf5 Qd3 4.Rh5 Qd2+ 5.Kg3 Qe1+ 6.Kg2 Qe2+ 7.Kg3 Qf1 8.Kf4 Qf2 9.Rb5 Kf7 10.Rb7+ Kg6 11.Rb5 Qd2+ 12.Kg3 Qe1+ 13.Kf4 Qe8 14.Rh5 Qb8+ 15.Ke3 Qb6+ 16.Kf4 Qd6+ 17.Ke3 Qb6+ 18.Kf4
-+ (-4.29) Depth: 24/65 00:00:30 117mN, tb=228
1.Rc5 Qb7 2.Rh5 Qd7 3.Rf5 Qd3 4.Rh5 Qe2+ 5.Kg3 Qf1 6.Kf4 Qf2 7.Rb5 Qh2+ 8.Ke3 Qg1+ 9.Kf4 Kf7 10.Rd5 Kg6 11.Rb5 Qh2+ 12.Ke3 Qa2 13.Rh5 Qa7+ 14.Kf4 Qc7+ 15.Ke3 Qb6+ 16.Kf4 Qd6+ 17.Ke3 Qb6+ 18.Kf4
-+ (-4.29) Depth: 25/65 00:00:33 129mN, tb=256
1.Rc5 Qb7 2.Rh5 Qd7 3.Rf5 Kf7 4.Kg3 Qd2 5.Rh5 Qe1+ 6.Kf4 Qg1 7.Rb5 Qh2+ 8.Ke3 Qd6 9.Rb7+ Ke6 10.Rb5 Qc6 11.Rh5 Qb6+ 12.Ke4 Qb3 13.Kf4 Qd3 14.Kg3 Qc3 15.Rb5 Qc7+ 16.Kf2 Qh2+ 17.Ke3 Qa2 18.Rh5 Qb2 19.Kf4 Qb8+ 20.Ke3 Qb4 21.Kf2 Qd4+ 22.Kg3 Qd7 23.Kg2 Qd3 24.Kg3 Qc3
-+ (-4.31) Depth: 26/65 00:00:38 148mN, tb=342