... in my list of unknowns and it seems to have come from the ECE3 test suite, at least that is what Dann provided over a decade ago at this site:

http://www.open-aurec.com/wbforum/viewt ... 23#p185631

Well, the first move (Rb8+) is easy for a computer, as it eventually avoids the draw, but finding the mate score was an ordeal. The only engine I could get a score out of was H6/T1 with Nalimov-6 which settled on M52 at depth 24 in 34 seconds on my PC (see signature block for details).

I then tried all the usually suspects and although a lot of them found the win (Syzygy engines), none could resolve the win to a score.

I only have 16Gb hash, so perhaps those with mega builds can see if any other engines can find it.

Code: Select all

```
FEN: 5R2/8/7P/p7/6P1/5K1b/1kP5/4r3 w - - 0 1
Houdini 6 (N6):
8 00:00 218,945 2,065,000 +0.34 1.Rf5 Rg1 2.Rb5+ Kc3 3.g5 Rf1+ 4.Kg3 Bf5
9 00:00 437,890 2,329,000 +0.05 1.Rf5 a4 2.Rb5+ Kxc2 3.g5 Rf1+ 4.Ke3 Bf5 5.Ra5 a3 6.Rxa3
10 00:00 510,297 2,180,000 +0.29 1.Rf5 Rf1+ 2.Ke4 Re1+ 3.Kf4 Rf1+ 4.Ke5 Re1+ 5.Kf6 Bxg4 6.Rf4
11 00:00 1,198,867 2,110,000 +0.37 1.Rb8+ Kxc2 2.g5 Rf1+ 3.Ke2 Rh1 4.Ra8 Be6 5.Rxa5 Kc3 6.Re5 Bf7 7.Re7 Bg6 8.Rg7
12 00:01 2,642,440 2,317,000 +0.10 1.Rb8+ Kxc2 2.g5 Rf1+ 3.Ke3 Re1+ 4.Kf2 Rh1 5.Ra8 Be6 6.Rxa5 Kd3 7.Re5 Bc8 8.Kf3
13 00:01 3,085,763 2,431,000 0.00 1.Rb8+ Kxc2 2.g5 Rf1+ 3.Ke3 Re1+ 4.Kf2 Rh1 5.Ra8 Be6 6.Rxa5 Kd3 7.Re5 Bc8 8.Kg2 Rh5
14 00:01 3,281,810 2,450,000 0.00 1.Rb8+ Kxc2 2.g5 Rf1+ 3.Ke3 Re1+ 4.Kf2 Rh1 5.Ra8 Be6 6.Rxa5 Kd3 7.Re5 Bc8 8.Kg2 Rh5
15 00:01 3,807,147 2,394,000 0.00 1.Rb8+ Kxc2 2.g5 Rf1+ 3.Ke3 Re1+ 4.Kf2 Rh1 5.Ra8 Be6 6.Rxa5 Kd3 7.Re5 Bc8 8.Kg2 Rh5
16 00:03 7,188,467 2,179,000 +3.53 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kc1 4.Rh2 Rxh2 5.Kg3 Rd2 6.h8Q Rd3+ 7.Kh4 Ra3 8.Qd4 Kb1 9.g5 Bc8 10.Qd1+ Kb2 11.Qe2+ Kb3 12.Qe3+ Kb2 13.Qf2+ Kb1 14.Qg1+ Ka2
17 00:03 7,854,162 2,190,000 +3.54 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kc1 4.Rh2 Rxh2 5.Kg3 Rd2 6.h8Q Rd3+ 7.Kh4 Ra3 8.Qd4 Kb1 9.g5 Bc8 10.Qd1+ Kb2 11.Qe2+ Kb1 12.Qe4+ Kb2 13.Qe5+ Ka2 14.Qh2+ Ka1 15.Qg1+ Ka2
18+ 00:04 9,160,378 2,256,000 +4.41 1.Rb8+
18+ 00:04 9,663,546 2,282,000 +4.77 1.Rb8+
18- 00:04 9,981,530 2,290,000 +4.48 1.Rb8+ Kxc2
18+ 00:04 10,692,202 2,300,000 +4.86 1.Rb8+
18- 00:04 10,827,268 2,306,000 +4.37 1.Rb8+ Kxc2
18+ 00:04 11,186,932 2,332,000 +5.00 1.Rb8+
18 00:04 11,515,721 2,361,000 +5.35 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kc1 4.Rh2 Rxh2 5.Kg3 Rb2 6.h8Q Rb3+ 7.Kh4 Kb1 8.Qd4 Ra3 9.Qg1+ Ka2 10.Qf2+ Ka1 11.Qc2 a4 12.g5 Rb3 13.Qc4 Ra3 14.Qd4+ Kb1
18 00:04 11,523,780 2,360,000 +5.35 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kc1 4.Rh2 Rxh2 5.Kg3 Rb2 6.h8Q Rb3+ 7.Kh4 Kb1 8.Qd4 Ra3 9.Qg1+ Ka2 10.Qf2+ Ka1 11.Qc2 a4 12.g5 Rb3 13.Qc4 Ra3 14.Qd4+ Kb1
19+ 00:05 11,905,017 2,379,000 +5.42 1.Rb8+
19+ 00:05 12,135,298 2,397,000 +5.49 1.Rb8+
19+ 00:05 13,118,612 2,478,000 +5.95 1.Rb8+
19- 00:05 13,261,660 2,482,000 +5.79 1.Rb8+ Kxc2
19- 00:05 13,673,498 2,476,000 +4.96 1.Rb8+ Kxc2
19+ 00:05 13,899,286 2,479,000 +5.34 1.Rb8+
19+ 00:06 15,788,402 2,524,000 +7.10 1.Rb8+
19- 00:06 15,828,195 2,527,000 +6.29 1.Rb8+ Kxc2
19 00:06 16,013,208 2,530,000 +6.18 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kc1 4.Rh2 Rxh2 5.Kg3 Rd2 6.h8Q Rd3+ 7.Kh4 Ra3 8.Qd4 Kb1 9.Qc5 Ka2 10.g5 a4 11.Qd4 Kb1 12.g6 Ka2 13.Qd2+ Ka1 14.Qc1+
19 00:06 16,013,853 2,531,000 +6.18 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kc1 4.Rh2 Rxh2 5.Kg3 Rd2 6.h8Q Rd3+ 7.Kh4 Ra3 8.Qd4 Kb1 9.Qc5 Ka2 10.g5 a4 11.Qd4 Kb1 12.g6 Ka2 13.Qd2+ Ka1 14.Qc1+
20+ 00:06 16,306,226 2,539,000 +6.25 1.Rb8+
20- 00:06 16,494,874 2,543,000 +6.18 1.Rb8+ Kxc2
20+ 00:06 17,477,290 2,597,000 +6.25 1.Rb8+
20+ 00:09 27,380,052 2,765,000 +10.08 1.Rb8+
20- 00:09 27,435,299 2,764,000 +9.27 1.Rb8+ Kxc2
20+ 00:10 30,384,474 2,857,000 +10.30 1.Rb8+
20- 00:10 30,448,186 2,860,000 +8.99 1.Rb8+ Kxc2
20+ 00:11 32,871,550 2,888,000 +10.64 1.Rb8+
20- 00:11 33,027,827 2,888,000 +8.56 1.Rb8+ Kxc2
20+ 00:12 35,967,633 2,920,000 +11.18 1.Rb8+
20 00:12 38,311,361 2,987,000 +11.38 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kc1 4.Rh2 Rxh2 5.Kg3 Rd2 6.h8Q Rd3+ 7.Kh4 Ra3 8.Qd4 Kb1 9.Qc5 Kb2 10.g5 Ka2 11.g6 a4 12.Qf2+ Kb1 13.Qe1+ Kc2 14.Qe4+ Kb2 15.Qb4+
20 00:12 38,327,005 2,987,000 +11.38 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kc1 4.Rh2 Rxh2 5.Kg3 Rd2 6.h8Q Rd3+ 7.Kh4 Ra3 8.Qd4 Kb1 9.Qc5 Kb2 10.g5 Ka2 11.g6 a4 12.Qf2+ Kb1 13.Qe1+ Kc2 14.Qe4+ Kb2 15.Qb4+
21- 00:12 38,488,596 2,991,000 +11.31 1.Rb8+ Kxc2
21- 00:13 39,039,730 3,000,000 +11.24 1.Rb8+ Kxc2
21- 00:13 40,303,096 3,013,000 +7.31 1.Rb8+ Kxc2
21+ 00:13 41,483,208 3,011,000 +8.11 1.Rb8+
21+ 00:13 41,926,653 3,018,000 +9.69 1.Rb8+
21- 00:13 42,040,594 3,018,000 +8.39 1.Rb8+ Kxc2
21+ 00:14 42,722,408 3,022,000 +10.04 1.Rb8+
21- 00:14 42,780,950 3,023,000 +7.96 1.Rb8+ Kxc2
21+ 00:14 43,226,750 3,029,000 +10.57 1.Rb8+
21 00:14 45,396,979 3,075,000 +11.94 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kc1 4.Rh2 Rxh2 5.Kg3 Rd2 6.h8Q Rd3+ 7.Kh4 Ra3 8.Qd4 Kb1 9.Qc5 Ka2 10.g5 a4 11.g6 Rb3 12.Qd5 Bf1 13.g7 Ka3 14.Qd6+ Kb2
21 00:14 45,398,340 3,075,000 +11.94 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kc1 4.Rh2 Rxh2 5.Kg3 Rd2 6.h8Q Rd3+ 7.Kh4 Ra3 8.Qd4 Kb1 9.Qc5 Ka2 10.g5 a4 11.g6 Rb3 12.Qd5 Bf1 13.g7 Ka3 14.Qd6+ Kb2
22- 00:14 45,544,210 3,077,000 +11.87 1.Rb8+ Kxc2
22- 00:14 45,684,675 3,077,000 +11.80 1.Rb8+ Kxc2
22- 00:15 47,785,069 3,098,000 +8.85 1.Rb8+ Kxc2
22+ 00:15 49,236,037 3,124,000 +9.48 1.Rb8+
22- 00:15 49,347,482 3,126,000 +8.67 1.Rb8+ Kxc2
22+ 00:16 50,217,121 3,137,000 +9.70 1.Rb8+
22+ 00:16 51,883,929 3,151,000 +11.70 1.Rb8+
22- 00:16 52,011,315 3,151,000 +10.05 1.Rb8+ Kxc2
22+ 00:16 52,830,148 3,154,000 +12.13 1.Rb8+
22- 00:16 52,884,076 3,154,000 +9.51 1.Rb8+ Kxc2
22+ 00:16 53,652,905 3,169,000 +12.80 1.Rb8+
22- 00:16 53,691,137 3,169,000 +8.67 1.Rb8+ Kxc2
22+ 00:17 55,414,061 3,198,000 +13.85 1.Rb8+
22 00:23 73,493,645 3,092,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
22 00:23 73,509,308 3,092,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
23- 00:24 74,157,195 3,086,000 +M59 1.Rb8+ Kxc2
23- 00:30 93,707,744 3,046,000 +M66 1.Rb8+ Kxc2
23- 00:30 94,209,940 3,049,000 +15.05 1.Rb8+ Kxc2
23 00:32 98,236,470 3,033,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
23 00:32 98,236,614 3,033,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
24- 00:32 98,394,481 3,032,000 +M59 1.Rb8+ Kxc2
24- 00:32 98,506,581 3,033,000 +M66 1.Rb8+ Kxc2
24- 00:32 99,554,069 3,034,000 +93.60 1.Rb8+ Kc1
24 00:34 106,179,770 3,082,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
24 00:34 106,180,302 3,082,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
25 00:36 111,429,180 3,077,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
25 00:36 111,477,779 3,076,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
26 00:41 129,379,459 3,135,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
26 00:41 129,428,896 3,135,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
27 00:46 145,870,539 3,120,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
27 00:46 145,961,089 3,120,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
28 00:49 156,090,022 3,162,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
28 00:49 156,276,108 3,163,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
29 01:02 196,010,008 3,125,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
29 01:02 196,268,339 3,125,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
30 01:07 215,917,538 3,182,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
30 01:08 218,687,417 3,185,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
31 01:21 261,575,243 3,208,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
31 01:21 262,581,776 3,209,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
32 01:46 351,976,574 3,320,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
32 01:46 355,586,348 3,327,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
33 01:54 387,253,562 3,391,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
33 01:55 391,091,925 3,391,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
34 02:44 559,071,932 3,407,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
34 02:45 562,075,702 3,404,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
35 05:36 1,092,371,697 3,244,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
35 05:38 1,096,036,190 3,240,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
36 06:13 1,208,160,906 3,233,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
36 06:25 1,242,908,134 3,227,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
37 06:46 1,315,925,570 3,238,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
37 06:50 1,329,814,668 3,240,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
38 08:18 1,607,261,844 3,222,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
38 08:39 1,669,141,693 3,212,000 +M52 1.Rb8+ Kxc2 2.h7 Rh1 3.Rb2+ Kd3 4.Rh2 Rxh2 5.Kg3 Re2 6.h8Q Re3+ 7.Kh4 Bf1 8.Qd8+ Kc2 9.Qxa5
```