Some fun positions from my collection

[Rebel]

Position 3

[fen]N7/PPPPPPPP/K1k3rB/b1pnnb1p/8/1r6/pp3p2/7q w - -[/fen]
Promotions again, 8 knight promotions leading to a mate in 8 moves.

Not many engines find it quickly.

[Ajedrecista]

Hello Ed:

Position 3

[fen]N7/PPPPPPPP/K1k3rB/b1pnnb1p/8/1r6/pp3p2/7q w - -[/fen]
Promotions again, 8 knight promotions leading to a mate in 8 moves.

Not many engines find it quickly.

That is a funny composition, I saw it a few years ago. I have just realised that the problem was published in 1964, long time ago!

https://yacpdb.org/#274729

The whole pattern of knight underpromotions is amazing indeed.

Regards from Spain.

Ajedrecista.

[amanjpro]

Position 3

[fen]N7/PPPPPPPP/K1k3rB/b1pnnb1p/8/1r6/pp3p2/7q w - -[/fen]
Promotions again, 8 knight promotions leading to a mate in 8 moves.

Not many engines find it quickly.

Zahak has no issue with this one:

Code: Select all

position fen N7/PPPPPPPP/K1k3rB/b1pnnb1p/8/1r6/pp3p2/7q w - -
go infinite
info depth 1 seldepth 3 hashfull 0 nodes 12004 nps 609134 score cp -1923 time 19 pv c7c8q d5c7 a8c7
info depth 2 seldepth 4 hashfull 0 nodes 151677 nps 805610 score cp -1409 time 188 pv b7b8n c6d6 d7d8q f5d7
info depth 3 seldepth 6 hashfull 0 nodes 361520 nps 898321 score cp -1074 time 402 pv b7b8n c6d6 c7c8n d6e6 e7e8q d5e7
info depth 4 seldepth 13 hashfull 0 nodes 373148 nps 885799 score cp -1345 time 421 pv b7b8n c6d6 c7c8n d6e6 e7e8q d5e7 e8e7 e6d5 a8b6 b3b6 c8b6 g6b6 a6a5
info depth 5 seldepth 15 hashfull 0 nodes 428706 nps 902690 score cp -1543 time 474 pv b7b8n c6d6 c7c8n d6e6 e7e8q d5e7 e8e7 e6d5 a8b6 b3b6 c8b6 g6b6 a6a5 a2a1q a5b6
info depth 6 seldepth 12 hashfull 0 nodes 613357 nps 868654 score cp -908 time 706 pv b7b8n b3b8 a7b8n c6d6 d7d8q e5d7 e7e8n d6e5 a6a7 a5c7 b8d7 f5d7
info depth 7 seldepth 10 hashfull 0 nodes 680583 nps 852572 score cp -712 time 798 pv b7b8n c6d6 c7c8n d6e6 d7d8n a5d8 e7d8n e6f6 f7f8q e5f7
info depth 8 seldepth 10 hashfull 0 nodes 681078 nps 852159 score cp -712 time 799 pv b7b8n c6d6 c7c8n d6e6 d7d8n a5d8 e7d8n e6f6 f7f8q e5f7
info depth 9 seldepth 8 hashfull 0 nodes 689494 nps 852864 score cp -691 time 808 pv b7b8n b3b8 a7b8n c6d6 c7c8n d6e6 e7e8q d5e7
info depth 10 seldepth 13 hashfull 0 nodes 743590 nps 856615 score cp -641 time 868 pv b7b8n b3b8 a7b8n c6d6 c7c8n d6e6 e7e8q d5e7 e8e7 e6d5 a6a7 f2f1q f7f8q
info depth 11 seldepth 13 hashfull 0 nodes 753276 nps 853672 score cp -641 time 882 pv b7b8n b3b8 a7b8n c6d6 c7c8n d6e6 e7e8q d5e7 e8e7 e6d5 a6a7 f2f1q f7f8q
info depth 12 seldepth 14 hashfull 0 nodes 850306 nps 849368 score cp -530 time 1001 pv b7b8n b3b8 a7b8n c6d6 c7c8n d6e6 e7e8q d5e7 e8e7 e6d5 a6a7 f2f1q f7f8q b2b1q
info depth 13 seldepth 21 hashfull 0 nodes 953104 nps 838508 score cp -366 time 1136 pv b7b8n c6d6 c7c8n d6e6 d7d8n a5d8 e7d8n e6f6 f7f8q e5f7 f8f7 f6e5 b8c6 g6c6 d8c6 e5e4 f7d5 e4d5 g7g8q d5c6 h7h8q
info depth 14 seldepth 20 hashfull 0 nodes 1026661 nps 842179 score cp -175 time 1219 pv b7b8n c6d6 c7c8n d6e6 d7d8n a5d8 e7d8n e6f6 f7f8q e5f7 f8f7 f6e5 b8c6 e5e4 f7d5 e4d5 g7g8q f5e6 a8c7 d5c4
info depth 15 seldepth 22 hashfull 0 nodes 1040560 nps 843416 score cp 27 time 1233 pv b7b8n b3b8 a7b8n c6d6 c7c8n d6e6 d7d8n a5d8 e7d8n e6f6 f7f8q e5f7 f8f7 f6e5 b8c6 e5e4 f7d5 e4d5 g7g8q d5e4 g8c4 e4f3
info depth 16 seldepth 15 hashfull 0 nodes 1146407 nps 846557 score mate +7 time 1354 pv b7b8n b3b8 a7b8n c6d6 c7c8n d6e6 d7d8n a5d8 e7d8n e6f6 g7g8n g6g8 h7g8n f6g6 f7f8n
info depth 16 seldepth 15 hashfull 0 nodes 1146407 nps 846529 score mate +7 time 1354 pv b7b8n b3b8 a7b8n c6d6 c7c8n d6e6 d7d8n a5d8 e7d8n e6f6 g7g8n g6g8 h7g8n f6g6 f7f8n
bestmove b7b8n ponder b3b8

[MonteCarlo]

Zahak needed quiet sometime to find the mate:

Code: Select all

position fen 2n5/kP6/8/K7/4B3/8/8/8 w - - 0 1
go infinite
info depth 1 seldepth 1 hashfull 0 nodes 48 nps 704897 score cp 1527 time 0 pv b7c8q
info depth 2 seldepth 2 hashfull 0 nodes 253 nps 1054592 score cp 813 time 0 pv b7c8b a7b8
info depth 3 seldepth 3 hashfull 0 nodes 920 nps 1484261 score cp 812 time 0 pv b7c8b a7b8 c8d7
info depth 4 seldepth 4 hashfull 0 nodes 981 nps 1484802 score cp 752 time 0 pv b7c8b a7b8 c8d7 b8c7
info depth 5 seldepth 6 hashfull 0 nodes 1881 nps 1150576 score cp 692 time 1 pv b7c8n a7b8 c8d6 b8c7 d6c4 c7d7
info depth 6 seldepth 6 hashfull 0 nodes 2220 nps 1095484 score cp 731 time 2 pv b7c8b a7b8 c8h3 b8c7 h3g4 c7d6
info depth 7 seldepth 5 hashfull 0 nodes 2323 nps 1106646 score cp 738 time 2 pv b7c8b a7b8 c8e6 b8c7 e6a2
info depth 8 seldepth 5 hashfull 0 nodes 2587 nps 1156098 score cp 760 time 2 pv b7c8b a7b8 c8g4 b8c7 a5b4
info depth 9 seldepth 8 hashfull 0 nodes 3448 nps 1318522 score cp 777 time 2 pv b7c8b a7b8 c8g4 b8c7 a5b5 c7d6 b5b6 d6e5
info depth 10 seldepth 10 hashfull 0 nodes 7460 nps 1749965 score cp 771 time 4 pv b7c8b a7b8 c8a6 b8c7 a6d3 c7d6 a5b6 d6e5 b6c7 e5d4
info depth 11 seldepth 10 hashfull 0 nodes 10616 nps 1923746 score cp 779 time 5 pv b7c8b a7b8 c8e6 b8c7 e6d5 c7d6 a5b6 d6e5 b6c7 e5d4
info depth 12 seldepth 12 hashfull 0 nodes 18070 nps 2067882 score cp 771 time 8 pv b7c8b a7b8 c8g4 b8c7 g4f5 c7d6 a5b6 d6e5 b6c7 e5d4 c7d6 d4e3
info depth 13 seldepth 12 hashfull 0 nodes 19369 nps 2076358 score cp 771 time 9 pv b7c8b a7b8 c8g4 b8c7 g4f5 c7d6 a5b6 d6e5 b6c7 e5d4 c7d6 d4e3
info depth 14 seldepth 14 hashfull 0 nodes 27122 nps 2140088 score cp 796 time 12 pv b7c8b a7b8 c8g4 b8c7 g4f5 c7d6 a5b6 d6e5 b6c5 e5f4 c5d6 f4e3 e4d5 e3f2
info depth 15 seldepth 16 hashfull 1 nodes 113799 nps 2285683 score cp 796 time 49 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6d5 d6e5 b5c5 e5f4 c5d6 f4e3 e4g6 e3e2 g6f5 e2f2
info depth 16 seldepth 18 hashfull 1 nodes 170654 nps 2353371 score cp 790 time 72 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6d5 d6e5 b5c5 e5f4 c5d6 f4e3 e4g6 e3f2 g6d3 f2e3 d3b5 e3f2
info depth 17 seldepth 19 hashfull 2 nodes 272510 nps 2449385 score cp 794 time 111 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6d5 d6e5 b5c5 e5f4 c5d6 f4e3 e4g6 e3f2 d6c7 f2e2 g6f5 e2e3 c7d6
info depth 18 seldepth 20 hashfull 4 nodes 524830 nps 2538152 score cp 790 time 206 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6d5 d6e5 b5c5 e5f4 c5d6 f4e3 e4g6 e3d4 g6f5 d4e3 f5d7 e3e2 d6c7 e2d3
info depth 19 seldepth 20 hashfull 4 nodes 566362 nps 2538404 score cp 815 time 223 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g3 d4e3 g3h4 e3f4 h4h5 e4d5 h5h6 f4e5 h6g5
info depth 20 seldepth 23 hashfull 7 nodes 779766 nps 2504734 score cp 828 time 311 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g3 d4e3 g3h2 e4d5 h2g3 f5d7 g3h4 e3f4 h4h5 f4f5 h5h4 f5f6
info depth 21 seldepth 27 hashfull 15 nodes 1499698 nps 2503139 score cp 835 time 599 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g3 d4e3 g3h4 e3f4 h4h5 e4d5 h5h4 f5d7 h4h5 f4e5 h5g6 d7f5 g6g5 d5c4 g5h5 e5d6
info depth 22 seldepth 23 hashfull 32 nodes 3873028 nps 2566210 score cp 835 time 1509 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h5 e5f4 h5h6 e4d5 h6h5 f4e5 h5g5 d5c4 g5h5 e5d6
info depth 23 seldepth 27 hashfull 35 nodes 4336240 nps 2573653 score cp 837 time 1684 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h5 e5f4 h5h6 e4d5 h6h5 d5f3 h5h6 f5d3 h6g7 f4e5 g7f7 d3f5 f7e8 e5d6
info depth 24 seldepth 25 hashfull 49 nodes 6356590 nps 2564557 score cp 837 time 2478 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h5 e5f4 h5h4 f5e6 h4h5 e4f5 h5h6 f5d3 h6h5 e6d5 h5h4 f4e5
info depth 25 seldepth 26 hashfull 84 nodes 14198181 nps 2502577 score cp 820 time 5673 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h5 e5f4 h5h4 f5e6 h4h5 e6d7 h5h6 f4e5 h6g5 e4d5 g5g6 e5d6 g6f6
info depth 26 seldepth 28 hashfull 86 nodes 14658449 nps 2500517 score cp 823 time 5862 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h5 e5f4 h5h4 f5e6 h4h5 e4f5 h5h6 f4e5 h6g5 f5d3 g5h4 e5f4 h4h5 e6d5 h5h6
info depth 27 seldepth 29 hashfull 107 nodes 17228849 nps 2480765 score cp 835 time 6944 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h5 e5f4 h5h4 f5e6 h4h5 e4f5 h5h6 e6d5 h6h5 f5d3 h5h4 d3f1 h4h5 f1b5 h5h4 f4e5
info depth 28 seldepth 31 hashfull 175 nodes 30035944 nps 2421466 score cp 823 time 12404 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h5 e5f4 h5h4 f5e6 h4h5 e4f5 h5h4 f5h3 h4h5 h3g4 h5h4 g4f5 h4h5 e6d5 h5h6 f4g4 h6g7 g4g5
info depth 29 seldepth 31 hashfull 177 nodes 30842304 nps 2422793 score cp 830 time 12730 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h6 e4f3 h6g5 f3d5 g5h5 e5f4 h5h4 d5e4 h4h5 e4f3 h5h4 f3d5 h4h5 f5e4 h5h4 e4d3 h4h3 f4e5
info depth 30 seldepth 33 hashfull 240 nodes 42232254 nps 2403326 score cp 825 time 17572 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h6 e5f4 h6h5 f5e6 h5h4 e6c8 h4h5 e4f3 h5h4 f4e3 h4g5 e3d4 g5g6 d4e5 g6g7 c8f5 g7f7 f3e4 f7f8 e5d6
info depth 31 seldepth 31 hashfull 254 nodes 48759266 nps 2394733 score cp 835 time 20361 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e4f5 d6e5 f5h3 e5f4 b5c5 f4g3 c5d4 g3h4 h3g4 h4g5 d4e5 g5g6 e5f4 g6g7 e6d5 g7g6 f4e4 g6g7 e4d4 g7f8 g4h3 f8g7 d4e5 g7h6 h3f5
info depth 32 seldepth 33 hashfull 387 nodes 78661636 nps 2375737 score cp 833 time 33110 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e4d5 d6e7 b5c5 e7f6 c5d4 f6g6 d4e4 g6g5 e4f3 g5h5 f3g3 h5g5 e6g4 g5h6 g3f4 h6g6 d5e4 g6f6 e4f5 f6e7 f4e5 e7f8 f5e4 f8f7 g4f5 f7f8 e4d5
info depth 33 seldepth 33 hashfull 462 nodes 135078846 nps 2300947 score cp 831 time 58705 pv b7c8b a7b8 c8e6 b8c7 e4d5 c7d8 d5c4 d8e8 a5b5 e8e7 b5c5 e7f6 e6c8 f6e5 c4d5 e5f6 c5d4 f6g6 d4e3 g6g5 c8e6 g5g6 e3f4 g6h5 e6f5 h5h4 f4e3 h4g3 d5g8 g3g2 e3f4 g2g1 g8d5
info depth 34 seldepth 36 hashfull 471 nodes 150877686 nps 2304782 score cp 843 time 65462 pv b7c8b a7b8 c8e6 b8c7 e4d5 c7d8 a5b4 d8e7 b4c5 e7f6 c5d6 f6g5 d6e5 g5h4 e5f4 h4h5 e6g4 h5h4 g4f5 h4h5 f4g3 h5g5 d5e4 g5h5 e4g2 h5g5 f5g4 g5f6 g3f4 f6e7 f4e5 e7f8 g2d5 f8g7 g4f5 g7f8
info depth 35 seldepth 38 hashfull 512 nodes 174607813 nps 2295258 score cp 853 time 76073 pv b7c8n a7b8 c8d6 b8c7 d6f5 c7d7 e4d5 d7e8 a5b6 e8f8 b6c7 f8e8 c7c6 e8f8 c6d6 f8e8 d6e6 e8f8 d5c6 f8g8 e6e7 g8h7 c6e8 h7g8 e8f7 g8h7 f7h5 h7g8 e7e6 g8h8 e6f7 h8h7 h5e2 h7h8 e2g4 h8h7 g4f3 h7h8
info depth 36 seldepth 40 hashfull 533 nodes 190390038 nps 2288433 score cp 859 time 83196 pv b7c8n a7b8 c8d6 b8c7 d6f5 c7d7 e4d5 d7e8 a5b6 e8f8 b6c7 f8e8 c7c6 e8f8 c6d6 f8e8 d6e6 e8f8 d5c6 f8g8 e6e7 g8h7 c6e8 h7g8 e8f7 g8h7 f7h5 h7g8 h5e8 g8h7 e7f7 h7h8 e8d7 h8h7 d7b5 h7h8 b5c6 h8h7 c6d5 h7h8
info depth 37 seldepth 17 hashfull 586 nodes 270009288 nps 2268408 score cp 821 time 119030 pv b7c8n a7b8 c8d6 b8c7 d6f5 c7d7 e4d5 d7c7 d5f7 c7b8 f7e6 b8c7 a5b4 c7b7 e6b3 b7a8 b4c5
info depth 38 seldepth 23 hashfull 587 nodes 287380396 nps 2248316 score mate +11 time 127820 pv b7c8n a7b8 c8d6 b8c7 d6f5 c7d7 e4d5 d7c7 a5b5 c7b8 b5b6 b8c8 d5c6 c8b8 c6d7 b8a8 f5e7 a8b8 d7c8 b8a8 c8b7 a8b8 e7c6
info depth 38 seldepth 23 hashfull 587 nodes 287380396 nps 2248315 score mate +11 time 127820 pv b7c8n a7b8 c8d6 b8c7 d6f5 c7d7 e4d5 d7c7 a5b5 c7b8 b5b6 b8c8 d5c6 c8b8 c6d7 b8a8 f5e7 a8b8 d7c8 b8a8 c8b7 a8b8 e7c6
bestmove b7c8n ponder a7b8

Does that output indicate your engine thinks it's mate in 11? Might be some issue with mate reporting if so (the correct mate is longer, mate in
26 I think).

Cheers!

[amanjpro]

Zahak needed quiet sometime to find the mate:

Code: Select all

position fen 2n5/kP6/8/K7/4B3/8/8/8 w - - 0 1
go infinite
info depth 1 seldepth 1 hashfull 0 nodes 48 nps 704897 score cp 1527 time 0 pv b7c8q
info depth 2 seldepth 2 hashfull 0 nodes 253 nps 1054592 score cp 813 time 0 pv b7c8b a7b8
info depth 3 seldepth 3 hashfull 0 nodes 920 nps 1484261 score cp 812 time 0 pv b7c8b a7b8 c8d7
info depth 4 seldepth 4 hashfull 0 nodes 981 nps 1484802 score cp 752 time 0 pv b7c8b a7b8 c8d7 b8c7
info depth 5 seldepth 6 hashfull 0 nodes 1881 nps 1150576 score cp 692 time 1 pv b7c8n a7b8 c8d6 b8c7 d6c4 c7d7
info depth 6 seldepth 6 hashfull 0 nodes 2220 nps 1095484 score cp 731 time 2 pv b7c8b a7b8 c8h3 b8c7 h3g4 c7d6
info depth 7 seldepth 5 hashfull 0 nodes 2323 nps 1106646 score cp 738 time 2 pv b7c8b a7b8 c8e6 b8c7 e6a2
info depth 8 seldepth 5 hashfull 0 nodes 2587 nps 1156098 score cp 760 time 2 pv b7c8b a7b8 c8g4 b8c7 a5b4
info depth 9 seldepth 8 hashfull 0 nodes 3448 nps 1318522 score cp 777 time 2 pv b7c8b a7b8 c8g4 b8c7 a5b5 c7d6 b5b6 d6e5
info depth 10 seldepth 10 hashfull 0 nodes 7460 nps 1749965 score cp 771 time 4 pv b7c8b a7b8 c8a6 b8c7 a6d3 c7d6 a5b6 d6e5 b6c7 e5d4
info depth 11 seldepth 10 hashfull 0 nodes 10616 nps 1923746 score cp 779 time 5 pv b7c8b a7b8 c8e6 b8c7 e6d5 c7d6 a5b6 d6e5 b6c7 e5d4
info depth 12 seldepth 12 hashfull 0 nodes 18070 nps 2067882 score cp 771 time 8 pv b7c8b a7b8 c8g4 b8c7 g4f5 c7d6 a5b6 d6e5 b6c7 e5d4 c7d6 d4e3
info depth 13 seldepth 12 hashfull 0 nodes 19369 nps 2076358 score cp 771 time 9 pv b7c8b a7b8 c8g4 b8c7 g4f5 c7d6 a5b6 d6e5 b6c7 e5d4 c7d6 d4e3
info depth 14 seldepth 14 hashfull 0 nodes 27122 nps 2140088 score cp 796 time 12 pv b7c8b a7b8 c8g4 b8c7 g4f5 c7d6 a5b6 d6e5 b6c5 e5f4 c5d6 f4e3 e4d5 e3f2
info depth 15 seldepth 16 hashfull 1 nodes 113799 nps 2285683 score cp 796 time 49 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6d5 d6e5 b5c5 e5f4 c5d6 f4e3 e4g6 e3e2 g6f5 e2f2
info depth 16 seldepth 18 hashfull 1 nodes 170654 nps 2353371 score cp 790 time 72 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6d5 d6e5 b5c5 e5f4 c5d6 f4e3 e4g6 e3f2 g6d3 f2e3 d3b5 e3f2
info depth 17 seldepth 19 hashfull 2 nodes 272510 nps 2449385 score cp 794 time 111 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6d5 d6e5 b5c5 e5f4 c5d6 f4e3 e4g6 e3f2 d6c7 f2e2 g6f5 e2e3 c7d6
info depth 18 seldepth 20 hashfull 4 nodes 524830 nps 2538152 score cp 790 time 206 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6d5 d6e5 b5c5 e5f4 c5d6 f4e3 e4g6 e3d4 g6f5 d4e3 f5d7 e3e2 d6c7 e2d3
info depth 19 seldepth 20 hashfull 4 nodes 566362 nps 2538404 score cp 815 time 223 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g3 d4e3 g3h4 e3f4 h4h5 e4d5 h5h6 f4e5 h6g5
info depth 20 seldepth 23 hashfull 7 nodes 779766 nps 2504734 score cp 828 time 311 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g3 d4e3 g3h2 e4d5 h2g3 f5d7 g3h4 e3f4 h4h5 f4f5 h5h4 f5f6
info depth 21 seldepth 27 hashfull 15 nodes 1499698 nps 2503139 score cp 835 time 599 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g3 d4e3 g3h4 e3f4 h4h5 e4d5 h5h4 f5d7 h4h5 f4e5 h5g6 d7f5 g6g5 d5c4 g5h5 e5d6
info depth 22 seldepth 23 hashfull 32 nodes 3873028 nps 2566210 score cp 835 time 1509 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h5 e5f4 h5h6 e4d5 h6h5 f4e5 h5g5 d5c4 g5h5 e5d6
info depth 23 seldepth 27 hashfull 35 nodes 4336240 nps 2573653 score cp 837 time 1684 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h5 e5f4 h5h6 e4d5 h6h5 d5f3 h5h6 f5d3 h6g7 f4e5 g7f7 d3f5 f7e8 e5d6
info depth 24 seldepth 25 hashfull 49 nodes 6356590 nps 2564557 score cp 837 time 2478 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h5 e5f4 h5h4 f5e6 h4h5 e4f5 h5h6 f5d3 h6h5 e6d5 h5h4 f4e5
info depth 25 seldepth 26 hashfull 84 nodes 14198181 nps 2502577 score cp 820 time 5673 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h5 e5f4 h5h4 f5e6 h4h5 e6d7 h5h6 f4e5 h6g5 e4d5 g5g6 e5d6 g6f6
info depth 26 seldepth 28 hashfull 86 nodes 14658449 nps 2500517 score cp 823 time 5862 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h5 e5f4 h5h4 f5e6 h4h5 e4f5 h5h6 f4e5 h6g5 f5d3 g5h4 e5f4 h4h5 e6d5 h5h6
info depth 27 seldepth 29 hashfull 107 nodes 17228849 nps 2480765 score cp 835 time 6944 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h5 e5f4 h5h4 f5e6 h4h5 e4f5 h5h6 e6d5 h6h5 f5d3 h5h4 d3f1 h4h5 f1b5 h5h4 f4e5
info depth 28 seldepth 31 hashfull 175 nodes 30035944 nps 2421466 score cp 823 time 12404 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h5 e5f4 h5h4 f5e6 h4h5 e4f5 h5h4 f5h3 h4h5 h3g4 h5h4 g4f5 h4h5 e6d5 h5h6 f4g4 h6g7 g4g5
info depth 29 seldepth 31 hashfull 177 nodes 30842304 nps 2422793 score cp 830 time 12730 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h6 e4f3 h6g5 f3d5 g5h5 e5f4 h5h4 d5e4 h4h5 e4f3 h5h4 f3d5 h4h5 f5e4 h5h4 e4d3 h4h3 f4e5
info depth 30 seldepth 33 hashfull 240 nodes 42232254 nps 2403326 score cp 825 time 17572 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e6f5 d6e5 b5c5 e5f4 c5d4 f4g5 d4e5 g5h6 e5f4 h6h5 f5e6 h5h4 e6c8 h4h5 e4f3 h5h4 f4e3 h4g5 e3d4 g5g6 d4e5 g6g7 c8f5 g7f7 f3e4 f7f8 e5d6
info depth 31 seldepth 31 hashfull 254 nodes 48759266 nps 2394733 score cp 835 time 20361 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e4f5 d6e5 f5h3 e5f4 b5c5 f4g3 c5d4 g3h4 h3g4 h4g5 d4e5 g5g6 e5f4 g6g7 e6d5 g7g6 f4e4 g6g7 e4d4 g7f8 g4h3 f8g7 d4e5 g7h6 h3f5
info depth 32 seldepth 33 hashfull 387 nodes 78661636 nps 2375737 score cp 833 time 33110 pv b7c8b a7b8 c8e6 b8c7 a5b5 c7d6 e4d5 d6e7 b5c5 e7f6 c5d4 f6g6 d4e4 g6g5 e4f3 g5h5 f3g3 h5g5 e6g4 g5h6 g3f4 h6g6 d5e4 g6f6 e4f5 f6e7 f4e5 e7f8 f5e4 f8f7 g4f5 f7f8 e4d5
info depth 33 seldepth 33 hashfull 462 nodes 135078846 nps 2300947 score cp 831 time 58705 pv b7c8b a7b8 c8e6 b8c7 e4d5 c7d8 d5c4 d8e8 a5b5 e8e7 b5c5 e7f6 e6c8 f6e5 c4d5 e5f6 c5d4 f6g6 d4e3 g6g5 c8e6 g5g6 e3f4 g6h5 e6f5 h5h4 f4e3 h4g3 d5g8 g3g2 e3f4 g2g1 g8d5
info depth 34 seldepth 36 hashfull 471 nodes 150877686 nps 2304782 score cp 843 time 65462 pv b7c8b a7b8 c8e6 b8c7 e4d5 c7d8 a5b4 d8e7 b4c5 e7f6 c5d6 f6g5 d6e5 g5h4 e5f4 h4h5 e6g4 h5h4 g4f5 h4h5 f4g3 h5g5 d5e4 g5h5 e4g2 h5g5 f5g4 g5f6 g3f4 f6e7 f4e5 e7f8 g2d5 f8g7 g4f5 g7f8
info depth 35 seldepth 38 hashfull 512 nodes 174607813 nps 2295258 score cp 853 time 76073 pv b7c8n a7b8 c8d6 b8c7 d6f5 c7d7 e4d5 d7e8 a5b6 e8f8 b6c7 f8e8 c7c6 e8f8 c6d6 f8e8 d6e6 e8f8 d5c6 f8g8 e6e7 g8h7 c6e8 h7g8 e8f7 g8h7 f7h5 h7g8 e7e6 g8h8 e6f7 h8h7 h5e2 h7h8 e2g4 h8h7 g4f3 h7h8
info depth 36 seldepth 40 hashfull 533 nodes 190390038 nps 2288433 score cp 859 time 83196 pv b7c8n a7b8 c8d6 b8c7 d6f5 c7d7 e4d5 d7e8 a5b6 e8f8 b6c7 f8e8 c7c6 e8f8 c6d6 f8e8 d6e6 e8f8 d5c6 f8g8 e6e7 g8h7 c6e8 h7g8 e8f7 g8h7 f7h5 h7g8 h5e8 g8h7 e7f7 h7h8 e8d7 h8h7 d7b5 h7h8 b5c6 h8h7 c6d5 h7h8
info depth 37 seldepth 17 hashfull 586 nodes 270009288 nps 2268408 score cp 821 time 119030 pv b7c8n a7b8 c8d6 b8c7 d6f5 c7d7 e4d5 d7c7 d5f7 c7b8 f7e6 b8c7 a5b4 c7b7 e6b3 b7a8 b4c5
info depth 38 seldepth 23 hashfull 587 nodes 287380396 nps 2248316 score mate +11 time 127820 pv b7c8n a7b8 c8d6 b8c7 d6f5 c7d7 e4d5 d7c7 a5b5 c7b8 b5b6 b8c8 d5c6 c8b8 c6d7 b8a8 f5e7 a8b8 d7c8 b8a8 c8b7 a8b8 e7c6
info depth 38 seldepth 23 hashfull 587 nodes 287380396 nps 2248315 score mate +11 time 127820 pv b7c8n a7b8 c8d6 b8c7 d6f5 c7d7 e4d5 d7c7 a5b5 c7b8 b5b6 b8c8 d5c6 c8b8 c6d7 b8a8 f5e7 a8b8 d7c8 b8a8 c8b7 a8b8 e7c6
bestmove b7c8n ponder a7b8

Does that output indicate your engine thinks it's mate in 11? Might be some issue with mate reporting if so (the correct mate is longer, mate in
26 I think).

Cheers!

I do not take special care when storing mate score in TT, and when tried to add special code about it, the engine started playing worse, so I abandoned it

[MikeB]

There are not so many engines that find the only good move instantly.

My 65 year old egghead found it in about one second.

[Jouni]

Lc0 is very buggy, because it has no move with syzygy access! But generally tablebases have distroyed this position. SF also sees fast mate in 27 without them. Solved like twice:

Analysis by Stockfish 060921:

+- (#27) Depth: 53/54 00:00:26 377mN
1.bxc8N+ Kb8 2.Nd6 Kc7 3.Nf5 Kd7 4.Bd5 Ke8 5.Kb5 Kf8 6.Be6 Ke8 7.Kc5 Kf8 8.Kd5 Ke8 9.Ke5 Kf8 10.Kf6 Ke8 11.Nh4 Kd8 12.Ke5 Kc7 13.Kd5 Kb6 14.Bd7 Kc7 15.Bc6 Kb6 16.Nf5 Kc7 17.Ng7 Kb6 18.Ne8 Ka7 19.Kc5 Kb8 20.Ng7 Ka7 21.Kb5 Kb8 22.Kb6 Kc8 23.Ne6 Kb8 24.Bd7 Ka8 25.Nc7+ Kb8 26.Na6+ Ka8 27.Bc6#