BeyondCritics wrote: ↑Fri Nov 29, 2019 10:06 am
[pgn]1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 6. Bg5 e6 7. f4 b5 8. e5
dxe5 9. fxe5 Qc7 10. exf6 Qe5+ 11. Be2 Qxg5 12. O-O Ra7 13. Qd3 Rd7 14. Ne4 Qe5
15. Nf3 Qc7 16. Qe3 Bb7 17. a4 b4 18. Kh1 Bxe4 19. fxg7 Bxg7 20. Qxe4 Bxb2 21.
Rab1 Bc3 22. Ng5 h5 *
[/pgn]
[d]1n2k2r/2qr1p2/p3p3/6Np/Pp2Q3/2b5/2P1B1PP/1R3R1K w k - 0 23
This highly theoretical position stems from the Polugaevsky variation of the Najdorf Defence, when white plays 10.exf6 and black defends with 15...Qc7,16...Bb7. It is critical for the 16...Bb7 line.
There are some good moves, but only one move wins. Your task -- if you choose to accept it -- is to show this move. Extra credit for explanations.
Note that Parimarjan Negi, in his highly praised repertoire book about the Najdorf from 2015, failed to show the correct refutation of 16...Bb7. IMHO this demonstrates how fast engine chess is still evolving.
Lc0 (network J13B.3-200) with 100M nodes suggests Bd3 is best:
1129 06:13:10.492107 140174937810688 ../../src/mcts/search.cc:384] Stopped search: Reached visits limit: 100000235>=100000000
1129 06:13:10.495849 140174937810688 ../../src/chess/uciloop.cc:218] << info depth 42 seldepth 98 time 5508878 nodes 100000235 score cp 73 hashfull 271 nps 18130 tbhits 2387 multipv 1 pv e2d3 h5h4 h2h3 h8h6 e4e3 c3d4 e3d2 d4c3 d2e3 c3d4 e3c1 h6f6 b1b4 f6f1 c1f1 b8c6 b4c4 c7b6 g5f3 d4f6 c4f4 b6d8 f1e1 d7d5 e1f1 d5d7 f1e1 d7d5 e1f2 d8e7 f3h4 f6e5 f4g4 e5d4 f2f4 d4e5 f4f2 e5d4 f2f4 d4e5 f4e3 e5c7 h4f3 e7d6 g2g3 c6b4 d3e4 d5d1 h1h2 b4d5 e4d5 d1d5 h3h4 d6c6 f3d4 c6a4 c2c4 a4c4 d4e6 c4c2 h2h3 d5e5 e6g7 e8e7 e3f3 c2c5 h4h5 c5d5 f3d5 e5d5 h5h6 d5d8 h3h4 c7e5 g4e4 e7f6 g3g4 d8d5 h4h5 e5b2 g7f5 d5d1 f5h4 d1d5 h4f5 d5d1
More:
Nodes: 100M, N/s: 18.1k, Time: 1h 31m (limit met)
62.5% Bd3 h4 h3 Rh6 Qe3 Bd4 Qd2 Bc3 Qe3 Bd4 Qc1 Rf6 Rxb4 Rxf1+ Qxf1 Nc6 Rc4 Qb6 Nf3 Bf6 Rf4 Qd8 Qe1 Rd5 Qf1 Rd7 Qe1 Rd5 Qf2 Qe7 Nxh4 Be5 Rg4 Bd4 Qf4 Be5 Qf2 Bd4 Qf4 Be5 Qe3 Bc7 Nf3 Qd6 g3 Nb4 Be4 Rd1+ Kh2 Nd5 Bxd5 Rxd5 h4 Qc6 Nd4 Qxa4 c4 Qxc4 Nxe6 Qc2+ Kh3 Re5 Ng7+ Ke7 Qf3 Qc5 h5 Qd5 Qxd5 Rxd5 h6 Rd8 Kh4 Be5 Re4 Kf6 g4 Rd5 Kh5 Bb2+ Nf5 Rd1 Nh4 Rd5+ Nf5 Rd1 (N: 98.2M, P: 4.61%)
61.0% Rf3 Qe5 Rxb4 Qxg5 Rxb8+ Ke7 Rxh8 Bxh8 Qb4+ Ke8 Bxa6 Rd1+ Bf1 f5 a5 Qc1 Qc4 Ke7 a6 Bd4 h4 Kf6 c3 Be5 a7 Qa3 Qe2 Ra1 Qd2 Qxa7 Qg5+ Kf7 Qxh5+ Kf8 Qh6+ Kf7 Qh5+ Kf8 (N: 473k, P: 5.14%)
58.7% Nxf7 Rxf7 Qg6 Nc6 Bxh5 Nd8 Rbd1 Qc5 Qd3 Qc7 Qg6 Qc5 Qd3 Qc7 Qxd8+ Qxd8 Rxd8+ Kxd8 Bxf7 Rf8 Rd1+ Ke7 Bg6 a5 Kg1 Rb8 Rd3 b3 cxb3 Rxb3 h4 Ra3 Kh2 Be5+ Kh3 Rxa4 Rf3 Rf4 Ra3 a4 Bc2 (N: 254k, P: 9.66%)
58.4% Rbd1 Rxd1 Bxd1 Qe5 Qxe5 Bxe5 Nxf7 Rf8 Bxh5 Ke7 Rf3 Bd4 Ng5 Rc8 Rf7+ Kd6 Bd1 Nd7 h4 Nc5 a5 Be3 Kh2 Bxg5 hxg5 Rg8 Rf4 Rxg5 Rxb4 Nd7 Ra4 Rc5 Be2 Nb8 Bd3 Nc6 g4 Ke7 Kg3 Nxa5 Kh4 Nc6 (N: 225k, P: 9.22%)
61.2% h3 h4 Bd3 Re7 Rbd1 f5 Qe3 Rh6 Ne4 Bg7 Nc5 Qe5 Qf2 Qg3 Qg1 Bc3 Rf3 Qe5 Nxa6 Nxa6 Bxa6 Kf7 Bc4 Kg7 Qf2 Qc7 Bb3 Be5 Qd2 Bc3 Qe2 Rg6 (N: 192k, P: 1.64%)
59.9% Qf3 h4 Ne4 h3 gxh3 Nc6 Bxa6 Ne5 Qg2 Kf8 Bb5 Rd5 Ng5 Ke7 Ne4 Kf8 Rbd1 Rg8 Ng3 Rxd1 Rxd1 Qb6 Qa8+ Kg7 Nh5+ Kh8 Qe4 f5 Qf4 Qb7+ Rd5 Qxd5+ (N: 142k, P: 3.67%)
56.3% h4 Rd4 Rxf7 Rxe4 Rxc7 Rxh4+ Nh3 Be5 Rb7 Rg8 R1xb4 Rxb4 Rxb4 Ke7 Rb7+ Kd6 Nf2 Rc8 Ne4+ Kd5 Bd3 h4 Kg1 Rf8 Rh7 Rf4 Ng5 Rxa4 c4+ (N: 89.3k, P: 5.51%)
59.7% Rf4 Qe5 Rxb4 Qxg5 Rxb8+ Ke7 Rxh8 Bxh8 Qb4+ Ke8 Bxa6 Bc3 Qb8+ Ke7 Rf1 Be5 Qb4+ Bd6 Qe4 Qe5 Qh4+ Kf8 Re1 Qc3 Bd3 Bc7 Rf1 Qe5 g3 Rd4 Qf6 Qxf6 Rxf6 h4 Kg2 Rxa4 (N: 87.0k, P: 2.38%)
51.9% Qh4 Qe5 Ne4 Rd4 Nf6+ Kd8 Ng4+ Ke8 Nf6+ Kd8 Ng4+ Ke8 Nf6+ Kd8 (N: 59.4k, P: 6.29%)
55.1% Rf2 Qc5 Qf4 Be5 Qh4 Rd4 Qh3 Rg4 Rxf7 Qxc2 Re1 Qc3 Qxc3 Bxc3 Bxg4 Bxe1 Rb7 Nc6 Bxe6 Nd8 Rb8 Ke7 Bc4 Rh6 g3 Rc6 Be2 h4 Kg2 hxg3 hxg3 (N: 40.2k, P: 2.95%)