Test Position: Ivanhoe-Rybka (brilliant knight sac)

[Terry McCracken]

In the recently finished match between Rybka 4 and one of the gazillion builds of Ivanhoe, played on fantastic hardware and match conditions, Rybka uncorked my favorite move of the match:

[d]3r2k1/2qrbb2/pp3pp1/2pnpn1p/P1N1N2P/1PPP1BP1/RBQ2P2/R5K1 b - - 0 36

36...Nf4!!!

Since Ivanhoe didn't see it coming, despite also running on 6-cores at 4 GHz, and playing at tournament time controls, it is safe to say this is tough one.

That is a nice move. Ivanhoe looks a bit confused here.

Confused ? It sees the move in 29 sec.
3r2k1/2qrbb2/pp3pp1/2pnpn1p/P1N1N2P/1PPP1BP1/RBQ2P2/R5K1 b - - 0 1

*Yawn* Yes, confused as it didn't see it in the game beforehand and some of it's pieces aren't ideally located. Guess which ones?

Post Mortem Snipped

[Don]

For me, all the engines I tried except Stockfish and Zappa found it in under ten minutes.

Komodo is very weak tactically but finds it in 1:15 seconds.

Rybka (00:28):
3r2k1/2qrbb2/pp3pp1/2pnpn1p/P1N1N2P/1PPP1BP1/RBQ2P2/R5K1 b - - acd 17; acn 140995385; acs 562; bm Nf4; ce 132; pv Nf4 gxf4 Nxh4 Be2 Bxc4 bxc4 f5 fxe5 fxe4 d4 cxd4 cxd4 Rxd4 Bxd4 Rxd4 Qb3 Qxe5 c5+ Kg7 cxb6 Nf5 b7 Rb4 Qh3 Rxb7 Qg2 Rb4 Qh2 Qe6 Qc7 e3;

Houdini (04:03):
3r2k1/2qrbb2/pp3pp1/2pnpn1p/P1N1N2P/1PPP1BP1/RBQ2P2/R5K1 b - - acd 22/74+; acn 1967099871; acs 502; bm Nf4; ce 46; pv Nf4 gxf4 Nxh4 Be2 Bxc4 bxc4 f5 fxe5 fxe4 d4 cxd4 Qxe4 d3 Bd1 a5 Ba3 Qb7 Qxb7 Rxb7 Bc1 Rf8 Rb2 Bc5 Bg5 Nf3+ Bxf3 Rxf3 Kg2 Rbf7 Bf6 Rf4 Rd1 Rg4+ Kf3 Rd7 e6 Rd6 Bd4 Rxe6;

Stockfish:
3r2k1/2qrbb2/pp3pp1/2pnpn1p/P1N1N2P/1PPP1BP1/RBQ2P2/R5K1 b - - acd 27+; acn 1531010269; acs 507; bm Kg7; ce 56; pv Kg7 Be2 Qb7 Qd2 b5 axb5 axb5 Ra7 Qxa7 Rxa7 Rxa7;

IvanHoe (02:29):
3r2k1/2qrbb2/pp3pp1/2pnpn1p/P1N1N2P/1PPP1BP1/RBQ2P2/R5K1 b - - acd 25+; acn 2246707887; acs 497; bm Nf4; ce 39; pv Nf4 gxf4 Nxh4 Be2 Bxc4 bxc4 f5 fxe5 Qc6 d4 cxd4 cxd4 Rxd4 Bxd4 Rxd4 Rd1 Rxe4 Rd5 Rxe5 Qb3 Kg7 a5 b5 Rad2 bxc4 Bxc4 Re4 Bf1 Bb4 Rd7+ Kh6 R2d5 Rg4+ Kh1 Qc1 Rd1 Qf4 Be2 Rg2;

Critter (06:12):
3r2k1/2qrbb2/pp3pp1/2pnpn1p/P1N1N2P/1PPP1BP1/RBQ2P2/R5K1 b - - acd 21/65-; acn 1498827290; acs 518; bm Nf4; ce 69; pv Nf4 gxf4 Nxh4 Be2 Bxc4 bxc4 f5 fxe5 Qc6 d4 cxd4 cxd4 Rxd4 Bxd4 Rxd4 Rd1 Rxe4 Rd5 Rxe5 Qd1 Kh7 Qd2 Re4 Qd3 Bc5 Rd7+ Kh6 Qd2+ g5 Qd5 Qe6 Qb7 Be7 Rdd2;

Junior (01:44):
3r2k1/2qrbb2/pp3pp1/2pnpn1p/P1N1N2P/1PPP1BP1/RBQ2P2/R5K1 b - - acd 23; acn 3910805745; acs 470; bm Nf4; ce 64; pv Nf4 gxf4 Nxh4 Be2 exf4 d4 Qb7 f3 f5 Ned2 Bf6 Qc1 cxd4 cxd4 Bd5 Qf1 Qc6 Ne5 Qc2;

Naum (02:20):
3r2k1/2qrbb2/pp3pp1/2pnpn1p/P1N1N2P/1PPP1BP1/RBQ2P2/R5K1 b - - acd 21/62; acn 1332774336; acs 381; bm Nf4; ce 79; pv Nf4 gxf4 Bxc4 dxc4 exf4 Qe2 Nxh4 a5 bxa5 Rxa5 f5 Nxc5 Bxc5 Bd5+ Kh7 Kh1 f3 Qf1 Re8 Rxa6 Re2;

Zappa:
3r2k1/2qrbb2/pp3pp1/2pnpn1p/P1N1N2P/1PPP1BP1/RBQ2P2/R5K1 b - - acd 17/54; acn 935093176; acs 510; bm Qa7; ce 56; pv Qa7 Bg2 Be6 Re1 Qc7 Rea1 Bf8 Bc1 Bg7 a5 b5 Nb6 Rf7 Bh3 Qe7 Bd2 Nc7 Bg2 Rff8;