Test Position: Ivanhoe-Rybka (brilliant knight sac)

[Albert Silver]

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.

[zullil]

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

36...Nf4!!!

Stockfish-1.9.1 (8 threads) finds this too, though it takes a while:

Code: Select all

info depth 31 score cp 64 lowerbound time 1250103 nodes 9975832814 nps 7980008 pv d5f4 g3f4 f5h4 f3e2 f6f5 e4d2 e5e4 d3e4 c7f4 d2f1 f7c4 b3c4 d7d3 c2d3 d8d3 e2d3 h4f3 g1h1 f5e4 

Getting better ...

Code: Select all

info depth 31 score cp 88 lowerbound time 1425041 nodes 11428372283 nps 8019679 pv d5f4 g3f4 f5h4 f3e2 f6f5 e4d2 e5e4 d3e4 c7f4 d2f1 f7c4 b2c1 h4f3 e2f3 f4f3 b3c4 f3g4 g1h1 d7d1 

and better ...

Code: Select all

info depth 31 score cp 121 lowerbound time 1688962 nodes 13621807612 nps 8065194 pv d5f4 g3f4 f5h4 f3e2 f6f5 e4d2 e5e4 d3e4 c7f4 d2f1 f7c4 b3c4 d7d3 c2d3 d8d3 e2d3 h4f3 g1h1 f5e4 

[zullil]

and better ...

Code: Select all

info depth 31 score cp 185 lowerbound time 2331995 nodes 19044302268 nps 8166527 pv d5f4 g3f4 f5h4 f3e2 f6f5 e4d2 e5e4 d3e4 c7f4 d2f1 f7c4 e2c4 g8h7 c4e2 d7d3 e2d3 f4g4 f1g3 

[Dann Corbit]

Rybka finds it in 28 seconds on my machine (4 CPU @ 3GHz, 1 GB hash used, 64 bit)

[zullil]

Seems like Stockfish considers Nf4 to be a winner:

Code: Select all

33     +2.02 1:25:30   42907M Nf4 gxf4 Nxh4 Bh1 Rxd3 fxe5 Bxc4 bxc4 Qxe5 Qe2 f5 
                              Re1 fxe4 Qxe4 Qg5+ Kf1 Rd1 Ra1 Rxa1 Bxa1 Nf5 Bb2 
                              Qf6 Qf4 Bd6 Bd5+ Kg7 Qf3 Be5 Kg1 Nd6 Qh3 Rf8 Qf1 
                              Nf5 Qh3 Ne7 Qe3 

[beachknight]

Robbolito failed in ten minutes.

5:
3r2k1/2qrbb2/pp3pp1/2pnpn1p/P1N1N2P/1PPP1BP1/RBQ2P2/R5K1 b - - 0 1

Analysis by Robbolito TA04 analyse x64:


1...b5 2.axb5 axb5[] 3.Na5 Kg7 4.Be2 Be6 5.Qd2 Nd6 6.Bf3 Bf5 7.Qe2 b4 8.c4 Nxe4 9.Bxe4
= (-0.04) Depth: 13/30 00:00:00 786kN
1...b5 2.axb5[] axb5[] 3.Na5 Nd6 4.Nxd6 Rxd6 5.Nc4 R6d7 6.Na5 Rd6
= (0.00) Depth: 14/37 00:00:02 3284kN
1...b5 2.axb5[] axb5[] 3.Na5 Nd6 4.Nxd6 Rxd6 5.Nc4 R6d7 6.Na5 Rd6
= (0.00) Depth: 15/38 00:00:03 4418kN
1...b5 2.axb5[] axb5[] 3.Na5 Nd6 4.Nxd6 Rxd6 5.Nc4 R6d7 6.Na5 Rd6
= (-0.01 ++) Depth: 16/44 00:00:05 6955kN
1...b5 2.axb5 axb5[] 3.Ncd2 b4 4.c4[] Nc3[] 5.Bxc3 bxc3[] 6.Nxc3[] Nd4[] 7.Qb2 Nxf3+[] 8.Nxf3[] Rxd3[] 9.Ra7[] Qc6 10.Ne1 Rd2 11.Qc1 R2d7 12.R1a6 Qc8 13.Qe3 Rxa7 14.Rxa7 Rd7 15.Rxd7 Qxd7 16.Ne4 Qd4
= (0.02) Depth: 16/49 00:00:10 13848kN
1...Qc6
Depth: 17 00:00:31 39752kN
1...Qc6
= (0.01 ++) Depth: 17/49 00:00:46 59150kN
1...Qc6 2.Bh1 Kg7 3.Ng5 Bg8 4.Bg2 Bf8 5.Ne4[] Kh8 6.Re1 b5 7.Na5 Qe6 8.axb5 axb5 9.Raa1 Ra7 10.Qe2 Rda8 11.Nb7
= (0.05) Depth: 17/49 00:00:55 70564kN
1...Qc6 2.Bh1 Kg7 3.Ng5 Bg8 4.Bg2 Bf8 5.Ne4[] Kh8 6.Re1 b5 7.Na5 Qe6 8.axb5 axb5 9.Raa1 Ra7 10.Qe2 Rda8 11.Nb7
= (0.04 ++) Depth: 18/50 00:01:07 85141kN
1...Qc6 2.Bh1 Kg7 3.Ng5 Bg8 4.Bg2 Bf8 5.Ne4[] Kh8 6.Re1 b5 7.Na5 Qe6 8.axb5 axb5 9.Raa1 Ra7 10.Qe2 Rda8 11.Nb7
= (0.03 ++) Depth: 18/50 00:01:29 114mN
1...Qc6 2.Bh1 Kg7 3.Ng5 Bg8 4.Bg2 Nh6 5.Ne4[] Ng4 6.Qe2 Bf7 7.Bc1 Nc7 8.f3 Bxc4 9.bxc4 Nh6 10.Bxh6+ Kxh6 11.Qe3+ Kh7 12.Rd2 Ne6 13.Rb1
= (0.05) Depth: 18/50 00:01:29 114mN
1...Qc6 2.Bh1 Kg7 3.Ng5 Bg8 4.Bg2 Nh6 5.Ne4 Ng4 6.Qe2 Bf7 7.Bc1 Nc7 8.f3 Bxc4 9.bxc4 Nh6 10.Bxh6+ Kxh6 11.Qe3+ Kh7 12.Rd2 Ne6 13.Rb1
= (0.05) Depth: 19/50 00:01:42 130mN
1...Qc6 2.Bh1 Kg7 3.Ng5 Bg8 4.Bg2 Nh6 5.Ne4 Ng4 6.Qe2 Bf7 7.Bc1 Nc7 8.f3 Bxc4 9.bxc4 Nh6 10.Bxh6+ Kxh6 11.Qe3+ Kh7 12.Rd2 Ne6 13.Rb1
= (0.04 ++) Depth: 20/63 00:03:58 304mN
1...Qc6 2.Bh1 Kg7 3.Ng5 Bg8 4.Bg2 Nh6 5.Ne4 Ng4 6.Qe2 Be6 7.Qe1 Kg8 8.Bc1 Bf8 9.f3 Nh6 10.a5 b5 11.Nb6
= (0.04) Depth: 20/63 00:03:58 304mN
1...Qc6 2.Bh1 Kg7 3.Ng5 Bg8 4.Bg2 Nh6 5.Ne4 Ng4 6.Qe2 Be6 7.Qe1 Kg8 8.Bc1 Bf8 9.f3 Nh6 10.a5 b5 11.Nb6
= (0.03 ++) Depth: 21/67 00:07:11 555mN
1...Qc6 2.Bh1 Kg7 3.Ng5 Bg8 4.Bg2 Nh6 5.Ne4 Ng4 6.Qe2 Be6 7.Qe1 Kg8 8.Bc1 Bf8 9.f3 Nh6 10.a5 b5 11.Nb6
= (0.02 ++) Depth: 21/67 00:09:30 736mN
1...Qc6 2.Bh1 Kg7 3.Ng5 Bg8 4.Bg2 Nh6 5.Ne4 Ng4 6.Qe2 Be6 7.Qe1 Kg8 8.Bc1 Bf8 9.f3 Nh6 10.a5 b5 11.Nb6
= (0.00 ++) Depth: 21/67 00:12:52 996mN
1...Qc6 2.Bh1 Kg7 3.Ng5 Bg8 4.Ne4 Bf7
= (0.00) Depth: 21/67 00:13:02 1009mN

(, chessengines20 20.11.2010)

[beachknight]

Rybka finds in 3 minutes.

5:
3r2k1/2qrbb2/pp3pp1/2pnpn1p/P1N1N2P/1PPP1BP1/RBQ2P2/R5K1 b - - 0 1

Analysis by Deep Rybka 4 x64 3cpu:

1...Qc6 2.Re1 Bf8 3.Raa1 Qc7 4.Bg2 Bh6 5.Bf3 Be6 6.Bg2 Kh8
= (-0.20) Depth: 10 00:00:01 156kN
1...Qc6 2.Re1 Bf8 3.Raa1 Qc7 4.Bg2 Re8 5.Qe2 Be6 6.Qc2 b5 7.axb5 axb5 8.Ncd2 Rdd8
= (-0.20) Depth: 11 00:00:02 242kN
1...Qc6 2.Re1 Bf8 3.Raa1 Bh6 4.Qe2 Qc7 5.Bg2 Be6 6.Qc2 Re8 7.Bf3 Red8 8.Bg2 Re8 9.Bf3 Red8 10.Bg2 Re8 11.Bf3 Red8 12.Bg2 Re8 13.Bf3 Red8 14.Bg2 Re8 15.Bf3 Red8 16.Bg2 Re8
= (-0.21) Depth: 12 00:00:03 564kN
1...Qc6 2.Re1 Bf8 3.Raa1 Bh6 4.Qe2 Qc7 5.Bg2 Be6 6.Qc2 Re8 7.Ba3 Bf8 8.Bb2 Bh6 9.Ba3 Bf8 10.Bb2 Bh6 11.Ba3 Bf8 12.Bb2 Bh6 13.Ba3 Bf8 14.Bb2 Bh6 15.Ba3 Bf8 16.Bb2 Bh6
= (-0.21) Depth: 13 00:00:04 644kN
1...Qc6 2.Re1 Qc8 3.Ncd2 Qc7 4.Raa1 Kh7 5.Nc4 Kh8 6.Be2 b5 7.axb5 axb5 8.Ncd2 Qc6 9.Nf3 Kg8 10.Bf1 Be6 11.Bh3
= (-0.21) Depth: 14 00:00:12 2242kN
1...Qc6 2.Re1 Qc8 3.Ncd2 Qc7 4.Raa1 Kh7 5.Nc4 Kh8 6.Be2 Bf8 7.Bf3 Be7 8.Be2 Bf8 9.Bf3 Be7 10.Be2 Bf8 11.Bf3 Be7 12.Be2 Bf8 13.Bf3 Be7 14.Be2 Bf8 15.Bf3 Be7 16.Be2 Bf8
= (-0.21) Depth: 15 00:00:20 3598kN
1...Qc6 2.Re1 Qc8 3.Ncd2 Qc7 4.Raa1 Kh7 5.Nc4 Kh8 6.Be2 Bf8 7.Bf3 Be7 8.Be2 Bf8 9.Bf3 Be7 10.Be2 Bf8 11.Bf3 Be7 12.Be2 Bf8 13.Bf3 Be7 14.Be2 Bf8 15.Bf3 Be7 16.Be2 Bf8
= (-0.21) Depth: 16 00:00:52 9404kN
1...Qc6 2.Re1 Qc8 3.Ncd2 Qc7 4.Bg2 Be6 5.Nc4 b5 6.axb5 axb5 7.Ncd2 Nb6 8.Rea1 Kg7 9.Bf1
= (-0.21) Depth: 17 00:01:54 20874kN
1...Nf4 2.gxf4 Nxh4 3.Be2 Bxc4 4.bxc4 f5 5.Nd2 e4
=/+ (-0.33 ++) Depth: 17 00:02:55 33025kN
1...Nf4 2.gxf4 Bxc4 3.bxc4 Nxh4[] 4.Bh1 Rxd3[] 5.a5 bxa5 6.Rxa5 f5 7.Rxa6 fxe4 8.Bxe4 Rd2 9.Qb3 exf4 10.Qb6 Rd1+ 11.Kh2 Qxb6 12.Rxb6 Rxa1 13.Bxa1 Rd2 14.Rb2 Rxb2
=/+ (-0.48 ++) Depth: 17 00:04:25 51361kN

(, chessengines20 20.11.2010)

[Dann Corbit]

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

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;

[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.

[kgburcham]

I could not find a program that would play this move except Rybka 4.
My version of Houdini would not play this move.

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

Deep Rybka 4 SSE42 x64:

1...Nf4 2.gxf4 Nxh4 3.Be2 Bxc4
=/+ (-0.31 ++) Depth: 19 00:01:20 89685kN
1...Nf4 2.gxf4 Nxh4 3.Be2 Bxc4
=/+ (-0.46 ++) Depth: 19 00:01:26 98760kN
1...Nf4 2.gxf4 Nxh4 3.Be2 Bxc4
-/+ (-0.86 ++) Depth: 19 00:02:10 156mN
1...Nf4 2.gxf4 Nxh4 3.Be2 Bxc4 4.bxc4 f5[] 5.fxe5 fxe4 6.d4 cxd4[]
-/+ (-1.23) Depth: 19 00:04:11 309mN
1...Nf4 2.gxf4 Nxh4 3.Be2 Bxc4[] 4.bxc4 f5[] 5.fxe5 fxe4 6.d4 cxd4[]
-/+ (-1.35 ++) Depth: 20 00:06:23 485mN
1...Nf4 2.gxf4 Nxh4 3.Be2 Bxc4[] 4.bxc4 f5[] 5.fxe5 fxe4 6.d4[] cxd4[] 7.cxd4 Rxd4
-/+ (-1.27) Depth: 20 00:06:26 488mN
1...Nf4 2.gxf4 Nxh4 3.Be2 Bxc4[] 4.bxc4 f5[] 5.fxe5 fxe4 6.d4[] cxd4[]
-/+ (-1.39 ++) Depth: 21 00:10:09 793mN
1...Nf4 2.gxf4 Nxh4 3.Be2 Bxc4[] 4.bxc4 f5[] 5.fxe5 fxe4 6.d4[] cxd4[]
-+ (-1.54 ++) Depth: 21 00:17:14 1358mN
1...Nf4 2.Rd1 Rxd3 3.Rxd3 Rxd3 4.Be2 Nxe2+[] 5.Qxe2 Rd8 6.Kg2 Qc6
-+ (-1.61) Depth: 21 00:36:48 2847mN
1...Nf4 2.Rd1 Rxd3 3.Rxd3 Rxd3 4.Be2 Nxe2+[] 5.Qxe2 Rd8 6.Kg2 Qc6
-+ (-1.61) Depth: 22 00:36:48 2847mN
1...Nf4 2.Rd1 Rxd3 3.Rxd3 Rxd3 4.Be2 Nxe2+[] 5.Qxe2 Rd8 6.Kg2 Qc6
-+ (-1.61) Depth: 23 00:36:48 2847mN
1...Nf4 2.Rd1 Rxd3 3.Rxd3 Rxd3 4.Be2 Nxe2+[] 5.Qxe2 Rd8 6.Ra1 Kg7 7.Ncd2 Nd6
-+ (-1.63) Depth: 24 00:53:44 4251mN