Thursday, February 5, 2015

It's All About the Ply Depth

In recent posts, we have revealed some truths about so-called "Advanced Chess" (computer-assisted play) as well as advice for players who are new to this venue; see links below.

In his syndicated column, GM Lubomir Kavalek annotated  Ivanchuk-So, Wijk aan Zee 2015, a game featuring a recent TN (Theoretical Novelty) in the Ruy Lopez credited to a chess engine. Kavalek writes:

"It seems So surprised Ivanchuk with a knight sacrifice in the delayed Marshall Attack in the Spanish opening. The Ukrainian just followed Aronian's analysis from his Candidates game against Anand. But it became clear that Aronian's analytical team unplugged the computer too soon, leaving the piece sacrifice undiscovered. Suddenly, there it was on the board, the work of a number-crunching monster, too foreign to a human mind. And Wesley So knew about it."

From What is Advanced Chess ? "There is nothing revolutionary about opening preparation helping to win chess games - chess masters have been unleashing opening surprises on their opponents for 500 years. What is revolutionary is the ability of chess software to find TN's so deeply hidden that an unassisted human player could never discern them".

[Event "77th Tata Steel GpA"]
[Site "Wijk aan Zee NLD"]
[Date "2015.01.18"]
[Round "8.3"]
[White "Ivanchuk, Vassily"]
[Black "So, Wesley"]
[Result "0-1"]
[WhiteElo "2715"]
[BlackElo "2762"]
[ECO "C88"]

1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.0-0 Be7 6.Re1 b5 7.Bb3 0-0 8.h3 Bb7 9.d3 d5 10.exd5 Nxd5 11.Nbd2 Qd7!?

"Levon Aronian's novelty, connecting the rooks and planning to bring the queen rook into play ... it looks like Aronian's analytical team didn't let the computer work long enough to find the little combination" (Kavalek).

This refers to Anand-Aronian, WC Candidates 2014, which continued 12.Nxe5 Nxe5 13.Rxe5 Nf6? 14.Re1 Rae8 15.Nf3 Bd6 16.Be3 Re7 17.d4 Rfe8 18.c3 h6 19.Ne5 Bxe5 20.dxe5 Rxe5 21.Qxd7 Nxd7 22.Red1 Nf6 23.c4 c6 24.Rac1 R5e7 25.a4 bxc4 26.Bxc4 Nd5 27.Bc5 Re4 28.f3 R4e5 29.Kf2 Bc8 30.Bf1 R5e6 31.Rd3 Nf4 32.Rb3 Rd8 33.Be3 Nd5 34.Bd2 Nf6 35.Ba5 Rde8 36.Rb6 Re5 37.Bc3 Nd5 38.Bxe5 Nxb6 39.Bd4 Nxa4 40.Rxc6 Rd8 41.Rc4 Bd7 42.b3 Bb5 43.Rb4 Nb2 44.Bxb5 axb5 45.Ke3 Re8+ 46.Kd2 Rd8 47.Kc3 1-0 

Note: Komodo 8 and Houdini 4 engines don't find 11... Qd7 at 30 ply. Stockfish 5 is all over it at 38 ply, finding not only 11... Qd7 but also the sacrifical sequence 13... Nf4 and 14... Nxg2:

[Komodo 8 64-bit: Depth: 30 00:19:03  5355MN] 11... Nf4 12.Ne4 Na5 13.Bxf4 exf4 14.d4 Nxb3 15.axb3 f5 16.Nc5 Bxc5 17.dxc5 Qf6 18.Qe2 Qg6 19.Qe6+ Qxe6 20.Rxe6 Bxf3 21.gxf3 a5 22.Re5 a4 23.c6 axb3 24.Rxa8 Rxa8 25.cxb3 Ra6 26.Rxb5 Rxc6 27.Rxf5 Rg6+ 28.Kf1 Rb6 29.Rxf4 Rxb3 30.Rc4 Rxf3 31.Kg2 Rf7 32.Kg3 g6 33.Rc6 Kg7 34.f4 Rd7 35.Kg4 h5+ 36.Kg5 Rd5+ = (0.10)

[Houdini 4 x64B: Depth: 31/74 00:26:40  12588MN] 11... Nf4 12.Ne4 Na5 13.Bxf4 Nxb3 14.axb3 exf4 15.d4 f5 16.Ned2 Re8 17.c3 Qd5 18.Re5 Qf7 19.Qc2 Bd6 20.Rxf5 Qg6 21.Nh4 Qh6 22.Nhf3 Qg6 23.Nh4 = (0.00)  

[Stockfish 5 x64 Depth 38/56 00:42:40  12693MN]    11... Qd7 12.Nxe5 Nxe5 13.Rxe5 Nf4 14.Nf3 Nxg2 15.Kxg2 a5 16.c3 Ra6 17.d4 Rg6+ 18.Kh2 Bd6 19.Nh4 a4 20.Nxg6 hxg6 21.Qg4 Qxg4 22.hxg4 axb3 23.f4 Bxe5 24.fxe5 Ra8 25.a3 f6 26.Bf4 g5 27.Be3 Kf7 28.Kg3 Kg6 29.Re1 Re8 30.Bd2 Bd5 31.Rf1 = (0.05)

In Advanced Chess - Some Hints to Get Started  readers were admonished that "Advanced chess isn't speed chess. Never get in a hurry ... let the chess engine do its job!"  This advice also applies to home analysis; it  turns out Grandmasters and "teams of analysts" are not immune from basic computer analysis mistakes. 13... Nf6? demonstrates GM Aronian had not discerned the deep sacrificial possibilities (... Nf4 and ...Nxg2). If he had that analysis hidden away, was not a game against the previous world champion, in the candidates' tournament for the world's championship, the place to use it?
12.Nxe5 Nxe5 13.Rxe5

Position after 13. Rxe5

13 ... Nf4!

"This knight leap is more in the spirit of the Marshall gambit and leads to a piece sacrifice" (Kavalek).

[Stockfish 5 x64] 36:-0.37] 13...Nf4 14.Nf3 Nxg2 15.Kxg2 a5 16.c3 Ra6 17.d4 Rg6+ 18.Kh2 a4 19.Bc2 Bd6 20.Bf4 Rf6 21.Bxh7+ Kxh7 22.Qd3+ Kg8 -+.

14.Nf3 Nxg2!

"The Dutch grandmaster Anish Giri pointed out this sacrifice in the third issue of  New In Chess  last year. It was picked up by a few players, but the credit goes to computers.

"Komodo 8 suggests a different piece sacrifice: 14... Nxh3+ 15.gxh3 Bf6 16.Rh5 g6 with roughly equal chances" (Kavalek).

The rest of the Ivanchuk-So game: 15. Kxg2 a5 16. Rxe7 Qxe7 17. c3 Ra6 18. d4 Rf6 19. d5 a4 20. Bc2 Rd8 21. Qe1 Qd7 22. Ng5 h6 23. Ne4 Rg6+ 24. Kh2 f5 25. Ng3 Qxd5 26. Qg1 Qf3 0-1

Interested readers may also want to examine: Guliyev-Gustafsson, Baden-Baden 2014, 1/2-1/2 in 37 moves, and Jolly-Gozzoli, Erts 2014, 0-1 in 33 moves.