Engine Snacks! To sac or not to sac?

November 8, 2021 Matthew Sadler No comments exist

Engines are amazing at sacrificing material, both in attack and defense. Leela neutralizes unpleasant pressure against its position with a fabulous pawn sacrifice leaving Stockfish with no winning chances. All players should study how engines defend – nobody does it better!

Position after 13.Be2 (game)

One of the most difficult skills in practical chess is that of judging proportionality. By that I mean, knowing whether the course of action you are taking properly fits the needs of the position. I am frequently amazed at the ease with which engines sacrifice material when ahead, in particular daring positional exchange sacrifices which they then assess as +3! I give many examples of this in “The Silicon Road to Chess Improvement“. My struggle with such play is usually not the sacrifice itself, but my uncertainty as to whether I’m overdoing things when a simple, sober continuation would be more effective. “Less is more!” as the English expression goes!
Similarly, engines – in particular Stockfish and Leela – are extremely willing to give up material when defending. Once again the challenge is often in deciding whether you are overreacting! “Is my position that bad, do I really need to give material back?”
There’s no easy answer to it! Particularly in defense, giving back material is related to the skill of judging the long-term course of the game. You have to “feel out” the future course of the game and “sense” whether you need to take action to change it. I often try to do this by calculating sample lines and running them through my head. The lines aren’t necessarily best play, but they are plausible, natural play and hopefully give some insight into whether extraordinary actions are required or not.
This game taken from the 1st game of the Season 17 SuperFinal between Leela and Stockfish (won by Leela 52.5-47.5) is a beautiful example of Leela giving up a pawn to ease its defensive burden, but I’m still not 100% sure whether it was necessary!

Position after 13…h5!

Amazing! Chess24 did a review of the Season 17 SuperFinal halfway through the match and Anish Giri, Laurent Fressinet and Peter Heine Nielsen all expressed their amazement and awe at this move. White has sacrificed a pawn for general pressure against the black position. It’s hard to point at any specific White threats at the moment but the pressure against h7 and the passive black rook on h8 are definitely part of it.
13…h5 turns this last factor on its head! If 14.Bxh5, then White itself is under pressure on the h-file with its bishop pinned to the rook on h1! And after 14.Rxh5 Rxh5 15.Bxh5, the value of the h-file for White has been completely neutralized leaving Black with few problems. It’s a beautiful, clean equalizing idea. Somehow though, part of me curls its lip and stamps its feet and says “But I was a pawn up!”

14.Rxh5 Rxh5 15.Bxh5 Qe7 16.Nb3 c6 17.c4 dxc4 18.Rxc4 Bd7 19.Na5 0–0–0 20.Qb1 Be8 21.Bf3 Qc7 22.Qb4 Qb6 23.Qa3 Nc7 24.Nb3 Bd7 25.Rb4 Nb5 26.Qb2 Qc7 27.Nc5 Qa5 28.Nxd7 Kxd7 29.Kf1 Nd6 30.Qd4 Kc7 31.Rb2 Re8 32.Rd2 Rd8 33.Rb2 Nb5 34.Qe5+ Rd6 35.Qe7+ Rd7 36.Qe5+ Rd6 37.Qe7+ Rd7 38.Qe5+ Kb6 39.Qf6 a6 40.Kg1 Qa3 41.Rc2 Qe7 42.Qb2 Ka7 43.Bg4 Rd8 44.a4 Nc7 45.Rc4 Rd3 46.Be2 Rd5 47.Bh5 f6 48.Bf3 Rd3 49.Re4 Qd6 50.Rb4 b5 51.axb5 axb5 52.Qa2+ Kb6 53.Rb1 Ra3 54.Qf7 Qe6 55.Qg7 Ra4 56.Rc1 c5 57.Kh2 c4 58.Rb1 Qe5 59.Qd7 Ka5 60.Bc6 c3 61.f4 gxf4 62.gxf4 Qh5+ 63.Kg1 Kb6 64.Bxb5 Nxb5 65.Qd6+ Kb7 66.Qd7+ Kb6 67.f5 Qe2 68.Qd6+ Kb7 69.Qc5 Ra5 70.Qe7+ Kc8 71.Qe6+ Kc7 72.Qe7+ Kc8 73.Qe6+ Kc7 ½–½

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