Monday, August 17, 2015

Memorable Stockfish games, part 1

I am a Stockfish fan. I'm not a fanatic who thinks it should win every game, and I have nothing against other engines. I find the idea of an open source engine very appealing and a miracle that it can be developed by many collaborating programmers without being slowed down by bugs. When I started watching TCEC it was the new engine on the block, the underdog, and it finished a close second. In season 6 it was nearly invincible with a quick offensive style that was great to watch. In season 7 it had many disappointing games, and it made me feel frustrated. I don't get as emotional watching other engines play, it's just the way it is.

In the past 4 seasons there were many beautiful chess games in TCEC, usually I forget them after a few days. There are a few Stockfish games which I remember, not the specifics but a move or a situation which amazed me, made me stare in disbelief, enough to be stored in my long term memory. In this list of posts I will present these games as best I can.

Other Stockfish memorable games:
part 2
part 3

Season 5, stage 4, game 6.3, Stockfish - Houdini, +10 difference

Game on TCEC archive

This was the second game between Stockfish and Houdini in this stage. The reversed game ended in a draw without special events, and this game appeared to be uneventful as well. The pawn structure had been almost static for the past 15 moves, both engines moving pieces without any apparent aim. Then Houdini played 38 ... Rf4 with less than 90 seconds of thinking.

WHAT? Why is Houdini offering a rook? And being so cool about it? Apparently it thinks that after taking the white knight it can create enough pressure with the queen and knight to compensate, maybe get a perpetual check.

Sure enough, for the next 10 moves Stockfish goes along with the exact plan Houdini shows in its principal variation. At first Stockfish agrees with Houdini's evaluation, but at move 42 the score jumps to 2.18 and at move 46 it jumps to 7.33 !

Stockfish is convinced it's winning and Houdini can't see it. On move 48 Stockfish's score reaches 10.88, and Houdini still thinks it is safe. This +10 points difference is amazing. Only now does Houdini think hard and it realizes that white can escape the perpetual and the d pawn is unstoppable.

The game was over after a few more moves.

The huge difference in scores, the fact that it took Houdini 7 moves to realize something was wrong with its plan, long after Stockfish thought it was all over, all this was a clear demonstration of Stockfish's superiority over Houdini.

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