23 April 2018

A Double-edged King's Indian

In last week's post, Stockfish Wins TCEC Season 11, I noted,

The final score in the TCEC superfinal match was +20-2=78. A 59-41% margin of victory indicates that Stockfish is about 65 Elo points ahead of Houdini

In other words, Stockfish ('S' in the following discussion) beat Houdini ('H') convincingly. As in past TCEC superfinals, the engines took turns playing both sides of opening variations dictated in advance by the organizers. Stockfish had White in the odd-numbered games, and the following table shows how the two engines fared with each color, i.e. Houdini's two wins were with the White pieces:-

S-H: +13-0=37
H-S: +  2-7=41

In one pair of games -- the 29th and 30th -- Stockfish won both as White and as Black. The opening was labelled the 'King's Indian: Mar del Plata', and the first 14 moves were fed to the engines:-

1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nf3 O-O 6.Be2 e5 7.O-O Nc6 8.d5 Ne7 9.Ne1 Nd7 10.Be3 f5 11.f3 f4 12.Bf2 g5 13.Nd3 Nf6 14.c5 Ng6

The top diagram in the following chart shows the position where the engines started to think for themselves.

The bottom diagram shows the evaluations given to the resulting positions for the rest of the two games. On its first free move, Stockfish as White played 15.Rc1, while Houdini as White played 15.Kh1. The two moves make a sharp contrast. Stockfish's choice was offensive, while Houdini's was defensive.

For the rest of both games, Stockfish's evaluation of the position was invariably more accurate than Houdini's. Its forecast for the trend of the game came always a few moves ahead of Houdini's. If these had been human players, we could easily say that Stockfish had a better understanding of the position than Houdini.

As White, Stockfish won by breaking through on the Queenside, creating an advanced passed Pawn, and converting an endgame advantage. As Black, it won by a crushing attack on the Kingside. These are exactly the strategies that the position requires after move 14.

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