Friday, June 22, 2018

Season 12 superfinal, games 9-16

After 16 games Stockfish is leading 3-1 with 12 draws.

Stockfish had an eval advantage from the start of game 5.1, Komodo was less impressed as usual. The engines castled in opposite directions, Stockfish pushed pawns on the king side facing the black king. After opening the king side Stockfish had two pawns that looked dangerous, Komodo blocked them and used them as shields. Komodo had a passer in the center and its eval was still low.

Stockfish cleared the black queen side pawns and created a passer, Komodo exchanged pieces and removed the immediate threat to its king. The game reached a QRB vs QRN position, Stockfish's eval was over 2 but it was not clear how it would improve.

For a while Stockfish moved its pieces with no apparent purpose. This changed when it managed to capture the d pawn. Now it had a connected pair of passers on the queen side, still on the 2nd rank but very threatening in the long run, especially after the queens were exchanged.

Komodo did not have enough strength to stop the advancing passers, the game was soon adjudicated. 

There were many early exchanges in the reverse game 5.2. Evals were close to 0 after only RB vs RB were left on move 33, the game ended as soon as the pawns stopped moving and the draw rule was activated. Stockfish in the lead after 5 openings.

Stockfish started game 6.1 with an eval around 1. The engines castled in opposite directions, Stockfish pushed pawns on the king side. Evals started to increase as the white king moved to the corner away from Komodo's pieces. Stockfish opened the king side and its eval was over 2.

Komodo exchanged pieces to stop the king side attack. After it gave a rook for a knight and pawn the game reached a QRR vs QRN position, Stockfish's eval was over 3.

Stockfish avoided exchanging queens, it used the exposed black king to make threats and checks. In this way it managed to capture a pawn and only then to exchange queens. Evals continued to increase all the time.

It was clear that Stockfish was winning, it was just a matter of technique. The white pawns started to advance on the queen side, supported by the king. When Stockfish captured a pawn and created a passer the game was over.

In the reverse game 6.2 evals stayed low. Both engines castled short and there were no attacks. After a series of exchanges most pieces were gone by move 39, and a few moves later the game reached a queen ending. Evals were 0 and when pawns stopped moving the draw rule was activated. A second straight minimatch win for Stockfish.

Stockfish started game 7.1 with a rook for a knight advantage, eval around 1.4. Komodo's king was uncastled in the center, it found safety on the queen side. After move 25 evals started to fall, the position opened and the engines started to exchange pieces. On move 36 only RRB vs RBB remained, Komodo's bishop pair and advanced passer were strong enough to counter Stockfish's rook pair and hold the draw.
In game 7.2 evals turned negative despite the material advantage for white, Komodo's queen side was undeveloped and Stockfish attacked on the king side. Komodo exchanged queens and bishops to stop the immediate threat, Stockfish pushed pawns on the king side and created an advanced passer. Komodo gave a rook for a knight to remove the passer, the game reached a RBN vs RBN position on move 40 and the evals started to drift down to 0 and a draw.

In game 8.1 most pieces were on the board in an open position, Stockfish's eval fluctuated under 1 and Komodo's eval was around 0.5. Most of the action was on the queen side. After exchanging queens on move 43 the evals started to come down, and they dropped to 0 when the game reached a RN vs RB position on move 57. The game ended in a tablebase draw. In game 8.2 there were many early exchanges. Stockfish's eval was close to 0 throughout the game, Komodo's was close to 0.5 for a while and then came down. After exchanging queens the game reached a RN vs RB position, the game ended in a repetition.

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