Tuesday, June 26, 2018

Season 12 superfinal, games 27-32

After 32 games Stockfish leads 7-2 with 23 draws. The number of decisive games is quite high, Jeroen's openings are working better than expected. Most openings give a substantial advantage to one side, and yet none of the openings so far resulted in two wins, one per engine.

Stockfish's eval was around 1 from the start of game 14.1. Stockfish pushed pawns on the king side, leaving its king exposed. Komodo went up a pawn yet Stockfish continued to be ahead on eval. Stockfish created a passer in the center, and Komodo was reluctant to push its king side pawns to keep its king safe.

The position became static and the engines started to shuffle. The game seemed to be heading for a draw, evals slowly drifting down. Then with 19 moves left on the 50 move counter Stockfish's eval jumped as it pushed the d pawn forward. Komodo realized something was wrong two moves too late. Stockfish gave a second pawn and opened the queen side.

Komodo's defense collapsed quickly. Stockfish lost the d pawn but its a pawn became a passer. Komodo exchanged pieces, giving a rook for a knight, then it gave a knight to stop the white a pawn.

This meant Stockfish was a rook up in a RRB vs RB position. It took a while but there was no doubt Stockfish was winning.

In the reverse game 14.2 Komodo kept the king side closed. Stockfish's eval stayed close to 0, Komodo's eval was about 0.5 for a while. Komodo created a passer in the center but it wasn't strong enough. Stockfish exchanged pieces, clearing the queen side, evals were at 0 despite Komodo's bishop pair and queen side passer. The game was adjudicated by the draw rule.

Stockfish's eval climbed over 1 after the start of game 15.1. The engines castled in opposite directions, Stockfish pushed pawns on the king side and Komodo controlled an open file on the queen side. The engines started to shuffle essentially from move 27, evals staying constant. On move 70 Komodo moved a pawn unexpectedly. It then won a rook for a bishop, Stockfish's eval did not move but Komodo's eval came down.

Komodo was playing on increment, its king found safety behind the white pawns and Stockfish realized it couldn't attack on the king side. Then suddenly evals turned negative. Komodo doubled rooks on the g file and pushed its passer, even though this weakened its king's defense. Through a rook exchange the passer reached the f3 square in a QBN vs QRB position, evals over 1 for Komodo.

Both engines were blitzing moves, for a while Komodo looked for a way to improve and then evals continued to increase. Komodo gave a pawn to open the queen side, then used this to force a queen exchange. Evals were close to 5 at this point.

The white pawns started to fall as Stockfish had to block the passer and could not protect them. The black king came forward and three king side passers were good for a win. An amazing turnaround for Komodo.

There were many early exchanges in the reverse game 15.2. On move 25 only QRN vs QRB remained. Komodo was a pawn up but evals came down to 0, the game ended in a draw when the pawns stopped moving. Komodo wins its second minimatch, after winning the first one and losing 6 since.

Stockfish's eval was again over 1 quickly in game 16.1. The engines castled in opposite directions, this time Komodo castled long. Komodo made a hole on the king side and Stockfish pushed pawns on the queen side. After a few exchanges Stockfish had the bishop pair advantage.

For a while Stockfish's plan was not clear, the pieces moved around and evals did not change much. Then Stockfish traded a bishop for a knight, losing its bishop pair but gaining a pawn majority on the queen side.

Komodo struggled to stop the white queen side pawns and to keep its king protected. It tried to counter on the king side, giving a knight for 2 pawns and threatening the white king. Stockfish exchanged queens, with an eval over 4.

Stockfish was a piece up in a RRB vs RR position.The game was soon adjdicated though we didn't get to see how Stockfish converts the win.

In the reverse game 16.2 Stockfish exchanged queens early. The engines continued to exchange pieces until on move 31 only RB vs RN remained. Evals fell to 0 and the game was adjudicated as soon as the pawns stopped moving. Another minimatch win for Stockfish.

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