Tuesday, November 1, 2016

Season 6 superfinal, games 41-48

This is part 8 of my looking back at the Komodo-Stockfish superfinal match of season 6. Previous parts can be found at
part 1, games 1-8
part 2, games 9-16
part 3, games 17-24 
part 4, games 25-28
part 5, games 29-32 
part 6, games 33-36 
part 7, games 37-40

After 40 games Stockfish led 9-3 with 28 draws.

Stockfish was very happy after the opening of game 41, it had a knight for two pawns advantage and a queen side passer, as well as an eval over 1. Komodo had strong central pawns and as they advanced they started to look dangerous. Komodo then allowed Stockfish's knight to make a QR fork and gave a rook for the knight. Stockfish's eval jumped over 2 but Komodo saw a way out. Starting from move 41 both engines agreed on a 10 move sequence that removed most threats and left a QB vs Q ending. The evals were high but with almost no pawns left Komodo's queen was sufficient defense and the engines shuffled until a draw was agreed.
The reverse game was a lot less eventful. Stockfish gave two pawns on the king side to Komodo's queen, and this allowed Stockfish to force a repetition draw by attacking the queen.

In game 43 Stockfish again had an eval advantage after the opening, with a pawn up and a queen side passer. Evals clmbed to about 1 and stayed there for a while, but after several piece exchanges evals came down again. The game reached a drawn queen ending.
In the reverse game 44 Komodo started with the same pawn advantage and queen side passer. Stockfish exchanged queens and equalized before move 20.

Stockfish kept the initiative, got rid of Komodo's passer and the evals climbed above 1. After several exchanges Komodo's pieces could only hope to defend and block against Stockfish's threats.

For more than 15 moves it seemed Komodo was holding on, the engines were shuffling and the evals remained constant. Then after what appeared to be two blunders Stockfish exchanged B for N, the evals shot up and Komodo got itself in a world of trouble.

The c3 pawn was pinned and could not be defended. A few moves later Komodo's position collapsed, it faced queening threats and was about to lose material. Did Komodo really blunder the ending or was it going to lose in any case?

There were many early exchanges in game 45, with only RRB vs RRB remaining after move 25. Stockfish was a pawn up but with opposite color bishops that was not enough. After the rooks were exchanged the position was a drawn bishop ending. In game 46 again Stockfish was ahead with evals over 1.5 after sacrificing a bishop for pawns in return for a strong queen side attack on the white king. Komodo gave its queen for a rook and got out of immediate danger. In the RRN vs QR position it seemed the engines were shuffling with no real progress and evals did not move much. It took the engines more than 50 moves to realize it was a draw and 10 more for adjudication.

After the opening of game 47 Komodo kept playing moves Stockfish didn't expect. Komodo's eval stayed close to 0 while Stockfish's was close to 1. Then on move 21 Stockfish had enough, this time its eval shot up to over 2.

By playing d5 Stockfish blocked the center, making it hard for Komodo to move pieces around. This move also chased away the knight and opened up the diagonal for the bishop on f2. A few moves later Komodo realized it was in trouble after Stockfish sacrificed the bishop and exposed the black king.

Komodo could not defend against all the white pieces converging on its king. The game was over by move 33 before Stockfish gained enough material to force a win. It's very unusual to see such a short decisive game at this level.
The reverse game 48 developed along very different lines. Both engines castled to the queen side, Stockfish opened the e file and exchanged rooks and queens through it. The evals were never far from 0 and the game continued until the engines reached a drawn tablebase position.

In the last 4 openings Stockfish got 2 wins and 2 more games where it had a significant advantage and Komodo managed to draw. Komodo could not achieve anything in these openings, it is now trailing 11-3 with 34 draws and has no practical chance to win the match.

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