Sunday, November 15, 2015

Season 8 superfinal, games 11-20

After 20 games in the Komodo-Stockfish superfinal match Komodo is ahead by 2 wins, with 18 draws. The games continue to be quite fast, about 5 hours per game, which is remarkable given that each engine has 3 hours for the game plus increments. The high draw rate was to be expected but it's still annoying. Stockfish hasn't been able to win a game yet, and the Stockfish fans (myself included) are getting nervous. Is Komodo too strong this season?

In game 11 Komodo held on to an eval advantage that reached almost 0.5 at its peak. The pieces left in the middlegame were RRBN vs RRBB with Komodo a pawn up. Stockfish defended well, at one point it initiated a combination that left it with a bishop for two pawns down, one of which was an advanced passed pawn.

In order to stop the pawn Stockfish lost a bishop, reaching a drawn endgame of opposite color bishops with Komodo a pawn up. In the reverse game the small advantage Stockfish had as white evaporated much faster. The game contained a series of 16 consecutive plys where 15/16 were captures, leading to a quick tablebase draw.

Game 13 started with Komodo maintaining an eval advantage of about 0.4. Starting at move 20 Stockfish started moving the bishop and knight forward and back again, allowing Komodo several tempi to arrange the pieces for an attack.

Komodo put pressure on the d file until it was ready for the c5 push. When it came there started a series of captures that resulted in a double rook endgame with Komodo ahead by a knight for three pawns.

Stockfish put up a fight, and it was a slow technical endgame. The black pawns were slowly taken as well as a pair of rooks. Komodo had to keep at least one pawn to avoid a RN vs R ending.

Stockfish also was getting low on time, down to the increments. The 1 second overhead worked well to keep from time failure, but Komodo converted the win on the board. 

In the reverse game 14 Komodo defended differently against Stockfish's advantage in the opening. The position simplified quickly as before but this time the heavy pieces were left as well as almost all pawns.Stockfish space advantage was meaningless in this position and the eval remained constant for a while and then began to decrease. Komodo held the draw, adding an official win from this opening.

There was one unexpected event in game 15, a negative eval !! This was very rare, a first for this superfinal if I am not mistaken. It was only for about 5 moves and only got as far as -0.09, but at least we know it is possible. In game 16 Stockfish's eval gradually increased to about 0.4, with a pawn advantage. Komodo blockaded well and then exchanged a rook for a bishop to take over the 2nd rank. The white and black threats canceled out, another draw.

The negative eval came back in game 17, this time up to -0.14. Other than that there's not a lot to say about this draw. Stockfish needs much better scores if it wants to win a game. In game 18 Stockfish built an eval advantage of 0.8 when Komodo sent a rook forward and had to play carefully to get it back. The rook was caught and exchanged for a bishop in the end, but by then the position was simplified and the evals closer to 0. Komodo sealed the draw with a rook sacrifice and perpetual check.

Game 19 featured many captures from the start, reaching a RB vs RB endgame by move 23 which continued to a tablebase draw. In game 20 the pieces lasted longer but the evals sank to 0 again and another draw.

As the match progresses I find it difficult to both write reports and watch the games. I need more time !! 

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