Sunday, February 25, 2018

Season 11 premier division, after RR3

Crosstable after RR3

Stockfish and Houdini lead the table. Komodo in 3rd had a weak RR with 3.5/7 points including a loss to Houdini. Houdini is the only engine without loss.
Ginkgo closes the table with no wins. Fizbo is in 7th after a solid 3/7 points in the RR, including an unexpected win against higher placed Chiron. The gap to Andscacs in 6th place increased to 2.5 points.

A few interesting games

Stockfish - Chiron: Stockfish had an eval advantage after the opening, material was equal but Chiron had two weak pawns that were targets for attack. Evals increased over 1.5 after Chiron gave a pawn, trying to activate its pieces. In a QBN vs QBN position Chiron tried to build a fortress. After a series of checks Stockfish captured a second pawn and that was enough for a win. This win was important for Stockfish fans, in season 10 stage 2 Chiron drew its 4 games with Stockfish and that was part of the reason Stockfish did not qualify for the superfinal.

Fire - Fizbo: The game was balanced with a small eval advantage for Fire. Evals jumped over 1 when Fire gave a rook for a bishop and created a passer in the center. In a QBB vs QRN position the passer was too strong. Fizbo tried to counter with a desperate attack on the white king, the game was adjudicated before it lost more material.

Ginkgo - Stockfish: Stockfish took over the game with a pawn push in the center that resulted in a R for BN trade and a black pawn on the 2nd rank. Ginkgo gave a knight for the passer and the game reached a RB vs RR endgame, Ginkgo up 2 pawns. The endgame was difficult but Stockfish had no real problem. It brought the king forward and exchanged a pair of rooks. Ginkgo seemed ahead on material when the game was adjudicated but the white king side pawns were about to be eliminated.

Komodo - Andscacs: Andscacs left its king exposed facing Komodo's rooks in open files. Komodo chased the black king while winning material, eventually it was a rook up when the game was adjudicated.

Stockfish - Fizbo: After exchanging queens Stockfish blocked the king side with its knights, evals rising over 1. Fizbo countered on the queen side as Stockfish was a pawn up in a RRN vs RRB position. Fizbo lost more material and the game was over.

Houdini - Ginkgo: Houdini's eval was close to 1 out of book, Ginkgo's position was completely blocked and Houdini patiently prepared its king side attack. When Houdini was ready evals were already close to winning and the game was adjudicated before the captures began.

Ginkgo - Chiron: Ginkgo had a small eval advantage and was a pawn up. The center was cleared and Ginkgo's king exposed, Chiron's pieces started to target the white king and the eval changed to negative. Ginkgo pushed a passer to the 7th rank but couldn't go further. After Chiron captured the passer and the engines exchanged most pieces the game reached a BN vs BB ending with Chiron a pawn up. The white pieces were passive and the bishop pair was decisive for Chiron. This is the third loss in a row for Ginkgo, two playing white.

Stockfish - Fire: Stockfish started with an eval close to 1. Fire thought it was relatively safe for a while, material remained equal but Stockfish's gradually increased. When Stockfish pushed a central passer to the 7th rank Fire started to feel the pressure. The game reached a QRB vs QRB position, Fire got rid of the white passer and material was still balanced. However, through checks and pins Stockfish captured a pawn and traded down to a winning rook ending.

Fizbo - Chiron: Fizbo started with an eval close to 1 which Chiron didn't believe. As the game progressed and pieces were exchanged it became clear that Chiron had two weak pawns that Fizbo could target, and Chiron had less space for its defending pieces. In a QRB vs QRB position the black pieces were too busy and gradually Fizbo forced Chiron to let go of a pawn. The game was adjudicated before Fizbo won more material. A surprising win for Fizbo against a better opponent.

Andscacs - Ginkgo: Andscacs started with an eval advantage which gradually increased. Eventually Ginkgo lost a piece without real compensation, the game reached a QR vs QB position won for white.

Fire - Houdini: Fire was slightly ahead for the first 30 moves, evals were close to 0 after it gave a rook for a bishop and an advanced passer. Houdini exchanged pieces and captured the passer, evals became slightly negative though Fire still had queen side passers in a QBN vs QRN position. The evals jumped when Houdini found a way to make mate threats, forcing exchanges and reaching a won B vs R ending, despite being 3 pawns down.

Featured game: Houdini - Komodo
Premier division, round 15
Link to game on TCEC

Houdini had an eval advantage after the opening. The engines castled in opposite directions and both kings were slightly exposed, though not directly threatened. Houdini had a bishop pair and a better pawn structure, Komodo had weak c and h pawns.

Evals slowly increased and were above 1 when Houdini captured the black h pawn. Komodo didn't try to protect the pawn, instead it countered in the center with a forward rook. Houdini was a pawn up with a king side passer that looked like a potential problem for black.

The engines exchanges bishops and started to shuffle. For a long time evals remained constant, Houdini was reluctant to push its passer while Komodo took over the 2nd rank and was threatening the white king. The evals started to climb again after Houdini exchanged rooks and finally moved the passer forward.

Houdini still had to keep its king safe but after exchanging queens the threat was over and Komodo had to scramble to stop the advancing passer. Komodo stopped the passer only to reach a losing rook endgame. This was Komodo's first loss in the disivion. Was it always winning for white? Could Komodo have defended better?

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