Saturday, March 17, 2018

Season 11 premier division, after RR9

Crosstable after RR9

RR9 was one of the more interesting RRs of the division. Nine of the first eleven games were decisive, though only 5 of the remaining 17 games. Houdini lost its first game of the division, Ginkgo won its first.
Stockfish had its best RR score with 6/7, and with a win against Houdini it extended its lead to 4 points. Despite the loss Houdini is still 4.5 points ahead of Komodo, Houdini beat Komodo for the third time. 
Fizbo with a weak 1.5/7, including a loss to Ginkgo, it is now 4 points behind Chiron in 6th place.

A few interesting games
Stockfish - Chiron: Stockfish had an eval close to 1 after the start, it had a lot more space and it pushed pawns to open the king side. Evals jumped after Stockfish blocked the retreat of a forward black bishop, locked the queen side and started attacking on the king side. Chiron's position collapsed, it was down a rook for a knight when the game was adjudicated, with more material loss coming.

Houdini - Komodo: Houdini had an eval advantage that increased steadily. It advanced pawns on the king side, its king was exposed but safe with no black piece around. On the king side the pawns pushed back Komodo's bishops. Komodo exchanged one bishop but the other was trapped. Komodo tried to counter on the queen side, it sacrificed a pawn and created a passer. Houdini stopped the passer on the second rank and was two pawns up, it had no problem to convert this to a win - though the game was adjudicated before the win could be seen. This was Houdini's third win against Komodo in the division.

Ginkgo - Fire: The game reached a RBB vs RBN position on move 28 with evals close to 0. Fire had a strong pair of central pawns and Ginkgo traded a rook for a knight to get rid of them, leading to a B vs R endgame. Fire's evals increased constantly as the pawns were eliminated. The game reached a winning 6-man position, that was then played out for 60 moves since Ginkgo had no tablebase support.

Fire - Fizbo: Fizbo pushed pawns on the king side giving Fire the opportunity to exchange them and expose the black king. Fire gave a rook to get rid of a strong Fizbo knight and immediately regained the material to reach a QR vs QR position with evals over 1.5. The black pawns were all isolated and Fire was quickly two pawns up and winning.

Komodo - Ginkgo: Evals remained low while the position was closed. After opening a file on the queen side evals climbed over 1, and stayed there in a QRN vs QRB position as the engines shuffled for 15 moves. Ginkgo then opened another file on the queen side and captured the knight, this allowed Komodo to launch a deadly attack on the black king and force a R for Q trade. A queen side passer cost Ginkgo its bishop and the game was over.

Houdini - Chiron: Houdini's eval was over 2 already on move 16. Chiron's pawns were all isolated and Houdini had a strong king side threat, but evals did not move for 10 moves. Then Houdini shifted to the queen side, got a rook on the 7th rank and captured 2 pawns. The white passers on the queen side were enough for a win.

Ginkgo - Stockfish: Stockfish had an eval of about 1, the engines shuffled for a while behind the pawn lines. When Ginkgo walked its king to the queen side Stockfish opened files there and moved its pieces to prepare an attack. Ginko's king had no pawns to protect it, Stockfish had full control of the light squares with its LSB. Soon Ginkgo ran out of ideas and the game was adjudicated, PVs showing total collapse.

Fizbo - Komodo: Fizbo was ahead by a rook for a knight, Komodo with two extra pawns to balance the material. The game reached a RRB vs RBN position with evals slightly in Komodo's favor. In the endgame Komodo played much better, its king walked to the queen side and after exchanging bishops the queen side passers were unstoppable.

Stockfish - Fizbo: The engines castled in opposite directions and Stockfish had an eval advantage. Fizbo tried a pawn storm on the king side, with one pawn reaching the 2nd rank. Stockfish hid its king behind the black pawn and countered on the queen side with a much stronger attack. Fizbo had to give a rook for a bishop, leading to a winning QRB vs QBN position.

Houdini - Ginkgo: Houdini started with an eval advantage, Ginkgo's king remained uncastled in the center. Ginkgo had advanced pawns on the queen side, after move 24 the evals turned negative since the pawns were trapping a bishop and a rook in the corner. Evals increased to around 1, Houdini was busy blocking the pawns and it seemed that Ginkgo could find a way to break the defence. However, after move 46 the evals dropped to 0, Ginkgo lost the initiative and the engines exchanged down to a drawn RRB vs RRB position. Still no win for Ginkgo, a win in black against Houdini would have been an incredible upset.

Chiron - Komodo: Evals were close to 0 with a small advantage for Komodo. After exchanging queens the evals stayed constant for a long time in a RBN vs RBB position. The engines shuffled except for a few pawn moves and exchanges, reaching a N vs B ending. Komodo's eval suddenly jumped as it found the way to win. It brought the king forward and Chiron couldn't defend both sides of the board.

Stockfish - Fire: Stockfish had an eval advantage, climbing over 1 after it captured a pawn on the queen side. Stockfish gave a pawn to create a queen side passer, and Fire lost a piece to get rid of it. Fire had three pawns as compensation, but Stockfish used a king side attack and a second queen side passer to get a decisive advantage. Fire had to give a rook for a knight, and Stockfish converted the QRR vs QR position easily.

Houdini - Andscacs: For 35 moves the evals were close to 0, after exchanging queens Houdini's evals started to climb in a RBN vs RBB position. Andscacs' king was trapped in the corner and under threat of mate, with only a pinned bishop on the back rank defending. Houdini allowed all its pawns to be captured as it brought the knight forward, Andscacs escaped the mate but lost its rook. The black pawns were not enough in a RN vs B ending, a win for Houdini.

Ginkgo - Fizbo: Ginkgo was a pawn up early in the game, the engines started to shuffle with evals at around 1. After several exchanges only QRB vs QRB were left, the evals climbed to a new level and the shuffling resumed. After 30 moves Ginkgo was ready with its pieces and it attacked the queen side, creating a passer. After trading the queen for a rook Ginkgo queened the passer, and with a rook up it was winning. Finally a win for Ginkgo in the division.

Featured game: Stockfish - Houdini
Premier division, round 58
Link to game on TCEC

Stockfish had an eval advantage from the opening. Houdini chose to give a knight for pawns early, exposing the white king for counterplay.

Stockfish was not afraid of leaving its king on its own, even moving it forward. Houdini played defensively, trying to avoid exchange pieces. Stockfish had time to get its knight to a strong square on the king side where it could reach both the central pawns and the black king. The evals climbed higher, though Houdini was still not convinced.

Houdini gave a rook to get rid of the white knight, capturing another pawn. Stockfish was up a rook for 4 pawns, and many of the black pawns were easy targets. Houdini's position was desperate, and its only hope was to get the queen forward and try to check the exposed white king.

Stockfish had to be careful not to allow a perpetual check draw. Eventually Houdini ran out of checks and it gave up. This was the first loss for Houdini in the division, it was the only engine that was undefeated up to this game. Stockfish lead grew to 3.5 points over Houdini, it is hard to imagine that Houdini can close this gap in the remaining games.

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