Thursday, July 7, 2016

Season 9, stage 2, rounds 16-18

Table after 18 rounds:

The draw rate is 81/144 (56%).
Remember that the first 12 games of the stage were draws? 8/12 of the rematches were decisive ! Another confirmation of Cato's excellent opening choices, as if it is needed. Cato is the best.
Komodo and Stockfish are leading, only 0.5 points separating them. Jonny and Fire are still unbeaten in the stage. The battle for 8th place is fought between Ginkgo, Rybka, Hannibal and Nirvana. Only one of seven games within this group has been decisive so far.

Some of the game highlights

Raptor became very excited against Naum, a rare occasion for Raptor in this stage. It had a strong queen side attack on the black king and Naum's pieces were on the other side of the board. First Raptor won a rook for a bishop, then Naum's counterplay resulted in further exchanges leaving Raptor a full knight ahead. When all other pieces were removed the knight guaranteed the win for white.

Ginkgo's king came under attack very quickly against Komodo. Evals for black increased rapidly as Komodo gave a rook for a bishop, exposing the white king to its QBB. Ginkgo exchanged pieces to stop the attack, reaching a RBN vs RBB endgame two pawns down. Komodo continued patiently to improve its position, taking pawns and exchanging pieces slowly. The game was stopped in a bishop ending with Komodo four pawns up.

Houdini - Protector had stable pawn lines and stable evals that were close to zero for about 50 moves. Then a few pawns were exchanged and white's evals increased a little, but still it seemed Protector was holding for another 20 moves. The first breakthrough came when Houdini won a pawn, and then exchanged a rook for a knight and pawns. The evals were above 2 in a RNN vs RRN position, and stayed there for a while. Houdini finally sealed the win when the pawns started to march and Protecor started to lose material. Slow win, 114 moves.

Stockfish was up a pawn against Chiron at the start of the game. The evals started jumping when Stockfish was able to get a rook and a queen to the black back rank, the win was just a matter of time. The game was stopped with Stockfish a knight and three pawns up.

Vajolet2 - Andscacs started with an advantage for white but Andscacs equalized and then took the initiative. For a long time the evals remained stable as pieces were being exchanged. In a R vs BN position with two king side pawns for each engine I was sure the game was a dead draw. However, instead of the 50-move rule suddenly the evals started to jump again. Andscacs found a way to get the king to help and take a white pawn. The game was won with a queening threat for black. Not using tablebases - well done Andscacs.

Jonny had an eval advantage against Raptor from the start. For a while it seemed Raptor could hold the pawn line but Jonny found the right moves to open up the king side. The white attack through the g and h files was deadly, game was stopped before Raptor lost material.

A king side attack gave Gull a pawn advantage over Vajolet2, and then through gradual maneuvering was able to attack the weak pawn structure of black and gain two more pawns. Vajolet2 tried to counter with an attack on the white king but Gull had no trouble defending. It was just a matter of time until the game was over.

Hannibal had an eval advantage against Stockfish, but Stockfish equalized and gave two rooks for a queen. After exchanging pieces and pawns the position opened up and Stockfish gained the initiative in a RRN vs QB endgame. It won a pawn and created a passer, while the black king found relative safety in the center. Hannibal could not stop the passer until it had to commit a rook for blocking, the game was over a few moves later. Stockfish won both sides of this opening, a first for this stage.

It was a mini surprise that Komodo could only draw against Naum. Komodo had a clear eval advantage out of the opening but Naum equalized quickly and most of the game was waiting for a draw with evals at zero.

Raptor chose to exchange RN for a queen early against Komodo, and both engines thought they had an advantage. This went on for more than 25 moves, Komodo's eval kept increasing until Raptor realized it had a problem. While it was keeping the rooks out of its back ranks Komodo grabbed a pawn, advanced its pawns and the evals climbed to winning values. The game stopped without showing us the path Komodo would take to victory, but the PVs displayed more pawn grabbing and exchanging down. Komodo with a first double win as well.

Ginkgo had an eval advantage against Chiron, but it was difficult to get past the pawn line. By exchanging rooks Ginkgo created a passer that forced Chiron to block it with a piece. When Ginkgo found a way to open up the position it just exchanged everything, grabbing pawns when possible. The end position was a rook ending with white two pawns up, three passers.

Houdini had an eval advantage over Hannibal, but it seemed that Hannibal's defense was strong. Both engines started shuffling pieces and we were waiting for the 50-move rule to end the game. Suddenly Houdini's eval jumped to over 3 and Hannibal agrees - what? If you think it's a blunder why make the move?? The whole position collapsed with pawns and pieces exchanged, and the end result was a winning rook ending with two pawns up for Houdini. 

Stockfish was up a rook for a bishop against Andscacs. For a while it seemed the black bishop pair was enough compensation for a defence, evals stayed more or less constant. In the RN vs BB ending Stockfish was able to find a win, perhaps it was the lack of tablebases for Andscacs that helped.

Featured game: Jonny - Rybka
Stage 2, round 16
Link to game on TCEC

Jonny was unbeaten so far in the stage (not counting Chiron's crash in a winning position...)
and generally playing better than what was expected. In the first round game Jonny played black. The game was uneventful and ended in a draw. Could Rybka, as a past champion, stop Jonny in white? 

After a series of exchanges in the center Jonny was a knight down for two pawns, one pawn was an advanced passer. The evals were still very close to zero.

Rybka was a little careless in the defence. It had several opportunities to exchange queens (Jonny expected this in its PV) but it chose to grab a pawn instead. In the meantime Jonny slowly advanced the e pawn until it connected with the d pawn.

BOOM. The evals jumped to almost 3. The threat of the pawn pair was too much for Rybka, and it immediately gave a bishop to take them out. By that time Rybka realized it was in trouble, and Jonny's evals were over 11.

Jonny had too many threats on the exposed black king. To get out of the mating net Rybka had to give significant material, and the game was stopped. Impressive, Jonny is playing well in this stage.

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