Saturday, January 27, 2018

Season 11 division 1, after 2RR

Crosstable after 2RR

The current draw rate is 44/56 (78.6%). The high number of draws could be explained by the bookless openings. Another possibility is that the engines in division 1 are similar in strength. I hope that in the next RRs the book sequences will help reduce the draw rate.

The score differences between the engines are small so far, only 2.5 points separate first and last place after 14 rounds. Fizbo, Andscacs and Gull are leading, these are the engines with a positive score. The rest of the engines are more likely to struggle against relegation. The division 2 engines Laser and Jonny are in the bottom of the table together with Nirvana. Laser has 4 losses and is still in the race due to its wins against Jonny and Nirvana. I still think it is the most likely engine to finish last in the division.

There were two crashes so far, Nirvana crashed on move 1 against Fizbo, Hannibal crashed against Nirvana.

A few interesting games

Laser - Andscacs: Andscacs equalized after the opening, and following a series of exchanges only RRB vs RRN were left at move 22. Laser had an isolated passer that Andscacs blocked with the knight, Andscacs had a pawn majority on the king side and was ahead on eval. The pawns on the board limited the rooks' movement, Andscacs found a path for one rook and was able to capture a pawn. Evals were over 1 and rising, Andscacs brought its king to support the king side pawns. Laser exchanged a pair of rooks but could not avoid defeat. This was the first decisive game after 9 draws. It is interesting to note that Andscacs won the endgame without tablebase support, while Laser does have access to tablebases.

Hannibal - Jonny: The game reached a 6-man drawn position KQP vs KRB. Jonny knew this was a draw but Hannibal did not have tablebases support and gave a winning eval, even a ridiculous mate in 15 eval at one point.

Nirvana - Fizbo: Fizbo was sure it was ahead, with evals constantly increasing. After exchanging almost all pieces the game reached an opposite color bishops ending, and despite being 2 pawns up and evals over 3 Fizbo could only get a draw.

Jonny - Gull: There were almost no exchanges for the first 25 moves and evals were close to 0. On move 34 Gull created a pawn majority on the queen side, Jonny chose to trade a knight for a pawn and eliminate the queen side pawns. The extra piece was enough for Gull to win the game. Why did Jonny give a piece for a pawn, was it losing in any case?

Laser - Nirvana: Most pawns remained on the board in the beginning of the game, all knights were off on move 24. Laser's pawn structure looked a mess, but it was ahead on eval. It managed to capture a pawn and then stabilize the king side with its bishop. Evals were over 1.5 after several exchanges that left QRB vs QRB, Nirvana with a queen side passer and Laser 2 pawns ahead. Laser chose to exchange queens, and since the bishops were of opposite color there was a potential for a draw despite the eval and pawn advantage. However, after a long period of shuffling Laser found the winning line, its king joining the king side pawns as they marched forward.

Andscacs - Fizbo: Fizbo came out of the opening with a better pawn structure. On move 34 it was a pawn up, with a passer on the queen side an eval over 1.5. Andscacs defended well, it captured the passer and exchanged down to a RN vs RN position. Fizbo continued to fight but Andscacs secured a draw. It was surprising for me that Andscacs could get in trouble with white, and with no book. Perhaps Fizbo is stronger than I think.

Booot - Gull: Booot sacrificed a bishop for 2 pawns and exposed the black king, with a small eval advantage for white. Gull gave the material back and the engines exchanged pieces until reaching a rook ending with Booot a pawn up. Gull was sure it was safe, its eval remained constant. Booot, though, found a way to improve and realized it was winning. The game ended in a tablebase RP vs R win (usually these are draws).

Laser - Hannibal: Only RB vs RB were left by move 27. Laser had tablebase support and gave a rook for a bishop to get a 6-man draw. Hannibal had no tablebase support and it thought it was winning for 70 more moves.

Gull - Laser: Gull outplayed Laser after the opening, with the black queen stuck in the queen side Gull took over the center with a strong bishop. Laser exchanged knights for the two strong bishops, but then Gull was a pawn up with central passers. Evals continued to increase as Laser was forced to lose a knight to stop the passers. The game reached a RN vs R position, a win for Gull. 

Fizbo - Booot: Booot played the opening badly and Fizbo's eval was over 1 after 10 moves. Fizbo's king remained in the center while it opened up the king side and threatened the black king. Booot exchanged queens and a pair of rooks, in a RBN vs RNN its king was out of immediate danger but evals were climbing. Fizbo's pieces were much better placed, Booot's knights could hardly move and its king was still under threat. Fizbo won a pawn and the game was adjudicated before we could see the actual win.

After 1RR Fizbo, Andscacs and Gull are leading at +1; Jonny, Nirvana and Laser are behind at -1; Booot and Hannibal are at 0. 

Fizbo - Laser: Fizbo attacked on the king side, Laser realized it was in danger when it was too late. The defending black pieces could hardly move and Fizbo began capturing pawns and advancing a passer. The game was quickly over.

Gull - Nirvana: The game reached a BN vs NN position on move 34 with evals close to 0. Nirvana chose to sacrifice a knight for pawns, but this turned out to be a mistake. Gull had enough time to stop two queen side passers and another on the king side, and it kept a single pawn that was enough to secure a win.

Laser - Jonny: Jonny sacrificed a bishop for pawns to expose the white king. Laser secured its king and there was no immediate threat. The engines exchanged pieces until only QRB vs QR were left. Jonny had 3 extra pawns but it was Laser's central passer than made the difference. Laser advanced the passer to the 7th rank, tying down the black rook. The white bishop was the same color as the queening square, and eventually Laser used it to capture the black rook, winning the game.

Featured game: Andscacs - Laser
Division 1, round 14
Link to game on TCEC

Andscacs had a small eval advantage from the opening, it increased to about 0.6 and stayed there for a long time. Laser seemed to be holding in a RRN vs RRB position with a slightly worse pawn structure.

Andscacs' king came forward with evals jumping over 2. The king was the extra piece that was needed to break Laser's defense. The black pawns were all isolated, the pieces guarding them needed to be protected as well.

After exchaging a rook pair Andscacs focused on the black f pawn. It was protected by the bishop and the other black pieces could not help and had other targets to defend.

Laser had to let go of the pawn eventually. This created a passer for white, enough to win the game.

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