Friday, May 24, 2019

Season 15 superfinal, games 61-70

After 70 games Leela leads 10-5 with 55 draws. Leela added two wins, winning a game pair from both sides. This is quite unusual for top level engines, Stockfish made a serious error of judgment in the opening as white. WIth 30 games left it is likely that Leela is going to win this match.

In game 61 evals were around 1 at the start. Leela thought Stockfish's 18th move was a blunder and its eval jumped over 1 (negative) while Stockfish's eval remained positive. Two moves later Leela had a protected passer on the king side.



The engines continue to shuffle with all pieces still on the board. Stockfish did not see any danger until move 33, by then Leela's eval was over 4. On move 37 the first pieces were exchanged and Leela added a second passer on the king side.


Leela opened a file on the queen side and threatened the white king. Stockfish was careful not to exchange pieces that would weaken its defense. After some shuffling Leela gave a rook for a knight, exchanged queens, captured a pawn and created a third passer in a RRB vs RRN position.


The black pawns started to move and Stockfish couldn't stop them and its counter attack was weak. Stockfish gave a rook and bishop to capture all three passers, the game was adjudicated in a R vs RNN position.

In game 62 the engines opened the center and the black king was forced to move early. Leela's eval climbed over 2 while stockfish's eval remained low. Stockfish moved its king to the queen side in a slow long castling, then the engines locked the queen side pawns. After opening a file on the king side Stockfish's major pieces faced the white king but were not strong enough to attack. Leela's eval jumped over 3, after exchanging queens it went a pawn up and created a king side passer.



Stockfish exchanged a bishop for a knight and got the pawn back. Both engines applied pressure on their opponents' weak pawns, in the end it was Leela who had the upper hand. After exchanging a pair of rooks it won the f5 pawn and connected a second passer on the king side in a RBN vs RNN position.



Stockfish captured the c4 pawn as well, material was equal but Leela had a winning advantage. It could block the black passer while pushing its own, Stockfish had to give a knight to stop it. The game was adjudicated when the second white passer pushed forward. An unexpected double win for Leela in this opening.

Evals were low throughout game 63. There were many early pawn exchanges and open files. The two kings were vulnerable to attack. In the end Stockfish gave two rooks for minor pieces and finished with a repetitive check draw. In game 64 Stockfish's eval was 0 right from the start. The center was blocked, Leela exposed the black king with a knight sacrifice, and got the material back a few moves later. Only QB vs QB remained on move 36, both kings were exposed and the queens gave checks. Leela gave a bishop to get a pawn to b7, Stockfish continued to give checks until the game was adjudicated on move 138.

In games 65-66 the engines castled in opposite directions. Leela was active on the queen side in game 65, it sacrificed a knight to clear the white pawns and exposed the white king. Evals stayed low as Stockfish moved its king to the center and Leela created a queen side passer. In a series of exchanges Stockfish gave two minors for a rook and only RR vs RB remained on move 46. All the remaining pawns were passers but the engines couldn't force a queening. The game reached a tablebase draw on move 74. In game 66 Leela was active on the king side but could not break the black defense. Evals stayed low, when Leela sent all its major pieces forward Stockfish atacked the white king with its queen and found a perpetual check draw.

In games 67-68 again the engines castled in opposite directions. In game 67 Stockfish pushed pawns on the king side, after a long series of exchanges only RRB vs RRN remained on move 27. Leela was a pawn up, Stockfish moved both its rooks to the 7th rank and forced a perpetual check draw. In game 68 Leela pushed pawns on the king side and again there were early exchanges, this time the engines kept the queens on the board. Stockfish's eval came down to 0, Leela's eval stayed around 1. Stockfish went a pawn up on move 34, Leela pressed the king side but did not find a way in. The engines exchanged a pair of rooks and Leela avoided exchanging another pair. Stockfish ended the game with a rook sacrifice and perpetual check.

Games 69-70 started with a 24-ply book in the Semi-Slav Defense, with black two pawns up and a development advantage for white. There were many early exchanges in game 69, Stockfish forced the black king side rook to move and Leela kept its king in the center. Evals came down as queens were exchanged, the game reached a RB vs RN position on move 29. Stockfish equalized material, both engines had a passer they pushed forward. Once the pawns stopped moving the game was adjudicated. In game 70 Leela's eval jumped over 1 after a few moves and started climbing. The black king stayed in the center and the queens did not come off. The game reached a QRB vs QRN position on move 38 with equal material, Leela's eval was over 2. After exchanging the rooks Stockfish's dropped to 0. Leela had a queen side passer, Stockfish threatened mate and Leela gave checks until it could make a pawn move safely. The passer stopped on the 7th rank and Leela continued with checks. It could queen the pawn but the resulting QB vs Q ending would be a draw. This only delayed the inevitable, the game finally reached a tablebase draw on move 202.

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