Monday, July 6, 2020

Season 18 superfinal games 81-90

After 90 games Stockfish leads 20-14 with 56 draws. There was only one decisive game, Stockfish's lead increases to +6. Only 10 games left, Leela is still in the race but with no practical chance of catching up.

In games 81-82 the engines castled in opposite directions. There were many early exchanges in game 81 and the game reached a RRN vs RRB position on move 19. After a few moves the pawns stabilized on the queen side, the engines opened a file on the king side and exchanged a pair of rooks. Stockfish's eval came down to 0 and the engines started to shuffle with a few pawns moves. Leela lowered its eval slowly, the game was adjudicated on move 104. In game 82 Stockfish captured a pawn on the king side and created an advanced passer. Leela exchanged pieces and reduced to a RRN vs RRN position on move 25. Evals were close to 0, both engines had passers that were not strong enough to advance. After exchanging a pair of rooks Stockfish gave the knight for two pawns, the game was adjudicated a few moves later. 

Queens were off early in game 83, the engines exchanged pieces in an open position until only minor pieces were left on move 26. Leela was a pawn up, the engines reduced to a B vs N ending and Stockfish regained the pawn. Evals came down and the game was adjudicated when the pawns stopped moving. The engines exchanged queens early again in game 84, Stockfish forced the black king to move and then the engines reduced to a RRN vs RRN position on move 27. Leela was two pawns up, but its king was exposed and Stockfish chased it all over the board. Evals came down, Stockfish captured pawns and exchanged the rooks. The game reached a drawn knight ending with white a pawn up, and the game was adjudicated quickly.

Stockfish castled long in game 85, Leela moved most of its pieces to the queen side and tried to use a half open file to apply pressure. After some exchanges the game reached a QRB vs QRN position on move 31, Stockfish was a pawn up but Leela had an eval advantage with an advanced passer in the center. However, Leela made no progress and the engines shuffled for a long while. After exchanging queens the shuffling resumed, Leela reset the 50-move counter with a bishop sacrifice. Evals were close to 0 and the game ended in a tablebase draw. Both engines castled long in game 86 and all pieces were on the board until move 25 except a pair of minors. Stockfish created a passer on the king side and pushed it forward. Leela exchanged queens and went a pawn up, then more exchanges led to a RBN vs RBN position on move 33. Leela gave the pawn back and created a passer of its own, Both passers were blocked, Stockfish's eval came down to 0 but Leela captured another pawn and kept trying. The game continued until move 81.

Games 87-88 started in the King's Gambit Accepted, Quade Gambit variant, with black a pawn up. In game 87 Leela pushed a pawn on the queen side and castled short, despite having no pawn cover and a black passer on f3. Leela opened the queen side, took over two files and regained the pawn. Stockfish countered on the king side, it gave a rook for a knight and forced a 3-fold repetition draw.

Stockfish waited for Leela to castle long before it made a move on the queen side in game 88. Leela reacted by trading its queen for 3 minor pieces. Stockfish's eval shot up, after opening a file on the queen side the black king was very close to being mated.


Stockfish captured the knight on g2 and Leela couldn't retake with the bishop since it was a crucial defender. While Leela strengthened its center Stockfish captured a pawn on the king side and pushed its pawns forward. It created a passer which advanced to the 7th rank.


Leela tried to attack the white king, this led to a series of exchanges and the net effect was that Stockfish lost the passer but captured a bishop. The game ended in a Q vs N position. Stockfish wins the game pair and the lead is now +6.

Games 89-90 started with a 20-ply book, a popular line in the Benoni, Czerniak defense variation. In game 89 the engines kept their pawns and the pieces stayed mostly behind the pawn lines. The engines locked the queen side, then opened a file in the center and exchanged a pair of rooks. On move 39 only QNN vs QNN were left and the engines started to shuffle. It took more than 50 moves and a few exchanges for Leela to lower its eval for the draw rule. In game 90 there were only a few exchanges until move 20, then Stockfish pushed a pawn in the center and opened the position. The engines started to exchange pieces and pawns until reaching a rook ending on move 41. Stockfish was a pawn up, but with all pawns on the king side as well as the two kings the ending was a draw. This time Stockfish wouldn't lower its eval and the game continued until move 82.

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