Sunday, May 26, 2019

Season 15 superfinal, games 71-80

After 80 games Leela leads 10-5 with 65 draws. The last 10 games were all draws, including the bookless pair of games. Only 20 games are left, Leela is going to win almost surely.

In games 71-72 black started a pawn up in the Vienna Gambit. Stockfish's eval was 0 almost throughout game 71. Leela had an advanced passer on the king side, after a series of exchanges the white king side pawns were gone and Leela had a second passer. Stockfish's king walked to the queen side to get out of trouble. Leela gave a piece in a series of exchanges, its two passers reached the 6th and 7th ranks in a QRB vs QR position on move 29. Stockfish gave checks and then blocked the passers, Leela's eval came down and the game was adjudicated. In game 72 Stockfish had the same passer on the king side but its eval came down to 0 very quickly. Leela castled long and gave a rook for a bishop to remove the black passer. Most of the king side pawns were gone and Stockfish moved its king to the queen side. The engines shuffled for a while, then Stockfish gave two pawns and opened the queen side. Leela's king was under attack, after a series of exchanges the game reduced to a drawn queen ending. Leela continued playing until adjudication on move 81. 

Games 73-74 started with white a pawn up and with a queen side passer in the Benko Gambit. In game 73 evals started over 1. Stockfish had to move its king early, it walked to the king side. The white passer got to the 5th rank and Leela blocked it with pieces. Evals came down slowly, the engines exchanged most of the minor pieces. After a while the center and king side were blocked and the pawns on the queen side couldn't advance. The engines shuffled and the game was adjudicated early on move 38. In game 74 both engines castled short, Leela kept its queen side pawns back and its eval remained over 1.5. After a series of exchanges only QN vs QB remained on move 30, Leela's eval jumped over 2 while Stockfish's eval dropped to 0. Leela went up 3 pawns but could only give checks, or stop and allow Stockfish to give checks. Leela's eval slowly came down, it lost its knight and then the engines exchanged queens. The game ended in a tablebase draw.

In game 75 both engines castled long, most pieces and pawns were on the board and evals slowly came down. Stockfish pushed a pawn on the queen side and threatened the black king with its queen. The attack was not strong enough, evals were close to 0 and Stockfish ended the game with a perpetual check. In game 76 Stockfish pushed pawns on the queen side, Leela opened a file on the king side and exchanged rooks. The black king remained in the center, the white king castled long, both were vulnerable to attack. The engines exchanged most pieces and only QB vs QB remained on move 39. Stockfish's eval was at 0, Leela played on. On move 64 the queens were exchanged to reach an opposite color bishop ending. The game ended in a tablebase draw only on move 142.

Games 77-78 were bookless. Stockfish started game 77 with e4, and it turned into an Italian opening. All pawns remained on the board and evals stayed low. Leela concentrated its major pieces on the king side while Stockfish opened the queen side. After a series of exchanges the game reached a RNN vs RBN position on move 28. Stockfish could have finished the game with a repetition but continued and the engines reduced to a rook ending. The game ended in a tablebase draw. Leela started with d4 in game 78 and the game continued in a closed Catalan opening. On move 16 Leela's eval started climbing though it was a pawn down. It was over 1.5 for a few moves and then came down slowly. Stockfish remained calm, it gave the pawn back and exchanged pieces. The game reached a QN vs QB position on move 37 and Stockfish's eval was 0. Leela avoided exchanging queens until move 69, its eval came down and the game was adjudicated not long afterwards.

In game 79 the engines played behind the pawn lines, there was one piece exchange and one pawn exchange in the first 25 moves. On move 32 Leela's eval turned negative over 1, the king side pawns locked in a pawn line with a black pawn on g3 and the h file open. The engines started to shuffle, Leela trying to break in and Stockfish defending the entrances from within. The engines exchanged a pair of rooks on move 63, Leela's eval started to climb. The remaining rooks were gone on move 82 and the shuffle continued. Stockfish's eval suddenly jumped over (negative) 1.5 on move 111, evals climbed over 2. Then on move 125 Stockfish's eval dropped to 0, did Leela miss something? The engines started exchanging pawns and pieces and the game reduced to a queen ending, Stockfish found a perpetual check draw. In game 80 again there were few exchanges in the opening. Stockfish's eval stayed low, the engines opened a file on the queen side and Stockfish controlled it. A pair of rooks was exchanged on move 40, after some shuffling Leela's eval came down. The game reached a RB vs RB position and was adjudicated a few moves later.

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