After 60 games Stockfish leads 11-10 with 39 draws. There were 4 consecutive double draws followed by a double win game pair, no change in Stockfish's lead. The tension is rising as the end of the match approaches, only 20 more game pairs to play and the engines are only 1 point apart.
Games 51-52 started with a 26-ply rare sideline of the Ruy Lopez, Chigorin defense variation. All pawns and pieces were on the board at the start. In game 51 Stockfish moved a knight forward to f4 and Leela exchanged it. The engines opened the b file and exchanged a pair of rooks, evals started to come down. The engines mainly shuffled for a while, then opened the a file. After some more shuffling the engines exchanged the remaining rooks and the white queen moved forward on the queen side. The engines traded pawns and Leela created a central passer, it got to the 6th rank and was blocked. Evals were close to 0, after exchanging queens he game was adjudicated. In game 52 there were no exchanges after the start, on move 26 the engines exchanged a pair of pawns and opened the b file. Leela doubled rooks on the open file, the engines shuffled for a while and Stockfish prepared a pawn push on the king side. On move 50 Stockfish started with the h pawn, driving a black bishop away to the queen side where it captured a pawn. The g pawn followed and Stockfish opened the king side, however evals came down. There were many piece exchanges and the black king ran to the center. The game reached a QRN vs QRN position with black a pawn up. Stockfish chased the black king to the queen side, the engines exchanged queens and Leela gave a knight to queen a passer. Evals were close to 0 and the game was adjudicated, PV showed Stockfish reducing to a tablebase draw.
Games 53-54 started with a rare sideline of the Dutch classical variation. In game 53 early exchanges opened files on the queen side. The exchanges gradually continued while evals came down, the game was adjudicated in a drawn rook ending on move 42. In game 54 the engines opened the c file, there were no piece exchanges until Stockfish gave a rook for a knight on move 18. Stockfish opened the king side and exchanged queens, its eval came down faster than Leela's. Stockfish chased the exposed black king with its minor pieces, it had a strong bishop pair in the center. Eventually Leela gave a rook for a bishop and got rid of the white bishop pair, Leela gave a knight and went 3 pawns up. Evals were close to 0 and the game was adjudicated.
Games 55-56 started with a rare sideline of the QGA Smyslov variation. In game 55 there were no pawn exchanges after the start, the engines exchanged most of the minor pieces and stabilized their pawn lines. Starting from move 29 the engines shuffled and evals came down. On move 73 Stockfish gave a bishop for two pawns and a rook for a bishop, it attacked the white king and captured more pawns. The game was adjudicated in a QR vs Q with black 6 pawns up. In game 56 the engines exchanged minor pieces and a pair of pawns that opened the d file. After exchanging queens the engines reduced to a RB vs RB position and evals came down. The game was adjudicated when Leela lowered its eval for the draw rule.
Games 57-58 started with a 22-ply line in the English, Nimzo-English variation not seen in human chess, where black is a pawn up after taking the white g pawn. In game 57 Leela castled long and developed a rook through the g file. In a long PV agreement Leela regained the pawn, the engines had long pawn lines across the center and queen side, with a black knight filling a hole. Leela's eval increased over 1 while it considered an attack on the king side, but the engines mainly shuffled for a long time. On move 93 the engines exchanged a pair of bishops and resumed shuffling. Leela's eval slowly came down, on move 121 Stockfish moved a pawn and shut down any attempt to open the queen side. On move 171 Leela gave a pawn in the center, the position opened up with exchanges and Stockfish ended the game in repetitive check. In game 58 Stockfish kept its king in the center, it pushed the c pawn forward and opened the queen side. The engines exchanged queens and Stockfish went a pawn up and created an advanced passer. Leela gave a rook for two minors and the game reached a RR vs RBN position. Evals were close to 0, after exchanging a pair of rooks the game was adjudicated.
Games 59-60 started with a rare sideline of the Pirc defense. In game 59 the engines castled in opposite directions and there were a few exchanges in the center. Leela pushed pawns on the king side, in a long PV agreement the king side was opened, the black king was exposed and the game reached a QRR vs QRR position by move 25.
Stockfish pushed the h pawn forward but had to abandon it when the white king advanced to support the f pawn. Leela pushed the f pawn to the 7th rank, then gave a pawn and created a second passer on the queen side. Stockfish could not stop both passers, it lost material and the game ended in a tablebase win.
In game 60 Stockfish locked the center before castling long. A minor piece exchange forced the black king to move without castling and Stockfish's eval started to increase. The black king walked to then king side, Stockfish pushed its king side pawns until they locked the black pawns. Leela pushed pawns on the queen side, one reached a3.
Leela managed to capture the d pawn, but after a pawn exchange the white e pawn became a passer. Stockfish reduced to a knight ending, Leela couldn't prevent a queening and was mated. There were two white wins in this game pair, Stockfish leads 11-10.
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