After 80 games Stockfish leads 19-6 with 55 draws. Stockfish added 3 more game wins, increasing its lead to 13. There are only 10 more game pairs to play, Leela's chance of winning is mathematical at best since it needs to win biased game pairs from both sides.
Games 71-72 started with a 14-ply book sideline in the Robasch defence. In game 71 the engines exchanged pawns on the queen side and opened a file. After some shuffling Leela gave a pawn but evals kept decreasing. The first pieces to be exchanged were the queens on move 37, the engines continued to exchange pieces including a bishop for rook trade by Stockfish. The game reached a RB vs BN position with black two pawns up, Leela managed to capture one pawn but no more. The game was adjudicated when Leela lowered its eval for the draw rule on move 95.
In game 72 there were no exchanges after the start, on move 17 the engines opened a file on the queen side. Stockfish thought Leela's move 19 was a blunder and its eval increased quickly. Leela saw the game continuation in its PV but it thought it was perfectly safe, its eval even decreased. A series of exchanges opened the board and exposed the black king. Leela was surprised by Stockfish's move 29.
Leela's eval jumped over 2. Stockfish's plan involved getting a knight to e3, then a queen sacrifice for a knight brought the black queen to d6 and a knight fork on f4 captured the black queen. The result was a BN vs R ending.
Leela was on time to stop the white passer on b5, Stockfish abandoned it but used its piece advantage to capture all the remaining black pawns. The game reached a 7-man tablebase win that Stockfish had no problem to convert. Stockfish wins the game pair, it leads 16-5
Games 73-74 started with a 15-ply book sideline in the KID normal variation, with a black bias. In game 73 Stockfish gave a pawn to open the queen side, Leela moved its king without castling. (Negative) evals came down, the engines started to exchange pieces and clear the board. The game reached a RN vs Q ending, Stockfish a pawn up with all pawns on the king side. Stockfish thought it had an advantage but other than trade a pair of pawns it could only shuffle. An occasional pawn move reset the counter and Stockfish wouldn't lower its eval. The game was finally adjudicated on move 153. Up to transposition game 74 repeated the reverse for 14 plys, with Stockfish a pawn up and its king unable to castle. The engines exchanged minors, then in a long PV agreement Stockfish gave a rook for a bishop and pawn. Evals came down, Stockfish pushed a passer in the center to the 6th rank. Leela captured the passer and the engines exchanged a pair of rooks, evals were low enough in a QBN vs QRB position for an early adjudication.
Games 75-76 started with a 24-ply book, a sideline of the closed Ruy Lopez, Ragozin-Petrosian variation. In game 75 Leela locked the center, there were no exchanges until move 22. Then in a PV agreement the engines opened the queen side and exchanged a few pieces. Leela went up a pawn and evals slowly increased. The engines moved their remaining major pieces to the queen side and then exchanged them, leaving a BNN vs BNN position on move 40.
Stockfish had to block the extra white pawn as well as protect its weak pawns against Leela's knights, it saw it was in trouble and its eval jumped. On move 57 Leela captured a second pawn, then exchanged a pair of knights and created an advanced passer in the center.
Leela traded bishops and pushed its passer to the 7th rank. It finished the game by reducing to a king and pawns tablebase win.
In game 76 Stockfish chose not to lock the center, there were no exchanges until move 21 and evals were stable. The engines exchanged a pair of pawns and then Stockfish pushed a pawn to h6, trapping a black bishop in the corner. After another pawn exchange Stockfish moved its queen forward on the king side. From move 37 Stockfish's eval started to increase, Leela moved its queen to the queen side, ignoring the danger to its king. Stockfish thought Leela made a mistake on move 38 and its eval jumped over 3 as it offered a knight on the king side.
Leela refused to take the knight and expose its king to attack. Its eval jumped only 3 moves later, in a series of exchanges the engines removed all rooks and Stockfish went up a pawn with a doubled passer in the center. For a while the engines shuffled, Stockfish improved its pieces' position. When it was ready it gave a pawn and opened the f file. Leela's defence collapsed and Stockfish captured a piece.
The white king was exposed but Stockfish was able to find a safe square. The engines exchanged queens and Leela lost its bishop to stop a passer, mate was a matter of time. There were two white wins in this game pair, Stockfish leads 17-6
Games 77-78 started with a rare sideline of the Vienna game. In game 77 Stockfish kept its king uncastled, Leela's eval increased for a short while. Stockfish pushed pawns on the king side and evals came down, Leela offered a knight in the center and Stockfish didn't take for a few moves. After Stockfish captured the knight the center opened, there was a series of exchanges that reduced to a rook ending. Leela was a pawn up but evals were close to 0 and the game was adjudicated.
In game 78 Leela blundered on move 8 (!), at least according to Stockfish. Stockfish went on the attack, it opened the king side and moved its queen forward, forcing the black king to move without castling. In a few moves all the white pieces on the board were involved in hunting the black king, it looked scary for Leela.
Leela exchanged queens to get its king out of immediate danger. Stockfish went a pawn up and the engines continued to exchange pieces until only RB vs RN remained.
Stockfish's advantage appeared to be small but Stockfish was confident it was winning. It slowly pushed the h pawn forward, ignoring Leela's plan on the queen side. Eventually Leela captured the bishop but gave a rook to stop the passer. It took Stockfish 35 moves to convert the R vs N ending, including a beautiful use of zugzwang to capture a pawn. Stockfish wins the game pair, it leads 18-6
Games 79-80 started with a 12-ply book in the English opening, three knights system, played in a few high level human chess games. In game 79 Stockfish's eval increased for a few moves after the start, then came down while there was a series of exchanges in a PV agreement. Leela was a pawn up, after some shuffling the engines reduced to a QRB vs QRB position. The shuffle continued, evals were low but there were too many pawns for the draw rule. After more exchanges the game reached a queen ending, Leela gave pawns and pushed a passer to the 7th rank, Stockfish ended the game with checks and the draw rule.
In game 80 Stockfish's eval increased from the start, a series of exchanges in a PV agreement (not the same as the reverse game) opened the position and Stockfish was a pawn up. Stockfish created a passer on the queen side, it looked dangerous though it was still on its initial square.
Stockfish pushed the passer to the 7th rank while Leela captured pawns on the king side and exposed the white king. Leela attacked with queen and knight, it captured the white queen but lost a rook and Stockfish queened the passer. Leela delayed as much as it could with checks, but when the white king found a safe square Stockfish hunted the black king and mated. Stockfish wins the game pair, it leads 19-6.
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