After 80 games Stockfish leads 8-5 with 67 draws. Stockfish won 3 game pairs, the largest gap in the match so far. There are only 20 more games to play, Leela needs wins to have a chance of winning the match. It is interesting to note that two of the game pair wins started with variants of the French opening, usually considered a strong opening for Leela.
In game 71 there were a few minor pieces exchanged after the start. Both engines left their kings in the center uncastled, Stockfish pushed a pawn to h6. By move 15 Leela moved both its rooks and there was no option of castling, Stockfish opened a file on the queen side and its eval started to increase. The black king side opened and Stockfish's eval was over 2.
Leela's h7 pawn was vulnerable and the black pieces were too far to assist. Stockfish moved its king to the king side to find safety, then in a long PV agreement it gave its queen for a rook and cleared the way for its h pawn. Leela couldn't stop the pawn promoting, in a series of exchanges the engines reduced to a RBN vs RN position, Leela 3 pawns up.
Leela wasn't in panic mode yet, it thought its pawns gave it some compensation for the bishop. Stockfish did not try to attack the black pawns, instead it focused on pushing the black king back to the back rank. Leela pushed a passer to the 2nd rank, but in a series of checks and forced moves Stockfish managed to trade pieces and capture the passer. This left a BN vs R position on move 56.
The material difference was minimal but both engines knew white was winning. Stockfish captured the two black pawns, Leela avoided taking a white pawn since that was a tablebase win. Leela played on until one of the white pawns queened, forcing the capture and the end of the game.
In game 72 Stockfish played h5 early and blocked the white h pawn. The engines opened a file on the queen side and Leela castled short. Evals were under 1, the engines exchanged a pair of rooks and Stockfish went a pawn up. Stockfish gave a bishop for 2 pawns and castled short to get its king away from the open queen side. Its eval went over 1 for a while, in a QRB vs QR position Leela attacked on the queen side. However the engines exchanged rooks and evals came down again. After a while Stockfish ended the game in a check repetition. Stockfish wins the game pair, it leads 6-5.
In game 73 the engines opened a file on the queen side after both engines castled, then exchanged a pair of rooks. Evals came down as the exchanges continued, the game reached an opposite color bishop ending on move 35. Stockfish was a pawn up and it took a while before it lowered its eval, the game was adjudicated on move 58. In game 74 Leela pushed pawns on the king side and moved its king forward. Stockfish opened the king side and threatened the white king. The black queen came forward and Leela exchanged queens. Stockfish gave a rook for a bishop, giving it control of the dark squares surrounding the white king. Two black knights came forward and there were many fork threats. Evals were close to 0, the engines reduced to a RRN vs RBN position with black two pawns up. The pawns didn't move and the game was adjudicated.
In game 75 the engines developed pieces without exchanges after the start. Then in a series of exchanges Stockfish cleared the black queen side pawns and created a passer. Queens were exchanged and all pieces moved to the queen side. Stockfish pushed the passer forward and Leela exchanged pieces. In a RN vs RB position the passer queened and Leela gave a rook for a knight to capture it. Stockfish thought it had an advantage in the R vs B ending, its eval jumped to 2.5. However, Leela kept the white king away and Stockfish could only shuffle. Stockfish extended the game with pawn moves and finally lowered its eval for the draw rule on move 172. In game 76 all pieces and pawns were on the board until move 26, the engines locked the center and Leela had a space advantage. The black queen came forward and the engines exchanged queens. The engines could have opened either the e or f files, but they chose to shuffle instead. After 50 moves Leela exchanged minor pieces, evals came down and the draw rule was almost activated. On move 100 finally the f file opened and the exchanges began, the game reached a tablebase draw on move 120.
Games 77-78 started with a 20-ply book in the Sicilian Najdorf, English attack, with the engines castled in opposite directions. In game 77 Stockfish pushed pawns on the king side until Leela captured one. Stockfish's eval jumped over 1 on move 18 and continued to increase after it created a passer on d6. Leela created a passer on the king side, Stockfish gave a rook for the DS bishop that controlled the d8 square, then moved the other rook to the 7th rank. Leela lost its passer on the 2nd rank, it had 3 more on the king side but it started to feel uncomfortable and its eval slowly increased.
Stockfish hid its king behind a black pawn and prepared for pushing its passer forward. After exchanging queens there was a long PV agreement that started with a bishop sacrifice by Stockfish and ended with the white passer on the 7th rank. Stockfish queened, and a series of exchanges led to a Q vs BN position, black two pawns up.
The endgame was long and difficult, though Stockfish never had doubt it could convert. It captured one black pawn quickly, but then it was unclear how it could involve the king, capture another pawn or push its last pawn forward. the white king came to the center of the board, Stockfish pushed the black king forward on the king side. On move 84 it forced Leela to move its g pawn and reset the 50-move counter. On move 91 it captured the black a pawn and its last pawn became unstoppable. The game ended with two white queens on the board.
In game 78 there were many early exchanges, all knights were gone and the game reached a QRB vs QRB position on move 23. Leela gave a pawn and moved a black pawn to c3, trapping the white king. Stockfish exchanged bishops, captured a second pawn and drove the black king to the open queen side. Evals were low enough for adjudication once the pawns stopped moving. Stockfish wins the game pair, it leads 7-5.
Stockfish's eval was over 1 from the start of game 79. The white king side rook developed through the h file, Stockfish didn't castle and Leela castled long. Stockfish pushed pawns on the queen side, disrupting the black pawn structure. A white pawn reached a6 and pushed the black king to the corner. Leela tried to attack an isolated white pawn on e5, Stockfish matched attackers with defenders. Leela appeared to shuffle as Stockfish moved a knight all the way to b7.
Evals were still close to their starting values, Leela's position looked miserable but it thought it could hold. For a while Stockfish didn't find a way in, the knight jumped between b7, c5 and d6 and restricted the black pieces. After Leela's move 37 Stockfish saw something and its eval jumped. Leela saw it too a few moves later, a series of exchanges reduced to a QR vs QR position. Stockfish had a pawn majority on the queen side, after exchanging rooks it created a passer there.
Material was still equal but Stockfish was winning. It captured the h pawn first, Leela guarded the a7 pawn and got rid of the white passer on the c file, but Stockfish captured another pawn on the king side and created a passer there. After exchanging queens the black king was too far to stop the passer, game over.
In game 80 there were several minor piece exchanges after the start, Stockfish moved its king early and couldn't castle. Leela castled long and on move 17 only QRR vs QRR remained. For a while Stockfish's eval was over 1, but it came down after the engines exchanged a pair of rooks. The pawns stabilized and the engines started to shuffle, Leela couldn't find a safe way to open the king side. After 40 moves the engines traded pawns on both sides and opened the position. Stockfish pushed a pawn on the queen side and gave it to expose the white king. The engines reduced to a queen ending, Leela was up a pawn but with both kings exposed and evals close to 0 the game was soon adjudicated. Stockfish wins another game pair, it leads 8-5.
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