Stockfish won a game in black, starting with a very unusual imbalance after book. Leela had another missed win, it had quite a few of these in the match. Stockfish is back in the lead after being behind from game 49. There are only 10 games left, 5 openings, are we going to see drama in the final games?
In games 81-82 black started a pawn up. In game 81 Leela pushed pawns to a6 and h6, two fawn (thorn) pawns! After several exchanges Stockfish captured the pawn on a6, it was two pawns up but its eval was 0 and Leela's eval was over 1. Leela gave a third pawn and reduced to a QRB vs QRB position, its compensation was total control of the dark squares and a mate threat on the long diagonal. Leela gave the rook for a bishop and pawns and the h6 pawn became a passer. However, Leela couldn't push its passer forward and the engines started to shuffle and trade pawns. Leela wouldn't lower its eval and pawn moves kept resetting the 50-move counter. The game ended in a tablebase draw on move 270. In the reverse game 82 evals stayed low throughout the game. Leela gave the pawn back and after a long series of exchanges only RR vs RNN were left on move 27. All pawns were on the king side with Stockfish a pawn up. The rest of the game was shuffling, a few pawn moves and exchanging a pair of rooks. The game was adjudicated on move 150.
Both engines castled long in game 83. Leela pushed pawns on the king side and had a space advantage. Stockfish countered by attacking the queen side and forcing the white king to go to the center. The engines reduced to a QB vs QB position on move 49 and started to shuffle. The game reached an opposite color bishop ending and was adjudicated. In game 84 Stockfish castled short and pushed its king side pawns while Leela kept its king in the center. Leela gave two pawns and reduced to a RBN vs RBB position on move 26, evals were over 1. After the engines exchanged the rooks Stockfish's eval dropped to 0. Despite being two pawns down Leela managed to hold, first with its bishop pair and then in an opposite color bishop ending.
Games 85-86 started with a 24-ply book sequence in the King's Indian Saemisch opening, with an unusual imbalance of Q vs BBPP, and the white king unable to castle. In game 85 evals turned negative after a few moves, Stockfish captured a pawn on the queen side. On move 24 Stockfish's eval jumped over 1.5, it captured another pawn and opened a file on the king side. The black rooks looked dangerous with the white king exposed.
Evals came down after a few moves, it seemed Stockfish didn't have the strength to attack the white king. The engines traded NN for R and made the imbalance even more unusual. Leela was left with only its major pieces, it concentrated them on the king side both as protectors for its king and as attackers on the open files. The engines exchanges a pair of rooks and evals climbed back above 1.5.
Stockfish's eval jumped over 3 and stayed there for a while. Both kings were vulnerable, Leela was down to its last pawn. On move 54 Leela thought it found a way out, it gave its rook for a knight and its pawn became a passer supported by the queen. Leela's eval dropped, it was sure the threat of promotion was enough to force a draw. Stockfish thought it was winning and its eval shot over 7. This went on for a few moves, on move 59 Stockfish saw the mate.
Only now Leela realized it was free to promote its pawn, but its king was in a mating net and there was no defense without losing material. Either way Stockfish was winning and the game ended a few moves later with mate in sight. What a game!
Queens were off early in game 87. Stockfish's eval was low and became 0 despite Leela having a bishop pair advantage. The files were closed except for an open file on the queen side, Stockfish guarded it with its pieces. On move 31 Stockfish unexpectedly moved a knight and let a white rook advance to b7, Leela's eval immediately jumped close to 3. Stockfish captured the rook for a knight, and realized it was in danger.
The engines played a line they both saw in the PV, Stockfish gave back a rook for a bishop and Leela created an advanced passer in a RB vs RN position. The white king moved forward to support the passer and the black rook moved behind the white pawns. Stockfish created its own queen side passer, forcing Leela to trade passers. Leela was still a pawn up but Stockfish reduced to a rook ending and Leela's advantage was gone. Evals slowly came down, the game was adjudicated on move 114 in a tablebase position. Leela was close to winning this game.
In the reverse game 88 most pieces remained on the board. Stockfish had a space advantage and evals climbed over 1.5. Leela's pawns stopped moving on move 25 and the engines started to shuffle. On move 42 Stockfish traded its last knight, and without knights it was difficult to penetrate the black fortress. Stockfish agreed to lower its eval only 130 moves later, the game was adjudicated on move 189.
In game 89 all pieces remained on the board for the first 14 moves and the first pawn exchange was on move 23. Leela's eval started over 1 and climbed to around 2 though material was equal and there was no visible advantage. The engines cleared most of the queen side pawns and started to shuffle on move 32. Leela acknowledged that it had nothing 40 moves later and its eval dropped. Leela gave a rook for a bishop and broke through the black pawn line, Stockfish sacrificed a rook and ended the game in perpetual check. In game 90 there were a few early piece exchanges and Leela captured the b2 pawn with its queen. Evals were under 1, both kings did not castle. The engines exchanged queens and opened the queen side, then reduced to a RRN vs RRB position on move 28. After a long shuffle the engines lowered their evals and the game was a 50-move draw.
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