After 40 games the score is tied 4-4 with 32 draws. There was one game pair with two white wins, in very different styles. Leela won in blitz after stalling for many moves like it did once before in the match. Stockfish's win was more direct and quicker. The match is getting near the half point and the scores are still tied.
There were only a few exchanges after the start of game 31 and evals stayed around 0.5. Leela built a long pawn line across the board and the engines mostly shuffled from move 26, with a few pawn moves by Stockfish. After a while the engines opened the queen side and evals came down. Stockfish attacked through the queen side and cleared all pawns there, the game reached a QRN vs QRB position on move 53. The engines continued to exchange pieces and pawns, the game was adjudicated with only one white pawn on the board. In game 32 there was a long series of exchanges after the start and the engines cleared all the pawns on the queen side and most pieces. Evals came down and by move 32 only RB vs RB remained. Stockfish was a pawn up but the position was a draw, the pawns stabilized and the game ended quickly.
Games 33-34 started with a 27-ply book, a high level line in the Sicilian Taimanov variation. The engines castled in opposite directions in this line. In both games the engines continued with a series of exchanges that led to a BNN vs Q imbalance with black two pawns up. In game 33 Leela moved its rooks to the open h file, targeting the h7 pawn. Stockfish alternated between defending its pawns and threatening the white king on the queen side.
Leela had two more pieces and its objective was to concentrate forces and to outnumber the black defenders. Stockfish disrupted the attacking lines with pawns and created threats that forced some white pieces to defend. After some shuffling Leela opened the king side and evals went over 1.5. However, Leela made no attempt to attack and the engines started to shuffle. More than a hundred moves were played and Leela only made a few pawn moves on the queen side, while evals slowly drifted down. On move 164 Leela exchanged a pair of pawns on the queen side, by the eval reaction it looked like the shuffle would continue for another 50 moves.
This time though evals started to jump. I don't know whether Stockfish started to see ghosts or just blundered in blitz mode, its eval went over 3. Nothing seemed different for a few moves, then somehow Leela got the black rooks in a skewer by the bishop.
Stockfish managed to save its rooks by moving Rh3, threatening to push its king side passer. Leela responded with Rc1, which both engines did not expect in their short thinking time. Stockfish could not avoid losing its queen for a rook while defending its king. Leela exchanged pieces and gave some material back to create connected passers on the queen side which could not be stopped.
In game 34 Stockfish chased after the black queen and soon forked the two black rooks with a bishop. In a series of exchanges Stockfish traded the bishop for a rook and also captured a pawn. The imbalance was RBN vs Q and one pawn, better than the previous game. Stockfish's eval was over 2 at this point.
Stockfish doubled rooks in the center while Leela countered against the white king on the queen side. The black queen moved forward and Stockfish's king looked exposed and vulnerable. Stockfish was also down to two pawns, it seemed important to keep at least one alive.
It was beautiful to watch how Stockfish kept all its pieces safe as they slowly went on the attack. It took Stockfish 10 moves to capture a black pawn, Leela started to give check with its queen. When the checks ran out Stockfish doubled rooks and got ready for the final attack.
Leela was forced to exchange rooks, it captured the white b pawn but Stockfish kept its other pawn safe and captured the remaining black pawns. The 7-man position was a win, the white pieces continued their synchronized dance until the game was adjudicated. The PV showed how the white pawn could not be stopped. Two very different wins in this opening, score is still tied.
In game 35 the engines blocked the center after the start. Stockfish pushed pawns on the king side and Leela attacked on the queen side. Leela started a combination with a knight for pawns sacrifice that led to a R vs BN imbalance, while creating connected passers. Stockfish's eval dropped to 0. It gave a bishop, opened the king side and attacked the white king. Leela gave material to avoid mate, Stockfish ended the game in perpetual check. In game 36 the engines opened a file in the center after the start. Stockfish exchanged queens and captured a pawn, then all rooks were exchanged and the game reached a BNN vs BBN position on move 25. After exchanging a few pawns and a pair of knights the engines started to shuffle. It took Stockfish a long time to lower its eval, it avoided the 50-move draw and the game was adjudicated on move 90.
Games 37-38 started with a short book in the French Winawer advance variation. Stockfish gave a pawn and castled long in game 37. Leela castled short, after a few exchanges it captured a second pawn but the f file was open for Stockfish to attack the white king. Evals were close to 0, Stockfish exposed the white king and temporarily sacrificed a rook. The engines quickly reduced to a king and pawns ending, the game ended in a tablebase draw. In game 38 Leela castled long, Stockfish did not castle but its king walked to the king side and its king side rook developed through the h file. The engines shuffled from move 21 until Leela decided to open the king side. Evals came down to 0, after several exchanges Leela was a pawn up. However the engines didn't move pawns and the draw rule stopped the game.
In both games 39-40 the black queen came forward on the queen side, black went a pawn up but was behind in development. In game 39 both kings moved forward, Stockfish exchanged queens and gave a knight for two more pawns. Evals dropped to 0, the engines continued to exchange pieces and pawns, the game reached a RB vs R position on move 40. The game ended in a tablebase draw. There were a lot less exchanges in game 40, evals were close to 0 almost throughout the game. Stockfish forced the black king to move, while the white king castled very late. Leela pushed pawns on the queen side and the white queen came forward to attack the black king. Stocfish gave a rook for a bishop and was close to a perpetual check draw, the draw rule ended the game.
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