After 30 games Stockfish leads 4-3 with 23 draws. There was one game pair with two white wins, the book start bias was probably a factor, but the two wins were not similar. Leela won a game pair to reduce the lead to just one point.
TCEC was hit by a typhoon during game 29, at least the TCEC hardware in Shanghai was. As a result there was a power outtage and the game had to be resumed after a break. There were still problems that forced a manual adjudication in a clear draw. The tournament was halted for a day to wait for the storm to pass.
I should also note that the Olympic games in Tokyo have started, causing some distraction for me and my TCEC posts.
In game 21 there were no exchanges after the start, the engines developed behind the pawn lines. On move 18 a pair of pawns was exchanged and the a file was opened, Stockfish doubled its rooks in the open file. There was one more pawn exchange in the center and evals came down. Leela offered another pawn but Stockfish just shuffled, the draw rule ended the game with all pieces on the board. In game 22 Stockfish castled long, Leela opened the b file and Stockfish tried to open the king side with its pawns. Stockfish offered a rook for a knight but Leela preferred to use its knight to block the h file. After a few piece exchanges the engines started to repeat and shuffle and the game was adjudicated.
In game 23 Stockfish's eval started around 1 and it slowly drifted down, there were no exchanges after the start, Leela castled long and Stockfish kept its king in the center. The engines exchanged minor pieces but all pawns were on the board until move 29. Evals stated to drift up, the engines opened the king side, then Leela gave two pawns and opened the queen side. The black king scrambled for safety on the king side, Leela captured the pawns back and created a central passer. After exchanging queens Leela went a pawn up.
The engines played out a long PV agreement, there were no exchanges but evals kept increasing. Stockfish doubled rooks on the queen side but its attack on the white king was weak. Leela traded pawns on the king side and then all rooks were exchanged, leaving a BN vs NN position on move 64.
After trading pawns Leela created connected passers in the center, and with the king supporting them Stockfish could not stop their advance. Leela started to gain material and mated eventually.
The start of game 24 was similar to the previous game, with no exchanges and evals mostly stable. On move 17 the engines started a series of exchanges that opened the king side, and Stockfish went a pawn up. On move 28 Leela moved without thinking and Stockfish's eval immediately jumped over 2.5.
Leela saw right away that it blundered, after thinking for more than 10 minutes. The e3 knight was unprotected, Leela tried to save it for a few moves. In a series of exchanges the black knight was traded for a bishop, but Stockifsh captured a second pawn in the process. Leela moved its queen forward in a QBN vs QBN position, it avoided exchanges as long as it could but on move 52 Stockfish traded a bishop for a knight, its eval over 11.
Leela's defense crumbled, Stockfish exchanged pawns until all the black pawns were gone and there were two connected white passers in the center. Leela gave its queen to avoid a white queening, mate followed. There were two white wins in this opening, though the games were very different. Stockish leads 4-2.
In game 25 evals were below 1 after the start, the engines exchanged a pair of knights and opened a file on the queen side. Stockfish was a pawn up with a central passer, it offered a rook for a bishop but Leela wouldn't take since this would connect a second black passer. Stockfish's eval went over 1 first, then Leela's eval followed as the engines played a long PV agreement. In a series of exchanges the engines reduced to a RRB vs RBN position, with black 3 pawns up.
Evals continued to increase slowly. Stockfish gave a pawn and created a passer on the king side, then pushed it to the 2nd rank. Leela exchanged a pair of rooks, and watched the black passers carefully. It took Leela a while but eventualy it captured both black passers.
The white king moved forward, Stockfish didn't have the strength to protect all its pieces and pawns. Leela captured the black a pawn to create a passer, Stockfish was forced to lose a piece to stop it, game over.
Game 26 repeated the start of the previous game for 13 plys, Leela was a pawn up with a central passer, and an open file on the queen side. This time the engines exchanged queens and a pair of rooks through the open file, evals started to come down. The engines gradually exchanged pieces and pawns, only RBN vs RBN remained on move 35. Stockfish captured the black passer and went a pawn up, but evals were close to 0 and the game was adjudicated when the pawns stopped moving. Leela wins the game pair, Stockfish still leads 4-3.
In game 27 Leela pushed pawns on the king side and opened a file to expose the black king, then it castled long. After exchanging queens and a pair of rooks Leela was a pawn up, both kings moved to the center as most pieces were gone. The engines continued to exchange pieces until reaching a RNN vs RBN position, Stockfish created connected passers on the king side. Leela cleared the black pawns on the queen side while Stockfish pushed a passer to the 2nd rank. Leela lost a knight for the passer but was 3 pawns up. Evals came down slowly, Leela captured the remaining black pawn but didn't push its passers and shuffled instead. When Leela finally pushed its pawns forward Stockfish gave its bishop and captured 2 pawns. Leela was 2 pawns up in a RN vs RN position but both engines agreed the position was a draw and the game was adjudicated. In game 28 Stockfish pushed pawns on the king side, then didn't castle but moved its king to the king side despite having no pawn support. The engines exchanged a few pawns and pieces and opened files, evals came down close to 0. Both engines seemed ready for a draw, after exchanging all rooks the game was adjudicated.
Games 29-30 started with a short 6-ply book in the French Tarrasch variation. In game 29 the engines developed pieces behind their pawn lines, Stockfish pushed pawns on the queen side and Leela's king walked to the king side. Evals came down quickly, low enough for the draw rule on move 21. Leela opened the king side and attacked, Stockfish countered with a rook sacrifice and forced a perpetual check draw. Game 30 started similarly, this time Stockfish castled its king. Leela opened the queen side and gave a pawn to create a passer on the 2nd rank. Stockfish gave a rook for a bishop to capture the passer, the after a series of exchanges the game reached a rook ending with white a pawn up. Evals werew close to 0, the game was adjudicated once the pawns stopped moving.
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