After 50 games Stockfish leads 14-8 with 28 draws. Stockfish extended its lead to 6 after two game pair wins. There were 3 drawn game pairs, one of them with two white wins. Stockfish won twice in a queen endgame, Leela seems to be struggling in these, its eval is sometimes low when Stockfish already sees the win in its PV. At the half way point of the match Stockfish is leading by 6 wins, not a huge margin after 25 game pairs played. However so far Leela only won a single game pair, so I would say Stockfish is the clear favorite to win the match.
Games 41-42 started in the Scandinavian defense, Mieses variation, played in high level human chess. In game 41 the engines played out a long PV agreement, the black king moved without castling and white castled long. Evals were stable, most minor pieces were exchanged, Stockfish developed its king side rook through the h file. On move 29 the game reached a QRR vs QRR position.
The engines pushed pawns forward and evals started to increase. After a pawn exchange both engines created a passer on the queen side. All the pieces focused on the black e5 pawn, on move 57 the queens were exchanged.
Stockfish gave the e pawn, perhaps to activate its rooks. Leela catured another pawns and pushed two passers forward. Stockfish blocked the passers with its rooks and pushed its passer forward. Leela captured a rook, both engines queened, Leela had the material advantage to force mate.
In game 42 the engines repeated game 41 for 40-plys, this time Stockfish did not exchange its last knight. The engines shuffled for a while, then Stockfish moved the g pawn forward and captured a pawn. Evals started to increase, in a series of exchanges the engines reduced to a double rook ending.
All pawns were passers, Stockfish blocked a captured the black e pawn on the 2nd rank. It had two passers left, with the king support it slowly pushed them forward. Leela tried to avoid a 7-man position but Stockfish forced it when it queened a passer and Leela captured it. There was one white pawn left, the engines continued to play the won 7-man position for more than 30 moves, the game reached a tablebase win on move 135. There were two white wins in this game pair, Stockfish leads 12-8.
Games 43-44 started with a 22-ply rare sideline of the QGD Orthodox defense, Rubinstein variation. The engines castled in opposite directions, all pieces were on the board and the c file was open. In game 43 after a few moves the engines started a long PV agreement, they exchanged queens and a few minor pieces. Evals came down, Stockfish gave two pawns and the game reached a RB vs RB position. Leela was two pawns up with two doubled pawns, Stockfish had an advanced passer and also had a possibility of perpetual check. Evals were low enough for an early adjudication.
In game 44 Leela pushed pawns on the queen side and placed a rook on the open c file. Evals slowly increased, Stockifsh pushed pawns on the king side. In a long PV agreement Leela gave a pawn, opened the queen side further and the black queen joined the attack.
Stockfish made sure it had enough pieces to defend b2. After exchanging a pair of rooks Leela's attack appeared less threatening. The engines continued to exchange pieces and reduced to a QB vs QB position on move 47. The white king slowly moved forward, the bishops were exchanged on move 59.
Stockfish captured the black b pawn, Leela chased the white king with its queen for a long time. Leela's eval dropped below 1 for a while but then jumped back. On move 102 the white king reached the back rank, Leela started to lose pawns, Stockfish managed to queen a passer and mate. Stockfish wins the game pair, it leads 13-8.
Games 45-46 started in the KGA Bishop's gambit, Cozio variation. Black was a pawn up, the white king moved without castling and black had an eval advantage. In game 45 the engines developed their pieces, then Stockfish gave two pawns, opened the e file and placed a pawn facing the white king on the king side. Leela's (negative) eval jumped, Stockfish captured a pawn back and castled long. In a long PV agreement Leela's eval dropped back, the engines exchanged pieces and pawns until only QR vs QR were left on move 36.
Leela gave the d pawn, its eval was stable while Stockfish's eval steadily increased as it chased the black king to the center. On move 48 the rooks were exchanged, after a while the black h pawn became a passer after a pawn trade. Leela's eva; continued being low, below -0.5 at times as the game progressed. In some of the moves Leela spent a lot of time thinking, yet its eval did not reflect what Stockfish saw as a clear win. On move 76 Stockfish's eval was already over -95, Leela's eval was -.059.
Leela's eval slowly increased finally when Stockfish was already predicting a 7-man win. On move 94 Stockfish captured a pawn, a frew moves later it queened the passer, then it forced mate.
In game 46 Leela castled long early and Stockfish attacked the queen side. Stockfish's (negative) eval dropped, it gave a knight for two pawns and exposed the black king. Leela had to walk its king back to the center and Stockfish pushed a passer to the 7th rank. The black king continued to run to h6, Leela's eval dropped as well and Stockfish pushed a second passer on the queen side. Leela lost a rook for one passer, Stockfish gave a rook for a knight on the king side and exposed the black king to checks again. Evals were low enough and the game was adjudicated. Stockfish wins the game pair, it leads 14-8.
Games 47-48 started with a 23-ply line in the QGD exchange variation. The engines castled in opposite directions, there was only one pair of pawns exchanged, black had an eval advantage. In game 47 Stockfish went a pawn up, (negative) evals came down while the engines exchanged pieces and pawns. On move 28 the game reached a RRB vs RRB position, Leela regained the pawn. Evals were close to 0, after exchanging a pair of rooks the game was adjudicated. In game 48 Leela went a pawn up and pushed pawns on the queen side. Again evals came down as the engines exchanged pieces and pawns. Stockfish regained the pawn, the game reached a QB vs QN position and was adjudicated.
Games 49-50 started with a 20-ply line in the Robatsch (modern) defense. There were no exchanges and white castled long. In game 49 the engines developed pieces and Stockfish castled long as well. Evals came down as the engines played out a very long PV agreement, several pawns and pieces were exchanged and Leela went a pawn up. After the PVs diverged the engines reduced to a QR vs QR position, Stockfish regained the pawn and it had a passer on the king side. The engines shuffled, Leela wouldn't lower its eval, perhaps since the black king was exposed. It lowered its eval with less than 10 moves left on the 50-move counter, the game was adjudicated. Game 50 started with a 53-ply repeat of game 49. After the PVs diverged Leela regained the pawn, the engines shuffled for a while and then reduced to a RN vs RB position. White was again a pawn up but evals were low and the game was adjudicated.
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