After 60 games Stockfish leads 19-11 with 30 draws. Leela won a game pair after 14 straight game pairs without a win, losing 6 of them. However Stockfish won 3 game pairs and it extended the lead to 8. One game pair had two black wins. There are only 20 game pairs left to play in the superfinal, it's hard to imagine Leela can close the gap.
Games 51-52 started with a 19-ply line in the Ruy Lopez, Berlin defense, Anderssen variation with an advantage for black. In game 51 there was one pawn exchange after the start, evals were stable and the engines mostly played behind their pawn lines. On move 25 Leela exchanged pawns in the center and Stockfish's (negative) eval jumped over 1. Leela's eval reacted only 6 moves later, the black queen moved forward on the king side and Stockfish prepared an attack on the white king.
Leela couldn't get its king away, Stockfish captured the h pawn and while Leela exchanged pieces Stockfish captured another pawn. The game reached a queen ending with black two pawns up, Leela captured back two pawns but couldn't avoid a queening and mate.
In game 52 Stockfish castled long, it pushed the g pawn forward and opened the king side. The engines exchanged minor pieces and Leela captured a pawn. On move 37 the game reached a QRN vs QRB position with black a pawn up.
Leela kept its king safe and avoided perpetual check, (negative) evals slowly started to increase. Leela had a pawn majority on the king side, Stockfish captured a pawn on the queen side and Leela exchanged queens. The engines traded pawns and on move 66 Leela had connected passers on the king side and Stockfish had doubled passers on the queen side.
The black passers were more dangerous and easier to defend. Leela lost the d pawn and captured the two a pawns. It pushed one passer to the 2nd rank, then captured the knight for it. The game ended in a tablebase win. There were two black wins in this game pair, Stockfish leads 16-10.
Games 53-54 started with a 24-ply line in the KID Saemisch variation, with all pieces and pawns on the board except one pair of pawns. In game 53 Leela castled long, it pushed the h pawn and tried to open the king side. Leela's eval spiked over 1.5 for one move and then came back down. In a long PV agreement Stockfish gave both its rooks and a knight and captured the white queen. Despite the material imbalance evals came down quickly, Stockfish captured pawns and was 3 pawns up. The game reached a RRB vs Q position, Leela pushed a passer to the 6th rank and moved a rook forward, but kept its other pieces to protect its exposed king. Evals were low and the game was adjudicated.
In game 54 after Stockfish castled long Leela pushed the b pawn forward and Stockfish's eval started to increase. Stockfish pushed pawns on the king side, it gave two pawns and opened the g file. Leela saw a few moves ahead in its PV, Stockfish sacrificed a bishop and Leela expected to give back the material. Leela's eval was low while Stockfish's eval was over 3, it surprised Leela with its move 25, a discovered attack on the queen.
Leela thought for 9 minutes and its eval jumped over 3, it lost two minor pieces for a rook. Leela opened the b file and attacked the white king, Stockfish had to be careful. However the white king stayed safe while the black king was under attack. Despite being down on material Stockfish soon saw a win, the engines reduced to a QB vs QB position and the game ended in a tablebase win. Stockfish wins the game pair, it leads 17-10.
Games 55-56 started with a line in the Modern defense, two knights variation, played in high level human games but not recently. In game 55 Leela castled long, its eval went over 1 for a while but after Stockfish castled long Leela's eval slowly came down. A knight exchange opened the e file, Stockfish doubled its rooks there and then closed the file with a bishop. Leela captured a pawn, on move 45 the game reached a RRB vs RRB position. The engines mostly shuffled for a long time, on move 81 Stockfish gave the bishop for three pawns and moved its rooks forward. Leela captured two pawns back but Stockfish had a perpetual check draw. For fun Stockfish chose a different draw, it gave a rook for a white passer and reduced to a tablebase draw a rook down with only two pawns.
In game 56 Stockfish castled long as in the reverse game, however this time Leela castled short. Stockfish opened the g file and Leela's eval jumped over 1.5. In a long PV agreement Stockfish gave a rook for a bishop and two pawns. The engines exchanged queens and reduced to a RBN vs RRN position. Stockfish had connected passers in the center, it exchanged the bishop for a knight and pushed the passers forward.
Leela moved its rooks forward and attacked the white king. Stockfish lost its pieces but queened one of the passers. In the Q vs RR ending Stockfish soon saw the win, the white king found a safe square and Stockfish captured pawns with its queen. Eventually Stockfish queened a second passer and mated. Stockfish wins the game pair, it leads 18-10.
Games 57-58 started with an 18-ply line in the Nimzo-Indian defense that deviated early from standard theory. In game 57 Leela's eval increased from the start, all pawns were on the board and queens were off early. Both kings moved forward without castling, Leela captured a pawn on the queen side and its eval jumped quickly. The pawns stabilized and the engines shuffled, on move 38 Leela's eval was over 8 though it was not clear what the plan was.
The shuffling continued with some pawns moves on the king side, Stockfish's eval increased as well. On move 56 Leela gave a pawn on the queen side and exchanged a pair of rooks, both engines created a passer there. The game reached a RBN vs RBN position, Leela hid its king behind the black passer, on move 62 Stockfish exchanged a pair of pawns on the king side.
Leela pushed the e pawn, it gave the bishop and captured two pawns, creating passers on the queen side. Stockfish lost its rook and then its knight, it pushed its remaining pawns on the king side. Leela gave its pieces to stop the black pawns, then queened to win.
In game 58 Stockfish castled its king and the queens stayed on the board. The black king moved forward without castling, Leela opened the a file and blocked the center. Evals came down, after some shuffling the engines exchanged a pair of rooks. Stockfish captured a pawn and the game reached a QBN vs QBN position. Leela regained the pawn, after knights were exchanged the game was adjudicated. Leela wins the game pair, Stockfish leads 18-11.
Games 59-60 started with a rare 18-ply line in the French Winawer, advance variation. The center was blocked and all pieces and pawns were on the board. In game 59 the engines exchanged minor pieces and a pair of pawns, the black king stayed in the center uncastled. Evals came down and the black king walked to the queen side. The game reached a QRR vs QRR position and the engines shuffled for a while. Leela captured a pawn, allowing Stockfish to force a queen exchange and the game was adjudicated.
In game 60 Leela pushed a pawn on the queen side, Stockfish gave two pawns and let the black pawn reach the 2nd rank. Evals increased early, Leela's eval was even higher that Stockfish's. Stockfish captured the advanced black pawn and gave a knight, creating a passer on the queen side. Leela's king was in the center and its king side rook could not develop, Stockfish pushed the passer and moved a rook to the 7th rank. Leela lost a bishop for the passer, Stockfish added its queen to the 7th rank. The black king ran to the king side, Leela gave a rook for a knight and pawn. Then Stockfish added its second rook to the 7th rank, all three major pieces on the 7th rank !
Stockfish captured the black a pawn on the 2nd rank, Leela was anxious to get rid of the pieces on the 7th rank and it exchanged queens and a pair of rooks. The game reached a RB vs BN position, Stockfish traded pawns and created a passer on the king side. Leela pushed pawns in the center, Stockfish saw the win in its PV. It lost the passer and captured two pawns in the center, each engine was left with one pawn. Stockfish moved its pieces forward and trapped the black king. Leela lost material because of the mate threat and the game ended in a tablebase win. Stockfish wins the game pair, it leads 19-11.
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