After 20 games Stockfish leads 6-4 with 10 draws. Stockfish won a second game pair and increased its lead. There were 4 drawn game pairs, 3 with two draws and one with two wins. The Leela version playing in the superfinal seems to be closer in strength to Stockfish than the version that played in the premier division. Leela still has not been able to win a game pair.
Games 11-12 started with a sideline of the English opening, Great Snake variation. In game 11 the engines played a long PV agreement with all pieces on the board and only one pawn exchange after the start. Evals came down, after move 25 Stockfish gave two pawns and then there was a series of exchanges and the game reached a RB vs RB position with white a pawn up. Leela captured a pawn and created two passers on the king side. Stockfish managed to keep the white king away, after some shuffling Stockfish captured one of the passers. Leela's eval came down enough for the draw rule. Game 12 started with a 22-ply repeat of game 11. Stockfish concentrated on the center, it gave a pawn and opened files, then placed its major pieces there. Evals came down, in a series of exchanges Stockfish regained the pawn. The game reached a RBN vs RBN position, after the rooks were exchanged the game was adjudicated.
Games 13-14 started with a French, Tarrasch variation played in high level human chess. In game 13 Stockfish surprised Leela for a few moves, at first Leela's eval increased as if it thought Stockfish's moves were inaccurate. There were only a few exchanges, Stockfish kept its king in the center. On move 20 Stockfish's eval dropped, Leela's eval dropped after thinking for 8 minutes. In a series of exchanges the engines reduced to a RN vs RB position with white a pawn up. The engines traded pawns, Leela created connected passers on the king side and Stockfish had a passer in the center. Stockfish gave the bishop for the 2 white passers, Leela had one pawn left. Leela shuffled to avoid a 7-man draw, eventually it lowered its eval and the game was adjudicated.
In game 14 Leela castled its king, its eval was low after the start. There were a few pawn and minor piece exchanges, then Stockfish sacrificed a bishop and exposed the black king. Leela's eval jumped, then slowly decreased. Stockfish threatened the black king with its pieces and its eval increased, Leela was satisfied with its defense. On move 28 leela thought for more than 8 minutes and the eval drop suggested it thought that it was safe.
Stockfish played Rd2, seems like a small defensive move, I don't know, but not what Leela expected. Leela thought for almost 15 minutes and its eval jumped to 3. The PVs agreed, there was a series of exchanges and Stockfish gave checks. The end result on move 44 was a QR vs QRN position with white 4 pawns up.
Stockfish gave checks, protected its king and slowly pushed the h passer forward. Leela exchanged rooks but couldn't prevent a queening and the game ended in mate. Stockfish won the game pair, it leads 5-3.
Games 15-16 started with a sideline of the Sicilian, Sozin attack variation. Game 15 started with a long PV agreement, Leela castled long, Stockfish pushed the b pawn but couldn't open the queen side. Leela captured a pawn and the engines reduced to a double rook ending. Evals came down as the engines traded pawns, after exchanging a pair of rooks the game was adjudicated. Game 16 started with an 18-ply repeat of game 15. A series of exchanges reduced to a RRB vs RRB position and Stockfish went a pawn up. Evals came down as the engines traded pawns, after exchanging bishops Leela's eval slowly decreased and 15 moves later the game was adjudicated.
Games 17-18 started with a rare sideline of the French Winawer, poisoned pawn variation where black defends the g7 pawn with a knight on f5. In game 17 Leela exchanged a bishop for the defending knight and Stockfish moved its king to protect the g7 pawn, blocking its king side rook. Leela captured a pawn, by the time Stockfish freed its rook both engines had a passer on the queen side. The game reached a RRB vs RRB position, the engines traded a pair of rooks and captured both passers, then Leela captured two pawns. Despite being two pawns up Leela couldn't find a way to improve, evals came down and the game was adjudicated. In game 18 Stockfish left the g7 pawn alone, captured a pawn on the queen side and created a passer. Queens were exchanged and evals came down, Leela captured the white passer on the 7th rank. The engines traded pawns and reduced to a RBN vs RBN position. After exchanging rooks the engines shuffled until evals were low enough for the draw rule.
Games 19-20 started with a rare 6-ply sideline of the Philidor defense. In game 19 Stockfish gave a pawn and developed its queen early. The engines played out a long PV agreement, Leela kept its king in the center, there were many early exchanges and the game reached a RRB vs RRB position on move 21. Evals were stable but started to increase after move 27, the engines exchanged a pair of rooks and evals were around 2.
Leela created a passer in the center and supported it with its bishop. Stockfish captured pawns on the queen side and Leela captured pawns on the king side. Leela gave its center passer and replaced it with a passer on the king side.
Stockfish couldn't stop the white passers advancing, Leela queened and mated.
In game 20 Leela gave a pawn and castled long, Stockfish gave a bishop for two pawns and exposed the black king. The white queen move forward to the queen side facing the exposed king.
The white knight on f3 crossed the board to b5 and joined the attack. Leela traded a bishop for the knight, in a series of exchanges the engines reduced to a RN vs RNN position with white 4 pawns up on move 33.
The endgame was slow. Stockfish focused on the king side first, it traded pawns and exchanged a pair of knights, all the black pawns were eliminated and only the white h pawn remained on the king side. The white king moved forward and protected the queen side pawns, Stockfish slowly pushed the h pawn forward. Leela captured the h pawn on the 6th rank, its king was trapped in the corner and Stockfish mated with its pawns. There were two white wins in this game pair, Stockfish leads 6-4.
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