After 40 games Leela leads 8-7 with 25 draws. Leela won 4/5 game in white, in three of these game pairs Stockfish managed to win as white but in one it only drew. As a result Leela is in the lead again. Of the last 12 game pairs Leela won 3 times and Stockfish not once. This superfinal is more exciting than any we have seen in the last seasons, usually the winner (Stockfish) was clear by this stage of the match.
Leela has been playing a lot better than in the premier division. I'm not sure why that is, the chat mentioned a few configuration changes. I noticed a few things that are new to me. First there are a lot less instamove blunders. These caused many losses for Leela in past games, where it continues to play its PV with only a few seconds thinking time, only to find the move was a blunder in the next move. Another thing I noticed is that when thinking for a long time, even while following its PV, Leela sometimes changes its mind about the move to play. This usually is combined with an eval jump while still thinking. There were a few cases I saw where this was a deciding move that surprised Stockfish and changed the eval trend of the game. Lastly, many Leela wins come after a long period of stable evals around 1. Sometimes Stockfish's eval jumps first, as if it cannot wait any longer to see what Leela would do, but it knows this is a mistake. Whatever it is, Leela obviously has improved a lot and is a strong opponent to Stockfish, which it hasn't been for quite a while.
Games 31-32 started with a sideline of the Scandinavian defense, played at the highest level of human chess. In game 31 the engines started with a PV agreement in which a pair of minor pieces was exchanged and the engines castled in opposite directions. A pawn exchange opened the d file and created pawn majorities for each engine on the side it castled. Stockfish pushed pawns on the queen side, Leela's eval jumped on move 24. Stockfish's eval increased slowly as more pieces were exchanged, the game reached a QRN vs QRN position with white a pawn up.
Stockfish couldn't stop the passers, Leela queened and then reduced to a winning king and pawns tablebase win.
In game 32 Leela immediately attacked the king side with its queen, it gave a bishop for a rook. Stockfish castled long, then targeted the black queen and developed its pieces faster. On move 24 Leela thought for 11 minutes and its eval jumped. Stockfish thought Leela's move was not accurate and its eval jumped as well.
Stockfish pushed pawns on the queen side while keeping its king side pawns protected. Leela's eval increased very slowly, Stockfish saw it was winning many moves ahead. Eventually Stockfish exchanged pawns on the queen side and created a passer. Leela blocked the passer on the 7th rank with its king, thereby trapping its king in the corner. With mate threatened Leela lost its rook and the game. There were two white wins in this game pair, the score is 5-5.
Games 33-34 started with a line diverging from the KID anti Gruenfeld, not seen on human chess. White started a pawn up. In game 33 the engines exchanged pawns and minor pieces on the queen side, opening the a file. Stockfish avoided exchanging rooks, it doubled its rooks on the b file and attacked a white pawn. Evals came down, the center opened and Stockfish moved its queen forward to attack the black king. The engines exchanged a pair of rooks, Stockfish traded pawns to capture the white b pawn. In a series of exchanges the engines reduced to a queen ending, Leela was a pawn up but evals were low and the game was adjudicated. In game 34 there were less exchanges after the start, Stockfish had a passer on the a file. Stockfish pushed the passer to the 6th rank and doubled its rooks behind it. Exchanges opened the center, then Stockfish gave a rook for a knight and pawn on the queen side. In a series of exchanges the engines reduced to a BB vs RB position. Stockfish was two pawns up with connected passers on the queen side but evals were low and the game was adjudicated.
Games 35-36 started with a rare sideline of the French Winawer opening, Alekhine-Marocsy gambit. In game 35 the black king moved without castling. The center was blocked and there were no pawn exchanges until move 19. The engines shuffled for a while with stable evals, Leela doubled rooks on the b file. On move 26 Stockfish thought for 17 minutes and it changed its move from what it expected in its PV, evals started to increase. In a long PV agreement the engines opened the queen side and reduced to a QRB vs QRN position with white a pawn up.
Leela pushed its passer forward, it gave some material to queen the passer, game over.
In game 36 the engines played out PV agreements after the start, the moves played were not the same as the reverse game but again the black king moved without castling and the center was blocked. A pawn exchange opened the c file, there were only a few exchanges after the start. Stockfish also didn't castle its king, it developed the king side rook through the h file and walked its king to the corner. On move 23 Stockfish's eval started to increase slowly, reacting to what it considered inaccuracies by Leela. On move 30 Leela's eval also jumped, it didn't expect Stockfish's move.
Material was equal but Stockfish's pieces were better placed and its king was safe, while Leela's king was exposed to attacks. Stockfish moved its rook to the 7th rank, its queen was active across the board. Leela gave a pawn and exchanged queens, Stockfish had two passers facing the black king. Leela managed to capture one passer, but then lost material and was mated. There were two white wins in this game pair, the score is 6-6.
Games 37-38 started with a line that diverged out of human games from the Italian game. In game 37 there was a pawn exchange after the start, then the engines started playing out a long PV agreement. Stockfish changed a move in the middle, the game continued in a different PV agreement with a few minor piece exchanges. Evals were stable around 1, in another long PV agreement the engines opened the center and exchanged queens, then Leela went a pawn up. On move 38 Stockfish thought for almost 10 minutes and its eval jumped, Leela reduced to a RRN vs RRN position.
Leela had a pawn majority on the queen side, after exchanging a pair of rooks it created a passer on the b file. Leela pushed the passer slowly and carefully forward, it took 25 moves to reach the 7th rank. After queening it took Leela another 15 moves to end the game in a tablebase win.
In game 38 the engines repeated the reverse game for 7 plies, after the games diverged evals started to come down. The engines opened the center and exchanged minor pieces, then there was a period of mostly shuffling. A series of exchanges cleared all the queen side pawns, evals were close to 0 when queens were exchanged. The game reached a RB vs RN position and was adjudicated. Leela wins the game pair, it leads 7-6.
Games 39-40 started with a rare sideline of the Queen's Indian, Petrosian variation. In game 39 the engines opened the queen side with pawn and minor piece exchanges, almost all pieces on the board moved there. Evals were under 1 and stable, most moves were in PV agreement. On move 35 Leela changed its mind and made a move not in its PV, its eval started to increase and so did Stockfish's. In a series of exchanges the engines reduced to a RRB vs RRB position.
The endgame was very long. Leela slowly walked with its king to the queen side, on move 84 Leela managed to capture the black c7 pawn. Stockfish lost both its pieces to stop a queening, game over.
In game 40 Stockfish chose to avoid many exchanges after the start, the engines only opened the b file and exchanged a pair of rooks. Evals were over 1 and slowly increasing, Leela tried to hold a long pawn line. For a while it was unclear whether Stockfish would attack on the queen side where the black a pawn was weak, or attack the black king. On move 27 Leela accelerated the decision when it pushed the g pawn and created contact with the white pawns, Leela's eval also jumped as a result.
Stockfish exchanged the major pieces and reduced to a knight ending. It pushed the passer and Leela let it promote to a queen, mate followed. There were two white wins in this game pair, Leela leads 8-7.
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