After 90 games Stockfish leads 16-9 with 65 draws. Stockfish won another game pair and its lead is now +7. Leela's chance of catching up is only theoretical with 10 games left to play.
Games 81-82 started with a 21-ply book in the King's Indian Samisch variation, popular in games from the 90's. In game 81 there were no exchanges after the start, Leela castled long and the engines played behind their pawn lines. Stockfish opened the queen side, then gave a rook for a bishop and its eval dropped to 0. The engines cleared the queen side pawns and reduced to a QRR vs QRB position. Leela moved its pieces forward and Stockfish ended the game with perpetual check. Game 82 started similarly, Stockfish castled long and there were only a few exchanges. This time the engines exchanged a pair of pawns on the king side, Leela blocked the entry and the engines shuffled for a while. On move 34 Stockfish gave a rook for a bishop and created an advanced passer on the queen side . Evals were close to 0 and without pawn moves the game was quickly adjudicated, most pieces still on the board.
Games 83-84 started with a 20-ply book in the Sicilian Taimanov variation, with the engines castled in opposite directions. There were many early exchanges in game 83, the game reached a RBB vs RBB position on move 19. After a few pawn moves the engines started to shuffle, on move 53 the rooks were exchanged. After almost 50 more moves Leela gave a pawn and used a pawn majority on the queen side to create a passer. Another 50 moves went by, Leela realized it had nothing after another pair of pawns were exchanged and it lowered its eval. The game was finally adjudicated on move 161.
In game 84 Leela avoided exchanging knights immediately, it prefered to trade a knight for a bishop. Stockfish's eval jumped over 2, the black king faced advanced pawns and many white pieces while the black pieces were mostly on the queen side.
Leela had to exchanged its DS bishop with a knight, this got a white pawn to f6. Stockfish had several options to attack the black king, and the g6 pawn was a crucial defender. Leela had a counter threat against the white king but Stockfish protected its b2 pawn and continued the pressure on the king side. On move 28 Stockfish was willing to give a rook to get the g6 pawn out of the way.
Leela refused to take as it knew this would lead to a quick loss of material or mate on either g7 or h7. Instead there was a quick series of exchanges, queens were off and Stockfish traded its f6 pawn with the black c5 pawn. Material was equal in a RRB vs RRB position but Stockfish's queen side pawn majority was deadly. Leela's pawns on the king side could never be quick enough, the white pawns started to march and Leela had to lose pieces to stop them. Stockfish wins the game pair, its lead increases to +7.
Games 85-86 started with the QGD Chigorin defense with black a pawn up, and in both games black played a very rare move of retreating a knight to b8 immediately out of book. In game 85 Leela regained the pawn, there were almost no exchanges as the engines formed long pawn lines. On move 32 Stockfish completed a line across the board and the engines started to shuffle. On move 90 the engines started to exchange pawns and opened the position, Leela went a pawn up and created a queen side passer and Stockfish had a passer on the king side. On move 107 the game reached a RB vs RN position, Leela gave the bishop and pushed its passer to the 7th rank. However Stockfish gave checks and the game was adjudicated before it lost its knight and stopped the passer. Game 86 started similarly, Stockfish regained the pawn and the engines developed their pieces without exchanges. Stockfish pushed a pawn to a6, then the engines opened the queen side and exchanged a pair of rooks. After some shuffling the evals came down, a series of exchanges reduced to a RB vs BNN position. The engines cleared the remaining queen side pawns and the game reached a R vs B ending. It took a while for Stockfish to lower its eval enough for the draw rule to stop the game on move 93.
Games 87-88 started with a 26-ply book in the Ruy Lopez Flohr system. The white 13th move in book was rare, but in both games the engines transposed back to the main line for a few moves. In game 87 the engines continued without exchanges until move 29, Stockfish pushed pawns on the queen side and created a passer. Stockfish gave a rook for a bishop and a series of exchanges cleared all the white pawns on the queen side. Evals came down as the exchanges continued more slowly, on move 62 the game reached a R vs N ending. Leela managed to capture the black passer, the game was adjudicated in a 7-man draw. In game 88 there were no exchanges until move 29 as well, though the development was not the same. Leela had a pawn majority on the queen side but it didn't push the pawns too much forward. Instead Leela tried to create some pressure on the king side with its queen and knight. Evals were close to 0 when the engines started to exchange pieces and the position opened up. Stockfish had a back rank threat, and when Leela captured a rook Stockfish ended the game in a perpetual check repetition.
In game 89 Stockfish captured an early pawn but its eval was over 3 very quickly. Leela regained the pawn and developed all its pieces, while Stockfish was slow developing its queen side. Leela started attacking on the king side and Stockfish traded RN for Q on move 21.
The white queen was very strong in the open board and Stockfish had to deal with multiple threats. The black defense crumbled quickly, on move 34 Leela captured a rook for a knight.
Leela captured the bishop and Stockfish saw the mate coming when the game was adjudicated.
The start of game 90 was more peaceful, the engines developed their pieces without exchanges. Only Stockfish's increasing eval gave a hint that something was happening. The black pieces had only a small space to move, on move 19 Leela gave a pawn and tried to open the queen side. Stockfish's eval jumped over 3.
Stockfish pushed pawns in the center, it gave the e pawn and created a passer on the d file. The white DS bishop was en prise for 4 consecutive moves but Leela had more urgent things to do like protecting the f7 pawn. Eventually the engines exchanged their DS bishops, Leela went a pawn up and Stockfish pushed the passer to the 7th rank. In a series of exchanges the engines reduced to a QRB vs QRN position and Stockfish captured the black pawns on the queen side. Now Stockfish was a pawn up with connected passers.
Leela did not have a threat against the white king and it needed to keep the white pawns from queening. With a pawn on the 7th rank the engines exchanged rooks and Stockfish captured another pawn. The game was adjudicated before Stockfish won more material. There were two white wins in this opening, Stockfish continues to lead +7.
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