Season 24 superfinal games 71-80

After 80 games Stockfish leads 15-11 with 54 draws. Stockfish increased its lead after winning two game pairs. This is the biggest lead of the match so far, and with 10 game pairs more to play a gap of 4 wins seems decisive. The last Leela game pair win was in games 37-38, so 21 consecutive game pairs without a win for Leela.

Games 71-72 started in the KGA Mason-Keres gambit, with a bias for black. In game 71 Stockfish attacked the black king and let Leela capture a rook with a knight. Leela's eval started very low but jumped over 1 after the rook sacrifice. The white knight was trapped in the corner but Stockfish was focused on the attack. Leela exchanged queens, Stockfish gave a knight but its remaining pieces all targeted the black king. Leela gave a rook, the position finally stabilized and Stockfish captured the trapped knight. The game reached a RB vs RBN position, Leela was two pawns up with a passer on the 7th rank. Evals came down, Leela captured another pawn and placed a second passer on the 7th rank. Both passers could not advance, after Stockfish made sure all its pieces were secure it captured both passers, and Leela created a passer on the king side. The engines started to shuffle on move 41 and evals came down. Pawn moves extended the shuffle until finally Stockfish gave the knight for a pawn and the game was adjudicated, on move 188. In game 72 Leela prevented the white knight fork that would capture its rook. Stockfish's evals immediately dropped, the attack on the white king was over quickly when the engines exchanged queens. Both evals were low, the game was adjudicated on move 36 after enough pieces were exchanged.

Games 73-74 started with the Benoni defense, a line played at the highest level of human chess. In game 73 there were no exchanges after the start. Starting from move 16 the engines played out a long PV agreement, they exchanged minor pieces and opened files on the queen side. Evals came down, Stockfish had a passer on the queen side and Leela created a passer in the center. In another PV agreement Stockfish gave a bishop, both passers were captured and the queens were exchanged. Leela gave a rook for a knight and a pawn, the game reached a RBN vs RR position with one pawn left for each engine. The engines started to shuffle on move 43, evals were close to 0 and the game was adjudicated on move 93 after the engines exchanged a pair of rooks. In game 74 the engines followed theory for a while, again there were no exchanges after the start. After move 19 the engines opened the queen side and Stockfish went a pawn up, though evals came down. Leela regained the pawn and created a passer on the queen side. Then in a long PV agreement there was a series of exchanges that reduced to a same color bishops ending, evals were low enough for the draw rule.

Games 75-76 started with a rare sideline of the Gruenfeld defense, Zaitsev gambit. In game 75 Leela went a pawn up and opened the queen side after the start. The engines continued to develop pieces without exchanges, both queens move forward. After move 22 the engines started to exchange pieces and evals came down. The game reached a RN vs RB position, the pawns stabilized and the game was adjudicated when Leela's eval was low enough.

In game 76 Stockfish let Leela regain the pawn, its eval increased as it pushed pawns in the center. In a series of exchanges Stockfish created a passer in the center and captured a rook for a bishop. The white king was exposed and it walked to the king side. Leela's eval drifted down in a PV agreement, it captured a pawn and created a passer on the queen side. Stockfish moved its pieces to the king side, it expected Leela to capture another pawn on the queen side, but Leela had other ideas. Almost all black pieces were on the queen side, Leela felt safe and Stockfish followed Leela's PV. Stockfish's eval jumped quickly, on move 26 the action started with a rook sacrifice, still in PV agreement.

The white queen moved forward and attacked the exposed black king. Leela's eval jumped many moves too late, the black pieces were too far away and not coordinated. Stockfish gave a rook but captured the black queen, reducing to a Q vs RB position on move 39.

The endgame was long but Stockfish never had a doubt about the outcome. It captured two pawns on the queen side, then slowly pushed the a pawn forward. Leela managed to capture the passer but lost its rook. Stockfish then mated using only dark squares, invisible to the black bishop. Stockfish wins the game pair, it leads 13-10.

Games 77-78 started with a rare sideline of the Sicilian four knights variation. In game 77 there was a long PV agreement early, the center opened and the queens were exchanged, the engines traded rook and pawn for two knights. Evals started to come down and the engines mostly shuffled. The game ended in a 3-fold repetition which seemed to surprise Leela, it expected to play on.

In game 78 there was a different early PV agreement, there were no exchanges after the start, all pieces remained on the board and Stockfish castled long. Leela kept its king uncastled. Stockfish's eval increased slowly while Leela's eval drifted down. After move 20 there were a few exchanges and the king side opened. Leela moved its king without castling and on move 25 Leela's eval jumped, it had tripled pawns on the f file and the two adjacent files were open.

In a long PV agreement Stockfish gave a pawn on the queen side and moved its queen forward on the king side to join the attack. Leela attacked first, it gave a bishop for two pawns and cleared the white queen side pawns. The exposed white king ran forward to the center, Leela pushed a passer to the 2nd rank but Stockfish had the back rank covered with two rooks. The white queen moved forward, after exchanging queens the game reached a RRB vs RR position with black 3 pawns up.

Leela chased the white king but was not strong enough. Stockfish pushed the h passer forward, after exchanging a pair of rooks Leela captured the white passer but lost its advanced a passer. Stockfish protected its last pawn and slowly captured black pawns. The white king moved forward and soon the black king was in a mating net. The game ended in a tablebase win just before mate. Stockfish wins the game pair, it leads 14-10.

Games 79-80 started with a rare sideline of the Caro-Kann, two knights attack. In game 79 Leela moved its queen forward early, it captured a pawn on the queen side. Stockfish pushed pawns across the board, it opened the c file and exchanged queens. Evals started to increase, on move 25 the game reached a RBB vs RBN position with white a pawn up. 

Leela used its bishops to protect the center pawns and to keep the black rook away. Leela captured the black a pawn and created doubled passers. Stockfish gave up its bishop and captured the white b pawns, the game reached a RB vs R position. 

Leela gave the d pawn, Stockfish had weak pawns to defend and it needed to keep the white king back. Stockfish gave a pawn to weaken the white pawn chain, Leela used its bishop to protect its pawns. Leela pushed the h pawn forward and Stockfish started to lose material. After exchanging rooks Leela queened and mated.

In game 80 the engines repeated the reverse for 17 plies, Stockfish captured the pawn on the queen side with its queen. Leela drove the queen back and then opened the c file. Stockfish's eval started to increase as it opened the g file, a few moves later Leela's eval reacted after the game reached a RBB vs RBN position.

The engines exchanged bishop for knight, then cleared pawns on the queen side, Stockfish was two pawns up with a passer. Leela pushed the h pawn and tried to give its bishop to create a passer. Stockfish saw the trap, it let Leela capture the h pawn and pushed the d pawn until it was a passer too. Stockfish was first to promote a pawn, Leela lost its bishop, it captured the white a pawn but lost its h pawn. With patience Stockfish converted the RB vs R ending. There were two white wins in this game pair, Stockfish leads 15-11.