Season 23 superfinal games 61-70

After 70 games Stockfish leads 15-5 with 50 draws. Leela won a game after 50 games without a win. It also won a game pair, its second of the match. Stockfish managed to win two game pairs and its lead increased to 10. As expected the opening bias is increasing, there were 3 decisive game pairs and one with two white wins.

Games 61-62 started in a rare sideline of the Pirc defence, Bayonet attack. In game 61 the engines played out a long PV agreement, both kings were exposed and moved without castling to the king side. Queens were exchanged and Leela was a pawn up with a central passer. The game reached a RBN vs RBN position and evals slowly came down. The engines mostly shuffled for a long time, Stockfish captured the passer on the 7th rank and the game was adjudicated on move 72. 

In game 62 the engines entered a different PV agreement, this time the h file was opened and both engines castled long. Evals were stable for a while, Stockfish thought Leela's move 26 was a mistake and its eval jumped. Leela thought for 11 minutes and its eval also jumped, it was very difficult to see what the engines understood. It was evident that Leela moved a knight and moved it back, losing 2 tempi. Also, Leela had a knight on h5 that was weak, almost trapped. Evals slowly increased though the engines seemed to be shuffling. 

Evals continued to increase, Leela played waiting moves while Stockfish slowly moved its pieces to the queen side. When it was ready Stockfish pushed pawns on the queen side and opened the a file. Now the black king was in danger and Leela was effectively playing a piece down. 

Leela gave a rook for the bishop and freed its knight, but it was too late. Stockfish exchanged queens, captured two pawns and pushed a passer to the 7th rank. Leela lost material and was mated. Stockfish wins the game pair, it leads 13-3.

Games 63-64 started with a rare sideline of the French defence, Paulsen variation. In game 63 the engines castled in opposite directions. Evals started to increase on move 15, both queens moved forward and captured a pawn defender of the opposing king, then queens were exchanged. Stockfish pushed pawns on the king side and the game reached a RRB vs RRB position. 

Stockfish opened the king side and the white king walked to the center. Leela gave a pawn and opened the queen side, it pushed a passer and Stockfish gave a bishop to capture it. After exchanging a pair of bishops Stockfish was two pawns up with two passers while Leela was down to 2 pawns.

Leela captured the f pawn while Stockfish pushed its passers. Leela captured a passer and was on time to protect its pawns with the king and prevent Stockfish from queening the second passer. Leela captured the remaining black pawns, the game ended in a tablebase win.

In game 64 the engines castled in opposite directions again. Stockfish gave a pawn on the queen side and half opened the a file for its rook. There were a few minor piece exchanges, Stockfish had strong pawns in the center and evals slowly increased. Leela gave a pawn on the king side to develop its rook, then it created a passer on the queen side, giving Stockfish a central passer at the same time. The black king had weak pawn support and evals jumped. In a series of exchanges the engines reduced to a RRB vs RRB position. 

After a few pawn trades only one black pawn remained on the queen side and the black king was an easy target for the white rooks. Both engines had passers on the g file, both were blocked one square before promoting. Leela had to use a rook as a blocking piece, effectively Stockfish had a piece advantage and it was able to capture the black passer on g2. 

Stockfish captured the black f pawn, then slowly pushed its d pawn forward. Leela delayed with checks but ultimately had to give its bishop to stop the queening. After that Leela gave up and was mated. There were two white wins in this game pair, Stockfish leads 14-4.

Games 65-66 started with a 14-ply book in the KID semi Averbakh system. In game 65 Leela pushed pawns on the king side and kept its king uncastled. Leela's eval increased after move 14 and it surprised Stockfish on move 15. Stockfish thought for 21 minutes, it captured a pawn on the queen side and its eval jumped over 2. Leela pushed a pawn to h6 and trapped a black bishop in the corner. On move 20 Leela regained the pawn on the queen side, Stockfish thought this was a mistake and its eval dropped back. There was a series of exchanges that opened the position, Leela captured a knight and had a passer on the 7th rank, but Stockfish threatened the white king. Stockfish captured the passer and a knight, Leela was a pawn up but evals were close to 0. There were too many pieces for the draw rule, the game was adjudicated after the engines exchanged a pair of rooks.

In game 66 again Stockfish pushed pawns on the king side and didn't castle its king. The engines opened a file on the queen side, Stockfish walked its king to the king side corner. On move 19 Leela chose to exchanged a pair of bishops, Stockfish thought this was a mistake, evals started to increase. Stockfish concentrated forces on the king side and the black king walked back to the center. When it was ready Stockfish opened the h file.

The engines exchanged a pair of rooks, Leela defended the back rank against the white pieces. Stockfish managed to capture a pawn, the black king ran to the queen side for safety. Stockfish reduced to a QRN vs QRN position and captured two more pawns. 

Stockfish had 2 passers, after exchanging queens and trading a pair of pawns Stocfish added another  passer. Leela captured one passer, lost its knight for the second one but the third promoted to a queen and Stockfish mated. Stockfish wins the game pair, it leads 15-4.

Games 67-68 started in the Trompovsky attack, Raptor variation. In game 67 Stockfish grabbed an early pawn with its queen, Leela pushed a pawn to h6 and both kings stayed in the center uncastled. The engines opened the board with a few exchanges and then queens were off.

Evals increased though it seemed the engines were shuffling, Stockfish had many weak pawns to protect and Leela moved its pieces trying to decide where to attack. After a while Leela captured two pawns and exchanged a pair of rooks. Stockfish captured a pawn back, equalizing material but evals were high.

Stockfish's defence gradually collapsed, Leela captured the g pawn and then the h pawn, creating and advanced passer. Stockfish had to give a bishop to stop the promotion. Leela slowly improved using its piece advantage. Stockfish couldn't prevent a queening followed by mate.

In game 68 there were no exchanges after the start, the engines locked pawns in the center and king side to form a long pawn wall. On move 34 a pawn exchange opened the b file, after a bishop exchange the engines started to shuffle. Stockfish wouldn't lower its eval, it extended the game with piece exchanges and by move 152 only BN vs BN remained. After Stockfish's eval was low enough there were still too many pawns for the draw rule, the game finally ended on move 256 by a 3-fold repetition. Leela wins the game pair, Stockfish leads 15-5

Games 69-70 started with a sideline of the French, Winawer, retreat variation, with the center locked and black a pawn up. In game 69 Leela used a rook to regain the pawn and sent its queen forward on the king side. Stockfish didn't castle its king, its king side rook moved and the queen side was open. Leela castled late and evals came down, the engines traded a pair of rooks and started to shuffle in a QRN vs QRN position. There were too many pawns, the engines reduced to a queen ending and the game was adjudicated on move 93. In game 70 Stockfish used its queen to regain the pawn, Leela moved its king without castling and Stockfish also kept its king uncastled. The engines opened the king side a little but did not try to attack, instead they shuffled for almost 50 moves. A few exchanges opened the queen side, evals came down and shuffling resumed. On move 113 the engines started to exchange pieces, and the game was adjudicated on move 131.

Season 23 superfinal games 51-60

After 60 games Stockfish leads 12-3 with 45 draws. Stockfish won two game pairs and increased its lead to 9. It looked like Stockfish would win another game pair, but its eval dropped from 4 to 1 suddenly and the game ended in a draw. Leela hasn't won a game pair, or indeed a game, for a long time. The main question seems to be the lead Stockfish will have at the end of the match.

Games 51-52 started with a 17-ply book sideline of the KID Saemisch variation, with the center pawns locked. In game 51 Leela pushed pawns on the king side and opened the g file, then castled long. Stockfish didn't castle, but walked its king to the king side. The engines exchanged a pair of rooks and a pair of bishops, then started to shuffle with a few pawn moves and exchanges. On move 37 Stockfish went a pawn up, it had a pawn wall across the board except for two files on the king side. Evals came down and the engines reduced to a QN vs QN position. There were too many pawns for adjudication, the game ended in a 50 move draw on move 117. In game 52 Stockfish castled long and Leela castled short, the engines opened the c file. Evals came down as the engines shuffled for a while, including a knight exchange. On move 37 Stockfish captured a pawn, Leela's pieces were active on the queen side facing the white king. Evals dropped to 0, the engines reduced to a double rook ending and Leela regained the pawn. The game was adjudicated when enough pawns were exchanged.

Games 53-54 started in the Caro-Kann, Hillbilly attack variation, with black a pawn up and a black bias. In game 53 Leela chose not to exchange queens, Stockfish's (negative) eval started to increase slowly. In a long PV agreement Leela castled short and Stockfish castled long, Leela pushed a pawn and opened a file on the queen side but its eval started to increase as well. In a series of exchanges the engines reached a material imbalance of QN vs RRB.

Evals were stable for a while and the minor pieces filled the center. Stockfish's eval started to jump, Leela's eval followed 2 moves later. The engines exchanged minors and reduced to a QB vs RRB position, then Stockfish gave two pawns as it formed a winning plan.

The idea was for to use dark squares, the black king moved forward through the center and Stockfish moved a rook to the back ranks. The threat of mate was more dangerous than any white passer that Leela created. After clearing all the queen side pawns both rooks came forward. The white queen tried to help, Stockfish captured it for a rook. The final moves were played only on dark squares, with the white bishop helpless to stop mate. 

In game 54 Stockfish chose to exchange queens, forcing the black king to move. The engines played out a PV agreement and evals slowly came down. Stockfish castled long and then evals dropped when in a series of exchanges the engines reduced to a RB vs RB position. Stockfish was a pawn up with a central passer. The engines mostly shuffled for a long time, the game was adjudicated when enough pawns were exchanged. Stockfish wins the game pair, it leads 11-3.

Games 55-56 started with a 16-ply book sideline in the QGA Alekhine system variation. In game 55 the engines exchanged minor pieces and there were no exchanges after that. Stockfish did not castle its king, after move 20 evals came down a little and the black king walked to the king side. There was a period of shuffling and a few pawn moves, on move 48 the engines exchanged minors and resumed shuffling. After move 66 there was a series of exchanges and evals dropped to 0, the game reached a rook ending and was adjudicated. Game 56 started similarly, a minor piece exchange and Leela not castling. On move 17 the engines started a long PV agreement, Stockfish gave a rook for a bishop and two pawns and opened the queen side. Stockfish cleared all the black pawns on the queen side, the game reached a RBN vs RRN position with white two pawns up and two passers, one advanced. Stockfish pushed the passer to the 7th rank, its eval was over 4. Then without warning Stockfish's eval dropped, while playing a move in its PV. In fact Stockfish and Leela predicted the game continuation many plys into the future, but Stockfish suddenly changed its mind about its winning chances. In another PV agreement Leela captured the passer and Stockfish captured a rook for a knight. The engines traded pawns until there were only a few on the king side. It took Stockfish a long time to reduce its eval for the draw rule.

Games 57-58 started with a sideline of the Philidor defence. In game 57 Stockfish pushed pawns on the queen side, Leela pushed pawns on the king side and neither engine castled its king. The engines exchanged minor pieces and evals came down, all pawns were on the board until move 33. The engines shuffled for a while, exchanged a pair of rooks and resumed shuffling. On move 79 Stockfish gave two pawns and moved its queen forward to end the game in check repetition.

In game 58 the engines repeated the reverse game for 21 plys up to transpositions. On move 20 Stockfish went a pawn up and created a passer on the queen side. Leela castled short and Stockfish pushed a pawn and opened the king side. On move 31 all the pieces were still on the board, the engines started to play out a long PV agreement. First queens were off, evals increased as the engines reduced to a RNN vs RBN position.

For a while Leela's eval came down a little, Leela exchanged rooks and regained the pawn. Stockfish's eval jumped higher as it pushed the a pawn forward. Leela was still optimistic after it gave a knight to capture the passer, resulting in a 7-man NN vs B position.

The position was a tablebase win, Leela's eval jumped a few moves later. Stockfish used only 6-man tablebases but it made no mistake and won. Stockfish wins the game pair, it leads 12-3.

Games 59-60 started with a sideline in the Caro-Kann, Bronstein-Larsen variation. In game 59 Stockfish kept its king in the center, there was weak pawn support on both sides. Leela pushed a pawn in the center and it became an advanced passer. The engines opened the queen side and exchanged pieces, evals came down and the game reached a QRR vs QRR position. The game was adjudicated when evals were low enough for the draw rule. In game 60 Leela walked its king to the king side, pieces stayed longer on the board. In a long PV agreement Stockfish gave 3 pawns and opened the center, exposing the black king to attacks. Evals came down, Stockfish got two pawns back and the game reduced to a RB vs RN position. Stockfish had a blocked passer on the 7th rank, the engines traded pawns and Leela captured the passer. The game was adjudicated a few moves later.

Season 23 superfinal games 41-50

After 50 games Stockfish leads 10-3 with 37 draws. Stockfish won two more game pairs, one after a rare blunder by Leela. Leela realized it was a blunder immediately in the following move, suggesting it hadn't considered Stockfish's reply - a bit strange. At the half way point Stockfish has a lead of 7, and Leela only won one game pair so far. The opening bias is slowly increasing, we should see more Leela wins but it is safe to sat that Stockfish will win the match easily.

Games 41-42 started with a 4-ply book 1.e4 c5 2. Nc3 b6. In both games the engines transposed into more popular variations of the Sicilian closed opening. In game 41 there was one pawn exchange after the start, Leela castled long and Stockfish kept its king in the center. Starting from move 17 the engines exchanged minor pieces, evals came down and the game reached a QRR vs QRR position. The engines continued to trade pawns and a pair of rooks, the game was adjudicated a few moves later. In game 42 again Stockfish castled long and Leela did not castle its king. Stockfish gave a bishop for two pawns, it forced the black king to move and opened the h file. Evals came down as the engines exchanged queens and a pair of rooks, Stockfish attacked the back rank with its remaining rook. The engines exchanged rooks and only minors remained, exchanges continued until only B vs BN remained. Stockfish captured all the black pawns, it was 4 pawns up when the game was adjudicated. 

Games 43-44 started with a 26-ply book in the Sicilian Dragon, Yugoslav attack, that was played in high level human chess (including a Karpov-Kortschnoi game from 1974). Up to a transposition the games repeated for 21 more plys, white pushed pawns on the king side and black kept the files closed, most pieces were still on the board. In game 43 Leela's evals increased a little, then came back down after Stockfish captured a pawn and reduced to a QRB vs QRN position. The engines traded pawns, evals were low enough for the draw rule. In game 44 played out another long PV agreement after diverging from the reverse game, resulting in a QRB vs QRN position. Evals came down as Leela attacked the white king, they dropped to 0 after the queens were exchanged. The game was adjudicated when enough pawns were exchanged. 

Games 45-46 started with an 8-ply book in a rare Queen's pawn game variation. In game 45 Leela weakened the black pawn structure using early exchanges, its eval increased a little. Stockfish pushed a pawn to e4, this restricted the white pieces a little. The engines played out a long PV agreement, the d pawn became a white passer but evals came down. Stockfish gave two pawns to open the king side, then it sacrificed a rook but got it back a few moves later. The game reached a QB vs QN position, Leela was up a pawn but the white king was exposed to checks, evals were close to 0 and the game was adjudicated. 

In game 46 Stockfish castled long, the engines mostly agreed in their PV and evals were stable after the start. A minor piece trade opened the g file, Stockfish thought Leela would also castle long but Leela instead chose to capture a free pawn. Stockfish's eval immediately jumped over 3 in a knight sacrifice that surprised Leela.

Leela's eval also jumped (why then make that move??), taking the knight weakened the black e pawn and now the black king was in danger. Stockfish captured two pawns and created two advanced passers. In a series of exchanges Leela captured one passer and reduced to a RRB vs RRN position. material was equal but Stockfish had a protected passer on the 7th rank.

Progress was very slow but evals increased steadily. It took Stockfish 25 moves to capture a pawn on the king side, then exchange a pair of rooks. Leela captured the white passer, but Stockfish reduced to a won B vs pawns ending (Leela could have taken the bishop and lead to a king and pawns ending which was also a white win). Stockfish wins the game pair, it leads 9-3.

Games 47-48 started with a sideline of the Queen's Indian accelerated. In game 47 the engines castled in opposite directions, Leela captured a rook for a knight and evals came down in a series of exchanges. The game reached a QR vs QB position with Stockfish two pawns up, Stockfish captured another pawn but its king was exposed. Leela moved its queen forward and gave checks, evals were low enough for the draw rule.

In game 48 the engines blocked the center, and again castled in opposite directions. There were no exchanges after the start and evals were stable, after a pawn exchange on move 18 the c file opened and Stockfish's eval increased slowly. On move 32 there was another pawn exchange on the king side, all pieces were still on the board.

Leela has to protect the pawns on b5 and g6, and its king was not safe with the g file half open. Evals continued to increase as Stockfish moved all its major pieces to the g file. On move 49 Stockfish pushed the f pawn forward, the first pieces were removed when the engines exchanged a bishop pair. Stockfish opened the g file to attack the black king, and on move 56 it finally went a pawn up.

Leela was busy defending its king and it had to abandon the b5 pawn. Stockfish exchanged all rooks and captured the remaining black pawns. It was 5 pawns up in a BN vs BN position and mated after queening twice. Stockfish wins the game pair, it leads 10-3.

Games 49-50 started with a 14-ply book sideline in the Sicilian closed variation. In game 49 both engines castled and then a pawn exchange opened the f file and both evals jumped a little. The engines exchanged a pair of rooks, then continued to exchange pieces and evals drifted down. Leela was a pawn up in a QRB vs QRB position, evals were close to 0 but the game continued until enough pawns had been exchanged. In game 50 Leela castled and Stockfish kept its king in the center. The engines played out a long PV agreement where Stockfish gave a bishop and then in a long series of exchanges regained the material. The game reached a RRN vs RRB position and evals came down. The engines continued to trade pawns, Stockfish went a pawn up while Leela pushed a passer on the king side. Stockfish captured the passer and exchanged a pair of rooks, the game was adjudicated when evals were low enough.

Season 23 superfinal games 31-40

After 40 games Stockfish leads 8-3 with 29 draws. Stockfish won a game pair and its lead increased to 5. The low exit evals continued in the last 5 game pairs and there was only one decisive game. After 40 games Leela has only one game pair win, Stockfish has 6 and it appears to be heading for another superfinal win.

Games 31-32 started in a variation of the Dutch defence. In game 31 Stockfish moved its king early without castling while Leela castled long. Evals came down as the engines played out consecutive PV agreements and exchanged pieces. The game reached a RR vs RBN position with Leela two pawns up, evals were low enough for the draw rule. Game 32 started similarly with Leela moving its king and Stockfish castling long. The games did not repeat but again the evals came down while the engines exchanged pieces, mostly in PV agreements. The game reached an opposite color bishop ending, Stockfish two pawns up with doubled passers. Stockfish wouldn't lower its eval, the engines shuffled and the game ended only on move 80. 

Games 33-34 started with a variation of the Trompowsky attack played in high level human chess, where black was a pawn up. In game 33 there was a long PV agreement from the start, after which both engines castled long and queens were exchanged. Leela captured a rook for a knight, evals remained stable and not very high as the engines exchanged pieces. The game reached a R vs B ending with Stockfish a pawn up. It took Leela a long time to lower its eval, the game ended on move 86. Game 34 repeated the reverse for a while, both engines castled long again but queens stayed on the board longer. Evals came down to 0 while the engines played without exchanges. A series of exchanges that started on move 43 reduced to an opposite color bishop ending and the game was adjudicated.

Games 35-36 started with a sideline of the French defence, Petrosian variation, after the white queen moved forward on the king side. In game 35 Stockfish kept its king uncastled and the king side rook and bishop did not develop. There were several exchanges in the center that opened files and evals came down. Stockfish opened the king side to activate its king side rook, it managed to move the DS bishop and exchanged it for a knight. The game reached a RRB vs RRN position and evals were low enough for adjudication.

In game 36 Stockfish moved its queen back, there were no restrictions on the black king side. Leela castled long and its eval was low while Stockfish's eval increased slowly. Stockfish pushed pawns on the queen side and Leela's eval increased a little. All pieces were on the board until move 24, then a series of minor piece exchanges opened the center.

Leela had several weak pawns, Stockfish didn't capture the free g pawn, it probably didn't want to open the king side to avoid attacks on its king. Leela's eval decreased for a few moves, it move its queen forward on the queen side. Stockfish captured the e pawn and Leela's eval jumped though it captured a pawn on the queen side. The engines reduced to a QRR vs QRR position. 

The black pawn structure was much worse, Stockfish captured a pawn quickly and then avoided a queen exchange. An attack on the queen side got Stockfish a second pawn and then the game reached a rook ending. 

Stockfish captured all the black pawns for the price of its queen side pawns. With 3 connected passers on the king side the win was just a matter of time. Stockfish wins the game pair, it leads 8-3.

Games 37-38 started in the KID Makagonov variation. In game 37 there were no exchanges after the start and the engines locked pawns in the center. A series of exchanges opened the king side and evals came down. The game reached a QRB vs QRB position, Leela was up a pawn and Stockfish threatened the white king through an open file. After exchanging queens the engines traded pawns until the game was adjudicated. In game 38 there were only a few exchanges after the start. Stockfish formed a line of pawns across the board with knights filling the gaps. Leela had no knights left, its two bishops were not an advantage in a closed position. The engines started to shuffle on move 23, one pawn move reset the move counter, the game ended in a 50 move draw on move 114.

Games 39-40 started in a sideline of the Modern defence, Averbakh system, with the center pawns locked. In game 39 the engines opened the a file and exchanged a pair of rooks, the other files on the queen side were locked. After exchanging queens and a pair of bishops the engines started to shuffle. Evals were stable as the white king walked to the queen side. On move 58 Stockfish opened the king side, the engines reduced to a RNN vs RNN position and evals came down. Stockfish moved the rook forward, Leela gave a knight and captured two pawns. Leela pushed a passer to the 7th rank, Stockfish was on time to force a check repetition draw. In game 40 the engines played on the king side after the start. In a series of pawn exchanges the engines opened the king side, they continued to exchange pieces at a steady pace. Evals came down, the game reached a RBN vs RBN position and a few moves later the game was adjudicated.

Season 23 superfinal games 21-30

After 30 games Stockfish leads 7-3 with 20 draws. Stockfish won another game pair and extended its lead to 4. There was only one decisive game in the last 10, after 9 decisive games in the first 20. According to the bookmakers description from game 21 onward the book bias should slowly increase.

In game 21 the engines pushed pawns on the king side and later castled long. There were a few minor piece exchanges and the king side opened, evals came down slowly. Leela went up a pawn and the game reached a QRN vs QRN position, evals were low enough for adjudication. In game 22 Stockfish did not push pawns on the king side, instead it castled long, opened the center and went a pawn up. Leela gave a second pawn and opened the queen side, then castled short. Evals came down, the material advantage for white was offset by the threat on the white king. The engines exchanged pieces until only BN vs BB were left, and the game was adjudicated. 

Games 23-24 started with a 15-ply book, a sideline of the Sicilian Scheveningen variation with high exit evals. In game 23 evals remained high as the engines played out a PV agreement, Stockfish castled short and the queens were exchanged. Stockfish had two isolated pawns on the queen side to protect. On move 26 the pawns stopped moving and the engines started to shuffle. After exchanging bishops the game reached a RRN vs RRN position, Leela's eval slowly decreased while Stockfish's eval dropped to 0. The engines exchanged knights, there were too many pawns for the draw rule and the game ended in repetition on move 77. 

In game 24 Leela pushed pawns on the queen side, a pawn exchange opened the a file and Leela had only one isolated pawn left. Stockfish then pushed pawns on the king side, Leela castled short anyway and evals stayed high.

Stockfish moved its king back to the center to avoid attacks from the open file, then pushed a pawn to g6. Leela did not exchange pawns, it moved the king to the corner. Evals increased rapidly as Stockfish prepared an attack on the black king, it gave a rook for a knight and pawn to remove a defender. 

A series of exchanges stopped the attack, Stockfish managed to get a pawn to the 7th rank and Leela gave a bishop to stop it. The game reached a knight vs pawns ending. 

Stockfish captured a few pawns, queened a pawn and mated. Stockfish wins the game pair, it leads 7-3.

Games 25-26 started with a 16-ply book, a sideline of the KID Saemisch variation. In game 25 Leela castled long and Stockfish pushed pawns on the queen side. Pawn exchanges opened the queen side and the engines exchanged queens. Evals came down as the engines continued to exchange pieces, the game reached a king and pawns ending on move 31. Leela was a pawn up but evals were low and the game ended by the draw rule. PV suggested that both engines could queen a pawn, leading to a drawn queen ending. In game 26 Stockfish castled long, the engines opened a file on the queen side but pieces stayed longer on the board. Stockfish opened a file on the king side and created a passer, but its attack on the black king was weak. Evals came down and the engines exchanged pieces until only QNN vs QBN remained, the game was adjudicated a few moves later.

Games 27-28 started with the St. George defence. In game 27 Stockfish pushed pawns on the queen side, the engines opened a file and exchanged a pair of rooks. Evals came down and the engines exchanged pieces, most of the queen side pawns were gone and Leela went a pawn up. After a period of mostly shuffling the engines exchanged the remaining rooks and the game was adjudicated. In game 28 again a file was opened on the queen side and the engines exchanged a pair of rooks, evals were high a little longer. Stockfish went up a pawn and created a passer on the queen side. Leela's pieces were more active and evals came slowly down. Stockfish pushed the passer forward, Leela gave a rook for a knight and threatened the white king in a QRB vs QBB position. Stockfish lost its passer and the game was adjudicated.

Games 29-30 started with a 3-ply book 1. e4 Nc6 2. b4 with a black bias. In game 29 Stockfish captured the b pawn, Leela used the time to push pawns in the center. The engines exchanged minor pieces and evals came down. Stockfish pushed pawns on the queen side where it had a pawn majority, in a QRR vs QRR position it gave a pawn to create a passer on the 3rd rank. Leela had perpetual check threats, Stockfish exchanged queens to avoid this and it lost its passer. The game as adjudicated a few moves later. In game 30 Leela captured the b pawn, this time the engines opened a file in the center. Evals came slowly down while the engines developed pieces without exchanges. After some exchanges, Leela created a passer on the queen side. Evals were close to 0 and the game reached a RBN vs RBN position. Stockfish created a passer and the engines exchanged knights before the game was adjudicated.

Season 23 superfinal games 11-20

After 20 games Stockfish leads 6-3 with 11 draws. Leela won its first game pair, winning as white and then holding a fortress in a position Stockfish was confident it could win. Stockfish responded with two game pair wins, extending its lead to 3.

Games 11-12 started with a 16-ply book, a sideline in the KID Saemich variation. In game 11 Leela pushed the g pawn forward and didn't castle its king. Stockfish opened the king side and its eval dropped to 0 while Leela moved its king to the corner. The engines waited for the draw rule from move 23, the game was adjudicated on move 45 after enough pieces and pawns were exchanged. In game 12 Stockfish exchanged pawns on the king side and castled short anyway. For a while Stockfish's eval increased but then it dropped though it followed its PV. The engines exchanged many pieces and Stockfish created a central passer while Leela had a passer on the queen side. Leela stopped the white passer on the 7th rank, the exchanges continued and evals came down. Both passers were captured, the game reached a RN vs RN position with Stockfish a pawn up, only enough for a draw.

In game 13 after a few early exchanges Leela had a pawn majority on the queen side. For a while Stockfish's eval came down a little, Leela's move 24 was a surprise and Stockfish thought for 18 minutes with an eval jump. Leela captured a pawn and created a doubled passer on the queen side, the game reached a RRB vs RRB position. 

Stockfish was busy blocking the passer on the queen side, the white king moved forward on the king side and Leela created a passer there. 

Leela abandoned the pawn on a6, but the h passer was unstoppable and Stockfish lost material to capture it. The game reached a RB vs R ending, Leela made sure it had a pawn left to guarantee a win.

In game 14 there were several early exchanges that opened the board. Leela captured a pawn on the queen side, Stockfish's eval increased as it opened the king side. Leela thought for 14 minutes and its eval also increased, then it moved without thinking for 6 straight moves while Stockfish regained the pawn and exposed the black king. Stockfish's attack resulted in a Q vs RB ending, Stockfish's eval was over 4 while Leela's eval decreased. Stockfish managed to capture the bishop but Leela created a fortress and just waited. There was nothing Stockfish could do, its eval came down very slowly and the game was adjudicated on move 229. Leela wins the game pair, Stockfish leads 4-3.

In game 15 Leela pushed a pawn to h6 and trapped a black bishop in the corner. Queens were off early, Stockfish managed to get its bishop out of the corner and to exchange it. The game reached a RRB vs RRN position, Stockfish captured the h6 pawn and evals came down. There were too many pawns for the draw rule, the game ended only on move 81 in a repetition.

In game 16 Stockfish exchanged the h pawn, then in a PV agreement Stockfish captured a rook for a bishop and pawn. Stockfish gave a pawn to open the d file, then moved its queen to the back rank and trapped a black bishop and rook on the queen side. Leela captured another pawn, it threatened a white knight but couldn't take since its king was in danger. Stockfish's move 23 with the knight was a surprise with an eval jump over 4.

Leela's queen was under threat and it realized it's best option was to exchange the knight for the DS bishop. Stockfish traded its bishop for a knight, with the center open Leela had to develop its queen side pieces. The game soon reached a RR vs RB position.

Stockfish had one last pawn, it captured black pawns until there was only one left as well. The 8-man position was not trivial, Leela delayed as much as possible but couldn't hold. Stockfish pushed its pawn slowly forward, eventually it used its two rooks to mate on move 80. Stockfish wins the game pair, it leads 5-3.

Games 17-18 started with a 17-ply book, a sideline of the KID four pawns attack with a significant black bias. In game 17 Leela tried to find safety for its king, it castled short but the king side pawns were far ahead. Stockfish exchanged knight for bishop and used Leela's weakness on light squares to threaten along the long diagonal. On move 21 Stockfish offered a rook to open the diagonal.

Leela didn't take the rook, Stockfish doubled rooks on the open f file and moved its queen forward. Leela exchanged pieces to save its king, the game reached a BNN vs BBN position with Stockfish a pawn up. 

The advantage was small but sufficient for Stockfish. After a few minor piece exchanges the engines reduced to a same color bishop ending. While Leela blocked a black passer Stockfish captured a pawn and created a second passer. Leela couldn't prevent a queening, game over.

In game 18 Stockfish kept its king in the center and opened the h file. In a long PV agreement Stockfish doubled rook and queen on the h file and threatened the black king, and the engines exchanged LS bishops. On move 20 Leela thought for 14 minutes and decided to diverge from the PV, Stockfish's eval dropped immediately. In a new PV agreement Stockfish castled long and the engines reduced to a QRR vs QRR position. Leela was a pawn up but evals were close to 0 and the game was adjudicated early. Stockfish wins the game pair, it leads 6-3.

Games 19-20 started with a KGA sideline and a black bias. In game 19 Stockfish exposed the white king which moved without castling. In a long PV agreement Stockfish castled long and moved its queen back, it didn't attack the white king that had no pawn support. The engines opened the g file, still Leela kept its king safe and (negative) evals came down. The engines exchanges pieces until only RN vs RN remained, Stockfish was a pawn up but evals were low and the game was adjudicated. Game 20 repeated the reverse game until move 19. The engines continued to exchange pieces in a PV agreement until only RRN vs RRN remained. The (negative) evals came down and the engines further reduced to a knight ending with Leela a pawn up. Evals were not low enough for the draw rule, the game was adjudicated on move 111.

Season 23 superfinal games 1-10

After 10 games Stockfish leads 4-2 with 4 draws. Stockfish won two game pairs, Leela beat Stockfish twice but in both cases Stockfish won in the reverse games. 

Openings for the superfinal were prepared by Jeroen Noomen and GM Matthew Sadler, see the details here. The two game pairs that Stockfish won were in Jeroen's list and they were ranked the most drawish. The 3 other game pairs were from Matthew's list and were supposed to be the most biased, yet games 5-6 ended in two draws. Expect the unexpected... 

Games 1-2 started with a 20-ply book in the Benoni defense classical variation, played at the highest level of human chess. In game 1 the engines left known theory quickly. Stockfish captured an early pawn but after thinking for 23 minutes its eval jumped. Stockfish gave a rook for a bishop and created connected passers in the center, evals kept increasing. The engines exchanged queens in a long PV agreement, then reduced to a RB vs NN position.

Leela captured the a pawn and created a passer, both engines pushed their passers forward. Stockfish kept its knights behind, it gave its two passers and captured the white a pawn, Leela captured the h pawn.

Leela drove away the black pieces from the king side and captured the last black pawn. Nothing could prevent a queening, game over.

In game 2 the engines took a different path away from theory. For a while Leela's eval was stable, it traded a rook for a knight and pawn, giving Stockfish a central passer. Stockfish surprised Leela and offered a pawn on move 24, after 16 minutes Leela did not take the pawn and its eval jumped. There followed many exchanges, Stockfish captured a pawn and the game reached a RRB vs RNN position.

Leela tried to hold on to its passer while keeping the white rooks back. Eventually the white king came forward and captured the e pawn, allowing Leela to capture a pawn on the king side. Stockfish then slowly pushed the black pieces back, it gave the passer but captured all the remaining black pawns.

Stockfish exchanged minors and offered a rook for a knight, Leela avoided a tablebase win and extended the game to be mated. There were two white wins in this game pair, score is 1-1. 

Games 3-4 started with an 18-ply book in the Slav defense, Smyslov variation. In game 3 there were no exchanges after the start, Leela's eval slowly increased. On move 20 Stockfish's eval dropped, it pushed pawns on the queen side and a pawn exchange opened a file. A few moves later Leela's eval dropped as well, the engines exchanged pieces until only QRN vs QRB remained. The game was adjudicated by the draw rule.

In game 4 Stockfish pushed pawns on the king side, where both kings were castled. There were no exchanges and evals were stable until move 24. Stockfish's eval started to jump as it attacked on the king side, Leela thought it was perfectly safe and its eval slowly came down. Stockfish trapped and captured a black knight on the king side, but Leela captured a knight on the queen side. Stockfish's move 32 caught Leela by surprise:

Only now Leela saw the danger to its king and its eval jumped. Leela quickly exchanged pieces and reduced to a RR vs RR position. It went a pawn up and created connected passers on the queen side, but Stockfish had a rook on the 7th rank and two passers, one facing the black king. 

Leela exchanged a pair of rooks to prevent two white rooks on the 7th rank. Stockfish stopped the black passers, the white king came forward and the game ended just before mate. Stockfish wins the game pair, it leads 2-1.

In game 5 the engines played a long PV agreement that opened the queen side, Leela was up a pawn with a passer. The game reached a RN vs RN position and evals came down. Leela lost the passer and created another, Stockfish captured the passer on the 6th rank and the draw rule ended the game. Game 6 repeated the same line and diverged on move 19. For a few moves Stockfish's eval jumped, then came back down after the game reached a rook ending. Stockfish was a pawn up but all pawns were on the king side. The evals weren't low enough for the draw rule, the game ended on move 122.

Games 7-8 started with an 18-ply book, a sideline in the Sicilian Scheveningen variation. In game 7 Leela castled long and pushed pawns on the king side, Stockfish still chose to castle short. For a few moves Stockfish's eval increased though the engines followed a PV agreement, then several pieces were exchanged and evals came back down. Leela opened the king side and went a pawn up, the game reached a RN vs RN position and evals dropped. The game was adjudicated when enough pawns have been exchanged.

In game 8 Stockfish again castled long and pushed pawns on the queen side, though the moves were different. Leela castled short and attacked the queen side, evals increased quickly. Leela gave a rook for a bishop in an attempt to keep the king side closed, more exchanges stopped the immediate threat but Stockfish was in control.

Stockfish increased the pressure on the black king, Leela tried to keep its pawns and pieces safe. After a while Stockfish's eval suggested the end was near.

The king side opened and Leela started to lose pieces, mate followed a few moves later. Stockfish wins the game pair, it leads 3-1.

In game 9 evals increased from the start. Queens were off early, Leela castled long and Stockfish kept its king in the center. On move 16 the engines started a long PV agreement that ended on move 29 in a RRB vs RRB position with Leela a pawn up. 

The white rooks were more active, Leela managed to get a rook to the 7th rank. Stockfish captured a pawn and created a passer on the king side, while Leela captured 3 pawns on the queen side.

Leela pushed the e pawn forward, Stockfish gave its bishop in an attempt to delay the pawn's advance. This only delayed the inevitable, Stockfish lost a rook for the passer and was later mated.

In game 10 Leela gave a pawn and opened the queen side, as a result Stockfish did not castle its king. Instead Stockfish gave back a pawn and opened a file on the king side, the black king couldn't castle as well and it had no pawn support. Stockfish gave a rook for a knight, it placed two knights on the 5th rank and threatened the black king. Leela gave back a rook for a knight, the game reached a QRN vs QRB position with Stockfish a pawn up.

The white king was also exposed but it managed to find safety using the nearby pawns. Leela had a harder time defending, it exchanged pieces until only the rooks remained and Stockfish captured a second pawn.

Stockfish pushed the b pawn forward, Leela tried to stop it but only delayed the promotion (Stockfish underpromoted to a rook for some reason). Mate followed a few moves later. There were two white wins in this game pair, Stockfish leads 4-2.