Season 28 superfinal games 41-50

After 50 games Stockfish leads 20-11 with 19 draws. Leela won (only) its second game pair of the match, but then it lost a game on time for the second time and Stockfish won a game pair from both sides - something we haven't seen in a superfinal for a long time. The other 3 game pairs were drawn and Stockfish extends its lead to +9 at the halfway point. At this rate the final score gap may be close to record high for a superfinal.

Games 41-42 started with a sideline of the Nimzo-Indian defense, St. Petersburg variation. In game 41 there were no exchanges after the start, the engines formed pawn lines and moved pieces behind them. The center and queen side were blocked, Stockfish had a bishop in front of the pawns. On move 29 there was a pawn exchange on the king side, after move 39 there were a few minor piece exchanges. Leela's eval was close to 2 at some point but then started to drift down as the engines shuffled. On move 82 there was another minor piece exchange, Stockfish moved its king to the queen side and Leela moved its king to the center. After move 112 evals started to increase, the black forward bishop was trapped (though safe) and Leela managed to exchange queens and capture a pawn, creating a passer.

The black bishop was out of the game, Leela moved its rooks to the king side and its bishop forward, then pushed the g pawn. Stockfish exchanged pawns and captured the passer, but after a pair of rooks was exchanged Leela moved its rook to the 7th rank, attacking the black pawns. Leela captured two pawns and Stockfish couldn't prevent a queening. Stockfish delayed with checks but was eventually mated.

In game 42 the engines blocked the center and queen side, similar to the reverse game. There were no pawn exchanges and Leela kept its bishops behind the pawns, on move 30 the engines exchanged a pair of bishops. The engines blocked the king side as well and started shuffling. On move 62 there was a pawn exchange, Stockfish's eval increase for a while and came back down when the shuffle continued. Stockfish had one pawn move left, the game ended in a 50 move draw on move 150. Leela wins the game pair, Stockfish leads 16-9.

Games 43-44 started with a rare sideline of the English, Anglo-Indian defense, the black queen moved forward in the center. In game 43 Leela pushed pawns in the center and moved its queen forward on the queen side. After Stockfish castled Leela pushed a pawn to h6, Stockfish captured a pawn on the queen side and created a passer for both engines. Stockfish pushed its passer, Leela captured a pawn and moved its queen forward. At first Stockfish avoided exchanging queens, but after Leela captured the black passer the queens were exchanged. The engines reduced to a RRN vs RRN position, Stockfish regained the pawn and the engines started to shuffle. Stockfish's eval was 0, Leela's eval slowly drifted down. On move 85 Leela pushed the passer and reset the 50-move counter, but then it failed to move on time and lost.

In game 44 Stockfish thought Leela castled too soon, both evals jumped as Stockfish exchanged pawns and opened the h file. The white king stayed in the center and Stockfish doubled queen and rook on the h file. Leela tried to threaten the white king, in a series of exchanges the engines reduced to a QR vs QB position with black a pawn up.

Stockfish moved its pieces to the center and its king to the king side. The rook moved to the back rank and pinned the black bishop. Leela tried to delay with checks, it avoided exchanging queens. Eventually Stockfish captured the bishop and mate followed. Stockfish wins this game pair from both sides, it leads 18-9.

Games 45-46 started with a rare sideline in the Scandinavian defense. In game 45 there were no exchanges after the start, Stockfish was late developing its queen side. Leela pushed a pawn on the king side, after exchanging a pair of knights the engines opened the g file. In a long PV agreement the center pawns were cleared, most pieces were exchanged and the game reached a RB vs BN position with black two pawns up.

For a while it seemed Leela was not sure how to proceed and evals remained stable. When Leela moved the rook to the back rank Stockfish's eval started to increase. Leela managed to trap the black king on the h file and its eval also increased. Eventually the rook moved to the h file, the black knight and king moved away and Leela captured the h pawn on move 71.

Stockfish tried to counter Leela's passer by pushing its own passer to the 2nd rank. Leela blocked with its king and threatened to take the a7 pawn, even by sacrificing its rook, since its a pawn would be unstoppable. Stockfish couldn't take the passer, the black king moved away from the king side and Leela slowly captured more pawns. Stockfish lost more material, Leela queened a passer and mated.

In game 46 Leela developed its queen side pieces quickly, the engines exchanged minor pieces and a pair of pawns in the center and opened the d file. Evals increased steadily, Stockfish gave a pawn on the king side while Leela moved a rook forward on the queen side. Stockfish captured pawns on the queen side and created connected passers.

Leela moved its queen back to stop the white passers, Stockfish exchanged knights and moved its queen forward through the center. Leela captured one passer but now its king was in danger, it exchanged pieces and reduced to a rook ending with white a pawn up. 

Stockfish had two passers, while Leela defended the white king captured the remaining black pawns. Stockfish then queened twice and mated. There were two wins in this game pair, Stockfish leads 19-10.

Games 47-48 started with a rare sideline of the Sicilian Najdorf, Zagreb variation. In game 47 the engines exchanged minor pieces and Stockfish moved its queen forward. Leela captured a pawn, opened the a file and exchanged a pair of rooks. Stockfish castled late and Leela kept its king in the center. Leela captured another pawn and created connected passers on the queen side. The game reached a QRB vs QRB position, Stockfish's eval dropped despite being two pawns down. The engines traded pawns, Stockfish blocked the white passers and Leela didn't find a way to improve. After exchanging queens Leela's eval dropped and the game was adjudicated. In game 48 the black queen stayed back, Stockfish pushed pawns on the queen side, opened files and created a passer. The black king moved to the king side without castling, Leela gave a rook for a knight and pawn and the game reached a QRR vs QRB position. Leela had passers in the center, Stockfish abandoned its passer and captured the two black passers. Leela's eval dropped as queens and more pawns were exchanged, Leela found a fortress, from move 51 it repeated rook moves while Stockfish shuffled. The game was adjudicated on move 99.

Games 49-50 started with a sideline in the Pirc defense. In game 49 the engines exchanged a pair of knights in the center, Leela moved a bishop to c6 and evals increased. Leela captured a pawn on the queen side and Stockfish gave a rook for the forward bishop and a pawn.

Leela opened the a file, doubled rooks there and moved a rook forward. Stockfish tried to keep the center and king side closed and to defend the open queen side. There was a pawn exchange on the king side, and Leela pushed a pawn forward on the queen side and created a passer. Then Leela captured another pawn in the center.

Leela captured pawns and opened files on the king side, threatening the black king. Stockfish lost more and more material and was mated. 

In game 50 the engines exchanged minor pieces, then exchanged pawns in the center and Leela captured a pawn. Leela tried to hold on to its extra pawn and it didn't develop its queen side pieces. Stockfish's eval increased while Leela's eval decreased until it realized it was in trouble after a 17 minute think on move 20. 

Leela moved its knight while Stockfish captured the e pawn and defended its passer, offering its bishop for several moves. Leela gave a rook for a knight in the center, Stockfish pushed the passer and Leela captured the bishop. Stockfish moved a rook to the 7th rank, then gave a pawn and opened the g file. Stockfish pushed the passer to the 7th rank and threatened the black king, in a series of exchanges Leela captured the passer and the game reached a Q vs RB position.

The engines traded pawns until there was only one white pawn and two black. Stockfish used checks and fork threats to push its pawn to the 7th rank, Leela gave the bishop to capture the passer. Stockfish converted the 6-man ending in 30 more moves. There were two wins in this game pair, Stockfish leads 20-11.

Season 28 superfinal games 31-40

After 40 games Stockfish leads 16-8 with 16 draws. There were 4 drawn game pairs in the last 5, one double draw and 3 double white wins. Stockfish managed one game pair win and it extended its lead to +8. Leela still has only one game pair win after 20 pairs. 

Games 31-32 started with a rare sideline of the Bird opening. In game 31 the engines blocked the center, Leela pushed pawns on the king side and both engines castled long. Leela placed a bishop on d6, then exchanged it for a knight, a pawn exchange opened the g file. Stockfish tried to attack the white king but was not effective. Leela doubled rooks on the g file, captured a pawn and created a passer.

Stockfish tried to block the white passer, Leela moved a rook to g7 and offered it for a bishop but Stockfish refuse because that would connect a second passer. Instead Leela gave a knight for a pawn to create connected passers. Stockfish tried to give a bishop for one of the passers, eventually Leela captured the bishop and kept the passers, though they became doubled.

In a QRN vs QRN position Leela captured another pawn and queened a passer, then it sacrificed a queen and mated with the other.

In game 32 Stockfish gave a pawn before blocking the center, both engines kept their kings in the center uncastled. The engines exchanged minor pieces and Leela captured a second pawn, evals remained low. Stockfish doubled queen and rook on the f file and threatened the black king, then it captured a pawn creating a passer in the center and forcing Leela to move its king, trapping the king side rook. Evals started to increase, Leela created a passer on the king side. Stockfish traded its passer for a pawn on the king side, then the game reached a RRN vs RRN position.

Leela was a pawn up but Stockfish had a rook on the 7th rank. The engines traded pawns, then exchanged a pair of rooks and Stockfish captured the black passer. After some shuffling Stockfish managed to capture another pawn and created two passers on the queen side.

Stockfish pushed a passer forward, it wanted to exchange knights but Leela gave its knight for free to avoid a 7-man position. This was only a small delay, Stockfish queened and mated. There were two white wins in this game pair, Stockfish leads 13-6.

Games 33-34 started with a sideline of the Caro-Kann defense, two knights attack. In game 33 there were no exchanges after the start, Leela pushed a pawn on the queen side all the way to a6. There was a minor piece exchange followed by some shuffling, evals drifted down. Another minor piece exchange opened the d file, the engines exchanged all rooks and reduced to a QB vs QB position. The engines traded pawns and created passers, but evals were low enough for adjudication.

In game 34 both queens moved forward early and after a minor piece exchange Leela grabbed a pawn in the center. The d file opened and the black king was in the center. In a long PV agreement most pieces were exchanged and the game reached a Q vs RB position with black a pawn up on move 27. Stockfish's eval was low, but after it created a passer on the king side its eval started to jump. Leela's eval dropped below 1.

Stockfish slowly pushed the passer while the black pieces threatened its king. Leela managed to capture the passer but the white queen got behind the black pawns. Stockfish equalized the number of pawns, it still had to work hard with its queen to be able to capture another pawn and create a passer. Leela's eval slowly increased but was still around 1.

Stockfish was very patient, the white king moved forward before Stockfish tried to push the passer. It took nearly 50 moves to force a pawn exchange and create a second passer, Leela captured one but was then mated. Stockfish wins the game pair, it leads 14-6.

Games 35-36 started with a line in the Bogo-Indian, Gruenfeld variation played in high level human chess. There were no exchanges and the center was blocked. In game 35 there was a pawn exchange on the queen side. The engines moved their major pieces to the queen side and shuffled for a while with evals stable. There were a few minor piece exchanges and evals increased a little. Then all the major pieces were exchanged and the game reached a BB vs BN position with white a pawn up.

Stockfish's eval increased faster than Leela's. The engines exchanged a few pawns, Leela captured a second pawn and created a passer. There was another pawn trade in the center and Leela added two more passers. 

Leela pushed its passers forward, Stockfish lost material, Leela queened and mated.

In game 36 there were no exchanges after the start, Stockfish kept its king uncastled. Evals remained stable as the engines mostly shuffled behind their pawn lines, the white king walked to the queen side. Stockfish thought that Leela's move 35 was a mistake, its eval jumped and Leela's eval jumped immediately too. Stockfish exchanged a pair of pawns and created a small opening on the king side. 

Leela moved the bishop to d4, Stockfish pushed the e pawn forward and captured on d6, creating a doubled passer. The engines started to exchange pieces and pawns, Leela captured a passer but lost a rook for a bishop. Leela managed to captured the second passer, Stockfish gave back the material and captured a knight. The game reached a QN vs Q position, Stockfish saw the win in its PV.

Stockfish pushed the b pawn forward and Leela couldn't stop it. After exchanging queens Stockfish queened and mated. There were two white wins in this game pair, Stockfish leads 15-7.

Games 37-38 started with a rare sideline in the KID Petrosian variation. In game 37 the engines exchanged a pair of pawns that opened the c file and blocked the center. Leela pushed pawns on the king side and kept its king in the center. Evals came down as the engines exchanged minor pieces and queens. The engines traded pawns and kept exchanging pieces until only RN vs RN were left, and the game was adjudicated. In game 38 the c file stayed closed, the engines blocked the center and most of the king side, Leela completed the king side pawn line with a bishop. The engines shuffled and Stockfish castled long, evals dropped to 0. After exchanging a pair of bishops Stockfish attacked the king side while Leela captured pawns on the queen side. The engines exchanged pieces until only QN vs QR remained and the game was adjudicated.

Games 39-40 started with a rare sideline of the Kangaroo defense. In game 39 after exchanging a pair of knights Leela castled long. Stockfish opened the c file and evals slowly increased. Leela blocked the center, Stockfish pushed pawns on the king side and exchanged a pair. Leela moved a rook forward, the engines exchanged all minor pieces and Leela captured a pawn. 

Leela moved its king forward on the queen side, the engines exchanged queens and Leela pushed the e pawn forward to the 7th rank. Leela exchanged a pair of rooks and captured almost all the black pawns, it then queened a passer and mated.

In game 40 Stockfish castled long as in the reverse. There was one pawn exchange in the center but files remained closed, evals increased steadily. Leela moved a pawn to b3 after a minor piece exchange, Stockfish doubled rooks on the d file and prepared a pawn advance.

Leela captured a pawn while Stockfish pushed the d pawn and it became a passer on d6. After some shuffling the engines exchanged queens, Stockfish gave a rook for a bishop and then won back a rook for the passer. The game reached a RN vs R position and each engine had a passer. 

Both engines queened a passer, Leela was first and it gave a few checks and captured a pawn. Then Stockfish attacked and the queen and knight were very effective together. Stockfish captured the black queen and mated. There were two white wins in this game pair, Stockfish leads 16-8.

Season 28 superfinal games 21-30

After 30 games Stockfish leads 12-5 with 13 draws. Leela won its first game pair of the match, but then lost 3 of the next 4 pairs. Stockfish increased its lead to +7 despite the loss. Leela lost a game on time, very unexpected.

Games 21-22 started with an 18-ply sideline of the KID orthodox variation. In game 21 the engines exchanged a pair of pawns in the center and pushed pawns on the queen side, then they opened the b file. Leela captured a pawn and created a passer, the engines exchanged a pair of rooks and evals increased. In a long PV agreement Leela pushed the passer forward and exchanged minor pieces, Stockfish created a passer in the center.

Stockfish pushed pawns on the king side, Leela avoided opening files there. Leela moved pieces forward, the black king was threatened. Leela gave a rook for a knight and a pawn, creating two more passers. 

Stockfish gave the passer, it lost more and more material until its king was exposed, mate followed.

In game 22 the engines opened the c file and kept the center closed, then mostly shuffled behind their pawn lines. By move 36 the pawn lines blocked the whole board except the open c file. The white king walked to the queen side and the shuffle continued for close to 50 moves. On move 80 evals suddenly jumped, Stockfish sacrificed a knight and created connected passers on the queen side. Leela also created passers there, a series of exchanges reduced to a QBB vs QBN position and evals came back down. The engines shuffled until exchanging queens, then the game was adjudicated. Leela wins the game pair, Stockfish leads 8-4.

Games 23-24 started with a 20-ply sideline of the Pirc defense. In game 23 Stockfish pushed pawns on the king side, then a long series of exchanges cleared the queen side pawns and Leela was a pawn up. Stockfish blocked the king side, the game reached a QRN vs QRB position and evals came down as the engines shuffled. The engines exchanged rooks on move 49, exchanged a few pawns after move 73 and the game was finally adjudicated on move 130.

In game 24 Leela exchanged a pair of pawns on the queen side, Stockfish gave a rook for a bishop and its eval increased. Leela was weak on the dark squares, it traded a knight for the white DS bishop, then Stockfish created a passer and captured a pawn. Stockfish thought Leela's move 23 was a mistake and its eval jumped, Leela agreed after a 20 minute think. Leela gave back the material and captured the white passer, Stockfish cleared the black pawns on the queen side and reduced to a queen ending with a pawn up.

Stockfish used checks to push the passer forward, Leela captured it on the 7th rank but lost a pawn on the king side. Stockfish saw the win in its PV, it captured another pawn and reduced to a 6-man tablebase win. Stockfish wins the game pair, it leads 9-4.

Games 25-26 started with a sideline in the English 4 knights variation. In game 25 the engines pushed pawns without exchanges, there were a few minor piece exchanges. Leela moved a bishop forward, the first pawn exchange on move 29 opened the a file and Leela moved a rook forward. Stockfish exchanged the forward bishop, a knight exchange blocked the center and reduced to a QRR vs QRR position. Evals came down, the engines exchanged a pair of rooks and Stockfish moved its pieces to the king side. Leela tried to open the king side, when it captured a pawn Stockfish moved a rook forward and gave checks. Stockfish gave the rook and Leela avoided a stalemate, giving time for the black queen to force perpetual check. In game 26 Stockfish exchanged minor pieces and castled long. The engines opened the d file, Leela moved its major pieces to the queen side and Stockfish exchanged a pair of rooks. Evals drifted down as the engines mostly shuffled, Stockfish captured a pawn and opened the a file. On move 69 the remaining rooks were exchanged, then on move 81 Leela failed to move in time and lost with evals close to 0. Stockfish wins the game pair, it leads 10-4.

Games 27-28 started with an 18-ply rare sideline in the Sicilian Najdorf variation, white castled long and the black king was still in the center. In game 27 Stockfish grabbed an early pawn on the king side, evals increased steadily from the start. The engines exchanged minor pieces on the king side and Stockfish created a passer. On move 28 Stockfish finally castled its king, despite having weak pawn support.

Leela captured the d6 pawn and moved a knight forward to f6, Stockfish gave a rook for the knight. Leela cleared the black queen side pawns and Stockfish cleared the white king side pawns so both engines had 3 passers. Each engine lost one passer and queens were exchanged, resulting in a RRN vs RBN position.

Leela pushed the passers forward and Stockfish defended with its rook and knight. Leela drove the black knight away, Stockfish gave material and tried a desperate passer run. Leela lost a rook for the passer, then queened and mated.

In game 28 the engines repeated the reverse game for 11 plys and Leela was up a pawn. Leela then decided to castle long, evals again increased steadily. Stockfish had a space advantage, for a few moves it could take a knight but refused so as to avoid a trapped bishop. When the black knight moved Stockfish exchanged bishops. In a long PV agreement Stockfish traded a rook for two minor pieces and created a passer on the king side. Leela had connected passers supported by rooks. 

Stockfish blocked the black passers and Leela managed to protect them but couldn't push them forward. The white passer became a threat and Leela moved rooks to block it. Stockfish then shifted major pieces to the open g file. Leela captured a pawn on the queen side while Stockfish moved a rook to the back rank and exchanged a pair of rooks. The game reached a QNN vs QR position, Stockfish saw the win in its PV.

Stockfish gave a pawn and started to chase the black king with just the queen and one knight. The black pieces couldn't help, Stockfish captured the black queen, queened a passer and mated. There were two white wins in this game pair, Stockfish leads 11-5.

Games 29-30 started with a rare sideline of the French defense, the c file was open. In game 29 there were no exchanges after the start, on move 20 a pawn exchange opened the f file. The engines blocked the center, in a series of exchanges all rooks were gone and then the engines reduced to a BN vs BN position. Stockfish's eval was close to 0 but Leela played on, the engines blocked the queen side and Leela's eval slowly decreased. The game was adjudicated on move 113.

In game 30 there were no exchanges after the start, Stockfish's eval started to increase and on move 19 there was a series of exchanges in the center. The engines exchanged a pair of rooks and Leela's eval also started to increase, Stockfish captured a pawn and opened the d file. After exchanging queens the game reached a RB vs RN position.

The black king moved forward, Leela captured a pawn on the queen side and Stockfish moved the rook forward. The black king moved back and was trapped on the back rank, Stockfish exchanged the minor pieces and reduced to a rook ending two pawns up. The engines exchanged a pair of pawns, Stockfish won the 6-man position after 40 more moves. Stockfish wins the game pair, it leads 12-5.

Season 28 superfinal games 11-20

After 20 games Stockfish leads 8-3 with 9 draws. Leela won two games and Stockfish won the reverse games twice. Then Stockfish won two game pairs and increased its lead to 5. Leela has no game pair win in the first 10 pairs.

Games 11-12 started with a sideline of the French Tarrasch, closed variation. In game 11 the center was blocked and the engines opened the c file. The engines shuffled and all pieces were on the board until move 30, Leela's eval slowly increased. In a series of exchanges of minor pieces Leela captured a pawn and created a passer on the queen side. The engines exchanged a pair of rooks, then continued to shuffle and Leela's eval drifted back to around 1. After move 50 Leela's eval increased again, it pushed the g pawn forward. 

The black queen was stuck on the king side, Leela exchanged pawns on the queen side and opened the b file. Stockfish regained the pawn and created a passer in the center while Leela moved its queen forward. The engines exchanged pieces and reduced to a BN vs BN position, Leela created a second passer.  

Leela exchanged minor pieces, Stockfish captured one passer but the white king moved forward on the king side and created more passers there. Leela queened one and mated.

In game 12 the engines repeated the reverse game for 23 plys with a transposition, the center was blocked and the c file was open. Stockfish pushed pawns on the king side and evals started to increase. Leela gave a pawn on the queen side, then a series of exchanges opened the board and gave Stockfish a passer in the center. Stockfish captured another pawn and created doubled passers on the queen side, Leela captured one of these passers. The black queen moved forward on the king side, Stockfish moved a rook forward on the queen side.

The white king was exposed and Stockfish had to be careful. After exchanging a pair of rooks the white queen moved forward. Stockfish abandoned its knight, it captured the black rook while Leela captured 3 white pawns.

Stockfish saw the win in its PV, it gave checks and pushed the passers forward, careful to avoid perpetual check on the other side. Eventually Stockfish exchanged queens, queened the passer and mated. There were two white wins in this game pair, Stockfish leads 5-2.

Games 13-14 started with a rare sideline of the Wade defense. In game 13 there was on minor piece exchange after the start. The engines slowly formed pawn lines without exchanges, Leela moved its king to the king side without castling, evals stayed mostly stable around 1. After move 26 there was a series of exchanges, the engines opened the board and reduced to a QRN vs QRN position.

Leela moved a rook forward on the queen side, captured a pawn and created a passer. In a long PV agreement Stockfish moved a rook forward behind the white passer, strangely Stockfish's eval increased while Leela' eval drifted down. Stockfish moved the queen forward as well and captured the white passer, then it gave a rook for a knight and pawn and created a passer. Leela exchanged queens and cleared all the queen side pawns. 

Stockfish saw the loss but it took 15 moves for Leela's eval to show a win. Stockfish gave a pawn and couldn't stop the white king advancing forward. Leela captured the remaining black pawns, it kept one last pawn, queened and mated.

In game 14 Stockfish moved its king without castling and Leela kept its king in the center. Stockfish's eval started to increase early, there was a pawn trade on the queen side, then the engines opened the g file. After a bishop exchange Stockfish captured a pawn and created a passer on the king side. It gave a knight and pushed the passer to the 7th rank, supported by two rooks. The white queen moved forward, in a series of exchanges Leela captured the passer and lost material, the game reached a Q vs RN position. 

Leela tried to hold the center, the white king slowly moved forward on the queen side. Eventually Stockfish cleared the black pawns on the queen side and created a passer. It gave the queen for a rook to queen the passer, mate followed. There were two white wins in this game pair, Stockfish leads 6-3.

Games 15-16 started with a rare sideline of the Indian defense, London system. In game 15 the engines exchanged most minor pieces in the center, Leela kept its king uncastled in the center. Stockfish pushed pawns on the queen side while Leela walked its king to the king side and freed the king side rook. The engines opened the d file and exchanged a pair of rooks, the exchanges continued and the game reached a queen ending. Leela was a pawn up, Stockfish's eval was at 0 but Leela continued to shuffle and trade pawns. The game was adjudicated on move 138 after Leela lowered its eval.

In game 16 Leela pushed pawns on the queen side, Stockfish kept its king in the center. After a few minor piece exchanges in the center Stockfish captured a pawn, then the engines reduced to a QRN vs QRB position. In a long PV agreement Stockfish created a passer on the queen side and captured another pawn. Both queens moved forward, Stockfish captured a third pawn but Leela regained two pawns before reducing to a queen ending on move 47.

Evals remained more or less stable for a long time, it seemed Stockfish was looking for the right sequence of moves. The white king moved all the way to the back rank, with the black queen chasing. Then the white king walked to support the passer, Stockfish gave a pawn and managed to push its passer forward after 40 moves. The passer was on the 7th rank and still Leela's eval was below 1. Leela's eval finally reacted, on move 122 it lost the queen for the passer and mate followed. Stockfish wins the game pair, it leads 7-3.

Games 17-18 started with a rare sideline of the Blumenfeld countergambit, white was a pawn up. In game 17 the engines opened the queen side and Leela created a passer there. The engines stablized their pawn lines and exchanged minor pieces, on move 42 the queens were exchanged and the engines started to shuffle. Evals slowly drifted down, Leela moved a pawn on move 54 and then on move 94. On move 130 the engines started to exchange pawns and pieces opening the board. Stockfish regained the pawn and evals were close to 0, the game was adjudicated on move 157 when enough pieces have been exchanged.

In game 18 the queen side stayed closed, Leela pushed the c pawn forward and Stockfish's eval increased. Leela gave two knights and attacked the white king. In a long PV agreement Leela captured a rook and a pawn, creating connected passers in the center.

The black passers looked dangerous but both evals were high. Leela exposed the white king, Stockfish captured one of the passers after exchanging a pair of rooks. Stockfish exposed the black king and captured the second black passer, then chased the black king. Leela lost material and was mated. Stockfish wins the game pair, it leads 8-3.

Games 19-20 started with a rare sideline of the Italian two knights defense, Traxler counterattack. White was a pawn up but its queen side was undeveloped, Black moved its king without castling. In game 19 there was a long PV agreement after the start, Leela developed its pieces and the engines exchanged minor pieces and queens. Evals started to decrease, the game reached a RRN vs RRB position and the engines started to shuffle. The engines exchanged minors and a few pawns, the game was adjudicated when evals were low enough. In game 20 the engines exchanged bishops and opened the f file. After some shuffling the engines opened the queen side. On move 51 a pair of rooks was exchanged, on move 67 there was a pawn exchange, on move 98 the game reached a QRN vs QRB position. Evals were close to 0, Leela gave the bishop and a pawn and threatened mate on the back rank, Stockfish secured a draw with perpetual check.

Season 28 superfinal games 1-10

After 10 games Stockfish leads 4-1 with 5 draws. There were two white wins in the first game pair, of the next 4 game pairs Stockfish won 3 and one was a pair of draws. Before the start of the superfinal Leela had a score of 1-1 in game pair wins against Stockfish, but after 5 more pairs played in the suprfinal the score is 4-1 in favor of Stockfish, with 4 draws. Which is a better preictor of the superfinal result?

The opening book was created by Jeroen Noomen, with computational help from Windfishballad and Kittenkaboodle. Details can be found here.

Games 1-2 started with a sideline of the Owen defense. In game 1 there were no exchanges after the start, Stockfish had problems with piece development and Leela gained space. There was one minor piece exchange and Stockfish castled long, evals were high and stable for a while. It seemed that Stockfish was trying to hold the pawn line, but evals started to increase, Leela doubled rooks on the a file and opened it on move 38.

A minor piece exchange created a white passer on a5, Stockfish tried to open the king side with a pawn exchange but Leela kept it defended. Stockfish gave a pawn to activate its light square bishop, Leela opened the e file and moved a rook forward. Stockfish captured a pawn on the queen side while Leela captured two and created two passers on the king side. On move 66 the engines exchanged queens.

Leela pushed the king side passers forward and Stockfish couldn't stop them. A few pieces were exchanged, then Leela queened and mated.

In game 2 there were many exchanges after the start, Leela gave a pawn and castled long. The engines played out a long PV agreement, the black queen moved forward on the king side, Leela gave another pawn and opened the f file. Stockfish captured a third pawn on the queen side and exposed the black king, Leela regained one pawn and exchanged queens and a pair of rooks, resulting in a RBN vs RBN position with white two pawns up.

Stockfish moved a rook forward, Leela captured a pawn and created a passer in the center. Then in a series of exchanges the engines reduced to an opposite color bishop ending with white one pawn up and a passer on the king side. Stockfish's eval was very high, Leela was less convinced.

The position was less drawish than usual for such endings. The black bishop had no pawn targets, Stockfish gave one pawn and captured two. The black king had to choose sides and could not create a passer on the queen side. The white king supported the passer on the king side, Stockfish promoted the passer and then exchanged pieces. It then queened another passer to win. There were two white wins in this game pair, the score is 1-1.

Games 3-4 started with a rare sideline of the Caro Kann advance variation. In game 3 the engines exchanged minor pieces and on move 20 the game reached a QRR vs QRR position. Stockfish's eval dropped to 0, Leela had a passer in the center but it couldn't move it forward. The white king walked to the queen side, Stockfish attacked with its queen and Leela exchanged queens. The engines shuffled until Leela lowered its eval for the draw rule.

In game 4 the engines exchanged a few minor pieces and Stockfish created a passer in the center. The engines exchanged a pair of pawns on the queen side, both queens were there but were not exchanged. Evals remained stable until move 32.

The engines seemed to shuffle but evals slowly increased. On move 47 a pawn exchange opened the a file. Leela captured a pawn and surprised Stockfish, Stockfish's eval dropped below 1 but then Leela again did not play what Stockfish expected and its eval shot back up. A series of exchanges reduced to a QRB vs QRN position.

Stockfish used the exposed black king to capture a pawn. Leela regained the pawn and exchanged queens. Stockfish then captured two pawns and Leela lost the rook for a passer. Stockfish created another passer, queened and mated. Stockfish wins the game pair, it leads 2-1.

Games 5-6 started with the King's gambit, bishop gambit Bledow variation, with a bias for black. The black queen was out on the king side and the white king moved without castling. In game 5 the engines exchanged queens after Stockfish castled. Stockfish pushed pawns on the king side, evals came down in a long PV agreement where Leela gave a rook for a knight and pawn. Most king side pawns were gone, Leela gave the second rook for a bishop and pawn. The black king moved forward and the engines reduced to a BBN vs RRB position. Leela had a passer in the center, Stockfish moved its rooks forward to attack the white king and chose to end the game in repetition. In game 6 the engines played out a long PV agreement in which they exchanged queens and Leela castled long. Stockfish's eval came down, Leela moved its knights forward and its eval stayed close to 1. The black knights were exchanged and the game reached a RRB vs RRB position, Leela with two passers. Stockfish captured one passer, Leela pushed the other to the 2nd rank blocked by a rook. The engines shuffled, after exchanging a pair of rooks Leela lowered its eval enough for adjudication.

Games 7-8 started with a rare line in the Sicilian Kan, Swiss cheese variation. In game 7 the engines exchanged a pair of knights and opened the d file. Leela blocked the file with a bishop and pushed pawns on the queen side. Stockfish moved a rook forward and sacrificed it for a bishop and pawn. Stockfish's eval came down, the engines reduced to a QRB vs QBN position and started to shuffle. After exchanging minor pieces the shuffling resumed, the game was adjudicated on move 115 after Leela lowered its eval.

In game 8 a series of exchanges in a PV agreement opened the c file, a few minor pieces were exchanged and evals increased. Leela created a passer in the center, Stockfish pushed a pawn to h6 and then created its own passer in the center. Stockfish captured a pawn on the king side and the h pawn became a passer as well, a series of exchanges reduced to a double rook ending with white two pawns up.

Stockfish let the h pawn be taken, it blocked the black passer and both kings moved to the queen side. Stockfish captured all the black pawns, the black king became trapped, Leela lost material and was mated. Stockfish won the game pair, it leads 3-1. 

Games 9-10 started with a 20-ply sideline of the KID fianchetto, classical main line.  In game 9 the center was blocked, the engines opened the c file. The engines pushed pawns on the queen side and opened the a file. All rooks were exchanged and after a while the queens were also exchanged. The game reached a BB vs NN position and the engines started to shuffle. Close to the 50-move limit Leela lowered its eval and the game was adjudicated on move 100.

In game 10 the engines repeated the reverse game for 10 plys, again opening the c file. The engines played out a long PV agreement, exchanging minor pieces and a pair of pawns and evals stayed stable. For a while the engines semmed to shuffle, though Stockfish's eval slowly increased. On move 36 Stockfish opened the center. 

It took Leela 3 more moves to see that it was in trouble. It surrounded its king with the major pieces while Stockfish captured the two supporting pawns on the king side. In a series of exchanges the queens were gone and Stockfish traded two bishops for a rook. Stockfish had connected passers on the king side, Leela gave back the two bishops for a rook to capture one passer. The game reached a RN vs RN position.

It took a while for Stockfish to push its passer, then it gave the rook for a knight and queened the passer, followed by mate. Stockfish wins the game pair, it leads 4-1.

Season 28 premier division statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins

Final draw rate was 59.4%. 

Game termination

The three most common game termination causes were:
47.8% - TCEC draw rule
40.6% - Mate
5.8% - 3-Fold repetition
5.8% - Fifty moves rule

There were no crashes in the stage.

Moves per game

Median= 81.5
Average= 86.2

There were 57 games longer than 100 moves, the longest was 270 moves (KomodoDragon - Ethereal, game 90, draw). 

Time per game (hours)

Median= 2:11
Average= 2:06

Openings

There were variable length book openings in this stage. The first letter of the ECO codes was distributed as follows: 

The engines had almost no freedom to choose the opening variant, all of the game pairs repeated the same ECO code and the opening variant twice.

Reverse pairs, wins

Reverse pairs, same moves

Pairs of reverse games diverged less quickly than usual, 12.5% diverged immediately out of book, 54.4% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 23 plys (Stockfish - Berserk, games 73 and 101, French Winawer, advance variation, Stockfish won as white).