Season 27 superfinal games 91-100, season summary

Stockfish is the winner of the season 27 superfinal. The final score is 35-18 with 47 draws. In the last 10 games Stockfish won 3 more game pairs, extending its lead to 17 wins. Game 94 was an example where Stockfish saw a win and Leela's eval was close to 0, such huge eval differences are quite rare in the recent superfinals. Leela had a promising eval advantage in game 98 but Stockfish managed to reduce to a drawn ending. 

Stockfish won the first two game pairs, but then Leela won 2 of the next 3 game pairs. The reverse games in the two Leela wins ended in a Q vs R endgame fortress, in one of them Stockfish thought it was winning for a while. Stockfish led 3-2 at this stage, it seemed possible the match would be competitive. Stockfish won two more pairs, in one of them Leela had high evals but missed the win in the reverse. Leela won another game pair and the score was 5-3 after 11 game pairs, then Stockfish won 3 pairs in a row and extended the gap to +5. After 16 pairs there were 11 decisive pairs and none had two white wins, then there were two pairs with two white wins and one with a Leela win that reduced to gap to +4. This was Leela's last pair win in the match, Stockfish won 13 more to finish with a +17 gap. There were 14 pairs with two white wins, so Leela won more games but couldn't hold the reverse. In many games Stockfish spent a lot of time in the beginning of the game, more than 40 minutes for one move in some cases. It ran out of time and played on increments as these games continued, sometimes finding a complicated win that neither Leela nor the spectators believed was possible. This season Stockfish again displayed its superiority in converting difficult endgames.

Season 27 leagues started with the entrance league, with 16 engines and 5 advancing. The newcomer Ceres led the league easily, Devre (another newcomer) and BlackMarlin also advanced with almost no game pair loss. For BlackMarlin this was a little surprising based on its predicted strength. Three engines were in the race for the last two qualification spots, in the last round Halogen lost it game, PlentyChess (newcomer as well) and akimbo finished in 4th and 5th places. In league 2 Ceres again won easily and without loss, PlentyChess finished a close second with one loss. There were 5 engines with a chance of qualifying, in the last RR Devre pulled away from the group but was caught again. In the last round Devre held on to 3rd place and Uralochka finished in 4th, tied with Devre and with a small lead over the chasing engines. 

TBD early leagues, premier division, personal

================================

Games 91-92 started with a sideline in the KID, Steiner attack variation. All pieces and pawns were on the board, the white king was in the center and the white king side pieces were not developed. In game 91 Leela castled long and exchanged a pair of bishops on the king side. Stockfish's eval came down, the white queen moved forward on the king side but the black king was safe. Stockfish captured a pawn and created a passer in the center. Leela captured a pawn and then a rook with a knight, but the knight was trapped. Before capturing the knight Stockfish moved a bishop to protect its passer. Leela captured a pawn and tried to expose the black king, Stockfish hid its king behind a white pawn. Then in a series of exchanges the engines reduced to a QR vs QBN position, the black passer was gone and Leela was up two pawns. Evals were low, after exchanging queens the game was adjudicated.

In game 92 Stockfish castled long, the black queen moved forward on the queen side and Leela's eval was unusually high for the first move, over 1.5. Stockfish immediately pushed the g pawn and Leela pushed the b pawn. The engines exchanged bishops on the king side and the white queen was on h6, Leela's eval came down while Stockfish's eval increased. Stockfish ignored Leela's threats on the queen side and prepared a king side attack. On move 17 Leela's eval jumped, Stockfish's g5 pawn attacked a knight defender on f6. 

Leela went on the attack despite the high evals. It gave the knight for a pawn and then gave the second knight to open the b file and create an advanced passer. The white king was in the corner and the black passer reached c2, but then it was Stockfish's turn to attack. Leela gave a rook for a knight to protect its king, Stockfish had time to block the black passer with its queen. After a series of exchanges the game reached a QRB vs QR position and the black c7 passer was gone. Stockfish kept the black pieces away from its king, on move 43 the engines exchanged rooks. 

Stockfish soon saw the win in its PV. It used checks by the queen to capture a few pawns and then forced a queen exchange. The game ended in a tablebase win. Stockfish wins the game pair, it leads 33-18.

Games 93-94 started with a 22-ply sideline in the Sicilian, Scheveningen, classical variation. There was one pawn exchange and all pieces were on the board, white had a space advantage. In game 93 the engines opened the d file, then in a series of exchanges the queens were off as well as minor pieces, Stockfish created a passer in the center. From move 24 the engines played out long PV agreements and evals came down. Leela captured a pawn and created a passer, the game reached a RBN vs RBN position. Stockfish pushed the passer to e2, Leela captured the passer and Stockfish captured the white passer. Both engines created a new passer, Leela captured the black passer on the 2nd rank again. Leela captured the last black pawn and was two pawns up, however evals were close to 0. The game was adjudicated after rooks were exchanged. 

In game 94 Stockfish pushed pawns on the queen side, the engines exchanged pawns, knights, bishops and queens, and opened the d file. The engines played out a long PV agreement and the game reached a RRB vs RBN position with black two pawns up. Leela had a passer on the queen side and its eval was low, Stockfish's eval was around 1.5. 

Stockfish's eval came down and moved back up, it captured the c5 pawn, the engines pushed pawns on the king side and then Stockfish moved a rook to the back rank. The engines cleared the queen side pawns, then Stockfish moved its other rook to the back rank. On move 57 Stockfish's eval jumped, the engines exchanged a pair of rooks. Stockfish was again on increments and Leela's eval did not move. Stockfish exchanged bishops and Leela's eval dropped even further. On move 64 Leela gave a pawn, Stockfish saw the win in its PV. In the 8-man position left, the contrast with Leela's eval was incredible.

Leela's eval started to react only on move 71. The white king and rook hunted the black knight, on move 79 the knight was close to being trapped and Leela gave it up. The game ended in a tablebase win. Stockfish wins the game pair, it leads 34-18.

Games 95-96 started with the Modern defense, Averbach system, played in high level human chess. White had a space advantage, all pieces and pawns were on the board and both kings were uncastled. In game 95 pawn exchanges in the center opened the e file, the engines castled in opposite directions and Leela captured a pawn on the king side. Pawn exchanges opened more files in the center, the game reached a RRN vs RRN position. Leela doubled rooks on the d file, Stockfish's eval came down and a pair of rooks was exchanged. The engines shuffled and Leela's eval also came down. There were a few pawn exchanges and knights were exchanged as well, the game was adjudicated when Leela's eval was low enough for the draw rule. In game 96 there were no exchanges after the start and both engines castled short. The engines blocked the center and a pawn exchange opened the a file. Evals came down as the engines exchanged all rooks as well as queens. The engines shuffled and there were a few pawns exchanges, the game was adjudicated after two more minor piece exchanges.

Games 97-98 started with a 17-ply sideline in the Alekhine defense, Marcozy variation. One pair of knights was exchanged, all pawns were on the board, black had a passer in the center and an eval advantage. In game 97 Leela blocked the black passer with bishops, Stockfish pushed pawns on both sides of the board. The black queen moved forward on the king side and the white king moved without castling. Stockfish's (negative) eval increased and the black queen retreated.  Stockfish pushed the g pawn to g3 and moved the king side rook forward to capture a pawn. Leela captured the g3 pawn, Stockfish gave the rook for a bishop yet Leela's eval also increased. In a pawn trade the white queen moved forward on the king side and Leela created a passer there, Stockfish castled its king long. In a series of exchanges the game reached a RRN vs RBB position, Stockfish captured the white passer and was a pawn up.

Pawn exchanges opened the queen side and Stockfish created a second passer. The black king moved forward and Stockfish pushed a passer to d3. Stockfish gave its rook for the knight and captured another pawn. 

Stockfish saw the win in its PV, it had a skewer attack on the two white rooks but refused to exchange. Stockfish pushed the second passer to a6, the white king moved to help block the white passers and the black king moved forward to support them. Leela lost a rook for one passer to avoid mate, Stockfish captured the remaining white pawns and the game ended in a tablebase win. 

In game 98 the start was similar but not identical to game 97, Stockfish blocked the black passer and Leela pushed pawns on the king side. Stockfish thought for 41 minutes on its 4th move, yet Leela chose a different continuation. The engines played out a long PV agreement, Stockfish captured a pawn on the king side, there was a minor piece exchange on the queen side and the white king moved without castling. Leela regained the pawn and castled long, the engines opened files on the king side and exchanged a pair of rooks. Stockfish's (negative) eval increased, Leela refused to exchange rooks, instead it captured two pawns and exchanged the rook for a bishop, resulting in a QRN vs QBB position with black two pawns up. Leela's (negative) eval started to increase, Leela gave a pawn on the queen side but when it didn't take back Stockfish's eval dropped. The engines exchanged queens and Leela's eval dropped as well. The game reached a B vs R ending, Leela was up two pawns with connected passers on the queen side. Leela pushed the passers forward, Stockfish blocked with its king in front and its rook behind the pawns and there was nothing Leela could do. The engines shuffled until Leela lowered its eval for the draw rule on move 93. Stockfish wins the game pair, it leads 35-18.

Games 99-100 started with a 22-ply sideline in the KID orthodox variation. The center was blocked, all pieces and pawns were on the board. In game 99 the engines exchanged pawns and a pair of knights on the queen side. Leela's eval increased, the engines opened the a file and exchanged a pair of rooks. The engines shuffled for a while and Leela's eval came down. The white king walked to the queen side and the shuffle continued until the engines exchanged rooks on move 59. The engines opened the h file, Leela's eval came down slowly. Stockfish captured a pawn and the black queen moved forward. Leela regained the pawn and captured a knight, Stockfish ended the game in a perpetual check. In game 100 Stockfish pushed pawns on the queen side until it was locked with white pawns on a6 and c6. Leela pushed pawns on the king side, the engines opened the h file but completed a diagonal pawn wall with a black pawn on h3. The engines exchanged a pair of rooks and started to shuffle. Stockfish extended the shuffle with a pawn move, evals came down. On move 126 Stockfish gave a knight for two pawns on the king side, after another shuffle the engines started to exchange pieces. The game reached a B vs N ending, Stockfish was two pawns up but evals were low and the game was adjudicated.

Season 27 superfinal games 81-90

After 90 games Stockfish leads 32-18 with 40 draws. Stockfish won 3 game pairs and extended its lead to 14 wins. The 3 game pair wins were all long endgames where Stockfish saw the win many moves ahead and Leela was still unsure, and Stockfish played with minimal time available. Since there are only 10 games left Stockfish will win the match. Leela hasn't won a pair in the last 26 pairs. 

Games 81-82 started with a 20-ply sideline in the Sicilian Richter-Rauzer variation. The engines castled in opposite directions, there was one pawn exchange and all pieces were on the board. In game 81 the engines exchanged minor pieces, a pawn exchange opened the d file. The black queen moved forward on the king side and came back, both engines moved their major pieces to the center. Evals increased for a while, Leela's eval was over 1.5 on move 25. Stockfish thought Leela's move was a mistake and its eval dropped. In a series of exchanges the engines reduced to a QN vs QN position, Leela's eval came down as well. The engines traded pawns and created a white passer on the queen side and a black passer on the king side. Both passers raced forward, both were stopped. Leela captured a pawn but evals were low and the game was adjudicated.

In game 82 the engines repeated game 81 for 13 plys, the d file was open. Evals increased while Leela doubled rooks on the d file. A white knight blocked the file but in a series of exchanges the knight was exchanged as well as a pair of rooks. The game reached a QRB vs QRN position on move 24, the engines opened the f file as well. 

Stockfish moved its major pieces forward, Leela pushed the h pawn to avoid back rank threats. Stockfish moved its rook to the back rank and exchanged rooks. The engines traded pawns and created two white passers on the queen side and two black passers on the king side. Both engines pushed a passer forward, Stockfish captured a pawn in the center and it seemed Leela was winning the race. Leela captured the white passer and its passer was on the 2nd rank, but Stockfish captured the black knight with check, it saw the win in its PV.

It didn't seem possible for Stockfish to stop the queening as well as protect its bishop, but Stockfish was confident it could. The first set of checks ended with the white queen on g2 and Stockfish protected its bishop with the b pawn. Leela didn't have a check, next move Stockfish connected its bishop and queen on the long diagonal to prevent a queening, giving Leela a pawn. Leela gave a few checks and the white king moved forward. Stockfish pushed the black king back and the white queen moved to the 7th rank. It allowed the queening in the end, before mating. Stockfish wins the game pair, it leads 28-16.

Games 83-84 started with a rare 20-ply sideline in the Pirc defense, classical variation. All pawns and pieces were on the board, white had a space advantage. In game 83 there was a pawn exchange in the center, then a pair of knights were exchanged. Evals came down, on move 21 Leela gave a knight for a pawn and created connected passers on the queen side. Leela captured another pawn on the queen side, then a third pawn to open the d file. In a series of exchanges the engines reduced to a RB vs RRB position, Leela was down a rook but up 3 pawns. For a long while the engines mainly shuffled and made some pawn moves. On move 72 Stockfish gave a pawn, on move 81 Stockfish gave the bishop for one of the white passers. The game was adjudicated on move 99 when Leela lowered its eval for the draw rule. 

In game 84  the engines started similarly, with a pawn exchange in the center and a knight exchange, though with slightly different moves. Evals were mostly stable, the engines shuffled for a while. Stockfish pushed pawns on the king side, on move 32 Leela gave a pawn to open the center. The d file opened and the black queen moved forward. Leela regained the pawn, Stockfish's eval started to increase. In a long PV agreement there was a series of exchanges that reduced to a RR vs RB position with black a pawn up. 

Stockfish was down to increments and Leela's eval was low, it was not clear whether Stockfish's eval was real but it kept increasing. Leela created a passer on the queen side, Stockfish moved its rooks forward and captured the passer. Leela seemed to have a fortress on the king side, with the king and rook protecting the f7 pawn and the bishop on the long diagonal holding back the white king and pawns. For a very long time Stockfish moved its king and rooks to limit the black bishop. For a while Leela's eval dropped close to 0, then came back up but was still low. On move 74 Stockfish finally managed to force the black bishop away from the long diagonal. It saw the win in its PV.

Stockfish made sure the bishop stays away, on move 85 it pushed the f pawn and exchanged pawns. Then it pushed the g pawn and the black king became trapped. The game ended in a tablebase win. Stockfish wins the game pair, it leads 29-16.

Games 85-86 started with an 18-ply rare sideline in the English opening. There was one pawn exchange and all pieces were on the board, white had more space and the white king was still uncastled. In game 85 Leela exchanged minor pieces and castled its king. Leela managed to get a protected bishop to c6, evals increased slowly. On move 22 a pawn exchange on the king side weakened the black king support, a minor piece trade got the white bishop to e6 with check. The white queen attacked and Stockfish exchanged queens.

Stockfish exchanged bishops, creating a white advanced passer on e6. The black king moved to the center and captured the passer. A pawn exchange on the queen side created a black passer on the queen side, Stockfish gave a rook for a knight and reduced to a RR vs RN position on move 41.

Leela moved a rook forward and the engines traded pawns. The second white rook moved forward and Leela captured two pawns, it had 3 passers and Stockfish had 2. Both engines pushed passers forward slowly, on move 78 one white passer reached the 7th rank. Leela gave a rook and queened the passer, Stockfish had a passer on the 2nd rank while Leela queened a second passer, the game ended in mate.

In game 86 the engines repeated game 85 for 21 plys with transposition, Stockfish castled its king and moved a bishop to c6. Leela pushed pawns on the queen side, trapped the white bishop and created a passer. In a series of exchanges the white c6 bishop was exchanged as well as the queens. The game reached a RRB vs RRB position on move 27, Stockfish had a blocked passer on c7. 

Stockfish's eval slowly increased while Leela's eval stayed stable around 1. Leela captured the white passer and Stockfish opened the d file. The engines avoided exchanging rooks, there was another pawn exchange and Leela doubled rooks on the c file. Stockfish blocked the black passer, the white king moved forward and a pair of rooks was exchanged. On move 58 Leela's eval started to slowly increase, the white king kept moving forward until it reached d8, attacking the black bishop. 

Leela tried to keep its bishop, it exchanged rooks and gave pawns to save it. The game reached an opposite color bishop ending, Stockfish had a passer on the queen side and it kept the black king away. Leela captured two pawns on the king side but lost its bishop for the passer, the game ended in a tablebase win. There were two white wins in this pair, Stockfish leads 30-17.

Games 87-88 started with a line in the French Winawer, advance variation played in high level human chess. The center was blocked, all pieces and pawns were on the board and both kings were uncastled. In game 87 Stockfish thought for 42 minutes on its second move, the engines pushed pawns on the queen side, Stockfish exchanged a pair of bishops and the white king moved without castling. The engines locked the queen side, evals slowly increased as Stockfish castled long and the white king walked to the queen side. Stockfish's eval came back down a little, Leela moved its major pieces to the king side, it captured a pawn and exchanged queens and a pair of rooks. 

The black king walked back to the king side, Leela moved its knights to the queen side and its eval drifted down. On move 46 Leela pushed the g pawn to open the king side and evals jumped. After a minor piece exchange Leela created a passer on f6, the white rook moved forward and the game reached a RB vs RN position. 

Stockfish captured the white passer, Leela captured the black b and d pawns and created two more passers. Stockfish captured the white d pawn and Leela captured the black h pawn. Leela pushed the h passer and Stockfish lost material to stop it, the game ended in mate.

In game 88 Leela made a different choice on its second move, there was a bishop exchange but the white king did not move. There was a pawn exchange on the king side, the queen side stayed active. Leela walked its king to the queen side, the engines exchanged pawns and a pair of knights in the center and evals increased. Leela moved its queen forward on the queen side and Stockfish blocked its retreat. A series of exchanges opened the c file, Stockfish created a passer on the d file and Leela had one on the a file. On move 36 the game reached a QRB vs QRN position. 

The white king was under threat but safe enough. Stockfish moved its major pieces forward on the king side and captured 3 pawns. Leela captured one pawn on the queen side but the white passers were much more dangerous than the black ones. Both minor pieces were captured, Stockfish saw the win in its PV. Leela captured a white passer on the 7th rank, there were more exchanges and the game ended in a tablebase win. There were two white wins in this pair, Stockfish leads 31-18.

Games 89-90 started with a 20-ply sideline in the open Ruy Lopez, Bernstein variation. There was one pawn exchange, all pieces were on the board and the black king was still uncastled. In game 89 Stockfish captured a pawn in the center, Leela used a pin to captured a pawn on the queen side. Leela opened the a file, the engines exchanged a pair of rooks and minor pieces. Evals came down, Leela was a pawn up but Stockfish had a bishop pair advantage. The game reached a QNN vs QBB position, in another series of exchanges the engines reduced to a N vs B ending on move 35. Leela's eval was too high for the draw rule, the game continued for 30 moves before adjudication.

In game 90 the engines exchanged pawns on the queen side and a pair of bishops. Stockfish pushed the e pawn and exchanged it, the black king moved without castling. After move 17 Stockfish's eval started to increase while Leela's eval drifted down. Stockfish doubled queen and rook on the a file, a series of exchanges started on move 23 and Leela's eval jumped. The engines exchanged knights and rooks and opened the a and b files.

The white queen moved to the back rank and pinned the bishop. All minor pieces were exchanged and the game reached a QR vs QR position with white a pawn up. Stockfish avoided exchanges and arranged its pawns, its eval increasing quickly while Leela's eval stayed stable. On move 46 the rooks were exchanged. 

Stockfish's eval was very high, again it was down to increments. Leela's eval did not increase, Stockfish repeated checks, n move 63 there was a pawn exchange on the king side. Leela chased the white king across the board and Leela's eval started to increase. On move 99 the white king reached e6, Stockfish saw the win in its PV. There were a few pawn trades and the game ended in a tablebase win. Stockfish wins the game pair, it leads 32-18.