Season 25 superfinal statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins

Final draw rate was 50%.

Game termination

The three most common game termination causes were:

45% - TCEC draw rule
27% - Mate

24% - SyzygyTB

There were no crashes in the stage.

Moves per game

Median= 77
Average= 83.2

There were 17 games longer than 100 moves, the longest was 379 moves (Stockfish - Leela, game 84, draw), a new TCEC record.

Time per game (hours) 

Median= 4:21
Average= 4:12

Openings

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

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

Reverse pairs, wins 

Reverse pairs, same moves 

Pairs of reverse games diverged slower than usual, 8% diverged immediately out of book, 46% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 53 plys (Leela - Stockfish games 49 and 50, Modern defense, two draws).

Season 25 superfinal games 91-100, season summary

Stockfish is the winner of the season 25 superfinal. The final score is 27-23 with 50 draws. Leela won another game pair and reduced Stockfish's lead to 4, the same gap as in the previous superfinal. The other 4 game pairs were drawn, 3 of them with two white wins. In the last 18 game pairs Leela beat Stockfish 4-0 in game pair wins, while after the first 32 game pairs Stockfish led 9-1. 

The superfinal started with 6 decisive games in 3 drawn game pairs. Stockfish won the first decisive game pair, and it slowly increased its lead. Of the first 14 game pairs Stockfish won 3, then Leela won its first game pair and Stockfish led by only 2 wins after 30 games. Stockfish then won several game pairs and increased its lead to 6 wins at the half way point. In some of the games Stockfish demonstrated superior endgame skills, for example in complex queen endgames. Stockfish extended its lead to a maximum of 8 wins after 32 game pairs, then Leela won its second pair of the match and reduced the lead to 7. From this point Stockfish did not win another game pair, it seemed that somehow Leela became stronger. Stockfish managed to get out of a game pair loss after a very late Leela inaccuracy in game 70. Leela slowly won more pairs, and the match ended with Stockfish ahead by 4 wins. Who knows what could have happened if more games were played.

Season 25 started with a Swiss event, however unlike in the previous season this event was not considered a replacement for the qualification. According to the current rules the top 6 engines of the Swiss event, not including those that are already included in one of the leagues, will play in the initial league stage. This season there were many engines from the last season that did not participate, either by the developer choice or since they are not in development any more. This included premier division participants Berserk and Koivisto. As a result almost all the engines that played in the Swiss event continued to the leagues. 

The first league event was the entrance league, including 16 engines of which 5 were new to TCEC. The four engines that advanced were all new: Viridithas, Clover, DeepSjeng and Caissa. Caissa managed to secure 4th place despite a bug that caused it to crash on time twice, Booot finished a close 5th. In league 2 the same 4 engines continued their journey and advanced again, in a different order. Caissa's bug was fixed and it finished 2nd, DeepSjeng and Arasan battled for 4th place and only a win in a direct encounter in the last rounds ensured that DeepSjeng would advance. League 1 was a different story for the 4 newcomers, none were strong enough to advance a third time. RubiChess dominated the league and finished in 1st place. rofChade was in 2nd place at the half way point, with Igel a close 3rd. In the last RR Igel managed to move ahead of rofChade and in the end it was Igel that advanced, despite losing two games to rofChade in the league.

The premier division was a month long 6-DRR event. The top3 engines, Stockfish, Leela and KomodoDragon were still dominant as in the previous several seasons, but this season there were greater score gaps between them. In the 90 top3-bottom5 game pairs the top3 did not lose a single game pair, and drew only 17. Stockfish finished first with no game pair loss at all, beating Leela 3 times and KomodoDragon 5 times. Leela beat KomodoDragon once, but it won 5 more game pairs than KomodoDragon against the bottom5 engines and finished 2nd. The top3 standings were obvious quite early in the division, the main race that was interesting was between Ethereal and RubiChess for 4th place that led to the division playoff stage. Ethereal and RubiChess were very close to one another from the start, each had one head to head game pair win in the first DRRs. After 5 DRRs Ethereal managed to lead RubiChess by 1.5 points. Then in the last DRR Ethereal unexpectedly lost a game pair to Igel, RubiChess also beat Ethereal in their final direct encounter game pair and this secured 4th place for RubiChess.

TBD - season summary: premier division playoff, personal

Games 91-92 started with a sideline in the QGA, Alekhine defense. The white queen was out on the queen side and a black rook was on a7 protecting the b7 pawn. In game 91 the engines opened files on the queen side and Stockfish castled short. There were many early piece exchanges, the game reached a QRN vs QRN position with white a pawn up on move 23. Stockfish moves its queen forward and Leela exchanged queens.

A pawn advantage with all pawns on the same side was small but significant, evals increased slowly. When it could Leela exchanged pawns while keeping its pieces on the board. On move 57 Leela created a passer in the center, on move 60 it connected a second passer while giving Stockfish a passer on the king side. 

Leela pushed its passers forward and Stockfish couldn't stop them. Leela gave a knight to queen one passer and mated. 

In game 92 the engines repeated game 91 for 16 plies with transposition, opening files on the queen side. Stockfish went a pawn up but all pieces stayed longer on the board. On move 27 the engines exchanged knight for bishop, the first pieces off the board. By move 32 all rooks were exchanged.

Leela avoided exchanging queens, Stockfish's eval started to increase as it pushed pawns in the center. In a complex position Leela chose to give a knight for 3 pawns and expose the white king. On move 47 Stockfish saw a win from far away, the engines reduced to a QBB vs QB position.

Leela gave many checks with its queen and captured the last white pawn. Stockfish found safety for its king in the center with the pieces blocking the black queen. It captured two black pawns and slowly improved its eval though it was hard to understand on the board. The white pieces slowly closed in on the black king, Stockfish had mate in its PV when Leela gave its queen and the game ended in a tablebase win. There were two white wins in this game pair, Stockfish leads 25-20.

Games 93-94 started with the Sicilian Lowenthal variation, played in high level human chess. In game 93 the engines castled in opposite directions. There was a long PV agreement and many early exchanges, the game reached a QRR vs QRR position on move 23. Evals started to increase, after exchanging queens Leela captured a pawn.

Stockfish had a passer in the center while Leela had a pawn majority on the queen side. Leela captured a pawn on the queen side, the black king moved forward to support the passer. Leela captured the second black pawn on the queen side, creating 3 connected passers. It blocked the black passer and pushed its own forward. Stockfish lost material trying to stop the white passers, Leela queened and mated.

In game 94 the engines repeated game 93 for 21 plies, Leela chose a different defense and Stockfish's eval started to increase. Again the game reached a double rook ending on move 29, this time material was equal but Stockfish had doubled rooks on the g file, blocking and threatening the black king on the open h file.

Leela's eval was stable for a long time, Stockfish wasn't in a hurry with repeating checks every few moves. The engines exchanged a pair of pawns and Leela created a passer. The passer was isolated and had to be protected. There was a threat of mate that Leela had to deal with as well. On move 58 Leela's eval jumped after a long think, Stockfish forced a small but significant change in the black rooks' placement. 

The white king managed to move forward to the center to block the passer. The queen side pawns stabilized, after many check repeats Stockfish exchanged a pair of rooks on move 82. Material was still equal, the engines traded pawns and both had only two pawns on the queen side. However, the black king was far on the king side and unable to help. Stockfish moved its king behind the black pawns and the game ended in a tablebase win. There were two white wins in this game pair, Stockfish leads 26-21.

Games 95-96 started with a 24-ply line in the French Winawer, retreat variation. The white queen captured two pawns on the king side and the black queen captured a pawn on the queen side. In game 95 the engines exchanged minor pieces after the start, Stockfish castled long and Leela moved its king forward without castling. Evals started to increase as Leela captured another pawn on the king side, Stockfish chased the white queen away and pushed the e pawn forward. As a result the e pawn became an advanced passer, while Leela had 3 connected passers on the king side. Stockfish captured a pawn and created a passer on the queen side, on move 31 the engines exchanged queens and the game reached a RRB vs RRN position.

Leela blocked the black passers with two pieces and slowly pushed its passers on the king side. The two black passers were stopped on the 2nd rank, Stockfish used its rooks to try to stop the white passers but Leela managed to queen one. Stockfish lost material and was mated.

In game 96 both engines castled long, Stockfish shifted its queen to the queen side. Stockfish pushed a passer on the king side but without support it stopped on the 5th rank. The engines mostly shuffled and evals came down, Stockfish gave a rook for a bishop and pushed the passer to the 7th rank. The engines traded RB for Q, Leela captured the passer, evals were low and the game was adjudicated. Leela wins the game pair, Stockfish leads 26-22.

Games 97-98 started with a sideline of the Indian defense, Wade-Tartakower variation. In game 97 Leela castled long, there were a few minor piece exchanges and Stockfish also castled long. The engines shuffled for a while and evals came down, then they exchanged a pair of rooks and reduced to a QRB vs QRN position. Leela captured a pawn and created a passer, Stockfish regained the pawn later. After exchanging queens evals were low and the game was adjudicated. In game 98 Stockfish castled long and Leela chose to castle short after the white queen captured the b7 pawn. Stockfish pushed pawns on the king side and Leela blocked them. Evals came down and the game reached a RRB vs RRN position. After exchanging a pair of rooks the game was adjudicated.

Games 99-100 started with a rare 22-ply sideline of the Caro-Kann, Panov attack. In game 99 there were no exchanges after the start, both engines placed their major pieces on the center files. After a knight exchange on move 22 Stockfish created a passer in the center. The engines shuffled for a while, then Leela created a passer in the center after a pawn exchange on move 35. On move 43 Leela captured the black passer and exchanged bishops.

Evals increased as the engines stabilized the pawns on the king side. Leela exchanged a pair of pawns on the queen side and then the engines started to shuffle. Evals drifted down as the 50-move counter got close to 0, Leela saw exchanges in its PV but Stockfish decided to initiate a queen exchange. Evals increased quickly, on move 106 the game reached a RB vs RB position.

Stockfish tried to stop the center passer and Leela captured the two black pawns on the king side. Stockfish couldn't avoid a queening followed by mate.

In game 100 both engines concentrated their pieces in the center, the exchanges started on move 18. Stockfish pushed the h pawn to h6 and exchanged it, on move 26 the game reached a QBB vs QBB position.

Stockfish's eval slowly increased but there were no exchanges except a pair of pawns on the queen side. The black king hid in the corner protected by the black queen and it seemed that Stockfish was shuffling. Slowly Leela's eval increased as well, Stockfish moved its king to the center and pushed the king side pawns. 

Leela had to defend its weak a5 and h7 pawns, and the possibility of a pawn attack on the king side. In the end Stockfish found a way to attack from the queen side, it exchanged a pair of bishops and saw the win in its PV. Stockfish reduced to a queen ending two pawns up. The white king moved forward, Leela lost its queen, Stockfish queened a passer and mated. There were two white wins in this game pair, Stockfish leads 27-23.

Season 25 superfinal games 81-90

After 90 games Stockfish leads 24-19 with 47 draws. Leela won another game pair and Stockfish's lead is down to 5 wins. There were 4 drawn game pairs, in one of these there were two white wins. Stockfish hasn't won a game pair in the last 13 played, while Leela won 3. There are only 5 game pairs to go so Stockfish is the favorite to win the match, but Leela is still fighting.

Games 81-82 started with a 22-ply rare sideline in the KID, Petrosian variation. All pieces and pawns were on the board and the center was blocked. In game 81 the engines pushed pawns across the board, Stockfish gave a pawn and opened a hole in the pawn line on the king side. Stockfish placed a knight on f5 and Leela moved its king to the corner. Evals came down and there was a long series of exchanges that opened the center and queen side. The result was that Stockfish was down a knight for a pawn with connected passers on the king side. After some shuffling Stockfish gave a rook and a bishop and queened a passer. The game ended in check repetition. In game 82 the engines opened the f file and the a file, then exchanged a pair of rooks. Evals came down, after exchanging a pair of bishops the engines started to shuffle. On move 40 Leela pushed the g pawn forward until Stockfish captured it. The engines reduced to a QB vs QN position, evals were low and the game was adjudicated.

Games 83-84 started with a rare sideline in the KID Fianchetto variation. In game 83 the engines blocked the center, Stockfish opened the queen side and Leela pushed pawns on the king side. The white king walked to the king side without castling. Stockfish had two strong knights in the center, it placed its major pieces on half open files on both sides. However evals slowly increased. Leela pushed a pawn to h6, then captured a pawn and created a passer on the queen side.

Leela exchanged a pair of knights, its passer shifted to the b file. With rook support Leela pushed the passer to the 5th rank where it was blocked. Stockfish doubled rooks on the f file, attacking the f3 pawn and trying to prevent it from moving forward. Leela captured one rook for a bishop, then threatened the back rank from the open c file. Stockfish blocked the c file and opened the way for the white passer to advance. Stockfish was desperate, it gave the second rook for a bishop to block the f pawn.

Stockfish quickly lost more material, Leela queened and mated.

In game 84 the engines blocked the center but there were no pawn exchanges after the start, only a few minor piece exchanges. Stockfish walked its king to the queen side, all files were blocked except the b and f files and the engines started to shuffle. Leela's eval dropped to 0, Stockfish couldn't find any safe way to move past the pawn lines. Pawn moves and captures reset the 50-move counter on moves 36, 83, 128, 175 (Stockfish gave a pawn), 204, 252 (Leela gave a pawn), 301 (knight exchange), 310 (Stockfish gave a pawn), and 329. The game finally ended on move 379 in a 50-move draw, after approximately 350 moves of nothing. This is a new TCEC record for most moves in a game. Leela wins the game pair, Stockfish leads 23-18.

Games 85-86 started with one of the main lines in the Czech Benoni defense, the center was blocked and all pieces and pawns were on the board. In game 85 there was one pawn exchange on the king side and Leela's eval started to increase. Stockfish captured a pawn, the engines played a long PV agreement and Leela's eval slowly came down. Stockfish gave back the pawn and Leela went a pawn up, then in a series of exchanges the engines reduced to a same color bishop ending. Leela wouldn't lower its eval for a long time, the engines shuffled and exchanged a few pawns. The game was adjudicated on move 118. In game 86 there were no exchanges after the start, the engines exchanged a pair of knights and mostly shuffled behind their pawn lines. On move 43 the engines exchanged a pair of bishops, then Stockfish captured a pawn but there was a stable pawn wall across the board. The engines shuffled for a long time, the 50-move counter was reset on moves 98 (knight for rook trade), 143, 182 (Stockfish gave a pawn), 224 (Stockfish gave another pawn), 233, 247 (queen exchange). On move 297 the game finally ended in a 50-move draw. Another long game with nothing happening.

Games 87-88 started with a rare sideline of the English symmetrical variation. In game 87 Stockfish exchanged minor pieces and its queen moved forward on the queen side. Stockfish captured two pawns and created 3 connected passers. Leela captured one passer and pushed its center pawns, Stockfish gave a rook for a bishop to protect its king. Stockfish pushed its passers forward, after exchanging queens the game reached a RB vs BN position on move 38.

Stockfish gave up the d and h pawns quickly, but it protected the others and Leela had a hard time trying to improve. The engines shuffled and evals drifted down. On move 65 Leela exchanged a pair of pawns on the king side, Stockfish's eval jumped.

The game was far from over but evals started to increase. Leela slowly moved its king to the center. The black king moved to the queen side and on move 85 Leela captured the black e pawn. The white f pawns became doubled passers, Leela slowly pushed them forward. Eventually Leela queened and the game ended in a tablebase win on move 121.

In game 88 the engines repeated game 87 for 20 plies, Leela captured one pawn on the queen side but Stockfish protected the second one. Stockfish regained the pawn and exchanged a pair of rooks, its eval started to increase. Leela captured the second pawn on the queen side and created two passers there but Stockfish captured one of them. After exchanging queens Stockfish gave a rook for two minors and reduced to a BB vs R ending. 

Stockfish exchanged a pair of pawns on the king side and created a 3 vs 1 pawn majority in the center. Its eval showed a clear win while Leela's eval increased very slowly. Leela pushed its passer and eventually captured a bishop for it. Stockfish slowly pushed the pawns forward, making sure the black rook couldn't stop them. It finally queened a passer on move 81, mating a few moves later. There were two white wins in this game pair, Stockfish leads 24-19.

Games 89-90 started with a 24-ply rare sideline in the Benoni classical variation, Czerniak defense. In game 89 after one move the engines started to play out a very long PV agreement. Stockfish gave a bishop and opened files on the king side. There was a threat to the white king, Leela gave back the piece and reduced to a RN vs RB position with white a pawn up. Stockfish's eval dropped, the engines traded pawns and then the rooks were exchanged. Leela wouldn't lower its eval for a long time, the game was adjudicated on move 92. Game 90 started with a 30-ply repeat of game 89. The game reached the same RN vs RB position, the engines traded pawns and Leela lowered its eval for an early adjudication on move 49.

Season 25 superfinal games 71-80

After 80 games Stockfish leads 23-17 with 40 draws. Leela won a game pair and reduced Stockfish's lead to 6 wins. The other game pairs were draws, with 3 having two white wins. Stockfish hasn't won a game pair for 8 straight pairs played, while losing 2. There is still hope for Leela, though it may be too late since there are only 10 game pairs left in the match.

Games 71-72 started with a rare sideline in the Nimzo-Dutch, Alekhine variation. In game 71 there were a few minor piece exchanges and the engines opened the d file. Stockfish gave a pawn, the engines exchanged a pair of rooks and evals were mostly stable. On move 28 the engines opened the a file.

Evals started to increase though the engines seemed to be shuffling. Leela gave two pawns on the queen side and captured a rook for a bishop. Leela then captured the two black pawns on the queen side, it was a pawn up in a QRB vs QBN position and evals were high.

Stockfish tried to avoid exchanges, Leela pushed the h pawn and it became a passer. Stockfish lost a bishop and captured the passer, it saw mate in its PV. Leela took a longer route, in the end a series of exchanges resulted in a tablebase win.

In game 72 more pieces stayed on the board, a pawn exchange opened the a file and evals came down. After some shuffling the engines opened the queen side and Stockfish went a pawn up. Stockfish traded its queen for a rook and a bishop, the engines reduced to a RBN vs QN position with white a pawn up. After 20 moves the engines traded minor pieces, when evals were low enough the game was adjudicated. Leela wins the game pair, Stockfish leads 20-14.

Games 73-74 started with a rare sideline in the Old Indian defense, normal variation. In game 73 the engines locked the center and there were no exchanges after the start. Leela offered a bishop and Stockfish refused to weaken its king. The engines opened the c file and exchanged a pair of knights, Leela captured the g7 pawn, then Stockfish captured two pawns on the king side. The black king looked vulerable, Stockfish exchanged queens and evals started to increase. The game reached a RRB vs RRB position on move 40.

After a pawn exchange on the queen side all the black pawns were isolated. Leela protected its d5 pawn with the bishop and started capturing black pawns. Stockfish held on to its a pawn, Leela pushed passers and moved its king forward. Stockfish lost material trying to stop the passers, the game ended in a tablebase win.

In game 74 there was one pair of pawns exchanged after the start, all files remained closed. The engines mostly shuffled behind their pawn lines but evals slowly increased. A pawn exchange on move 32 created passers in the center for both engines, on move 35 the first minor pieces were exchanged. Stockfish captured the doubled black passers in the center by move 42.

Leela had some initiative, its rooks controlled open files in the center. Leela attacked the exposed white king with a rook and queen, it also captured pawns on the queen side. Stockfish sent a rook and queen to attack the black king, it gave a rook for a bishop but then Leela had to give a rook to avoid mate. Both engines pushed passers forward, Stockfish queened first and mated. There were two white wins in this game pair, Stockfish leads 21-15.

Games 75-76 started with a 24-ply sideline in the Sicilian accelerated Dragon, Modern variation. White pushed pawns on the king side and its king was uncastled in the center, black had an eval advantage. In game 75 the engines played out a long PV agreement, pawn exchanges opened the center and king side, most pieces were exchanged and the game reached a RBN vs RBN position. Stockfish had a passer in the center, evals came down as Leela blocked the passer and kept its pieces safe. Leela gave a rook for a bishop, all pawns were captured and the game was adjudicated. Game 76 repeated game 75 for 39 plys, reaching the same RBN vs RBN position. Stockfish kept its pawns safe and blocked the black passer. The engines reduced to a rook ending, evals came down and the game was adjudicated.

Games 77-78 started with a 22-ply line in the Ruy Lopez, Arkhangelsk variation, played in high level human chess. All pieces and pawns were on the board and the black king was in the center uncastled. In game 77 Stockfish castled long and tried to attack the king side but was not strong enough. Leela's eval started to increase, it opened a file in the center and exchanged minor pieces. In a long PV agreement Stockfish's eval came down and then jumped up, Stockfish created a passer in the center while Leela captured a pawn and created an advanced passer on the king side. After another pawn trade Leela cleared all the black pawns on the king side and added 2 more connected passers.

In another long PV agreement each engine blocked an advancing passer and eventually captured it. The minor pieces were traded, on move 50 the queens were exchanged and the game reached a double rook ending with white a pawn up and two passers on the king side.

Leela pushed the passers slowly forward, Stockfish captured one while Leela captured a pawn on the queen side. Stockfish blocked the passer on the 6th rank and Leela captured another pawn and created a passer on the queen side. Leela pushed both passers to the 7th rank, Stockfish couldn't stop a queening and the game ended in a tablebase win.

In game 78 Leela was more active in its king side attack, it moved its queen to h3 and forced Stockfish to weaken the pawn support for its king. Stockfish ignored the attack, it opened the a file and moved its queen to the queen side. Leela gave a pawn, chose not to take the knight Stockfish offered and added a second rook to the attack.

Stockfish moved the queen to the king side, Leela captured the h pawn but that was the end of its attack. Leela's queen side seemed solid, yet evals continued to increase. Stockfish exchanged queens and a pair of bishops, then after a while it traded a rook for a knight and captured a pawn. The game reached a RNN vs RRB position.

Leela had a material advantage, but the white knights were very strong together and covered many squares. Stockfish exchanged pawns and created a passer in the center. Leela captured two pawns but lost the bishop, it gave a rook for a knight but couldn't stop the white passer queening, mate followed a few moves later. There were two white wins in this game pair, Stockfish leads 22-16.

Games 79-80 started with a rare sideline in the Queen's Indian defense, Kasparov-Petrosian variation. In game 79 the engines opened files with pawn exchanges in the center and queen side. Leela went a pawn up and exchanged queens, then it captured another pawn. In a series of exchanges Leela traded a rook for two minor pieces and the game reached a RB vs BBN position on move 30.

Leela pushed its two passers forward, Stockfish captured one but lost a bishop. Stockfish blocked the other passer with the knight, Leela had a very hard time trying to improve its position. On move 56 Leela captured a pawn, on move 73 it gave a pawn and then the black knight moved. Leela captured a pawn, only on move 88 it managed to push its passer forward. Stockfish saw a quicker win, but eventually it started to lose material and the game ended in a tablebase win on move 105.

In game 80 Stockfish pushed the h pawn forward and it was exchanged on h6, Leela castled short despite this and Stockfish kept its king in the center. Leela pushed pawns and opened the queen side, the engines exchanged minor pieces in the center. Stockfish's eval started to increase while Leela's eval was stable and even decreased a little.

The engines seemed to shuffle for a while, though Stockfish's eval steadily increased. After move 38 Leela's eval reacted as well. Stockfish blocked the center with its major pieces, on move 51 it exchanged a pair of rooks and reduced to a QRB vs QRB position.

Stockfish exchanged its b pawn and moved its queen to the back rank. It captured the black d pawn and exchanged bishops, seeing the win far in its PV. After exchanging queens the white king moved forward on the king side. Stockfish was only one pawn up, but after exchanging a pair of pawns it had a pawn majority in the center. Leela had a passer but the white king blocked it long enough until it captured the black e pawn. The white passers were faster and the black king was trapped, the game ended in a tablebase win before mate. There were two white wins in this game pair, Stockfish leads 23-17.

Season 25 superfinal games 61-70

After 70 games Stockfish leads 20-13 with 37 draws. Stockfish's lead is 7 wins after each engine won a game pair. There were 3 drawn game pairs, two had two white wins. Leela game pair win came after 17 game pairs which were either drawn or Stockfish wins. Leela almost won a second game pair, but an inaccuracy late in game 70 gave Stockfish the win and the game pair was drawn.

Games 61-62 started with a sideline of the QGD, Semi Slav defense, with the black king uncastled and the black queen on h6. In game 61 evals increased quickly after the start, Stockfish kept its king in the center and Leela forced it to move. Leela moved a knight forward and traded it for a rook.

Leela pushed pawns on the queen side, after some shuffling Leela captured a pawn on the king side and created a passer. The white queen moved forward on the queen side and captured two pawns, creating a passer there as well. Leela gave a pawn and add two more connected passers on the queen side.

Stockfish lost a bishop for two of the passers, Leela gained more material and mated.

In game 62 Stockfish pushed pawns in the center, it traded a rook and a pawn for two minor pieces. The black queen captured a knight and walked into a trap, Stockfish captured the queen for a rook. The game reached a QBN vs RRB position on move 25.

Leela was two pawns up, it doubled rooks on the open e file and its eval drifted down. Stockfish's eval steadily increased, it pushed pawns on the queen side and on move 41 exchanged a pair of pawns. Leela's eval started to increase as well, by move 56 the white queen captured two pawns and opened the queen side.

Leela pushed its passer to the 2nd rank, Stockfish traded its queen for the two black rooks and stopped the passer. The game ended in a tablebase win. There were two white wins in this game pair, Stockfish leads 18-11.

Games 63-64 started with a 20-ply sideline in the QGD, Albin counter-gambit, white was a pawn up and black had a passer in the center. In game 63 there was a long PV agreement after the start, the engines exchanged minor pieces and Leela captured the black passer. Evals came down, after exchanging queens the game reached a RRB vs RRB position. Stockfish slowly captured the pawns back, the engines reduced to a rook ending. Leela had a passer but it couldn't push it beyond the 6th rank. The game was adjudicated when Leela lowered its eval for the draw rule. 

In game 64 Stockfish pushed pawns on the queen side and captured the black passer. On move 20 Leela played h6, this weakened the black king and Stockfish's eval jumped. Stockfish attacked the king side with its queen and a knight, Leela gave a rook for the knight, Stockfish sacrificed another knight to expose the black king. Leela was forced to trade its queen for a rook to save its king from mate. On move 29 there was an imbalance of Q vs BBN on the board with high evals.

Stockfish ignored the black passer and continued to attack with its queen and rook. After exchanging rooks Stockfish captured the black passer. Stockfish pushed a passer on the king side, Leela lost a bishop for it. The white king moved forward and Stockfish mated. Stockfish wins the game pair, it leads 19-11.

Games 65-66 started with a 22-ply sideline in the Sicilian Taimanov, Szen variation, that appeared in a Fischer-Taimanov game. Both kings were uncastled, black had a strong knight on d4 as well as an eval advantage. In game 65 Stockfish grabbed the g pawn with a rook, this gave Leela time to improve its piece arrangement. Leela drove the black knight on d4 away, both kings moved forward and evals came down. The engines exchanged all rooks through the open g file and reduced to a QB vs QN position, evals were low and the game was adjudicated early on move 36.

In game 66 Leela also grabbed the g pawn as in game 65. The pieces stayed on the board longer, Stockfish moved a knight to d5, it drove the black knight from d4 and Leela moved it to c5. Stockfish castled long and (negative) evals started to increase. Leela managed to exchange the knights in the center, after queens were exchanged the game reached a RBN vs RBB position on move 40.

The engines blocked the queen side, Stockfish walked its king to the king side and pushed the h pawn forward. Leela exchanged pawns and got rid of the white e pawn, suddenly it was 3 pawns against 1 on the king side. Leela hid its king behind the white passer and shifted the rook to the queen side. The black rook moved to the 2nd rank and trapped the white king.

Leela captured the white h pawn, then gave a pawn to get the white f pawn out of the way. Leela pushed pawns on the king side and Stockfish lost pieces trying to avoid mate. Stockfish raced to queen a passer but was mated on the other side. Leela wins the game pair, Stockfish leads 19-12.

Games 67-68 started with a rare sideline of the KID, four pawns attack. In game 67 the engines opened the d file, a black knight made an unusual journey of 5 moves and was traded for a bishop. In a series of exchanges the engines reduced to a RRB vs RRB position and evals came down. Leela doubled rooks on the d file, after a few pawn exchanges the engines started to shuffle. After 40 moves Leela exchanged a pair of rooks and the game was adjudicated. In game 68 the engines opened the d file and also the b file, Stockfish moved its king forward without castling. The white queen moved forward, in a long PV agreement there were many exchanges and Stockfish gave a rook for a bishop. For a few moves Stockfish's eval jumped, then unexpectedly dropped back even though it anticipated Leela's move. Stockfish regained a rook for a bishop, after exchanging queens the game reached a rook ending. Stockfish was up a pawn with a passer, Leela gave a pawn and as a result all the white pawns were isolated and a pair was doubled. Leela held the draw, though it wouldn't lower its eval for a long time

Games 69-70 started with a rare sideline of the Pirc defense, Austrian attack. In game 69 Leela attacked the king side, the engines exchanged minor pieces and Stockfish was a pawn up but the black king was vulnerable. After a few pawn moves and some shuffling Stockfish moved its queen to a3, perhaps to attack the unguarded b3 pawn.

Leela thought this was a mistake and its eval jumped, Stockfish's eval reacted only 3 moves later. Leela attacked the black king and Stockfish quickly moved its queen back to help. Leela regained the pawn, after exchanging queens it created a passer on the queen side. Then it captured two more pawns and reduced to a RN vs RB position.

While Stockfish focused on the white a passer Leela managed to capture the last black pawn and create passers on the king side. Leela pushed passers forward, Stockfish stopped one before the game ended in a tablebase win.

In game 70 there were early exchanges, the engines opened the f file and exchanged a pair of rooks. The game reached a QRB vs QRN position on move 20, there were a few pawn moves and the engines started to shuffle. On move 74 the engines opened the a file and shuffling resumed, evals drifted down and the game seemed to be heading for a draw.

Stockfish thought Leela's move 89 was an inaccuracy and its eval started to increase, Leela's eval increased as well. Both engines were low on time and played in blitz mode. Stockfish managed to double rook and queen on the a file, then moved its rook forward and exchanged rooks. The white queen moved forward and used a mate threat to capture a pawn and create a passer. Stockfish blocked Leela's attempt to counter attack, then it captured a second pawn.

Stockfish exchanged queens, Leela managed to regain the two pawns including the passer on the queen side. However, the black king was too far to defend the isolated pawns on the king side, Stockfish captured two pawns, queened and mated. There were two white wins in this game pair, Stockfish leads 20-13.

Season 25 superfinal games 51-60

After 60 games Stockfish leads 17-10 with 33 draws. Stockfish extended its lead to 7 wins after another game pair win. There were two game pairs with two white wins. After 30 game pairs Leela still has only one game pair win. Stockfish won 5 of the last 15 game pairs.

Games 51-52 started with a rare 20-ply sideline in the KID Fianchetto, classical main line. In game 51 there was one pair of pawns exchanged after the start, the engines played behind their pawn lines for a long time. The first piece exchange was on move 32, afterwards there were a few pawns and minor pieces exchanged. On move 45 Stockfish's eval dropped, it gave a rook for a bishop and three pawns, then reduced to a QR vs QN position. Leela managed to capture 3 pawns back, its eval slowly came down and the game was adjudicated.

In game 52 Leela locked the center early, there was one pawn exchange on the queen side and the engines started to shuffle. Stockfish extended the shuffle beyond move 80 with pawn moves. Evals slowly started to increase, on move 88 Leela pushed the f pawn.

Both engines were low on time and played quickly. After a few moves Stockfish opened the king side, evals increased rapidly as the engines exchanged pieces and pawns. On move 106 the game reached a R vs NN imbalance with white two pawns up.

Stockfish captured another pawn and it had 3 passers on the queen side. Leela lost material quickly, Stockfish queened and mated. Stockfish wins the game pair, it leads 15-8.

Games 53-54 started with a rare sideline in the KID Saemisch, Yates defense, played in high level human chess. In game 53 the engines blocked the center and Leela castled long. Stockfish gave a pawn on the king side, giving Leela a passer and hiding its king behind it. Leela gave a knight for two pawns to open the king side and evals dropped. In a series of exchanges the engines reduced to a RR vs RBN position, white two pawns up. Leela still had 7 pawns, its rooks were not effective and the engines shuffled. Leela gave two pawns and captured a knight, evals were low enough and the game was adjudicated. In game 54 Stockfish opened the d file and captured a pawn, queens were off early and evals came down slowly. The engines shuffled for a long time, Stockfish moved a pawn to reset the 50-move draw counter, Leela pushed a passer to the 2nd rank. Stockfish captured another pawn and gave a rook for a knight, the game reached a BN vs RN position with low evals and was adjudicated.

Games 55-56 started with a rare sideline in the Nimzo-Indian defense, three knights variation. In game 55 a series of exchanges opened the center. Stockfish kept its king uncastled and Leela forced it to move, blocking the king side rook. Evals came down after most minor pieces were exchanged, on move 29 the game reached a QRR vs QRR position. Stockfish freed its trapped rook, Leela traded its two rooks for the black queen. The engines traded pawns, Leela was a pawn up but Stockfish held the draw. The game was adjudicated when Leela lowered its eval for the draw rule. Game 56 started similarly with small variations, again the black king side rook was trapped. Leela developed the rook through the h file. There was a lot of shuffling and some pawn and piece exchanges, evals came down. On move 53 the engines reduced to a Q vs RR position. Stockfish was two pawns up but not enough to win, the game was adjudicated when Stockfish lowered its eval for the draw rule.

Games 57-58 started with a rare 22-ply sideline in the Ruy Lopez closed variation. In game 57 the center was blocked and there were no exchanges after the start. Evals slowly increased, Leela pushed pawns on the king side, after move 28 there were a few pawns and minor pieces exchanged and Leela placed a pawn on h6. 

Queens were exchanged, more pawn exchanges opened the board. On move 50 Stockfish gave a rook for a bishop and the white h pawn, the game reached a RRN vs RBN position. Stockfish was a pawn up with connected passers on the king side, but Leela had a significant eval advantage.

The black passers were too far behind to be a threat. Leela captured the a pawn and pushed two passers forward. Stockfish lost material trying to prevent a queening, Leela queened a pawn in the end and the game was adjudicated before mate.

In game 58 again the center was blocked, this time Leela chose to open the b file with the first pawn exchange. Evals were stable, there were no other exchanges and the focus shifted to the king side. After some preparation Stockfish doubled rooks on the f file and on move 39 it pushed the f pawn forward.

Stockfish expected f6 and opening the f file, Leela chose to take with the g pawn. Stockfish took back with its knight and allowed Leela to take the knight. Stockfish thought these Leela moves were inaccuracies and its eval jumped, Leela's eval also jumped a move too late. The king side opened with the white major pieces attacking the black king. Leela gave a bishop back and exchanged pieces, on move 58 the game reached a QBN vs QR position. 

Both kings were exposed but Stockfish found safe squares for its king and slowly moved it forward. Stockfish captured a pawn and exchanged queens, then pushed a passer forward. Leela tried a stalemate trap, Stockfish captured the black rook and promoted the passer to a knight, then mated with minor pieces. There were two white wins in this game pair, Stockfish leads 16-9.

Games 59-60 started with a sideline of the Ruy Lopez, Bird defense variation. In game 59 both queens moved forward early, Leela forced the black king to move without castling. There were many early exchanges and the game reached a RB vs RN position with white a pawn up on move 26.

Leela thought Stockfish should have taken the rook with its king on move 26, its eval jumped and it offered a rook exchange. Stockfish's eval jumped as well and it refused the offer. Leela had a pawn majority on the king side, after a pawn trade it shifted to a pawn majority on the queen side. The white king slowly moved forward to assist, on move 57 Leela captured another pawn and created connected passers.

Leela pushed its passers forward, the white king switched to the king side and captured a pawn. Stockfish lost a rook for one passer, Leela queened and mated.

In game 60 the white queen moved forward on the king side, Leela castled short despite the threat. Stockfish pushed the f pawn forward and evals increased. The engines exchanged all bishops, Leela stopped the white pawn on f6 and exchanged queens. Only RRN vs RRN were left on move 27.

By the time Leela activated its queen side rook Stockfish moved both rooks forward, then captured the h pawn and created a passer. The engines traded pawns and exchanged a pair of rooks, Stockfish captured another pawn on the queen side and created a passer there. By move 56 all the black pawns were gone, Stockfish was two pawns up in a RN vs RN endgame. 

Stockfish moved its king forward and pushed its pawns slowly. Leela tried to avoid a 7-man position, this only prolonged the game for a few moves before adjudication. There were two white wins in this game pair, Stockfish leads 17-10.