Season 26 superfinal statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins

Final draw rate was 52%.

Game termination

The three most common game termination causes were:

48% - TCEC draw rule

28% - SyzygyTB
21% - Mate

There were no crashes in the stage.

Moves per game

Median= 79
Average= 83.7

There were 24 games longer than 100 moves, the longest was 167 moves (Stockfish - Leela, game 100, draw).

Time per game (hours) 

Median= 4:21
Average= 4:16

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, 12% diverged immediately out of book, 54% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 25 plys (Leela - Stockfish games 85 and 86, English opening, two white wins).

Season 26 superfinal games 91-100, season summary

Stockfish is the winner of the season 26 superfinal. The final score is 31-17 with 52 draws. In the last five game pairs Stockfish won two and extended its lead to a maximum of +15. Then in the last pair Leela finally managed to win and reduced the gap to +14 in the end. Leela had a chance of a game pair win earlier, but Stockfish managed to win the reverse game 94 in a blitz ending, with what both engines thought was a drawn position on move 90.

Stockfish won the first game pair of the match and it held the lead all the way to the end. It won again before Leela won its first pair, reducing the lead back to +1. Stockfish won 3 more game pairs, then Leela won two, after 14 game pairs Stockifsh led by +2. It seemed at that point that the match would be competitive, but in the next 14 pairs Stockfish won 6 times without loss. The lead was up to +8 before Leela managed to win a game pair. The hope for a Leela comeback, like in season 25, slowly diminished as Stockfish continued to increase the lead in the following games. Stockfish won 8 times without loss in the next 20 game pairs and the lead increased to +15. Leela finally won the last game pair, much too late to change anything. After two superfinals where Leela seemed to close the gap, this season Stockfish again dominated the superfinal.

The first league event of season 26 was the entrance league with 16 engines. There were 5 engines that were new to TCEC and 2 returning engines, including Berserk that was 4th in the premier division of season 24 and took one season off. Berserk dominated the league and won, the newcomer Obsidian and Velvet also qualified comfortably. There was a race for the fourth spot between newcomers Stormphrax and Altair, Altair led two rounds to go but Stormphrax closed the gap and advanced on a tiebreak. In league 2 Berserk and Obsidian again won easily. There were 3 more qualification spots - one more than usual because of SlowChess not starting the season. Several engines were involved in the race, after RR3 Viridithas, Velvet and Arasan opened a small gap ahead of the rest and kept it till the end. In league 1 there were 5 engines that led as a group: Seer, Caissa, Berserk, Obsidian and rofChade. After 3RRs rofChade was dropped but the other 4 engines were almost tied. In the last RR Berserk left the other engines behind to win the league. The other 3 engines ended up in a three way tie, the tiebreak decided that Seer was the second engine to advance. 

TBD: premier division, personal

Games 91-92 started with an unusual line in the English opening. In game 91 Leela kept its king in the center and pushed pawns on both sides of the board. The h file opened which was a potential danger for the black king, Leela's eval slowly increased. Leela didn't expect Stockfish's move 19, its eval dropped even though it trapped a black rook. On move 24 the engines started to exchange pieces, starting with a knight for rook trade. Stockfish regained the material and the game reached a RB vs RB position with white a pawn up. Leela wouldn't lower its eval, it gave the rook for a bishop and two pawns, the game continued for 35 more moves. In game 92 Stockfish castled its king, both engines played mostly on the king side. The pawns on the king side moved forward and both kings were exposed. Evals came down despite the fact that Stockfish captured a rook for a knight, the game reached a RRB vs RBN position. After a long shuffle the engines traded minor pieces and the game was adjudicated.

Games 93-94 started with a 22-ply line in the closed Ruy Lopez, Borisenko variation. All pieces and pawns were still on the board. In game 93 there were no exchanges after the start and the engines blocked the center and most of the queen side. On move 22 the engines exchanged minor pieces on the king side and Leela's eval started to increase. On move 27 the first pawns were exchanged on the queen side, opening the a file, Leela then pushed a pawn to h6. Stockfish's eval also started to increase, Leela captured a pawn on the king side and the queens were exchanged. 

Leela exchanged pawns in the center and created a passer, then offered a rook for a bishop. Stockfish thought about it but took the rook after a few moves, together with another pawn capture this gave Leela 3 connected passers in the center. Leela was not in a hurry to push the passers forward but Stockfish could not stop them. Leela queened eventually, followed by mate.

In game 94 the engines again blocked the center and there were no exchanges after the start. The first pawn exchange was on move 26 on the queen side, leaving a small opening there. The engines exchanged a pair of bishops, then Leela captured a pawn and opened the b file. Evals were low, the engines blocked the king side and exchanged the remaining bishops. Then there was a long shuffle, on move 88 a pair of rooks was exchanged and the shuffling continued. Stockfish's eval started to increase after move 100, then the engines reduced to a double knight ending. 

Leela was a pawn up but its knights could not advance while the white knights had several protected entry points. Leela gave back the pawn and exchanged a pair of knights, giving Stockfish a passer on the king side. Leela gave another pawn in the center, Stockfish gave it back and created another passer. Stockfish reduced to a king and pawns ending and saw the win. Both engines queened but Stockfish gave check first, then queened again and mated. There were two white wins in this game pair, Stockfish leads 29-16.

Games 95-96 started with a rare sideline of the KID Saemisch variation, the center was blocked and all pawns and pieces were on the board. In game 95 the engines exchanged pawns and knights on the queen side. Evals dropped after the black queen moved forward, queens were exchanged and the white king moved without castling. The engines opened the king side, then a series of exchanged reduced to a RB vs RB position. Leela captured a pawn, its eval increased just before adjudication. This only delayed the game's end by a few moves.

In game 96 Stockfish castled its king, the engines exchanged pawns and knights on the queen side and opened the v file. The engines seemed to shuffle but Stockfish's eval slowly increased after move 27, Leela's eval stayed around 1. On move 35 Stockfish pushed a pawn on the king side and exchanged a pair of pawns, then moved major pieces to the g file.

Leela's eval jumped over 2, it tried to defend the g6 pawn with all pieces it could get. The engines exchanged a pair of bishops, Stockfish took its time to get a second rook on the g file and move the queen behind the rooks. Then it moved the pawn to f6 and brought the knight to e7, forcing a knight for rook trade. The g file opened and the game reached a QRB vs QBN position. 

Stockfish captured a pawn after exchanging bishops, then it gave the rook for a knight and captured a second pawn. The two pawns advantage was enough for a win in the queen ending, the game ended in mate. Stockfish wins the game pair, it leads 30-16.

Games 97-98 started with a 22-ply sideline in the Sicilian, Scheveningen variation, with all pieces on the board and one pair of pawns exchanged. In game 97 Leela pushed pawns on the king side, a pawn exchange on the queen side opened the a file. Leela captured a pawn and exchanged a pair of rooks, its eval slowly increased. Leela thought Stockfish will exchange pawns on the king side, when that didn't happen Leela's eval dropped. On move 25 the engines started to exchange pawns and pieces, Stockfish gave a bishop and the game reached a QBB vs QB position. Stockfish had connected passers on the king side, Leela gave back a bishop to capture one passer. The white king was exposed and the black queen gave checks until the game ended in a 3-fold repetition.

In game 98 Stockfish thought Leela's first move after book was a mistake. Leela didn't expect Stockfish's response and its eval jumped immediately over 2.5. Stockfish attacked the king side, it sacrificed a knight and then Leela gave its queen for a rook. Stockfish let Leela capture another rook, it had a strong attack on the black king and Leela still had a rook and a bishop undeveloped on the queen side. 

Stockfish moved a bishop to h6, Leela offered a rook for the bishop but Stockfish preferred to keep its bishop pair. After trading bishop for knight Stockfish used a mate threat to capture a rook. The game reached a Q vs RB ending, Stockfish pushed a passer on the king side. Leela stopped the passer on the 7th rank, then lost the bishop and the game ended in a tablebase win. Stockfish wins the game pair, it leads 31-16.

Games 99-100 started with the main line of the Czech Benoni defense, the center was blocked and all pieces and pawns were on the board. In game 99 Leela pushed pawns on the king side and the white king went there without castling. Leela's eval slowly increased, after move 19 the engines exchanged pawns and opened the king side. The f file opened and the engines exchanged a pair of rooks on move 29, first piece exchange. Both engines had a passer in the center, more minor pieces were exchanged and both kings were left without any pawns protecting them.

Material was equal but the black e pawn was hard to defend. Leela first got its king to the center for safety, then exchanged queens and only then captured the e pawn. In a RBN vs RBN position Leela exchanged pawns on the queen side and then slowly captured the remaining black pawns. There were two connected white passers left, Stockfish could only delay with checks but eventually Leela queened. Stockfish lost material and the game ended in a tablebase win.

In game 100 the engines exchanged a pair of bishops, Stockfish pushed the h pawn and castled long. More minor pieces were exchanged, Stockfish pushed the pawn to h6 and the engines started to shuffle. Stockfish had a pair of advanced knights, but with all pawns on the board the major pieces could do nothing. On move 62 Stockfish gave a pawn, on move 98 the engines exchanged queens. Shuffling continued with evals at 0, the game was adjudicated on move 167 after enough pieces were exchanged. Leela wins the game pair, Stockfish leads 31-17.

Season 26 superfinal games 81-90

After 90 games Stockfish leads 28-15 with 47 draws. Stockfish won 3 game pairs without loss, increasing its lead to +13 with 5 game pairs left to play. Leela hasn't been able to win a game pair for 16 straight pairs, it is not making a comeback this season. There was on game pair with two white wins. 

Games 81-82 started with a line in the QGA, central variation, played in high level human games. All pieces were on the board, black was a pawn up and had a passer in the center. In game 81 there was a long PV agreement at the start, the engines exchanged minor pieces, Leela regained the pawn and attacked the black king. Stockfish moved its exposed king without castling, Leela captured two more pawns and cleared the black king side. There were 4 connected white passers but the white king was behind them. Stockfish captured one passer and Leela's eval dropped. In a series of exchanges the engines reduced to a RB vs RB position. Leela was two pawns up with a passer on the 7th rank, Stockfish also pushed a passer to the 2nd rank. Both evals were close to 0 and the game was adjudicated.

In game 82 Leela kept the pawn and kept its king safe, Stockfish's eval jumped when Leela castled its king and allowed a king and rook fork, losing a rook for a knight. Two moves later Leela's eval jumped even higher. Stockfish opened the c file and moved a rook forward, Leela pushed a pawn on the king side that reached h3 and the white king hid behind it. Stockfish used all its pieces to threaten the black king, Leela exchanged pieces and pawns, on move 44 the game reached a RR vs RB position.

Stockfish created a passer on the queen side, then managed to confine the black king on the h file. A zugzwang on move 62 forced Leela to move its blocking rook, Stockfish used mate threats to push its passer and gain more material. Stockfish queened and the game ended in a tablebase win. Stockfish wins the game pair, it leads 25-14.

Games 83-84 started with a rare sideline in the Robasch defense. In game 83 the engines castled in opposite directions. For one move Leela's eval spiked close to 2 after a 12 minute think, Stockfish surprised with a pawn push on the queen side and both evals dropped. The engines opened files and exchanged pieces rapidly. Stockfish was a pawn up in a QB vs QB position, Leela regained the pawn and exchanged queens, the game was adjudicated very early on move 34.

In game 84 the engines repeated the reverse game for 11 plys and castled in opposite directions. The black queen moved forward on the queen side, the engines exchanged pawns and minor pieces there. Stockfish captured a pawn, most of the black pawns on the queen side were gone and the black pieces there were a threat to the white king. Stockfish exchanged a pair of rooks and protected its pawn on e5 that kept the long diagonal closed. Leela's eval dropped on move 28, Stockfish's eval dropped 2 moves later. The engines exchanged pawns on the king side and opened files but it seemed Leela found a way to hold a draw. On move 38 Stockfish's eval jumped back up, Leela was surprised by the next white move.

The white bishop was hanging but Leela didn't take because of the threat of Qh4, allowing Stockfish to capture back and also threaten the black king. Stockfish had to be careful because Leela had mate threats as well, but Stockfish kept its king safe. Eventually Stockfish gave a bishop for a pawn and then captured the black knight so it was two pawns up. It chased the black king to the queen side and protected against a back rank mate.

Stockfish exchanged queens and captured the remaining black pawns. It was 3 pawns up in a RN vs RB position and the win was just a matter of time. Leela avoided exchanges, Stockfish pushed its passers forward and mated in the end. Stockfish wins the game pair it leads 26-14.

Games 85-86 started with the Old Indian, Tartakover variation, with the white queen out on the queen side. In game 85 Leela pushed a pawn on the king side, Stockfish captured it and opened the g file. The engines exchanged most minor pieces and both castled long. Leela regained the pawn and captured another one, evals slowly increased. Stockfish placed its pieces around the king and waited for the attack, on move 41 the engines exchanged a pair of rooks and the game reached a QRB vs QRN position. 

Leela attacked the center and opened the e file. After another pawn trade Leela created a passer on the king side. The engines exchanged queens and Leela pushed its passer. Stockfish lost more material as it created its own passer on the queen side. However Leela queened and the game ended in a tablebase win.

In game 86 the engines repeated the reverse game for 25 plys, exchanging most minor pieces and opening the g file, Leela was up a pawn. Stockfish moved its king to the king side without castling, stabilized its pawns and then reduced to a QRR vs QRR position. Leela castled long and Stockfish captured two pawns on the king side. On move 35 the engines exchanged a pair of rooks, evals were already high.

Stockfish captured a pawn on the queen side while Leela tried to attack from the king side. The black queen moved forward and the engines exchanged rooks. Stockfish saw the win in the queen ending though it was a long endgame. Leela captured a pawn, the white king move forward and captured two pawns in the center. Stockfish pushed passers forward and Leela lost its queen, the game ended in mate. There were two white wins in this game pair, Stockfish leads 27-15.

Games 87-88 started with a 20-ply sideline in the Nimzo-Indian, Saemich variation. The center was blocked with one pair of pawns exchanged and all pieces were on the board. In game 87 the engines played mostly behind their pawn lines, Leela's eval increased for a while and then came back down again. Stockfish exchanged a pair of pawns on the queen side, then blocked it with pawns and pieces. Leela was left without knights after an exchange, Stockfish also exchanged its last knight. Leela doubled rooks on the g file and used mate threats to capture a pawn. Stockfish doubled rooks on the a file and kept its king safe. After some shuffling the engines exchanged a pair of rooks, the game was adjudicated after queens were exchanged. 

In game 88 Leela pushed the g pawn early and Stockfish thought that was a mistake. Leela's eval stayed low while Stockfish exchanged a pair of pawns on the king side and doubled pawns on the f file. On move 19 Leela's eval spiked over 3, but Stockfish did not play what Leela expected and its eval dropped back. Then there was a series of exchanges, Leela's eval increased back to around 2 and the game reached a QRB vs QRN position.

Leela was a pawn up and its king seemed reasonably safe, but still evals were high and increasing. Stockfish shuffled and repeated for a long time, the focus was on the f6 pawn. After a while Stockfish managed to get the black king away from the pawn. Leela did not have enough defenders and it lost the pawn, the black king ran to the queen side. 

Stockfish gave a pawn in the center and created a passer, then exchanged queens. The passer moved forward, Stockfish gave a rook for a knight and queened the passer. The game ended in mate. Stockfish wins the game pair, it leads 28-15.

Games 89-90 started with a sideline of the French Winawer, advance variation. In game 89 the white queen moved forward on the king side, after a minor piece exchange the black king moved without castling. Leela gave a pawn and opened the b file, Stockfish exchanged a pair of rooks and reduced to a QRN vs QRN position. The engines started to shuffle, with a few pawn moves and pawn exchanges. Stockfish's eval was 0, Leela lowered it eval after a series of exchanges on move 111 that included the rooks, the game was adjudicated a few moves later. In game 90 the engines repeated the reverse for 26 plys with transpositions, the black king moved without castling, Stockfish gave a pawn and the b file was open. Again the engines reduced to a QRN vs QRN position, then started shuffling with a few pawn moves. Evals came slowly down, on move 114 Stockfish gave pawns, the game was adjudicated after a knight for rook trade.

Season 26 superfinal games 71-80

After 80 games Stockfish leads 24-14 with 42 draws. There were five drawn game pairs, 3 with two draws and two with two white wins. Leela hasn't won a game pair in the last 11 pairs. There are only 10 game pairs left in the match, I can safely say that Stockfish will be the champion. 

Games 71-72 started with a 24-ply line in the Four Knights symmetric, Metger unpin variation. All pawns were on the board and the pieces were behind the pawn lines. In game 71 the engines pushed pawns forward and continued to play behind their pawn lines. The first pawn exchange was on move 27, evals increased very slowly. The engines opened the b file, a minor piece exchange opened the c file as well. Leela captured a pawn in the center and the game reached a QRB vs QRN position. 

Leela took some time to arrange its pieces safely, it gave the pawn back and opened a diagonal for its bishop aimed at the black king. Stockfish tried to prevent the white pieces from moving forward, eventually Leela exchanged queens on move 69 and moved its rook to the 7th rank where it captured a pawn.

Leela captured another pawn on the king side, now it had two passers. Stockfish lost more material and the game ended in a tablebase win. 

In game 72 Stockfish blocked the center, Leela pushed pawns on the king side and moved its pieces there. The engines exchanged queens and minor pieces on move 27, all pawns were still on the board. Stockfish's eval started to increase, on move 34 the first pawns were exchanged and the engines opened the a file. 

Stockfish moved a rook forward on the queen side, Leela had to keep a knight on c8 to protect its b and d pawns. The white king moved to the center and Leela captured a pawn on the king side. Stockifsh moved its second rook forward, the black king was under threat and Leela exchanged pawns to try to get more space. Stockfish exchanged pieces and reduced to a RB vs RN position on move 62. It was a pawn down but evals were high. 

Stockfish captured the two black g pawns and created a passer. Leela moved its knight to the king side and Stockfish captured another pawn on the queen side. Stockfish saw the win, the engines reduced to a rook ending, Stockfish queened and mated. There were two white wins in this game pair, Stockfish leads 23-13.

Games 73-74 started with a 21-ply line in the KID orthodox variation, played in high level human games. There was one minor piece exchange and all pawns were on the board. In game 73 Stockfish traded bishop for knight and then gave a rook for a bishop. The center was blocked and it seemed Stockfish wanted to defend behind its pawns. Leela opened the center and gave a pawn, then tried to attack on the king side. Stockfish protected its king and evals came down, the engines reduced to a R vs N position with black two pawns up. The engines shuffled and traded pawns until Leela lowered its eval for the draw rule. In game 74 Leela gave a rook for a bishop, again trying to block the board. Stockfish exchanged a pair of pawns and opened the f file, the engines exchanged bishops and the game reached a QRB vs QNN position. The engines shuffled for a long time, the white king walked to the queen side, then returned to the center. On move 93 Stockfish gave a pawn and shuffling resumed. The game was adjudicated on move 119 after Stockfish gave a rook for a knight.

Games 75-76 started with a 20-ply sideline in the Caro-Kann advance, Van der Wiel attack. All pieces were on the board, there was one exchange of a pair of pawns and both kings were in the center. In game 75 Stockfish forked two minor pieces with a pawn, Leela castled long and pinned the pawn. The black king walked to the king side, Leela captured two pawns but evals came down. Leela captured another pawn and gave a rook, Stockfish was down to its last pawn and its king hid behind the pawn. Stockfish gave the rook back and reduced to a RN vs RNN position. Leela wouldn't lower its eval after exchanging knights, the engines shuffled and the game was adjudicated 25 moves later. In game 76 the engines started to exchange pieces in long PV agreements. By move 23 the game reached a RB vs RB position, the engines continued to trade pawns. Stockfish was a pawn up but evals came down, both engines had a passer on the king side. Not a lot happened, the game was adjudicated when Leela lowered its eval even though Stockfish pushed its passer to the 6th rank. 

Games 77-78 started with a 24-ply line in the Slav, Czech, Carlsbad variation played in high level human games. All pieces were on the board and the d file was open, the black king was in the center. In game 77 Stockfish castled its king, on move 20 the engines started to exchange pieces and the game reached a QRB vs QRN position. Stockfish's eval was 0, the engines exchanged rooks and started to shuffle. After exchanging queens Leela captured a pawn and created doubled passers, but Stockfish controlled them with its knight and prevented the white king from supporting the passers. The game was adjudicated a few moves later. In game 78 the engines exchanged pieces and pawns on the king side, the f file opened and Leela kept its king in the center. Stockfish was a pawn up with a passer in the center, evals came down as the engines shuffled and exchanged a pair or rooks. On move 43 the game reached a QBN vs QBB position, white was a pawn up and its passer was still on the 2nd rank. After exchanging a pair of bishops the game was adjudicated.

Games 79-80 started with a line in the Sicilian Najdorf, Opovcensky variation, played at high level human games but not recently. In game 79 Leela pushed pawns on the king side and Stockfish pushed a pawn on the queen side. As a result Leela went up a pawn and the b and g files were open. The white king walked to the king side and the black king stayed in the center, Leela's eval increased quickly. On move 39 Leela captured a second pawn and created a passer on the king side. 

Very little seemed to change for a long time, Leela pushed its passer to the 5th rank, Stockfish pushed the a pawn. The black king walked to the queen side, starting from move 70 Stockfish's eval started to increase. Leela moved a rook forward and exchanged a pair of rooks. The engines shuffled for a while and Leela's eval jumped, on move 102 Leela captured a third pawn.

After a minor piece exchange nothing could stop the white passer, Leela had two queens and Stockfish had no counter. The game quickly ended in mate. 

In game 80 the engines repeated the first 17 plys, opening the b and g files and Stockfish with a pawn up. Both kings moved forward, evals increased as the engines exchanged pieces. On move 28 the game reached a RBN vs RBB position. 

The pawns stabilized and the engines shuffled for a while, then Stockfish captured a pawn on the queen side, created a passer and exchanged rooks. The black bishops were strong enough to cover the passer's file and Stockfish kept it behind, while its king walked to the king side. When the knight moved to help Leela gave up the h pawn and Stockfish was 3 pawns up with a passer on the king side as well.

Stockfish managed to slowly push the king side passer to the 7th rank with only the black king blocking. Then it slowly pushed the queen side passer forward and Leela gave a bishop to stop it. Stockfish queened the other passer and mated. There were two white wins in this game pair, Stockfish leads 24-14.

Season 26 superfinal games 61-70

After 70 games Stockfish leads 22-12 with 36 draws. Stockfish won two game pairs and extended its lead to +10, the biggest lead so far. There was one game pair with two white wins, Leela was not able to win a game pair. In games 64 and 66 Stockfish won a very long endgame that seemed to be a draw. 

Games 61-62 started with the Zukertort opening, Nimzo-Larsen variation, with an advantage for black. In game 61 the engines blocked the center and exchanged a pair of bishops. Leela pushed pawns on the queen side, (negative) evals came down. The engines opened the queen side, the engines exchanged more pieces and pawns and Stockfish captured a pawn. Both engines used active knights to trade queens and a pair of rooks, leading to a RNN vs RBN position. After clearing the queen side pawns  and exchanging rooks the game was adjudicated. In game 62 the engines exchanged a pair of pawns on the queen side and then exchanged most minor pieces. Leela went up a pawn, Stockfish castled long and (negative) evals came down. After a series of exchanges on the d file the game reached a RN vs RN position. The engines cleared the queen side pawns and then started to shuffle. Leela wouldn't lower its eval for a long time, the game was adjudicated on move 75. 

Games 63-64 started with a 20-ply sideline of the Sicilian, Richter-Rauzer variation. White castled long while the black bishops were undeveloped. In game 63 Stockfish castled long, Leela captured a pawn and opened the f file. Leela moved a rook to the 7th rank, after a while the engines reduced to a RB vs RB position with white a pawn up. The king side was cleared, Leela had a passer in the center. Stockfish stopped the passer on the 6th rank and the engines started to shuffle. Leela wouldn't lower its eval, the game was adjudicated on move 115 approaching a 50-move draw.

In game 64 Leela castled long as well, Stockfish kept the king side closed and exchanged pawns in the center. Stockfish went up a pawn, both engines created passers in the center. Stockfish's eval slowly increased, Leela moved its queen forward and its eval dropped for a few moves. Leela pushed its passer to the 3rd rank, Stockifsh captured a second pawn and created a passer on the king side.

The black queen moved in front of the rook while defending the d3 pawn, Stockfish used this to push its central passer to d7 safely. Combining mate threats and attacks on pieces Stockfish managed to push its h passer slowly forward. Then in a series of exchanges Leela captured both white passers and gave a rook for a bishop. On move 55 the game reached a RR vs RB position.

Leela still had an advanced passer, after exchanging a pair of rooks the passer reached the 2nd rank but the bishop no longer controlled the promotion square. Stockfish saw the win, it created an unstoppable  passer on the queen side. After queening the game ended in a tablebase win. Stockfish wins the game pair, it leads 20-11.

Games 65-66 started with a sideline of the Owen's defense. In game 65 Leela's eval spiked close to 2 early. The engines opened the d file and then Leela thought for 10 minutes and its eval came back down. After a few pawn moves the engines started to shuffle and Stockfish's eval was close to 0. On move 62 the engines started to exchange pieces and pawns, Stockfish gave a bishop for 3 pawns and the game reached a QB vs Q position. After exchanging queens the game was adjudicated.

In game 66 there were many early exchanges and long PV agreements. The black king moved without castling and blocked the king side rook. Once the king walked to h7 the rook was freed, by then Stockfish managed to create an advanced passer on the queen side. The engines exchanged all rooks and the game reached a BN vs BB position on move 36.

Stockfish blocked the black passer and pushed its own to the 7th rank, Leela's DS bishop couldn't attack the passer safely. For a long time the engines shuffled, on move 77 they exchanged a pair of pawns on the king side. Evals stayed low until suddenly Stockfish's eval jumped over 2 on move 86. Nothing seemed to be different, but Leela's eval started to increase slowly as well. The white king moved closer to the passer, slowly Stockfish managed to move its pieces so that it could force a bishop exchange on move 103 (the d8 bishop can escape to e7 but then Bc5+ exchanges anyway).

Stockfish already saw the win. Of the next 19 moves after exchanging bishops the knight moved 15 times, Stockfish captured two pawns and finally managed to queen the passer with the knight blocking the possibility of taking the queen. A few moves later Stockfish mated. Stockfish wins the game pair, it leads 21-11.

Games 67-68 started with a rare line in the Philidor defense, Boden variation. In game 67 the engines castled in opposite directions, Stockfish pushed pawns on the queen side. A black pawn reached a3, Leela blocked the queen side and its eval started to increase. In a long PV agreement Stockfish gave a rook and captured a bishop using a mate threat. Leela gave pawns and opened the king side, after exchanging queens the game reached a RR vs RN position with black two pawns up. 

Stockfish's eval slowly increased, the white rooks were active as defenders and attackers. Leela managed to capture three pawns and created a passer on the queen side. Stockfish had a passer on the king side but it wasn't strong enough. Leela connected a second passer after a pawn exchange, Stockfish could not prevent a queening and mate. 

In game 68 Stockfish castled long, Leela gave a rook for a bishop to open the b file before castling short. Evals stayed below 1 for a long time, in a series of exchanges the engines reduced to a QRR vs QRB position. Leela captured a pawn and all the remaining white pawns were isolated. The engines shuffled for a while and on move 40 they exchanged queens. On move 47 Stockfish started to increase unexpectedly, the engines cleared the king side pawns.

For a long time nothing seemed to happen, Stockfish repeated a lot and Leela mostly waited for Stockfish to do something. Leela's eval didn't change until move 80. Stockfish attacked the black bishop with two rooks, Leela defended with king and rook and was very close to zugzwang. 

The engines blitzed, evals increased quickly and Leela's defense collapsed. The engines traded pawns until there was only one left for each side. Stockfish saw the win in an 8-man position, it offered the pawn but Leela avoided exchanges because a 7-man position was a loss. Eventually Stockfish exchanged rooks and the game was over. There were two white wins in this game pair, Stockfish leads 22-12.

Games 69-70 started with a 20-ply line in the Dutch Stonewall variation, all pieces and pawns were still on the board. In game 69 Stockfish pushed pawns on the king side and exchanged minor pieces. Leela tried to avoid a pawn blockade, the engines exchanged more minor pieces in the center and all knights were gone. Leela opened the b file and evals came down, the engines exchanged a pair of rooks. After some shuffling the engines exchanged queens, the game was adjudicated in a RB vs RB position. In game 70 the engines exchanged a pair of pawns and most minor pieces on the queen side. Evals came down and the king side was blocked. The game reached a QRR vs QRR position and the engines traded pawns. On move 53 the queens were exchanged, evals were low and the game was soon adjudicated.

Season 26 superfinal games 51-60

After 60 games Stockfish leads 19-11 with 30 draws. Leela won a game pair after 14 straight game pairs without a win, losing 6 of them. However Stockfish won 3 game pairs and it extended the lead to 8. One game pair had two black wins. There are only 20 game pairs left to play in the superfinal, it's hard to imagine Leela can close the gap.

Games 51-52 started with a 19-ply line in the Ruy Lopez, Berlin defense, Anderssen variation with an advantage for black. In game 51 there was one pawn exchange after the start, evals were stable and the engines mostly played behind their pawn lines. On move 25 Leela exchanged pawns in the center and Stockfish's (negative) eval jumped over 1. Leela's eval reacted only 6 moves later, the black queen moved forward on the king side and Stockfish prepared an attack on the white king.

Leela couldn't get its king away, Stockfish captured the h pawn and while Leela exchanged pieces Stockfish captured another pawn. The game reached a queen ending with black two pawns up, Leela captured back two pawns but couldn't avoid a queening and mate.

In game 52 Stockfish castled long, it pushed the g pawn forward and opened the king side. The engines exchanged minor pieces and Leela captured a pawn. On move 37 the game reached a QRN vs QRB position with black a pawn up. 

Leela kept its king safe and avoided perpetual check, (negative) evals slowly started to increase. Leela had a pawn majority on the king side, Stockfish captured a pawn on the queen side and Leela exchanged queens. The engines traded pawns and on move 66 Leela had connected passers on the king side and Stockfish had doubled passers on the queen side. 

The black passers were more dangerous and easier to defend. Leela lost the d pawn and captured the two a pawns. It pushed one passer to the 2nd rank, then captured the knight for it. The game ended in a tablebase win. There were two black wins in this game pair, Stockfish leads 16-10.

Games 53-54 started with a 24-ply line in the KID Saemisch variation, with all pieces and pawns on the board except one pair of pawns. In game 53 Leela castled long, it pushed the h pawn and tried to open the king side. Leela's eval spiked over 1.5 for one move and then came back down. In a long PV agreement Stockfish gave both its rooks and a knight and captured the white queen. Despite the material imbalance evals came down quickly, Stockfish captured pawns and was 3 pawns up. The game reached a RRB vs Q position, Leela pushed a passer to the 6th rank and moved a rook forward, but kept its other pieces to protect its exposed king. Evals were low and the game was adjudicated. 

In game 54 after Stockfish castled long Leela pushed the b pawn forward and Stockfish's eval started to increase. Stockfish pushed pawns on the king side, it gave two pawns and opened the g file. Leela saw a few moves ahead in its PV, Stockfish sacrificed a bishop and Leela expected to give back the material. Leela's eval was low while Stockfish's eval was over 3, it surprised Leela with its move 25, a discovered attack on the queen.

Leela thought for 9 minutes and its eval jumped over 3, it lost two minor pieces for a rook. Leela opened the b file and attacked the white king, Stockfish had to be careful. However the white king stayed safe while the black king was under attack. Despite being down on material Stockfish soon saw a win, the engines reduced to a QB vs QB position and the game ended in a tablebase win. Stockfish wins the game pair, it leads 17-10.

Games 55-56 started with a line in the Modern defense, two knights variation, played in high level human games but not recently. In game 55 Leela castled long, its eval went over 1 for a while but after Stockfish castled long Leela's eval slowly came down. A knight exchange opened the e file, Stockfish doubled its rooks there and then closed the file with a bishop. Leela captured a pawn, on move 45 the game reached a RRB vs RRB position. The engines mostly shuffled for a long time, on move 81 Stockfish gave the bishop for three pawns and moved its rooks forward. Leela captured two pawns back but Stockfish had a perpetual check draw. For fun Stockfish chose a different draw, it gave a rook for a white passer and reduced to a tablebase draw a rook down with only two pawns.

In game 56 Stockfish castled long as in the reverse game, however this time Leela castled short. Stockfish opened the g file and Leela's eval jumped over 1.5. In a long PV agreement Stockfish gave a rook for a bishop and two pawns. The engines exchanged queens and reduced to a RBN vs RRN position. Stockfish had connected passers in the center, it exchanged the bishop for a knight and pushed the passers forward.

Leela moved its rooks forward and attacked the white king. Stockfish lost its pieces but queened one of the passers. In the Q vs RR ending Stockfish soon saw the win, the white king found a safe square and Stockfish captured pawns with its queen. Eventually Stockfish queened a second passer and mated. Stockfish wins the game pair, it leads 18-10.

Games 57-58 started with an 18-ply line in the Nimzo-Indian defense that deviated early from standard theory. In game 57 Leela's eval increased from the start, all pawns were on the board and queens were off early. Both kings moved forward without castling, Leela captured a pawn on the queen side and its eval jumped quickly. The pawns stabilized and the engines shuffled, on move 38 Leela's eval was over 8 though it was not clear what the plan was.

The shuffling continued with some pawns moves on the king side, Stockfish's eval increased as well. On move 56 Leela gave a pawn on the queen side and exchanged a pair of rooks, both engines created a passer there. The game reached a RBN vs RBN position, Leela hid its king behind the black passer, on move 62 Stockfish exchanged a pair of pawns on the king side.

Leela pushed the e pawn, it gave the bishop and captured two pawns, creating passers on the queen side. Stockfish lost its rook and then its knight, it pushed its remaining pawns on the king side. Leela gave its pieces to stop the black pawns, then queened to win. 

In game 58 Stockfish castled its king and the queens stayed on the board. The black king moved forward without castling, Leela opened the a file and blocked the center. Evals came down, after some shuffling the engines exchanged a pair of rooks. Stockfish captured a pawn and the game reached a QBN vs QBN position. Leela regained the pawn, after knights were exchanged the game was adjudicated. Leela wins the game pair, Stockfish leads 18-11.

Games 59-60 started with a rare 18-ply line in the French Winawer, advance variation. The center was blocked and all pieces and pawns were on the board. In game 59 the engines exchanged minor pieces and a pair of pawns, the black king stayed in the center uncastled. Evals came down and the black king walked to the queen side. The game reached a QRR vs QRR position and the engines shuffled for a while. Leela captured a pawn, allowing Stockfish to force a queen exchange and the game was adjudicated.

In game 60 Leela pushed a pawn on the queen side, Stockfish gave two pawns and let the black pawn reach the 2nd rank. Evals increased early, Leela's eval was even higher that Stockfish's. Stockfish captured the advanced black pawn and gave a knight, creating a passer on the queen side. Leela's king was in the center and its king side rook could not develop, Stockfish pushed the passer and moved a rook to the 7th rank. Leela lost a bishop for the passer, Stockfish added its queen to the 7th rank. The black king ran to the king side, Leela gave a rook for a knight and pawn. Then Stockfish added its second rook to the 7th rank, all three major pieces on the 7th rank !

Stockfish captured the black a pawn on the 2nd rank, Leela was anxious to get rid of the pieces on the 7th rank and it exchanged queens and a pair of rooks. The game reached a RB vs BN position, Stockfish traded pawns and created a passer on the king side. Leela pushed pawns in the center, Stockfish saw the win in its PV. It lost the passer and captured two pawns in the center, each engine was left with one pawn. Stockfish moved its pieces forward and trapped the black king. Leela lost material because of the mate threat and the game ended in a tablebase win. Stockfish wins the game pair, it leads 19-11.

Season 26 superfinal games 41-50

After 50 games Stockfish leads 15-9 with 26 draws. Stockfish won two game pairs and extended its lead to 6, the highest so far in the match. This is the same result as in the last season's superfinal at the half way point. Last season Leela had a significant comeback in the second half, will we see this again this season? There were two game pairs with two white wins, Stockfish's win in game 46 displayed another case where Leela evaluates completely won endgames as a draw - this time it was an 8-man RB vs RB position with white two pawns up.

Games 41-42 started with a rare line in the QGD, Stonewall variation. In game 41 there were almost no exchanges after the start and all pawns were on the board. Leela pushed pawns on the queen side and Stockfish blocked with its pawns. On move 23 there was on pawn exchange on the king side, Stockfish placed a rook and a queen on the half open h file but Leela protected its pawns there. The engines started to shuffle, the white king walked to the queen side and evals came down. On move 79 Leela gave a pawn, then all rooks were exchanged. The game reached a QB vs QB position and was adjudicated on move 99. 

In game 42 the engines opened the b file and Stockfish moved a rook to the 7th rank. After some shuffling with low evals Stockfish exchanged a pair of rooks and its eval jumped over 1. The engines exchanged queens and the game reached a RBB vs RBN position. Leela's eval was still below 1, it felt safe.

Stockfish's eval went over 2 as it blocked the center, the white king walked to the queen side and the engines shuffled for a long time. Leela's eval also increased though it seemed nothing was happening. Stockfish placed a bishop on b5 and Leela did not capture it on multiple opportunities. The white king moved back to the center, finally on move 91 Stockfish moved the rook to the king side and captured two pawns.

Stockfish gave a rook for the black e pawn, then captured the a pawn, so it had 3 passers. It pushed the a pawn to the 7th rank, Leela managed to capture it with its knight but lost its bishop. Stockfish gave a pawn but secured the h8 square, Leela captured the h pawn and lost its knight. Stockfish queened the 3td passer and mated. Stockfish wins the game pair, it leads 12-7

Games 43-44 started with a 22-ply book in the Sicilian Richter-Rauzer variation. In game 43 the engines exchanged all knights, Stockfish kept its king in the center and its king side rook developed through the h file. The engines played out a long PV agreement and evals started to increase, despite a black doubled passer on the king side. The black king tried to find safety on the king side, Leela captured a pawn on the queen side and created connected passers. Stockfish captured a pawn on the king side and connected another passer there.

Stockfish exchanged a pair of rooks and moved its queen forward, Leela just pushed its pawns forward on the queen side, the c pawn became a third passer. After exchanging queens Stockfish pushed its passers on the king side and Leela stopped them. A series of exchanges reduced to a same color bishop ending, Leela queened twice and mated. 

In game 44 only one pair of knights was exchanged. Evals gradually increased, the engines opened the h file and exchanged a pair of rooks. Leela castled long, then in a series of exchanges the engines reduced to a QBB vs QBN position on move 29.

The black king was exposed and threatened by the white pieces. After exchanging a bishop for a knight Stockfish saw the win, it captured a pawn and waited for the right moment to exchange queens. Stockfish was two pawns up in an opposite color bishop ending, the white king moved forward and Leela couldn't block all the white passers. Stockfish queened and the game ended in a tablebase win. There were two white wins in this game pair, Stockfish leads 13-8.

Games 45-46 started with a rare Queen's pawn, anti Torre line. In game 45 both queens moved forward on the queen side. Leela's eval started to increase early while Stockfish still thought it was safe. In a series of exchanges the queen side was opened, queens were off, Stockfish was a pawn up with a passer on c3. Leela pushed a passer to d6, Stockfish castled long and its eval increased as well. Leela also castled long, the game reached a RRB vs RRN position, Stockfish captured a second pawn while Leela connected a second passer in the center. Stockfish used its two rooks to block the white passers.

Stockfish's only strength was the queen side passers, the black king moved forward and supported their advance. Leela captured the c3 pawn and then cleared the king side and created a passer there. Stockfish managed to switch a blocking rook with a knight and capture the e pawn, but then Leela captured all the three queen side pawns. Stockfish couldn't prevent a queening, the game ended in a tablebase win.

In game 46 the engines opened the queen side and both castled short. Stockfish moved its queen forward and exchanged queens. Evals stayed below 1 though Stockfish captured a pawn, the game reached a RRB vs RRB position on move 39. Stockfish captured a second pawn but both engines were still unconvinced.

The engines traded a pair of pawns and exchanged a pair of rooks, leaving an 8-man position with only two white pawns on the king side. Evals stayed low for a while, perhaps because of the opposite color bishop ending that would be the result of exchanging the rooks. Starting from move 65 Stockfish's eval slowly increased, then jumped over 2 when it pushed a passer safely to h6. Leela's eval became even lower while Stockfish's eval was a clear win, the white king and g pawn slowly moved forward. On move 93 Stockfish's eval was over 90, Leela's eval only 0.32 !!

Leela's eval finally started to react, while Stockfish saw the win in its PV. On move 114 Stockfish pushed the g pawn and reset the 50-move counter, then it drove the black king forward out of the corner. Stockfish queened one of the pawns and the game ended in a tablebase win. There were two white wins in this game pair, Stockfish leads 14-9

Games 47-48 started with a line in the Dutch, Ilyin-Zhenevsky variation played in high level human games. In game 47 the engines exchanged pawns and knights in the center and evals came down. From move 22 the engines exchanged pieces until the game reached a QR vs QR position. Evals were low and the game was adjudicated early on move 37. 

In game 48 the engines exchanged a pair of pawns and a pair of knights in the center, like the start of the reverse game. Then the engines opened the c file and Stockfish moved a rook to the 7th rank. Stockfish's eval slowly increased while Leela's eval remained low. Stockfish moved a second rook forward, in a series of exchanges the queens were off and Stockfish gave a rook for a bishop and two pawns. The black king was exposed and white had two connected passers on the king side, Leela's eval was still low.

Leela thought for 10 minutes and its eval jumped. In a series of exchanges the engines reduced to a rook ending with white a pawn up. Leela also had connected passers but they were slower, and Stockfish had an additional passer on the queen side. Leela tried but couldn't stop the white passers, Stockfish queened twice and mated. Stockfish wins the game pair, it leads 15-9

Games 49-50 started with a the Semi-Benoni variation of the Benoni defense, the center was blocked. In game 49 there were only a few exchanges after the start, Stockfish placed a bishop on h3 and exchanged the other. Leela exchanged a pair of knights and its eval increased to over 1.5. Stockfish's eval came down, it opened the f file and gave a rook for a knight. Stockfish captured a pawn on the king side and the exposed white king walked to the queen side. Leela's eval came down, Stockfish gave another rook for a bishop and threatened the white king. Leela reacted with a threat on the black king through the open g file. The engines reduced to a QR vs QN position and the game was adjudicated. In game 50 the engines exchanged pawns and minor pieces and opened the e file. Evals stayed under 1, after a while the engines exchanged a pair of rooks and evals came down. Stockfish captured a pawn and the game reached a QRN vs QRB position. The game was adjudicated after queens were exchanged.