Season 14 superfinal statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins


Final draw rate was 81%.


Game termination

The three most common game termination causes were:

37% - SyzygyTB
29% - TCEC draw rule

19% - TCEC win rule

Moves per game


Median= 83.5
Average= 99.5

The games were much longer than in previous TCEC stages. This was mainly because Leela's evaluation is designed differently, it is reluctant to lower its eval in drawn positions and the draw rule application is delayed. There were 40 games longer than 100 moves, the longest was 362 moves (game 86, draw, new record for longest game in TCEC history).

Time per game (hours)


Median= 4:35
Average= 4:28

This is also longer than usual, not by a lot because of the increment of 15 seconds.

Openings

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


The book determined the opening in all cases, all the game pairs repeated the same ECO code twice and repeated the same opening variant.

Reverse pairs, wins


Reverse pairs, same moves 

Pairs of reverse games diverged very quickly, 70% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 19 plys (games 43-44, Sicilian Velimirovic attack, two draws).     

Season 14 superfinal, games 91-100

Stockfish won the season 14 superfinal. The final score is 10-9 with 81 draws.
The last 10 games ended in a draw and weren't that exciting, except for the anticipation at the beginning of each game to see whether it would turn out to be decisive. In the end Stockfish held on to the small one point lead to win the match.

Superfinal summary
This superfinal match has been one of the best I've seen in TCEC, if not the best so far. After several seasons of Stockfish dominance this superfinal was really competitive and the result was very close until the very end. Leela's journey in this season was remarkable, it got better every time it was updated on its way up from division 3. I was surprised that it was so close to winning based on its performance in the premier division. Recall that it was very close to Houdini and Komodo, Stockfish had a much better score.

There were many decisive games at the start of the match, Stockfish led 6-3 after 22 games, including one game pair where Stockfish won from both sides. Leela closed the gap to 6-6 after 30 games, and after 19 straight draws Leela took the lead, after 60 games it was ahead 8-7. Leela continued to lead by 1-2 points but Stockfish kept close until it equalized to 9-9 after 80 games. Then Stockfish won a game to lead 10-9 and held on to this small lead until the end.

Stockfish may have won this superfinal, but it seems likely that Leela (NN based engines in general) may be the future of computer chess. There were many games where Leela played the opening much better than Stockfish, getting to positions where Stockfish realized it was worse or losing. Leela's closing skills are still lacking, it allowed Stockfish to escape many times. There was even one game where Leela failed to convert a 7-man tablebase win, despite having access to 6-man tablebases. Some of Leela's losses were a result of not looking far enough ahead and making a losing move, sometimes realizing it was losing immediately and sometimes many moves later. To summarize, it seems Leela is already better than Stockfish in some aspects of the game, and it needs to improve its skill in converting wins and calculating ahead. There are suggestions of a hybrid approach, who knows how much better engines can get.

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Games 91-92 started with a 23 ply book sequence in the Frence Defense, Winawer variant, where both kings are still in the center and white has a king side passer. In game 91 Stockfish castled long and Leela kept its king in the center. Stockfish gave 3 pawns and moved pieces forward on the king side, Leela's eval climbed over 1.5. Stockfish then gave a rook for a bishop, its two knights attacked the king side and Leela had to be careful. The tension was resolved in a series of exchanges, Stockfish ended the game in a perpetual check. In game 92 Stockfish went a pawn up and pushed its passer to the 7th rank. Evals stayed below 1 and slowly came down. Leela blocked the pawn and slowly exchanged pieces, by move 47 the passer was gone and the game reached a rook ending. The game was adjudicated 20 moves later.

Games 93-94 started with black a pawn up and white with much better developement and a king that cannot castle. In game 93 Leela's eval started over 1. Stockfish gave back the pawn and created a passer on the queen side, then pushed it all the way to the 2nd rank. Leela controlled the center and the black king remained uncastled. Leela temporarily sacrificed a knight and opened the king side. Leela's eval jumped over 2 and then after a series of exchanges only RRN vs RRN remained on move 39. Leela tried to give a rook for a knight, but couldn't break Stockfish's defense. The game ended in a tablebase draw on move 122. In game 94 the evals stayed under 1. Stockfish traded NN for R and opened the king side, Leela gave a rook for a bishop that resulted in an unusual imbalance RR vs BBN. Evals dropped to 0 and the game was adjudicated by the draw rule on move 36, with perpetual check expected in the PV.

Games 95-96 were another King's Gambit variant, black started a pawn up. In game 95 Leela gave a second pawn and the queens were off early. Both kings moved and didn't castle, evals were negative but started to come down after move 20. Leela equalized the material, Stockfish still had a king side passer it pushed to the 3rd rank. Stockfish gave material to clear the path for its passer, then won the material back after the passer promoted. The game reached a B vs R ending and a tablebase draw. In game 96 there were many early exchanges and only RBN vs RNN were left on move 21. Leela's eval was negative over 1, Stockfish's eval dropped to 0 after the engines reduced to a BN vs R ending. The rest of the game was a long shuffle until Leela lowered its eval, and then a tablebase draw again.

Stockfish's eval stayed low in game 97, Leela's eval was under 1. The black king remained in the center, Leela gave a rook for a bishop but didn't get any initiative as a result. Stockfish gave the material back and the engines reduced to a queen ending on move 36. Stockfish ended the game in a perpetual check more than 50 moves later. In game 98 Leela pushed pawns on the queen side and had a space advantage. Only one pair of pawns was exchanged until move 20 and evals were close to 0. The engines started to exchange pieces and pawns gradually, on move 48 Leela gave a knight for pawns and the game reached a RBN vs RB position. Stockfish stopped the black passers on the 2nd rank and the game ended in a tablebase draw.

Games 99-100 started with a 26-ply book sequence in the Sicilian Najdorf opening. In game 99 Stockfish kept its king in the center, its eval was 0 after 2 moves and stayed there throughout the game. It opened the queen side and attacked with its queen, Leela's king was forced to run to the center. Leela exchanged queens so its king would be safe despite being exposed, on move 34 only RBN vs RBN remained. After exchanging rooks Leela went up two pawns, but the bishops were of opposite colors and  there wasn't enough material for a win. The game ended in a tablebase draw. Stockfish was almost sure of winning the match at this stage, one point ahead and a white bias in the last game. Leela castled short in game 100, then pushed pawns on the queen side towards the white king. Stockfish allowed a black pawn to get to b2 and hid its king behind it. Leela concentrated its major pieces on the queen side and the white king walked to the center. The engines reached a standoff, evals came down and the engines started shuffling. Thankfully, Leela reduced its eval close to 0 and the game ended quickly by the draw rule. This draw confirms Stockfish is the winner of the superfinal.

Season 14 superfinal, games 81-90

After 90 games Stockfish leads 10-9 with 71 draws.
Stockfish won a game in black, starting with a very unusual imbalance after book. Leela had another missed win, it had quite a few of these in the match. Stockfish is back in the lead after being behind from game 49. There are only 10 games left, 5 openings, are we going to see drama in the final games?

In games 81-82 black started a pawn up. In game 81 Leela pushed pawns to a6 and h6, two fawn (thorn) pawns! After several exchanges Stockfish captured the pawn on a6, it was two pawns up but its eval was 0 and Leela's eval was over 1. Leela gave a third pawn and reduced to a QRB vs QRB position, its compensation was total control of the dark squares and a mate threat on the long diagonal. Leela gave the rook for a bishop and pawns and the h6 pawn became a passer. However, Leela couldn't push its passer forward and the engines started to shuffle and trade pawns. Leela wouldn't lower its eval and pawn moves kept resetting the 50-move counter. The game ended in a tablebase draw on move 270. In the reverse game 82 evals stayed low throughout the game. Leela gave the pawn back and after a long series of exchanges only RR vs RNN were left on move 27. All pawns were on the king side with Stockfish a pawn up. The rest of the game was shuffling, a few pawn moves and exchanging a pair of rooks. The game was adjudicated on move 150.

Both engines castled long in game 83. Leela pushed pawns on the king side and had a space advantage. Stockfish countered by attacking the queen side and forcing the white king to go to the center. The engines reduced to a QB vs QB position on move 49 and started to shuffle. The game reached an opposite color bishop ending and was adjudicated. In game 84 Stockfish castled short and pushed its king side pawns while Leela kept its king in the center. Leela gave two pawns and reduced to a RBN vs RBB position on move 26, evals were over 1. After the engines exchanged the rooks Stockfish's eval dropped to 0. Despite being two pawns down Leela managed to hold, first with its bishop pair and then in an opposite color bishop ending.

Games 85-86 started with a 24-ply book sequence in the King's Indian Saemisch opening, with an unusual imbalance of Q vs BBPP, and the white king unable to castle. In game 85 evals turned negative after a few moves, Stockfish captured a pawn on the queen side. On move 24 Stockfish's eval jumped over 1.5, it captured another pawn and opened a file on the king side. The black rooks looked dangerous with the white king exposed.

Evals came down after a few moves, it seemed Stockfish didn't have the strength to attack the white king. The engines traded NN for R and made the imbalance even more unusual. Leela was left with only its major pieces, it concentrated them on the king side both as protectors for its king and as attackers on the open files. The engines exchanges a pair of rooks and evals climbed back above 1.5.

Stockfish's eval jumped over 3 and stayed there for a while. Both kings were vulnerable, Leela was down to its last pawn. On move 54 Leela thought it found a way out, it gave its rook for a knight and its pawn became a passer supported by the queen. Leela's eval dropped, it was sure the threat of promotion was enough to force a draw. Stockfish thought it was winning and its eval shot over 7. This went on for a few moves, on move 59 Stockfish saw the mate.

Only now Leela realized it was free to promote its pawn, but its king was in a mating net and there was no defense without losing material. Either way Stockfish was winning and the game ended a few moves later with mate in sight. What a game!

In game 86 Stockfish attacked the king side immediately after book and evals were positive. Leela was careful not to open the king side and it took out the two white knights, one of them for a rook. Stockfish was left with major pieces and after stabilizing the queen side pawns the black king left the king side and the engines started to shuffle. After two sets of almost 50 moves Stockfish's eval dropped to 0, but Leela's eval turned negative. Two more sets went by and then Stockfish's eval jumped again. The game went on and on, in the end breaking the record of longest TCEC game 362 moves - one more than previous record! Almost 7 hours, still a draw. Stockfish wins the game pair and is leading once again.

Queens were off early in game 87. Stockfish's eval was low and became 0 despite Leela having a bishop pair advantage. The files were closed except for an open file on the queen side, Stockfish guarded it with its pieces. On move 31 Stockfish unexpectedly moved a knight and let a white rook advance to b7, Leela's eval immediately jumped close to 3. Stockfish captured the rook for a knight, and realized it was in danger.

The engines played a line they both saw in the PV, Stockfish gave back a rook for a bishop and Leela created an advanced passer in a RB vs RN position. The white king moved forward to support the passer and the black rook moved behind the white pawns. Stockfish created its own queen side passer, forcing Leela to trade passers. Leela was still a pawn up but Stockfish reduced to a rook ending and Leela's advantage was gone. Evals slowly came down, the game was adjudicated on move 114 in a tablebase position. Leela was close to winning this game. 
In the reverse game 88 most pieces remained on the board. Stockfish had a space advantage and evals climbed over 1.5. Leela's pawns stopped moving on move 25 and the engines started to shuffle. On move 42 Stockfish traded its last knight, and without knights it was difficult to penetrate the black fortress. Stockfish agreed to lower its eval only 130 moves later, the game was adjudicated on move 189.

In game 89 all pieces remained on the board for the first 14 moves and the first pawn exchange was on move 23. Leela's eval started over 1 and climbed to around 2 though material was equal and there was no visible advantage. The engines cleared most of the queen side pawns and started to shuffle on move 32. Leela acknowledged that it had nothing 40 moves later and its eval dropped. Leela gave a rook for a bishop and broke through the black pawn line, Stockfish sacrificed a rook and ended the game in perpetual check. In game 90 there were a few early piece exchanges and Leela captured the b2 pawn with its queen. Evals were under 1, both kings did not castle. The engines exchanged queens and opened the queen side, then reduced to a RRN vs RRB position on move 28. After a long shuffle the engines lowered their evals and the game was a 50-move draw.

Season 14 superfinal, games 71-80

After 80 games Stockfish evens the score to 9-9 with 62 draws.
There were 9 draws, in which Leela had 2-4 missed opportunities to win. Then came game 80, a spectacular game. Leela's evaluation was misleading and Stockfish won with two white queens on the board.

There were almost no exchanges in the first 35 moves of game 71. The center and queen side were blocked by pawn lines, Leela concentrated forces on the king side and its eval steadily increased. Stockfish's king ran to the queen side as Leela opened the g file and white pieces moved forward into black territory. Leela's eval peaked over 5, Stockfish also thought it was in trouble with an eval over 2.

Leela's attack seemed to lose steam at this point. The white pieces couldn't attack from the king side, the white king was exposed and Stockfish threatened to attack with its queen. Leela gave a rook for a bishop and got a passer to the 7th rank, Stockfish blocked with a rook and its eval dropped to 0. Leela's attack was over and the game was adjudicated 20 moves later. Was this another missed chance for Leela?

In the reverse game 72 there were more exchanges and the position was open. Evals started around 1 and gradually came down, despite the fact that Leela gave a rook for a knight. Leela had two forward knights near the white king that looked intimidating. In a series of exchanges the game reached a Q vs QN position, Leela 3 pawns up. Stockfish exchanged queens and was in time to stop the white pawns with its knight, resulting in a draw.

There were many early exchanges in game 73, only QBN vs QBB were left on move 26. Leela had a queen side passer, Stockfish's eval was 0. The engines reduced to a queen ending and Stockfish gave checks for almost 50 moves. The game was adjudicated when Leela lowered its eval enough for the draw rule. In game 74 Stockfish was up a pawn with a queen side passer and eval above 1. Leela created a pawn line across the board and the engines started to shuffle from move 22. After about 50 moves there were several exchanges and evals came down, then the engines resumed shuffling. The game ended in a draw by the 50-move rule.

In game 75 evals didn't move a lot after the opening. By move 25 the engines cleared two files on the queen side, all pieces were still on the board. The center was locked, then all rooks and queens were exchanged off by move 35. Evals started to increase slowly though material was equal, Leela's eval reached over 2 and stayed there for another 20 moves. Then Leela pushed pawns on the king side and its eval jumped over 4.5.

Leela had a bishop pair and a queen side passer, Stockfish's pieces had very little space. However, Leela seemed to have no plan how to continue and the engines shuffled for 30 moves, Leela's eval slowly decreasing. The engines cleared the king side pawns and Stockfish's eval dropped. The black bishop was free to move, Leela's advantage was over. The game continued until reaching a tablebase draw on move 159.

There were more early exchanges in game 76, and several minor pieces were off. Stockfish attacked on the king side but wasn't strong enough. Leela gave a pawn in the center and evals came down. Mostly major pieces remained, Leela covered the back ranks and didn't allow the white pieces to get there. The position stabilized and the game was adjudicated by the draw rule.

Games 77-78 started with a 23-ply book sequence in the Benoni Defense. There were many early exchanges in game 77, only QRR vs QRN remained on move 21. Stockfish was two pawns up and its eval was 0. The engines shuffled for a while when Stockfish's eval jumped over 2, it was convinced Leela had an advantage. This lasted for a few moves, then Leela exchanged a pair of rooks and opened the king side, Stockfish's eval fell back to 0. Leela's king was exposed and Stockfish had a perpetual check draw. Leela agreed to the draw on move 117. In game 78 there were only a few exchanges. Stockfish's eval stayed around 1, Leela blocked the board with a pawn line and the engines started to shuffle on move 33. Leela had a central knight that attacked two weak white pawns, forcing Stockfish to keep a defending piece for both. After 30 moves Stockfish opened a file on the king side, and for a brief moment its eval jumped close to 2. Leela remained calm despite being low on time, it captured a pawn on the queen side and evals fell immediately down to 0. Stockfish couldn't attack when it had to keep an eye on the black queen side passers. The engines shuffled and exchanged pieces until adjudication on move 149.

The position was closed in game 79 with very few exchanges. Leela had a space advantage, its eval was over 1 and it increased slowly. The queen side was blocked, Leela had a knight pair which is better in closed positions, Leela's eval went over 2.5. The engines shuffled pieces and pushed pawns on the king side until it was also locked. On move 90 Stockfish gave a rook for a knight and the engines continued to shuffle with evals coming down. On move 140 Leela traded its other knight and gave up its advantage. The game was adjudicated on move 191.

In game 80 the position was again closed. Stockfish had a space advantage and eval over 1, it preferred trading a knight for a bishop so Leela had the knight pair. Stockfish pushed pawns on the king side, Leela blocked with its pawns. Evals started to increase when Stockfish gave a knight for pawns and broke through the center. Stockfish followed with a knight for rook trade and its eval jumped over 3.



After exf7+ Leela moved its king to h7, assuming that Stockfish would take the knight, more or less equalizing material. Stockfish however chose to promote on f8, safe because of the pinned bishop. This cost a white rook but now Stockfish had an unusual 2 queens. Stockfish's eval shot up, Leela was incredibly cool.



Leela's eval started to react to the situation only on move 47, much too late. Stockfish's queens dominated the board and Leela couldn't stop them. The game ended with mate a few moves away. An incredible game, quite unexpected behavior by Leela. Stockfish wins the game pair and evens the score of the match.

Season 14 superfinal, games 61-70

After 70 games Leela leades 9-8 with 53 draws.
Each engine had one game pair win and Leela continues to lead by one point. Games 65-66 were the highlight. Leela had a winning 7-man position but couldn't convert in game 65. Then a network failure stopped game 66 which was then replayed twice. In the second replay Stockfish won. Leela fans were not happy...

There were many early exchanges in game 61, only RRN vs RRN were left on move 25 and evals stayed low. Leela's king was in a better position but not enough to make a difference. The engines reduced to a drawn rook ending. Evals stayed low in game 62 as well. The engines castled in opposite directions but the kings were not seriously under attack. Leela went a pawn up and its eval became negative. After a while the engines started to exchange pieces, on move 44 the game reached a rook ending. Draw was agreed more than 30 moves later.

Games 63-64 were a French Defense variation with a blocked center and a black king that moved, Leela was expected to do well. In game 63 Leela's eval was slowly increasing until move 16, then it jumped over 2.5. Stockfish was a pawn up, it seemed to disregard the danger to its exposed king and its king side rook trapped in the corner.

Stockfish quickly exchanged queens, Leela gave a pawn and its king side pawns started marching, only then Stockfish realized it was in trouble. It tried to keep the files closed so the white rooks won't come forward. Leela was 3 pawns down but its eval was close to 5.

Stockfish gave a pawn back and tried to get its trapped rook free. Leela used the time to move a rook to support the f pawn and push it forward. When it promoted Leela was a rook up and the game was over.

In game 64 both kings remained uncastled and the queens were off early. Evals slowly came down and after the pawns stabilized on move 24 the engines started to shuffle. This continued for 60 moves, with one pawn move that reset the 50-move counter. The engines then exchanged a few pieces and ended the game in a repetition. Leela wins the game pair and the lead is back to 2.

Leela started game 65 with an eval 1 and increasing. After the queens were exchanged on move 34 Leela's eval was close to 3. Material was equal but Stockfish had 3 weak pawns. Leela was patient, it took 30 moves to arrange the pieces, exchange pieces slowly and win a pawn. The game reached a 7-man position on move 73.

This was winning for white, both engines agreed. Stockfish calculated a winning line, Leela's eval remained below the win rule threshold. It seemed Leela was shuffling without a plan, the line Stockfish showed in the PV was long and slow with a pawn move many moves ahead. Leela couldn't find the right sequence of moves, its eval slowly came down. After 40 shuffling moves Stockfish realized it was too late and its eval dropped to 0. The game ended in a tablebase draw on move 143.

Game 66 looked drawish after 20 moves but then there was a network failure and the game had to be replayed. There was a long wait, the first replay was aborted as well (I don't know why, it happened while I was away from the screen. There were rumors of a Windows update). The second replay of game 66 worked. Evals were around 1 from the start, Stockfish didn't castle and kept its rook on the h file. It offered a knight but Leela wouldn't take since that would open the h file and its king would be in danger. It was clear Stockfish was better but Leela seemed to be holding. On move 37 Stockfish pushed a pawn on the king side and opened the g file. Then without warning Stockfish's eval jumped over 6.

Leela immediately saw the problem, its PV showed the game continuation. Why didn't it see it a move earlier?? Leela's king was under attack, after a series of exchanges Stockfish won a little material and the game reached a RRB vs QB position, Stockfish 3 pawns up.

The black king was in danger and Stockfish had 2 potential passers on the king side. All Leela could do was give checks with its queen, but only for a short while. Stockfish gave a rook for a bishop and created a third passer, the game was quickly over. After another unexpected save in the previous game Stockfish completes a game pair win and reduces Leela's lead to 1 again.

Games 67-68 were a variant of the King's Gambit. There were many early exchanges in game 67, by move 22 only RN vs RBN remained and Leela was 3 pawns up. Evals came down, Leela had two passers on the king side which Stockfish blocked. Leela's king moved forward on the queen side, the engines exchanged knights and Leela captured another pawn. Leela had the initiative but Stocofish made sure the white pawns didn't promote, the game ended in a draw. In game 68 the queens were off early, evals stayed below (negative) 1. The engines continued to exchange pieces until they reached a rook ending on move 34 with Leela a pawn up. Both engines had passers, one pawn advantage was not enough for more than a draw.

In games 69-70 white was a pawn up from the opening. In game 69 the engines castled in opposite directions. There were several exchanges after the start, Leela captured a rook for a bishop, all the pawns on the king side were gone except a black doubled pawn. Leela's eval was over 2 for a while but Stockfish was solid, it captured a pawn on the queen side and reduced to a QRB vs QBN position on move 30. Evals came down and Stockfish ended the game with a perpetual check draw. In game 70 both engines castled short, evals stayed around 1 and all pieces remained on the board until move 23. The engines then removed all the queen side pawns and reduced to a QR vs QB position on move 41. Stockfish wouldn't lower its eval, the engines shuffled for almost 50 moves before adjudication.

Season 14 superfinal, games 51-60

After 60 games Leela leades 8-7 with 45 draws.
Leela won another game pair, extending its lead to 2. Leela also had a very near miss in a game where both engines were convinced it was going to win. Stockfish finally won a game pair after 35 games without a win, reducing Leela's lead to 1 again. 

After many early exchanges in game 51 Stockfish's eval was 0 while Leela's eval was over 1. The game reached a QRN vs QRN position on move 34 and the engines started to shuffle. Leela's eval slowly came down. After exchanging queens the engines started to trade pawns and the game ended in a tablebase draw. In game 52 the pieces stayed longer on the board as well as most pawns. Evals were low when the queen side opened. Stockfish had a passer on the queen side but Leela captured it. Then Stockfish opened the king side and pressed on the g file. Leela blocked with a knight and kept the file closed. A series of exchanges ended the game in a tablebase draw.

Leela started game 53 with an eval over 1. It pushed its king side pawns and opened the black king side. The white king walked to the king side, Leela didn't want to move the rook. Stockfish didn't like either side of the board for its king and didn't castle. The center was blocked, Stockfish played on the queen side and captured a pawn, Leela's eval jumped over 2 as it gave another pawn and opened the king side. After 17 minutes of thinking Stockfish realized it was in trouble.



The engines exchanged queens and traded pawns. Stockfish had connected passers on the queen side, its knight on the sideline. Leela had a bishop pair, it controlled the center and could attack the exposed white king. Leela won a rook for a bishop and evals were over 3.



As we have already seen in other games, Leela does not take the fastest route to finish a game. The material advantage was not overwhelming and Stockfish had a chance of drawing if Leela took a wrong turn. Leela captured the queen side passers and reduced to a RR vs RB ending, with two white pawns and one black. It took 50 moves for Leela to move each pawn one square forward, this was enough for Stockfish to raise its eval above 10 and the game was adjudicated.

In game 54 Leela castled long and found safety for its king. Stockfish went a pawn up but its eval came down towards 0. Leela regained the pawn and the game reached a RRB vs RRB position on move 26. The engines shuffled and exchanged pieces and pawns, the game ended in a tablebase draw. Leela extends its lead to 2 after winning the game pair.

Leela started game 55 with an eval over 1, and it started to increase from move 13. Stockfish moved its pieces to the queen side, the center was blocked and Leela was stronger on the king side where the kings were. Through an exchange Leela managed to get a pawn to f6, the black king was alone defended by a pawn line. Stockfish rushed the queen to help, the game reached a QRB vs QRB position and the engines started to shuffle. Leela's eval was over 3, Leela hesitated more than 30 moves before it attacked the king side with its pawns.The king side opened, the engines exchanged queens and Leela's eval jumped over 7.

Leela pushed the h pawn and allowed the black rook to attack the white king, suddenly Stockfish's eval dropped. Leela couldn't escape the checks without letting the rook attack the white pawns from behind. Leela realized it couldn't win anymore and its eval dropped, but not to 0. The game was adjudicated only on move 264. This really looked like a won game for Leela, a very lucky escape by Stockfish.

In the reverse game 56 evals started around 1. Most pawns remained on the board, Leela concentrated on the queen side, Stockfish was more passive and did not attack the king side. Evals came down, the engines created pawn lines across the board and started to shuffle.This went on for a long while, in the end the engines reduced to a B vs N ending and the game was adjudicated on move 137.

In game 57 Leela's eval jumped over 1 when the engines exchanges queens. The game reached a RRN vs RRN position on move 31 and the engines began shuffling. It took a long time for Leela to lower its eval, the game ended in a tablebase draw on move 140.
In game 58 Stockfish's eval was around 1. Most pawns remained on the board, the engines castled in opposite directions. The black king was a little exposed but it seemed Leela had everything under control. On move 30 Leela completed 3 straight moves with a knight on the king side and Stockfish's eval jumped over 1.5 on the last one. It opened the king side, two rooks on the h file pinned the knight. A few moves later the white queen joined and added pressure, Stockfish's eval over 2.5.

The knight on h7 couldn't move and it needed 3 defenders, causing Leela's king side to freeze. Stockfish needed to unpin its knight on e3 and get the minor pieces involved in the attack. Eventually the engines exchanged all the knights, Stockfish broke through the h file with only QRB vs QRB remaining.

The black king was caught in the crossfire, Stockfish managed to create a queen side passer, exchange pieces and promote the pawn, reaching a QQ vs Q position. The game ended with mate within reach. Stockfish wins the game pair, after 35 games without a win. Leela's lead is back to 1.

Games 59-60 started with a long 31-ply book sequence of the Sicilian Dragon, Yugoslav attack. The position was very double edged, with white threatening to open the king side and attack the black king, and black with attacking potential on the queen side. The outcome however was two very fast draws. In game 59 Stockfish's eval was 0, it opened a file on the queen side and threatened the white king. Leela had no time for its own attack and the engines agreed to a draw on move 31. In game 60 Stockfish opened the king side, Leela reduced to a QR vs QR position and attacked the white king. Stockfish ended the game in a perpetual check on move 41.

Season 14 superfinal, games 41-50

After 50 games Leela leades 7-6 with 37 draws.
Finally a decisive game after 19 straight draws. For the first time in the match Leela is in the lead.

Leela's eval started above 1 in game 41, it increased rapidly and was over 2 on move 12. Stockfish was up a pawn, the engines castled in opposite directions, the white king was exposed on the queen side but relatively safe. It was the black king that seemed threatened by Leela's pawns and pieces. After exchanging queens Leela's eval jumped even higher and Leela regained the pawn. There was no immediate threat but Leela saw a long term advantage, perhaps its king side pawn majority.



Stockfish exchanged down to a knight ending on move 35. Leela's eval remained over 2 as the engines shuffled. After a while Stockfish's eval came down to 0 and Leela's eval started to decrease slowly. The game ended in a tablebase draw on move 175.
In the reverse game both engines didn't castle and both kings moved forward. Leela gave a bishop for 3 pawns, clearing the queen side and exposing the white king. Stockfish protected its king with its pieces. Evals came down and the game reached a RNN vs RB position on move 39. Leela pushed a pawn to the 7th rank before the game was adjudicated by the draw rule.

Games 43-44 started with a 21-ply book sequence of the Sicilian Velimirovic attack opening. The games diverged only on move 21 with castling in opposite directions and evals around 0.5. In game 43 Stockfish's eval was 0. Leela attacked the black king, Stockfish countered on the queen side and captured two pawns. The game reached a QRB vs QRN position with both kings exposed to checks. On move 63 the engines reduced to a queens ending, a draw was agreed 30 moves later. In game 44 the engines reduced to a RB vs RB ending on move 27. Evals came down quickly, after exchanging the rooks the game was adjudicated in an opposite color bishops position.

Evals were low at the start of game 45. Leela pushed pawns on the king side and Stockfish pushed pawns on the queen side, with almost no exchanges until move 23. Then a long series of exchanges left a RBB vs RBN position on move 33, Stockfish was a pawn up with an advanced passer and a weak knight, its eval was 0. Leela's eval slowly came down as the engines shuffled. The game continued with a few exchanges until adjudicated on move 128. In game 46 the engines kept the pieces on the board and exchanged only a few pawns, the first piece exchange was on move 38. The engines shuffled and exchanged pieces for a very long time. The game reached a N vs B ending and the engines agreed to a draw on move 173.

There were many early exchanges in game 47, the game reached a RRB vs RRB position on move 26, Stockfish's eval was 0. After exchanging a pair of rooks Leela gave the bishop for 4 pawns, there were only white pawns left, 3 on the queen side and 1 on the king side. Leela thought it was better with an eval over 2, but it couldn't break Stockfish's defense. It tried to push the pawns forward, Stockfish captured 2 pawns and forced a draw. In game 48 Stockfish pushed pawns on the king side and left its king exposed. Leela castled short with a white pawn on h6, evals stayed below 1. Stockfish opened the king side on move 33 and evals jumped, the game reached a RNN vs RBN position withevals close to 1.5. However Stockfish could only capture a pawn, it had a doubled passer that Leela blocked and evals gradually came down. The engines shuffled in a BB vs BN ending, the game was adjudicated on move 129.

Leela started game 49 with an eval over 1. Using a knight maneuver it managed to get a protected passer to e6 and its eval jumped over 2.



Stockfish focused on blocking the passer, Leela exchanged pieces gradually as evals crept slowly upwards. Stockfish started to feel the danger, its defenders were cramped and its king also had to be protected. Leela's eval jumped over 4, Stockfish finally got rid of the white passer and after a series of exchanges only RB vs RN were left.



Material was equal but the black pawn structure was a mess. Leela pushed its king side pawns and created connected passers. The game was adjudicated with Leela two pawns up in a winning position. First decisive game after 19 draws.

In the reverse game Stockfish's eval was around 1 after the start. The engines played a long PV agreement line that resulted in a RRN vs RRN position on move 22. Stockfish went a pawn up but the engines kept exchanging pawns and pieces until the game reached a tablebase draw on move 42. Leela wins this game pair and is leading the match.

Season 14 superfinal, games 31-40

After 40 games the score is even at 6-6 with 28 draws.
There were 10 straight draws, increasing the draw rate to a more normal 70%, still low for a superfinal.

Leela's eval was around 1 after the start of game 31. It castled long and pushed its king side pawns. Stockfish also castled long though the queen side was open. Stockfish's eval came down to 0 after the queens were off, and both kings came forward. After a series of exchanges the game reached a R vs BN ending on move 33. The engines traded pawns until only two white pawns remained, Stockfish was able to hold the draw. In the reverse game the engines opened the king side, Stockfish's eval started below 1 and gradually decreased. The queens were off early, Stockfish castled long and Leela didn't castle at all. Stockfish had a king side passer it couldn't support, after it was gone the engines reduced to a RN vs RB position. It took Leela 35 moves to lower its eval for adjudication.

Games 33-34 started with a long 21-ply book sequence in the King's Indian, Saemich opening. Both games then continued to play the same moves with first divergence on move 19. In game 33 Stockfish's eval dropped to 0, and after a series of exchanges the game reached a double rook ending on move 27. After exchanging a pair of rooks Leela went two pawns up, Stockfish countered with an advanced passer and secured a draw. In game 34 the pieces remained on the board longer. Evals came down to 0 and Leela's eval turned negative, it pushed pawns on the queen side facing the white king. The engines mostly shuffled pieces and then exchanged down to a RR vs RN ending and agreed to a draw.

Games 35-36 were a French Defense variant, a favorite opening for Leela. In game 35 Leela's eval was over 1 and increasing from the start. Stockfish locked the center, Leela was free to operate on the king side and its eval was over 2. The black king walked to the queen side to get away from danger, Leela opened the king side and its eval was close to 3. Stockfish had some counterplay on the queen side but it seemed that Leela was about to win.

Leela perhaps hesitated or wasn't sharp enough, suddenly Stockfish had initiative on the queen side and evals were heading down. Stockfish captured a rook for a bishop, then it gave a second bishop to remove the passer on h6. When the black queen joined the attack on the queen side Leela had to be careful not to get mated, Stockfish's eval came down to 0. Stockfish won a bishop and started to give checks. It took 90 moves to convince Leela it was only getting a draw out of the game.
In game 36 the position was closed and there were almost no exchanges at the start of the game. Stockfish's eval came down to 0 and Leela's eval turned negative again. The engines exchanged pieces gradually, opening the position. The game reached a RB vs RB ending on move 54 and ended in a tablebase draw 50 moves later.

Stockfish's eval was 0 throughout game 37. Both engines castled long and then slowly exchanged pieces. On move 38 only QRN vs QRB remained, on move 53 the knight and bishop were also gone. The game went on until move 121 before draw adjudication. In game 38 Leela kept its king uncastled in the center and built a fortress around it. Evals came down to 0, Leela attacked the white king on the queen side and its eval turned negative. Nothing came out of the attack, evals became positive again when Stockfish created a pair of connected passers on the queen side and exchanged queens. The game reached a BN vs BB position, Stockfish trapped the black LS bishop in the corner and Leela pushed a passer to the 7th rank on the king side. Neither engine could win and after 50 moves the game ended in a draw.

Games 39-40 were a King's Gambit variant. black started both with a significant eval advantage. In game 39 material was equal but Leela's pawn structure was ruined. After exchanging queens evals moved towards 0. Stockfish went a pawn up and created a queen side passer but it was a doubled pawn. The game reached a drawn opposite color bishops ending and continued until move 171. In game 40 queens were off very early, Stockfish's king did not castle and moved forward. Stockfish traded R for BN and was two pawns down, its eval down to 0 on move 19. The game reached a BN vs R ending on move 33. Leela pushed a pair of connected passers on the queen side, Stockfish gave a knight to capture one of them. The game ended in a tablebase draw.

Season 14 superfinal, games 21-30

After 30 games the score is even at 6-6 with 18 draws.
Stockfish had a rare double win in a game pair, at least one win was caused by an unusual blunder by Leela. On the other hand Leela won 3 game pairs and the score is even. The draw rate is an unprecedented low 60% so far.

Leela was up a pawn from move 16 in game 21, its eval over 1. The position was open, Stockfish had a central passer that wasn't going anywhere. Leela didn't seem to have a plan, its pawns remained in their initial squares, it moved its pieces to the first rank and then the white queen went forward alone into Stockfish territory. Stockfish's eval came down, it used the white queen as a target and took the initiative, even to make threats on the white king. Then very suddenly Stockfish's eval plunged to -4!!

Leela made a huge blunder, overlooking a simple combination (at least for a computer...). Analysis shows that after taking the bishop black can reach a winning BNN vs Q position, the trick is getting the white king to the e file and using a discovery check to win the white queen. Leela immediately saw that but one move too late. Stockfish won the rook for a bishop, the white king was under attack in the center and the white pieces pinned. Leela tried to untangle itself by exchanging pieces but lost more material, the game was adjudicated with Stockfish a rook up.

In game 22 evals were also around 1 from the start. Leela moved its king very early in the game, so it couldn't castle. It even moved its king forward to connect the rooks on the back rank. Stockfish captured a pawn and created a passer on the queen side, Leela countered on the king side and seemed to be holding, evals stayed around 1. Stockfish added a second passer on the queen side, Leela had two of its own. Then Stockfish's eval jumped over 2.5 without an obvious explanation. On move 35 Stockfish offered a pawn on the queen side.

It expected Leela to move c4+ (discovered check), exchange queens and continue to an endgame where Stockfish thought it was better. Instead Leela accepted, and suddenly the white queen attacked the king side while the black queen was too far to help. Stockfish's queen and knight were very effective, while Leela defended with two rooks. After a few moves Stockfish saw the mate and the game was adjudicated. A rare double win for Stockfish in this game pair.

In game 23 Leela had a space advantage and its eval climbed over 1.5. Stockfish remained calm and built a long pawn line across the board. Leela couldn't penetrate the line and the engines started to shuffle. After a few exchanges Leela managed to create a passer, Stockfish countered with a perpetual check draw. In the reverse game Stockfish pushed pawns on the king side, Leela countered with its queen side pawns. Evals came down to 0 and the engines exchanges pieces gradually. After a while Leela's eval became negative, still the engines shuffled and exchanged pawns and pieces, eventually reaching a B vs N ending on move 84. The game was adjudicated a draw almost 100 moves later.

Leela started game 25 with an eval around 1 while Stockfish's eval remained low. After about 30 moves evals started slowly to increase. The engines opened files and exchanged pieces, it was not clear what Leela's advantage was at this stage. On move 40 only RRB vs RRB remained, Leela's eval crossed 2.5, Stockfish's was still under 1.

The black bishop could hardly move, but it had to defend the d5 pawn and Stockfish assigned a rook to protect it. After exchanging a pair of rooks Leela's king moved forward and helped open up the king side. Stockfish's defense collapsed and Leela reduced to a winning king and pawns ending. Unusual to see Leela outplay Stockfish in an endgame.

In game 26 Leela kept its king uncastled in the center while it pushed pawns on the king side. The king side opened, Stockfish hid its king behind a black pawn and its eval fell to 0. Leela's eval turned negative and the engines started to exchange pieces. by move 39 only RRN vs RRB remained and both evals were at 0. The game reached a drawn rook ending and was adjudicated. Leela is only two points behind.

Evals were low after the start of game 27. Stockfish traded its knights for Leela's bishops early in the game, then Leela gave two pawns on the king side and evals jumped over 1. A few moves later Leela got one of the pawns back and the evals were above 2.

The threat was f6, attacking the bishop and winning the h pawn - an open h file could be deadly. Indeed f6 was played after a short delay, and in a series of exchanges Stockfish lost the bishop and the h pawn.

In a second series of exchanges the engines reduced to a RNN vs RB ending. Leela was careful to keep at least one pawn and not to exchange rooks. It took a while, Leela doesn't always pick the shortest route, but it managed to convert the win.

In the reverse game 28 there were no exchanges except a pair of pawns until move 38. The engines opened the position with a long series of exchanges, and evals dropped to 0. The game reached a RR vs RN ending with Leela two pawns up. Leela's eval turned negative but this only delayed the adjudication, draw on move 178. Two game pair wins in a row for Leela, Stockfish's lead is reduced to 1 point.

Leela's eval was over 1 after the start of game 29, Stockfish's eval remained low. The position opened after an early series of exchanges. The black queen captured the b2 pawn, this made it a target for the white rooks. Leela's eval jumped over 2 when it pushed a pawn to h6.


There was no king side attack, the black queen scrambled back and Stockfish exchanged off the minor pieces. Leela had a significant space advantage, the black pawn structure had many weaknesses. The game reached a double rook ending with evals over 4.

The kings moved forward and the rooks were all focused on the e6 pawn. Leela was able to trade the black e6 pawn with its f pawn and to push a white pawn to e6. The black pieces could hardly move, Stockfish saw the mate coming and the game was adjudicated.

In game 30 the position remained closed. Stockfish started with an eval around 1 but it remained there as the engines mainly shuffled. Leela's evals dropped below 0 after a series of exchanges on the queen side. The engines continued to shuffle for a very long time, moving a pawn or exchanging pieces occasionally to reset the 50-move counter. Only after the position opened, both engines queened and the checks started, did both engines lower their evals enough for the draw rule. The game lasted for 233 moves. Leela evens the score after 3 straight game pair wins.

Season 14 superfinal, games 15-20

After 20 games Stockfish leads 4-3 with 13 draws.
There have been 7 straight decisive game pairs. This is quite unexpected in a superfinal, the current draw rate is 65% which is quite low. 

In game 15 Leela castled long and Stockfish pushed its queen side pawns forward. Leela was better on the king side but it was too busy defending its king. A series of exchanges removed Stockfish's threats and the game ended quickly in a tablebase draw.
Game 16 started with a similar setup. Stockfish castled long and Leela pushed its queen side pawns. This time Leela was slower with its queen side attack, instead it broke up the white king side pawn structure, moving a rook so it couldn't castle. Leela captured a pawn, allowing Stockfish to take over the open h file with the black king in the center. Stockfish's eval jumped over 2 as it found a great outpost for its LS bishop, attacking from the queen side.



WIth the king trapped in the middle Leela didn't stand a chance. In a QRB vs QRN position Stockfish opened the center with its pawns and had enough strength to force either mate or significant material loss. Stockfish is back in the lead after this game pair.

In games 17-18 white started a pawn up in a Budapest Defense opening. Leela started game 17 with an eval around 1, then it gave back the pawn and its eval climbed over 1.5. On move 20 Stockfish captured a knight and expected it to be retaken by the white queen. Leela surprised with a retake with the pawn, its eval jumped over 3.



Stockfish traded its queen for two rooks leading to an unusual QBB vs RRNN position. Stockfish tried to build a fortress, it put its queen side pawns on dark squares based on c7, and tried to block the light squares with a protected knight on e4. It couldn't prevent Leela's LS bishop from getting to the queen side, and a mate threat caused the fortress to crumble.



Leela pushed its king side pawns and captured the c7 pawn, the game was adjudicated after Stocfish lost one of the knights.
In game 18 Leela exchanged queens early. Stockfish kept the pawn advantage, its evals stayed below 1. The game reached a RRB vs RRB position on move 22, evals came slowly down as the engines traded pawns. When only one white pawn was left Leela's eval became negative. It captured a rook for a bishop, the position was a 7-man draw that went on for 25 more moves. A win for Leela in the game pair and the score is equal again.

Leela started game 19 with an eval over 1. After a series of exchanges only QRN vs QRB remained on move 24, Stockfish's eval was 0 after exchanging queens. Leela insisted that the game would continue, it lowered its eval only 100 moves later in a drawn N vs B ending.
In game 20 evals stayed mostly below 1. A long series of exchanges that started on move 18 opened the board up, and led to a R for B imbalance. Leela was up a pawn and had an advanced pawn-bishop pair on the queen side.



Leela pushed the c passer forward and moved its pieces to support the queen side. Its bishop and two pawns looked very dangerous, even more when it captured the a2 pawn. Leela's eval was close to 0, it was sure that its advanced passers compensated for Stockfish's small material advantage. Stockfish surprised with a knight sacrifice, its eval jumping to 2.5.


This exposed the black king. Leela understood the danger only 3 moves later, too late. The white QRR attacked the black king, Leela did not have enough defenders and it started to lose material. Stockfish gave material back to remove the black queen side passers, the game reduced to a R vs B ending and a win for Stockfish. After this game pair win Stockfish is back in front.

Season 14 superfinal, games 11-14

After 14 games the result is 2-2 with 10 draws.
Leela equalized with two straight game pair wins. Stockfish's early lead is gone, and we have a real match this superfinal. 

Games 11-12 were a French opening variant, one of Leela's preferred openings. In game 11 Stockfish played unusual moves from the start, and Leela's eval was close to 2. The center and queen side were blocked, Leela shifted its pieces to the king side where it had a large space advantage. Stockfish saw the danger and its king started to walk to the queen side.


There was no contact between the opponents, Leela patiently arranged its pieces while evals increased. Stockfish tried to free its pieces by pushing the king side pawns, as a result the king side opened. All Stockfish could do was protect its pieces, it was almost paralyzed and too many black pieces were too far to help.


Leela continued to improve slowly. It created a passer on the g file and exchanged a pair of knights to get rid of a useful defender. Evals climbed fast though material was equal. Leela offered a rook for a bishop, Stockfish knew better since accepting would give Leela a second connected passer on the 6th rank.


Finally the tension was released with a series of exchanges starting on move 46, as a result Leela was a pawn up with two passers on the king side. A few moves later Leela won a second pawn and the game reached a QRB vs QRB position. Leela continued to move slowly, it wasn't looking for the fastest way to win. The game continued until move 76, it was adjudicated with Leela 4 pawns up. First win for Leela.

The engines played differently in the reverse game. The center and queen side were open and Leela castled short. Stockfish had an eval around 1 for 25 moves, but then it came down. Both engines had advanced passers, Leela captured a rook for a knight and Stockfish could end the game with a perpetual check. Instead the game continued, the engines exchanged pieces until only N vs R remained. Leela kept a small negative eval, both engines queened and the game was adjudicated only 40 moves later. Leela wins its first game pair of the match.

In game 13 Leela pushed pawns forward on both sides of the board without castling. The black pieces were pushed back, Leela had a significant space advantage and a small eval advantage despite its king in the center with only one pawn defender. It even managed to push a pawn to h6, kingcrusher's famous thorn (fawn?!) pawn.


Stockfish broke through the queen side, giving a rook for a bishop and two pawns. Leela's eval jumped over 2 while Stockfish still felt safe. 


The engines exchanged pieces gradually and Stockfish's eval started to climb. The game reached a RN vs BN position on move 40, Stockfish was up 3 pawns but its king and pieces were far away and the queen side pawns looked weak.


Stockfish traded two pawns, which left Leela with only one. However it was a queen side passer and Stockfish could only stop it by losing its knight. The black pawns did not compensate for a rook, a win for Leela. 

In the reverse game Stockfish castled its king and didn't push pawns forward. Evals came down to 0, and Leela's eval turned negative on move 27 with almost all pieces still on the board. The engines exchanged pieces gradually, by move 54 only QRN vs QRN remained and the quuen side pawns were all gone. The game was adjudicated a draw on move 87.

Season 14 superfinal, games 1-10

The season 14 TCEC cup is over, Leela is the winner. Leela had a long semifinal match against Komodo, after 16 consecutive draws Leela beat Komodo from both sides of an opening to win the match. The second semifinal between Houdini and Stockfish was also long, after 11 draws Houdini beat Stockfish after drawing the reverse. Stockfish's loss was surprising, though Houdini has shown it can be better in shorter time controls. I don't think there is doubt that Stockfish is better than Houdini, even if it loses games on occasion. In the final Houdini and Leela started with 7 draws, and another long match was expected when Leela beat Houdini in the 8th game and won the cup.

This season Leela has shown that it can compete with the best engines, better than I anticipated after the previous season. Stockfish was clearly better in the premier division, but Leela gets better from event to event. This superfinal should be exciting, the engines have different playing styles and different approaches to evaluation.  They may make moves that surprise their opponent as well as the spectators. I hope we see exciting draws, wins for both engines and a close result.

After 10 games Stockfish leads 2-0 with 8 draws.

Games 1-2 started with white a pawn up and the center pawns cleared. Game 1 reached a R vs BB imbalance on move 26 after a series of exchanges. Leela was two pawns up with a queen side passer, its eval was over 1 for a long while. Stockfish's eval dropped to 0, the engines mostly shuffled in a RN vs BBN position. Eventually after more exchanges Leela's eval dropped to 0 as well, the game ended in a tablebase draw on move 131. In the reverse Stockfish had an eval over 1 for 40 moves, the game reached an BN vs R imbalance with more pieces on the board, but reduced to a BN vs R position later. Leela had a queen side passer and evals dropped to 0 as it pushed it forward. After a long shuffle Stockfish countered with a passer on the king side, the game reached a tablebase draw on move 116.

In game 3 queens were off early, the engines gradually exchanged pieces until reaching a rook ending on move 36. Leela had a pair of connected passers on the queen side and it remained hopeful for a while. Stockfish countered with its pawns on the king side, and this was enough to hold a draw. In game 4 Stockfish had a small eval advantage, there were several early exchanges but the queens stayed on the board until move 30. The engines targeted the pawns, and by move 37 only two pawns were left for each engine. Evals dropped to 0, Stockfish could close the game with a perpetual check but changed its mind at the last move. In the end the draw rule adjudicated the game.

Leela's eval jumped over 1 after a few moves in game 5. It exposed the black king and pushed pawns on the king side. Stockfish exchanged pieces to stop the attack, then gave a knight for two pawns and reduced to a BN v B ending. Leela needed 30 more moves to lower its eval, the game ended in a tablebase draw. Stockfish started game 6 with an eval advantage,but its eval dropped to 0 by move 22. Leela's eval became negative, it threatened the white king on the queen side and Stockfish's pieces had less space to move. Stockfish reduced to a rook ending, and 40 moves later the game ended in a tablebase draw.

Games 7-8 were a King's Gambit variant, both started with black a pawn up and a significant eval advantage. In game 7 Leela castled short and Stockfish pushed its king side pawns forward. Leela pushed pawns on the queen side and captured a free pawn, but it delayed the development of the queen side pieces. Stockfish thought Leela's 15th move was a blunder, its eval jumped over 1.5 as it used its king side pawns to expose the white king.


Leela gave a rook for a bishop and Stockfish's eval was already over 4. Stockfish gave a knight and pawn, leaving the white king almost defenseless. The black major pieces joined the attack while most of the white pieces were still stuck on the wrong side of the board.


The white king was under mate threats and fighting for its life. Leela barely managed to defend, eventually exchanging pieces to save its king. The game reached a R vs RB position, black with two passers on the king side. The attack on the king was over but evals were close to 10.


There was no doubt Stockfish was winning. Due to a configuration bug the game continued beyond the normal win rule, the rooks were exchanged and white couldn't stop all the marching pawns. First decisive game of the match, with some help from the biased opening.

In the reverse game Stockfish castled long and kept its king safe. Leela kept the pawn advantage and had an eval of over 1 that constantly increased. The engines exchanges all major pieces by move 25 and Leela's eval was around 4. Stockfish's eval slowly increased, it seemed that Leela was slowly improving. The game reached a BBN vs BBN position with stable pawns, Leela just needed to find a way to capture a pawn and the white defense would collapse. Then suddenly Stockfish's eval dropped, it exchanged a bishop for a knight to get this position:


Leela's LS bishop had no targets and its DS bishop was blocked, Stockfish could keep the black king away,  a perfect fortress. Leela conceded the draw 70 moves later. A lucky escape for Stockfish, disappointment for Leela.

Leela started game 9 with a small eval advantage. Stockfish's eval was close to 0 after a few moves and stayed there throughout the game. The engines exchanged pieces and pawns gradually, by move 38 only QRB vs QRB remained. Leela's eval came down, but when it captured a pawn and reduced to a bishop ending its eval jumped over 2. Stockfish had an advanced passer, Leela gave its bishop to take it. That left two white passers, Stockfish's bishop and king were on time to stop them, the game ended in a draw.

The start of game 10 was similar, Stockfish started with an eval advantage and the engines opened the center. Stockfish's eval jumped over 1 as it captured a pawn on the king side and exposed the black king. Leela exposed the white king in return, and then Stockfish allowed the black king to capture its bishop.


Evals started to jump as Stockfish attacked the king side with all available pieces. The black king was in the open and there were not enough black defenders. In a few moves the black king was trapped and several black pieces were pinned down, evals were over 4.


Stockfish got the piece back for a pawn. Leela managed to get its king to safety on the queen side but it lost another piece in the process. The game reduced to a QRB vs QR position, black two pawns up.


Leela tried to counterattack the white king, this delayed the end a little. When the checks stopped the black king was in trouble again, the game was adjudicated before Leela lost more material.