Saturday, February 16, 2019

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.

Thursday, February 14, 2019

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.

Tuesday, February 12, 2019

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.

Sunday, February 10, 2019

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.

Friday, February 8, 2019

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.

Thursday, February 7, 2019

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.