Season 19 superfinal games 61-70

After 70 games Stockfish leads 10-7 with 53 draws. There was one double white win and Stockfish's lead remained +3, now with only 30 games left to play in the match.

Games 61-62 started with a 6-ply book in the Czech Benoni Defense, and both games left known theory very quickly. In game Stockfish kept its king in the center and developed its king side rook through the h file. After exchanging a pair of rooks Leela started to push pawns on the king side. Stockfish's queen came forward on the queen side and captured two pawns, its eval came down to 0. Leela opened the king side with a bishop sacrifice, and two connected passers advanced towards the black king. Stockfish lost a knight for one of the passers, Leela threatened mate on the open file. However the black queen could attack the exposed white king and Leela had to stop its attack to avoid a perpetual check. The draw rule ended the game quickly. In game 62 both kings did not castle, there was one minor piece exchange after the start and all pawns remained on the board. On move 24 the engines started to exchange pawns, Stockfish went a pawn up and created a passer on the queen side. The engines shuffled for a while and evals started to come down. A few exchanges later the game reached a RBN vs RBN position, Leela captured two pawns and was a pawn up, Stockfish's passer was more advanced then the black pawns. Stockfish equalized material and pushed its passer to the 7th rank, Leela exchanged minors and pushed its own passer to the 2nd rank. Both passers could not advance further and the draw rule stopped the game.

In game 63 Leela moved its king early and could not castle, it developed the king side rook through the h file. Stockfish castled long despite an open file on the queen side. The engines started to shuffle on move 28, evals drifted down to 0, a few pawn moves and exchanges extended the shuffle to move 138. A series of exchanges opened the position, both queens move forward and both kings were exposed. The game ended in a check repetition. In game 64 both engines did not castle, Leela pushed a pawn to a3 and gave it away. The kings walked in opposite directions, Stockfish developed its king side rook through the h file. Shuffling began on move 18, on move 56 Stockfish gave the pawn back and the shuffle continued. Stockfish wouldn't lower its eval until the engines ran out of pawn moves, the game was adjudicated on move 187.

Games 65-66 started in the Benko Gambit, with white a pawn up and a queen side passer while its king is unable to castle after it moved. In both games the white king found safety on the g2 square. In game 65 Leela gave the pawn back, the engines traded pawns on the queen side and by move 31 they were all gone. Evals were close to 0, the engines traded NN for R and then the game was adjudicated. In game 66 Stockfish kept the pawn and pushed the passer to a5 where Leela blocked it. After some shuffling the engines reduced to a RRB vs RRN position and Leela regained the pawn. Evals came down and the game was adjudicated after the king side pawns stopped moving.

In game 67 Leela pushed pawns on the king side and castled long, Stockfish kept its king in the center. There were almost no exchanges and evals did not change a lot. Leela waited before opening the king side, it saw an opportunity and captured a pawn on the queen side. After a few minor piece exchanges evals started to increase, Stockfish moved its major pieces to the queen side and threatened the white king. Leela finally opened a file on the king side on move 36.

Leela considered how to proceed and the engines shuffled, Leela had to be careful to defend its queen side pawns. Leela couldn't decide which pawn to push, finally on move 56 it pushed the b pawn and created connected passers on the queen side. It took a while to get the rooks on the queen side and then Leela exchanged pieces until reaching a rook ending.

Leela was up only one pawn but its rook kept the black king away from the passers. The a pawn moved forward supported by the white king, the game was adjudicated with the pawn on a6.

In game 68 Stockfish pushed pawns on the king side and castled long as before, this time Leela castled short. Leela went up a pawn, it was not afraid of the white pieces on the king side and it even exchanged a pair of pawns there. Stockfish thought Leela made a mistake on move 26 and its eval jumped over 3.

Stockfish exchanged the defending knight on f5 and moved its queen to h6. Then it opened the king side with a rook sacrifice and forced a RR for Q trade. The black king was exposed and Stockfish controlled the dark squares.

The white passer was an additional threat that Leela had to deal with. Stockfish pushed it to the 7th rank but Leela captured it there after the knights were exchanged. Stockfish didn't seem to have an immediate threat, however it was confident it was winning and evals increased steadily.

The white queen danced on the board, Stockfish used mate threats to keep the black rooks on the back ranks. On move 62 Stockfish captured a pawn and created a passer on the queen side. Leela ran out of options, by the time the game was adjudicated Stockfish captured all the black pawns and one rook for a bishop. There were two white wins in this opening, Stockfish continues to lead by +3.

In game 69 Leela pushed pawns on the king side and opened the g file. After exchanging queens Leela had a bishop pair advantage. It pushed the black king to the corner, but with a rook and a bishop could only threaten a perpetual check. Stockfish's eval dropped to 0, Leela kept trying but could not improve its attack. Eventually Leela's eval came down as well, the engines started to exchange pieces until the game reached a drawn king and pawns ending. In game 70 Stockfish pushed pawns on the queen side and opened files there. By move 24 the queens were off the board, Stockfish was 2 pawns up and there was only one white pawn left on the queen side. Leela used its bishop pair to drive the white rooks away, it exchanged one bishop and captured one pawn back. The game reached a RRB vs RRB position on move 31, the engines mostly shuffled until Stockfish lowered its eval for the draw rule.

Season 19 superfinal games 51-60

After 60 games Stockfish leads 9-6 with 45 draws. There were 6 decisive games in the last 10, two double white wins and two stockfish wins. A lead of +3 is still small but compared to the results so far it may be significant with 40 games left in the match.

In both games 51-52 the engines castled in opposite directions. In game 51 there were many early exchanges. Leela's eval was constant around 1 while Stockfish's eval increased steadily. Leela pushed pawns on the king side and one pawn reached h6. The game reached a RRB vs RRB position on move 22, material was equal yet Stockfish's eval was over 2.5.

The action was on the queen side and the black king walked slowly to get there. Stockfish was caught in a web of pins in the center, and Leela threatened to play c4 and open a file in the center for its rooks. Stockfish chose to give a rook for a bishop to release some of the pressure.

Leela slowly shifted its rooks to the queen side and targeted the b pawn.Stockfish tried to keep files closed and it allowed the white a pawn to advance and become a passer. Then the white king came forward and Leela created a second passer in the center, the game was adjudicated a few moves later.

In game 52 Stockfish's eval jumped over 2 on move 14. It prepared its pieces for an attack on the king side after exchanging a defending bishop. Leela saw an opportunity to fork two white pieces with a pawn, Stockfish ignored this and went ahead with the attack.

It was quite incredible to see how long the d4 pawn could take a white piece, Stockfish played on and ignored it and Leela had more urgent things to do defending its king. Stockfish pushed the f pawn and used it to expose the black king. Leela had to avoid taking another free bishop because of a mate threat along the h file. A temporary rook sacrifice opened another file on the king side, Stockfish got the rook back and continued the attack. On move 32 Leela finally took a bishop with the d4 pawn, both the pawn and the bishop were static for more than 10 moves.

The second white rook joined the attack and Leela was forced to give its queen for a rook to avoid mate.The engines reduced to a Q vs RN position, Stockfish started to capture pawns and the game was adjudicated. Two white wins in this opening, very different games. Stockfish continues to lead by one win.

Stockfish opened the center early in game 53. The engines started to exchange pieces and Stockfish's eval came down. On move 34 the game reached a queen ending. After a while Leela went a pawn up, but Stockfish threatened either mate or perpetual check and this prevented Leela from capturing more pawns. Leela lowered its eval very slowly, the game was adjudicated on move 126.

In game 54 there were less exchanges after the start and the center remained closed. Stockfish thought Leela blundered in move 18 and its eval jumped over 1.5. It pushed a pawn forward and used a pin to exchange a pair of pawns and to create a passer in the center. This was also a restriction on the movement and influence of the black DSB.

Leela tried to exchange queens and Stockfish refused twice. Stockfish focused on the queen side, after exchanging a pair of rooks it captured a pawn. Leela's king walked back to the center to help with blocking the passer, evals increased and were over 4 on move 38.

Leela moved its queen forward in a desperate counter, Stockfish gave a knight for another pawn on the queen side. The black king was caught in a mating net and the game was adjudicated before Stockfish won more material. Stockfish wins the game pair and increases its lead to +2.

Games 55-56 started with the King's Gambit Declined, Norwalde variation. In game 55 Stockfish was a pawn up while Leela was far ahead in developing its pieces. Leela's eval remained under 1 with a very slow increase, Stockfish's eval jumped over 2 after Leela gave a second pawn on the queen side. Leela's eval jumped a few moves later, Stockfish captured a third pawn while Leela prepared for an attack on the black king.

The immediate danger was the b1-h7 diagonal. Stockfish captured the b1 bishop with its rook, Stockfish exchanged knights on f6 before taking back. The second white knight came forward and the black king was still vulnerable. Leela gave a rook for a bishop, when it seemed the attack was over Leela used a queen sacrifice and a knight fork to reduce to a RBN vs RB position.

Stockfish was 4 pawns up but all its pawns were isolated. Leela used its extra piece to pick the black pawns up one by one. After 30 moves Stockfish was down to its last pawn and the game was adjudicated.

In game 56 Stockfish regained the pawn right away, evals remained almost constant for a long time. Stockfish had a two bishops aimed at the black king, its LSB was on a strong central square. However Leela's defense looked solid and Stockfish didn't seem to have a plan. On move 24 Leela exchanged a pair of pawns on the queen side and its queen moved forward. Stockfish exchanged a pair of knights, its eval started to increase and was approaching 2.

Stockfish doubled rooks on the f file and the plan seemed to be attacking the f7 pawn. Stockfish could potentially attack with 4 pieces, Leela had 4 defenders without counting the king. Stockfish's jumped when it opened the h file with its pawns, Leela still thought it was OK.

Leela expected a quick rook exchange on the h file, Stockfish had other ideas and Leela's eval immediately reacted. WIth one black rook in the corner Stockfish saw the opportunity, it exchanged the defending knight and captured the f7 pawn. The black king was caught between the open f and h files and Stockfish saw the mate coming. The game was adjudicated after Stockfish gave its queen for a rook, the PV showed how it could regain the material and win. Two white wins in the opening, Stockfish still leads by +2.

Leela captured a pawn and queens were off early in game 57. Stockfish placed a rook on the 2nd rank and then regained the pawn using a pin on the long diagonal. Stockfish captured another pawn and Leela placed a rook on the 7th file. Evals came down and in a series of exchanges the engines reduced to a RBN vs RR position on move 34. Both kings were exposed to checks by the rooks and the game was adjudicated by the draw rule. In game 58 Leela opened the queen side and after a series of exchanges the game reached a QRB vs QRB position on move 21. After a few pawn moves the engines started to shuffle. Stockfish controlled the open a file but Leela covered the back ranks. Leela's eval kept the game going, Stockfish captured a pawn and avoided the 50-move rule. The engines exchanged more pieces and pawns and the game was adjudicated in a drawn rook ending.

Games 59-60 started with the Alekhine defense modern variation, in a position from a Spassky-Fischer game. After a few early exchanges in game 59 the engines started to play behind their pawn lines. On move 26 Stockfish opened the c file, the engines exchanged all rooks and the game reached a QBB vs QNN position on move 34. Stockfish used its knights to block the open files and the engines started to shuffle. Leela wouldn't lower its eval, near the 50-move rule it reduced to a B vs N ending. Both engines had passers that raced forward, Stockfish was first and Leela lost its bishop for a passer. The black knight was in time to stop the white passers and the game reached a tablebase draw.

In game 60 there was one minor piece exchange after the start, all pawns remained on the board. The engines locked the center and queen side, with a small opening on the king side. Stockfish had more space and its eval was over 1.5, the engines started to shuffle on move 28. On move 73 Stockfish exchanged a pair of pawns on the queen side, its eval came down a llittle and shuffling resumed. On move 101 Stockfish moved a pawn, both engines were playing on increments. Stockfish's eval continued to drift down, it went under 1 for a while and then started to increase after move 140. Leela grabbed a free pawn on the queen side and suddenly Stockfish thought it had something.

The f6 square was vulnerable, Leela had to move its knight to let the king out of the corner. Stockfish exchanged the knight for a bishop and doubled rooks on the g file. Then it forced the g file open with a queen sacrifice and captured h7. The black king had to run away to avoid a back rank mate by the white rooks, and Leela could not stop the white h pawn queening.

Leela captured a knight, but with so much firepower on the back rank Stockfish regained the material quickly. A series of exchanges reduced to a bishop vs pawns ending and a win for white. An unexpected end to a very long game. Stockfish wins the game pair, its lead is +3.

 

Season 19 superfinal games 41-50

After 50 games Stockfish leads 5-4 with 41 draws. Stockfish won a game pair and it leads again, the score was tied since game 24. The match has reached the halfway point, so far there have been only 3 decisive game pairs and 3 double white wins. The engines seem to be of similar strength and the race is very close. 

In both games 41-42 black gave a knight for two pawns after the start, the black king was uncastled in the center and the h file was open for attacking the castled white king. There were many early exchanges in game 41 including the queens, Stockfish did not try to attack the king side. The engines continued to exchange pieces and on move 32 the game reached a N vs pawns position with black 2 pawns up. Evals were close to 0, the advancing black pawns and the white knight canceled out and the game was eventually adjudicated. In game 42 Leela focused on the center, it cleared the white pawns there and created connected passers. Stockfish exchanged pieces and on move 35 the game reached a RNN vs RB position with evals close to 0. Leela lost one central passer and created one on the queen side, the extra white piece was enough for a draw.

Games 43-44 started with a 22-ply book in the Nimzo-Indian Rubinstein variation, a position from games played by Karpov and Tal in 1980. In game 43 Stockfish went a pawn up and Leela castled long. Evals came down, the engines exchanged pieces and Leela regained the pawn. The game reached a double rook ending on move 41, Leela kept postponing the draw rule and the game was finally adjudicated on move 79. In game 44 Stockfish castled short and Leela went a pawn up. Leela gave back the pawn to open the queen side and develop its pieces there. After a few exchanges evals came down, the engines didn't move pawns and the draw rule stopped the game early.

Games 45-46 started with a 2-ply book 1. e4 g6. In game 45 the engines castled in opposite directions. There were many exchanges in a long PV agreement and only RRB vs RRB remained on move 17. The engines locked pawns on both sides and then shuffled for a while. A file opened on the queen side and all rooks were exchanged, leaving a same color bishop ending. Leela wouldn't lower its eval, the game continued until move 129. Game 46 diverged on move 5, the engines again castled in opposite directions. Stockfish pushed pawns on the king side but Leela kept the files closed to protect its king. Leela declined an offer of a rook so that its knight could keep the h file blocked. Stockfish started repeating and its eval came down, then it gave up on the king side and tried to attack the center. It captured a pawn and gave a knight for another pawn, but the attack wasn't strong. Leela traded RR for Q, both evals were close to 0 and the draw rule ended the game.

In game 47 Leela castled long and Stockfish opened a file on the queen side. There were many exchanges after the start and the game reached a QRR vs QRR position on move 29. Stockfish's eval dropped to 0, Leel'a eval also came down and the engines reduced to a rook ending. Leela was a pawn up but Stockfish held the draw.

In game 48 Stockfish castled short and there were no exchanges until move 25. There was a long line of white pawns across the board. Leela pushed pawns on the king side and through a pawn exchange created a pawn majority there, while Stockfish had strong pawns in the center. Stockfish's eval was around 1 from the start, after the queens were exchanged Stockfish's eval jumped over 1.5, it considered Leela's 30th move a blunder. Most of the black pieces were on the king side but the black pawns were between the pieces and the white king. Leela moved its pieces back while Stockfish created a passer in the center.

Leela's eval increased as it realized the danger. Stockfish slowly pushed the central pawns forward, eventually Leela gave a bishop to stop them but it also captured a rook for a knight on the white back rank. The material difference was minimal, both engines had the same number of pawns when the game reached a RBN vs RR position. The evals however showed that Stockfish had a clear advantage.

The white king came forward and captured the h pawn. Leela's last threat was the advanced f pawn, but when it pushed the pawn forward Stockfish was ready with a knight fork and the engines quickly reduced to a RN vs R ending. Stockfish covered the f pawn with its king and the game was over. Stockfish wins a game pair, it leads the match 5-4.

Games 49-50 started with a 2-ply book 1. f4 e5 and continued with white a pawn up. In game 49 the engines developed their pieces without exchanges and evals came down. The exchanges started on move 20, for a while there was a BN vs R imbalance but the engines reduced to a rook ending on move 46. The game continued for 20 more moves until the pawns stopped moving. Game 50 diverged on move 5, though there were few exchanges after the start similar to the reverse game. Stockfish pushed pawns on the queen side, then it offered a knight on the king side but Leela refused to expose its king. After a few exchanges Stockfish gave a rook for a knight and pawn and opened the king side. Leela gave the exchange back and the danger to its king was over. The game reached a same color bishop ending, Stockfish was a pawn up but could only get a draw.

Season 19 superfinal games 31-40

After 40 games the score is tied 4-4 with 32 draws. There was one game pair with two white wins, in very different styles. Leela won in blitz after stalling for many moves like it did once before in the match. Stockfish's win was more direct and quicker. The match is getting near the half point and the scores are still tied.

There were only a few exchanges after the start of game 31 and evals stayed around 0.5. Leela built a long pawn line across the board and the engines mostly shuffled from move 26, with a few pawn moves by Stockfish. After a while the engines opened the queen side and evals came down. Stockfish attacked through the queen side and cleared all pawns there, the game reached a QRN vs QRB position on move 53. The engines continued to exchange pieces and pawns, the game was adjudicated with only one white pawn on the board. In game 32 there was a long series of exchanges after the start and the engines cleared all the pawns on the queen side and most pieces. Evals came down and by move 32 only RB vs RB remained. Stockfish was a pawn up but the position was a draw, the pawns stabilized and the game ended quickly.

Games 33-34 started with a 27-ply book, a high level line in the Sicilian Taimanov variation. The engines castled in opposite directions in this line. In both games the engines continued with a series of exchanges that led to a BNN vs Q imbalance with black two pawns up. In game 33 Leela moved its rooks to the open h file, targeting the h7 pawn. Stockfish alternated between defending its pawns and threatening the white king on the queen side.

Leela had two more pieces and its objective was to concentrate forces and to outnumber the black defenders. Stockfish disrupted the attacking lines with pawns and created threats that forced some white pieces to defend. After some shuffling Leela opened the king side and evals went over 1.5. However, Leela made no attempt to attack and the engines started to shuffle. More than a hundred moves were played and Leela only made a few pawn moves on the queen side, while evals slowly drifted down. On move 164 Leela exchanged a pair of pawns on the queen side, by the eval reaction it looked like the shuffle would continue for another 50 moves.

This time though evals started to jump. I don't know whether Stockfish started to see ghosts or just blundered in blitz mode, its eval went over 3. Nothing seemed different for a few moves, then somehow Leela got the black rooks in a skewer by the bishop.

Stockfish managed to save its rooks by moving Rh3, threatening to push its king side passer. Leela responded with Rc1, which both engines did not expect in their short thinking time. Stockfish could not avoid losing its queen for a rook while defending its king. Leela exchanged pieces and gave some material back to create connected passers on the queen side which could not be stopped.

In game 34 Stockfish chased after the black queen and soon forked the two black rooks with a bishop. In a series of exchanges Stockfish traded the bishop for a rook and also captured a pawn. The imbalance was RBN vs Q and one pawn, better than the previous game. Stockfish's eval was over 2 at this point.

Stockfish doubled rooks in the center while Leela countered against the white king on the queen side. The black queen moved forward and Stockfish's king looked exposed and vulnerable. Stockfish was also down to two pawns, it seemed important to keep at least one alive.

It was beautiful to watch how Stockfish kept all its pieces safe as they slowly went on the attack. It took Stockfish 10 moves to capture a black pawn, Leela started to give check with its queen. When the checks ran out Stockfish doubled rooks and got ready for the final attack.

Leela was forced to exchange rooks, it captured the white b pawn but Stockfish kept its other pawn safe and captured the remaining black pawns. The 7-man position was a win, the white pieces continued their synchronized dance until the game was adjudicated. The PV showed how the white pawn could not be stopped. Two very different wins in this opening, score is still tied.

In game 35 the engines blocked the center after the start. Stockfish pushed pawns on the king side and Leela attacked on the queen side. Leela started a combination with a knight for pawns sacrifice that led to a R vs BN imbalance, while creating connected passers. Stockfish's eval dropped to 0. It gave a bishop, opened the king side and attacked the white king. Leela gave material to avoid mate, Stockfish ended the game in perpetual check. In game 36 the engines opened a file in the center after the start. Stockfish exchanged queens and captured a pawn, then all rooks were exchanged and the game reached a BNN vs BBN position on move 25. After exchanging a few pawns and a pair of knights the engines started to shuffle. It took Stockfish a long time to lower its eval, it avoided the 50-move draw and the game was adjudicated on move 90.

Games 37-38 started with a short book in the French Winawer advance variation. Stockfish gave a pawn and castled long in game 37. Leela castled short, after a few exchanges it captured a second pawn but the f file was open for Stockfish to attack the white king. Evals were close to 0, Stockfish exposed the white king and temporarily sacrificed a rook. The engines quickly reduced to a king and pawns ending, the game ended in a tablebase draw. In game 38 Leela castled long, Stockfish did not castle but its king walked to the king side and its king side rook developed through the h file. The engines shuffled from move 21 until Leela decided to open the king side. Evals came down to 0, after several exchanges Leela was a pawn up. However the engines didn't move pawns and the draw rule stopped the game.

In both games 39-40 the black queen came forward on the queen side, black went a pawn up but was behind in development. In game 39 both kings moved forward, Stockfish exchanged queens and gave a knight for two more pawns. Evals dropped to 0, the engines continued to exchange pieces and pawns, the game reached a RB vs R position on move 40. The game ended in a tablebase draw. There were a lot less exchanges in game 40, evals were close to 0 almost throughout the game. Stockfish forced the black king to move, while the white king castled very late. Leela pushed pawns on the queen side and the white queen came forward to attack the black king. Stocfish gave a rook for a bishop and was close to a perpetual check draw, the draw rule ended the game.

Season 19 superfinal games 21-30

After 30 games the score is tied 3-3 with 24 draws. Leela won its first game pair. There was a long shuffle in the game it won, the engines were in blitz mode after that. Perhaps this is a good strategy against Stockfish? There were two openings with a 2-ply book and in both pairs the games repeated for more than 11 moves. It seems Stockfish NNUE plays openings like Leela.

Games 21-22 started with a 2-ply book 1.e4 e5. Game 21 followed a high level line in the Ruy Lopez Berlin defense opening. Evals were low throughout the game, almost all pawns stayed on the board except a file that was opened in the center. The engines gradually exchanged pieces, on move 31 the game reached a same color bishop ending. The draw rule stopped the game 35 moves later. Game 22 followed the same line until move 12 (does Stockfish NNUE have the same opening rigidity that Leela has shown in the past?), evals again were low throughout the game. Queens were off early and the game reached a RBB vs RBN position on move 26, the engines started to shuffle and the game was adjudicated quickly.

The book exit in games 23-24 had black a pawn up, white threatening to take a rook on the long diagonal, and the white king unable to castle after it moved. In game 23 the engines played out a long PV agreement and Leela captured the rook for a bishop. Stockfish could not castle its king and both king side rooks were trapped. Evals gradually increased as the engines exchanged pieces, the game reached a RRN vs RBN position on move 33. Both kings left the back row to open a path for the trapped rooks, Stockfish had a pawn majority on the queen side and it created a passer.

The engines started to shuffle, it was reasonable that Leela would try something with its king side pawns but it seemed reluctant to do this. A few times in its PV Leela suggested Stockfish move a pawn, Stockfish kept shuffling and Leela's eval slowly came down. After 25 moves Leela pushed e4, but its eval continued to drift downwards. Leela moved its king forward and on move 77 it played e5. Quite unexpectedly Stockfish's eval jumped over 3.5 while Leela's eval did not change at all. The position opened and the knights were exchanged, it took Leela a few moves to start increasing its eval. The white rooks had open files and Leela captured a pawn. Stockfish's eval showed it was certain the game was lost.

Leela moved its rooks forward, the black rook was too far away and could not get back and Leela captured the bishop for the win.

In game 24 Stockfish immediately regained the pawn but it would not take the black rook. Leela had time to castle its king and move the rook to safety. Stockfish's eval was above 0.5 for a while, but it came down after the engines reduced to a RRN vs RRN position on move 28. Stockfish managed to capture a pawn but no more, the engines started to repeat and shuffle and the game was adjudicated. Leela wins its first game pair and the score is tied again.

Games 25-26 started with a 2-ply book 1. e4 d5. The engines followed a high level line in the Scandinavian defense for 13 moves with evals around 0.5. Stockfish castled short despite a white pawn on h6, its eval came down when its queen came forward and threatened the exposed white king. Stockfish got rid of the h6 pawn and Leela's eval came down as well. The engines exchanged pieces and the draw rule was applied in a QB vs QB position. Game 26 diverged on move 14, a long agreement like in games 21-22. Again Leela castled short and Stockfish had a pawn on h6. Almost all pawns stayed on the board, Leela stayed back and fortified a defense line. The engines started to shuffle on move 26, evals came down and the game was quickly adjudicated.

Games 27-28 started with white a pawn up in a Blumenfeld counter gambit. In game 27 Stockfish gave the pawn back, it had strong central pawns with one passer. The black king was exposed in the center, Leela captured a pawn while the black king walked to the queen side. Stockfish's eval dropped to 0, Leela prepared to attack and captured another pawn. However, Leela's eval also dropped and Stockfish forced a repetition draw. In game 28 Stockfish kept the pawn and both engines castled. After a series of exchanges all the queen side pawns were gone, Leela regained the pawn and it had an advanced passer in the center. Evals were close to 0, the engines reduced to a QR vs QR position, Stockfish captured the passer and the game was adjudicated.

Stockfish pushed pawns on the queen side in game 29, Leela kept its king uncastled. The game reached a RRN vs RRN position on move 23, evals came down as the exchanges continued. The engines reduced to a double rook ending, the game was adjudicated when the pawns stopped moving. In game 30 Stockfish placed its queen on h6 and castled long. Leela had to protect its king and could spare only a few resources for a queen side attack. Evals dropped to 0, the engines were close to a repetition draw but reduced to a drawn rook ending instead. The game ended 14 moves later.

Season 19 superfinal games 11-20

After 20 games Stockfish leads 3-2 with 15 draws. Stockfish wins the first decisive game pair of the match. There was another game pair with two white wins. So far neither engine seems to be stronger, still early in the match.

Games 11-12 started with a rare line in the Dutch defense where white has a significant eval advantage. In game 11 Leela gave a knight for 3 pawns, leaving the center and king side almost clear of black pawns. After exchanging queens the black king was forced to move, blocking Stockfish's queen side pieces.

Evals continued to increase gradually, the black king stayed in the center surrounded by pieces. Leela opened a file on the queen side and shifted its rooks there, while slowly pushing its central pawns forward. The 4 connected pawns started to look intimidating.

Stockfish gave a rook for a bishop and managed to remove two white pawns. Leela pinned the black knight on the back rank and the black king could not move. Leela had a protected passer on the 6th rank facing the king and Stockfish had to focus its available pieces on defense. The engines exchanged bishops and only RR vs RBN remained.

Leela pushed the b pawn forward and the black defense crumbled, the d pawn became a connected passer before the game ended. 

There were only a few exchanges after the start of game 12. Leela pushed pawns forward and gave a rook for a knight, then gave a knight for two pawns. Leela was determined to attack the exposed white king even at the price of a piece, however Stockfish's eval increased over 2.5.

Stockfish gave a bishop back, it was almost trapped in any case. The white queen came forward and Stockfish started attacking from the king side. With a white rook on the open f file the black king was in danger. Leela's advanced pawns looked dangerous but there was no time to move them while Stockfish threatened mate.

Leela managed to get one pawn to the 2nd rank but had to give up both central pawns to save its king. Stockfish had a winning advantage in a QR vs QB position and a pawn up. Two white wins in this game pair, the score is still tied.

The engines castled in opposite directions and opened a file in the center in game 13. Leela placed a pawn on f6 with the white queen on the king side while Stockfish pushed pawns on the queen side facing the white king. Leela stopped the black pawns, went a pawn up and created a queen side passer. Stockfish reduced to a QRB vs QRN position and its eval came down. Leela concentrated on its passer, it lost two pawns but after exchanging queens the passer reached the 7th rank. Stockfish lost the knight for the passer, the remaining black pawns were good for a draw against the white bishop. In game 14 Stockfish's eval was around 1 for a short while, both engines castled short and the center was open. Evals came down as the engines exchanged pieces and pawns, the game reached a double rook ending on move 28. The engines continued to play with exchanges and pawn moves, the game was adjudicated on move 51.

Games 15-16 started with a 20-ply book in the Gruenfeld defense, Smyslov variation. There were many early exchanges in game 15 and only RBN vs RBN remained on move 24. The engines reduced to a drawn rook ending, Leela wouldn't lower its eval and the game was adjudicated only on move 77. In game 16 the engines kept the queens on the board a little longer, the game reached a RBN vs RBN position on move 32. Stockfish was a pawn up, it gave the pawn back to create a passer on the queen side. Leela gave a rook for a bishop to stop the passer, all the remaining pawns were on the king side and Stockfish could not improve its position despite the material advantage. The engines shuffled until Stockfish lowered its eval for the draw rule on move 89.

Games 17-18 started in a Sicilian Taimanov variation that was played in a Karpov-Kasparov game. In game 17 Leela castled long and Stockfish kept its king in the center. The engines exchanged most minor pieces, Leela tried to force its way through the king side and Stockfish's eval went over 1 after the h file was opened. A series of exchanges reduced to a B vs N ending and Stockfish's eval dropped to 0. Leela was a pawn up, all pawns were passers and the black pawns were a little more advanced than the white ones. Both engines were not strong enough to push their own pawns while blocking their opponent's pawns, eventually they started to shuffle. Leela's eval came slowly down and the game ended on move 101.

Game 18 started similarly, Stockfish castled long and Leela kept its king in the center. There were fewer exchanges, Leela tried to threaten the queen side through an open file. Stockfish's eval was around 1.5, Leela gave a pawn and opened another file on the queen side to add pressure, Stockfish created a passer on the king side. Leela's eval was under 1 while Stockfish concentrated forces in the center, then suddenly Stockfish's eval jumped over 6 as it broke through the center with a sacrifice of a rook and a knight for a bishop and two pawns.

Leela saw the danger a move too late. The immediate problems were the white h pawn and the exposed black king. While Leela tried to defend Stockfish captured 3 more pawns and pushed both the d and the h pawns to the 6th rank. 

Stockfish exchanged the last black pawn and a pair of rooks. It gave up the passer on the king side, instead pushed a second passer towards the black king. After the bishops were exchanged Leela could not prevent a pawn promotion. First game pair win of the match goes to Stockfish.

Stockfish's eval dropped to 0 early in game 19, Leela's eval was also low. Leela castled long after all the knights were exchanged, Stockfish gave a pawn and opened the queen side. For a while Leela had an advanced passer, it was gone in a series of exchanges and only RRB vs RRB remained on move 29. The exchanges continued until each engine had only one pawn left and the game was adjudicated. Evals were low in game 20 as well. Stockfish castled long and this time the knights stayed on the board. After a while Leela pushed through the king side, creating a passer and capturing two pawns. Stockfish reacted with a rook sacrifice and a mate threat. Leela was forced to give its queen for a rook, Stockfish could have forced a perpetual check but it stopped repeating. However the game was adjudicated as both engines agreed the QN vs RRB position was a draw.

Season 19 superfinal games 1-10

After 10 games the score is tied 1-1 with 8 draws. There were two decisive games, a double white win in one opening. One game pair started with a KGA, both games had an explosive start but ended in draws. An explanation of the superfinal openings by Jeroen Noonen can be found here.

In game 1 the engines followed a popular line in a Sicilian Najdorf opening until move 13. Evals were close to 0 though the white king was exposed. Starting from move 21 there was a long PV agreement, Stockfish sacrificed a rook and started to give checks with its queen. The game was close to a repetition when it was adjudicated. In game 2 Stockfish chose a less popular line, evals were close to 0 again. The game reached a RRN vs RRN position on move 20, the engines exchanged pawns and pieces and the game was adjudicated in a drawn rook ending.

The center was blocked in game 3 and the engines stabilized the queen side pawns early. Stockfish opened a file on the king side and exchanged a pair of rooks on move 20, the engines mostly shuffled from then. There were a few pawn moves on the king side and several exchanges of minor pieces, evals came down and the draw rule ended the game in a QR vs QR position. There was a similar setup in game 4, there were fewer exchanges and the engines started to shuffle on move 20. Leela gave a pawn to open the queen side and create a passer, after exchanging queens the game ended in a repetition draw.

Games 5-6 started with a line in the French opening where black had a disadvantage when it retreated the knight to g8 after white played 4. e5. Evals increased slowly after the start of game 5, both kings did not castle and Leela developed its king side rook. By move 25 only two pairs of pawns and a pair of bishops were exchanged on the queen side, Stockfish had a passer but its eval was approaching 2.

The white king walked to safety on the king side and Stockfish finally castled on move 31. Leela captured a pawn on the king side, then captured the queen side passer. The engines reduced to a QRN vs QRB position with white two pawns up.

The engines shuffled for 20 moves, it seemed Leela was waiting for something before pushing pawns on the king side. Evals started to increase again after Stockfish offered to exchange queens.

Leela was more confident without the queens and its king side pawns advanced. Before too long Leela had a passer on the 6th rank and the game was adjudicated before another passer was created. First decisive game of the match.

In game 6 Stockfish's eval was more than 1 from the start. Leela pushed pawns on the queen side and gave a pawn early, causing Stockfish to double pawns but one of these was a valuable passer.

Both kings stayed in the center, Stockfish could develop its king side rook while Leela's rook was stuck. Leela exchanged pieces and regained the pawn, but by the time it opened a path for its rook Stockfish pushed the passer to the 7th rank and only RBN vs RBN remained.

Leela blocked the c passer with its knight and brought its rook to the queen side to cover both white passers. However both engines knew there was no defense.

Leela was able to capture both passers but lost all its pieces,  Stockfish was left with a knight and a bishop and the game was adjudicated. Two white wins in this opening, score is still a draw.

Games 7-8 started in the Geller gambit line of the Slav defense, with black up a pawn. In game 7 Stockfish gave the pawn back immediately and created a queen side passer. Evals dropped to 0 though the passer reached the 2nd rank, after a series of exchanges only RRB vs RBB remained on move 24. The draw rule was avoided by pawn moves and captures, Leela captured the black passer and Stockfish pushed another forward. Eventually the pawn moves stopped and the game was adjudicated. Game 8 started similarly, Leela gave a pawn and created a queen side passer. This time Stockfish captured the passer in a series of exchanges and evals came down. Stockfish sacrificed a bishop to expose the black king, then ended the game in perpetual check.

Games 9-10 started with a King's Gambit Accepted. In game 9 Leela gave a knight for a pawn early, Stockfish's (negative) eval increased over 1.5. Leela forced the black king to move, then sacrificed a bishop but attacked a pinned knight. Very suddenly Stockfish realized there was no advantage and its eval dropped, a series of exchanges equalized material and reduce to a RRN vs RRB position on move 21. The engines continued to exchange pieces and pawns, the game ended in a tablebase draw. Game 10 started with a repeat of game 9 for a few moves, then a PV agreement led to an unusual Q vs BNN imbalance on move 14. For a long while evals stayed negative under 1, Stockfish slowly pushed pawns on the queen side and prepared a fortress for its king on the king side. After several exchanges Leela was down to a queen and a rook, the engines started to shuffle and Stockfish's eval came down to 0. Leela opened the king side and the shuffle continued, on move 98 the rooks were exchanged and Leela could only give checks with its queen. Leela wouldn't lower its eval, pawn moves kept the game going until move 213.