Season 28 entrance league statistics

A summary statistics table of previous stages and seasons.  

Draw rate, wins

Final draw rate was 55%. 

Game termination

The three most common game termination causes were:
45% - mate
41.3% - TCEC draw rule
10.4% - 3-Fold repetition

There were no crashes in the stage. This season tablebase positions do not terminate the game.

Moves per game

Median= 78
Average= 82.0

There were 51 games longer than 100 moves, the longest was 284 moves (Stash - PlentyChess, game 176, draw). The change in game termination criteria caused games to be longer than before.

Time per game (hours)

Median= 1:05
Average= 1:03

Openings

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

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

Reverse pairs, wins

Reverse pairs, same moves

Pairs of reverse games diverged quickly, 30.8% diverged immediately out of book, 68.3% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 18 plys (Renegade - Arasan, games 15 and 135, QGD Slav, Steiner variation, two draws) 

Season 28 entrance league

The engines that will play in the season 28 entrance league are:

relegated from season 27 league 1: PlentyChess
relegated from season 27 league 2: BlackMarlin, Arasan, Minic, DeepSjeng
played in season 27 entrance league: Renegade, Altair, Booot, Patricia, Tucano
new to TCEC (played in Swiss tournament): Integral, Starzix, sirius
returning to TCEC: Clover (season 26 league 1), ScorpioNN (season 26 league 2), Stash (season 26 entrance league)

Final standings

Integral, PlentyChess, Booot, Starzix and Arasan advance to league 2. There was a tie in 5th place, Arasan and Clover played a tiebreak match and in the 5th game pair Arasan won.

Integral won 13/15 game pairs without loss, it lost only one game against Booot. PlentyChess won 12/15 game pairs and lost only to Integral. Arasan was in 2nd place after RR1 with 7 wins and one loss, in RR2 it played as black against stronger engines and it drifted down in the table. Booot finished in third without a game pair loss and only one game loss to Integral. Starzix had 3 game pair losses but 10 wins, it finished in 4th place. With only two rounds remaining Clover was able to tie the score with Arasan, their final results were almost identical. A tiebreak match was played and Arasan won. Interestingly both Arasan and Clover lost a game to Patricia, for Patricia the win against Clover was its only game pair win in the league. 

A tiebreak was played between DeepSjeng and ScorpioNN, not sure why it was needed. DeepSjeng won the 2-game match and is officially in 11th place, ScorpioNN is in 12th. 

The 5 qualifiers will play in league 2 together with:
played in season 27 league 1: Igel, Uralochka
played in season 27 league 2: Velvet, Ginkgo, Stormphrax
new in TCEC: Reckless, Horsie (I'm not sure why these are starting in league 2, perhaps based on their results in the Swiss tournament)

Interesting games

game 4, Integral - Starzix: Starzix pushed the f pawn and its king was vulnerable. Integral pushed a pawn to g6 and threatened a king side attack. The engines reduced to a double rook ending and Integral went a pawn up. Integral used a passer on the 7th rank to reach a winning rook ending.

game 8, Patricia - Clover: Patricia controlled an open file on the queen side. After a very long shuffle the king side opened, the white queen moved forward and drove the black king to the center. Patricia had a passer on the 7th rank and active knights, Clover lost material and was eventually mated.

game 12, Stash - Minic: Minic sacrificed a knight to open the king side, it tried to attack the white king. Stash protected its king, gave the piece back and reduced to a RB vs RB ending with a pawn up. Minic lost the bishop for a passer, the game ended in mate.

game 18, Arasan - Altair: Arasan had a space advantage, it gave pawns to open both sides and placed both rooks on the 6th rank. Arasan moved a pawn to g7 and threatened the black king, Altair exchanged pieces but lost material. Arasan converted a RB vs R ending.

game 26, PlentyChess - Clover: PlentyChess opened the queen side, captured a pawn and created a passer. Clover countered with a knight sacrifice to create connected passers on the king side. Clover gave a bishop to capture all remaining white pawns, in  BBN vs N position PlentyChess captured all black pawns and mated.

game 29, BlackMarlin - Minic: BlackMarlin doubled queen and rook on the open h file, Minic countered on the queen side and won a rook for a passer. However, BlackMarlin used the exposed black king to gain material and win a QN vs Q ending.

game 34, Integral - Booot: Booot opened the queen side but its king was stuck in the center. Integral had an active rook on the queen side and it pushed pawns on the king side. Booot kept the king side closed, Integral placed a pawn on the 7th rank. Booot lost material and was mated.

game 50, sirius - Arasan: The game reached a R vs B ending, Arasan was a pawn up with connected passers and one on the 2nd rank. sirius captured one passer and blocked the other, but it couldn't find the winning moves. The game was adjudicated after a very long shuffle on move 282.

game 53, Patricia - Renegade: Patricia went a pawn up in a closed position, after a long shuffle it captured a second pawn. The engines reduced to a double bishop ending, Patricia used a passer to win.

game 69, Clover - Altair: Altair kept the king side closed, Clover captured a pawn and opened the queen side. In a series of exchanges Altair lost two knights for a rook. Clover used a passer to gain more material followed by mate.

game 70, ScorpioNN - Renegade: ScorpioNN gave a rook for a knight and captured black pawns. The game reached a RB vs RR position with 3 white pawns and all black pawns gone. ScorpioNN pushed connected passers and seemed to be winning, but it let Renegade capture a pawn and block the connected passers to hold a draw.

game 78, Arasan - Patricia: In a RR vs RB position Patricia, with no tablebase support,  blundered and exchanged rooks. The result was a 7-man win for Arasan, 80 moves long. 

game 88, Starzix - BlackMarlin: In a closed position Starzix opened the center and its two bishops threatened the black king and pieces. After a series of exchanges the game reached a R vs B ending which Starzix won.

game 94, Integral - Clover: Integral opened the center and created a passer, Clover gave a rook for a knight and tried to counter on the queen side. After exchanging pieces Integral gave back the material, it captured the black pawns on the queen side while Clover captured the center passer. In a RB vs RN position Integral pushed a queen side passer, Clover stopped it but lost its pawns on the king side. Integral pushed passers on the king side to win.

game 101, PlentyChess - Arasan: The engines exchanged pieces in a closed position, PlentyChess created a passer on the queen side and only QB vs QN were left. After exchanging queens PlentyChess created a second passer on the king side to win.

game 106, Altair - BlackMarlin: Altair captured a pawn and reduced to a QRN vs QRN position. After a long preparation Altair captured a second pawn and then converted a knight ending.

game 107, Booot - Starzix: Booot was two pawns up early in a closed position. The engines exchanged pieces until only BBN vs BBN were left, Starzix gave two pieces for the remaining white pawns. Booot captured the black pawns and mated.

game 109, Integral - PlentyChess: Integral created a queen side passer, then captured a pawn and pushed another passer to the 7th rank in the center. PlentyChess blocked the passer, regained the pawn and created a king side passer. It tried to avoid exchanging queens, eventually Integral reduced to an opposite color bishop ending. Integral lost the advanced passer but captured all black pawns, PlentyChess couldn't avoid a queening and mate.

Standings after RR1: Integral +7, Arasan +6, PlentyChess +5, Booot +3, Starzix Clover +2, BlackMarlin Renegade 0, Altair DeepSjeng -1, Tucano -2, Patricia -3, sirius ScorpioNN -4, Minic Stash -5. Integral leads with no loss and one draw with white. Arasan and PlentyChess are close behind, each with one loss and one draw with white. Booot, Starzix and Clover are in the race for the first 5 places which qualify for league 2. 

game 123, BlackMarlin - Arasan: Arasan captured a rook for a knight while BlakMarlin created advanced connected passers in the center. Arasan tried to block, BlackMarlin exchanged pieces and gave a bishop to push a passer to the 7th rank in a Q vs QR position. Arasan could not stop the queenings, it lost material and was mated.

game 134, Integral - BlackMarlin: Evals increased from the start in a closed position, on move 37 Integral went a pawn up and created a passer in the center. Gradually Integral captured all the remaning black pawns, then queened a pawn to win.

game 149, Minic - BlackMarlin: In a closed position Minic managed to create connected passers in the center. BlackMarlin gave a bishop to capture both passers and the game reached a RBN vs RN position. BlackMarlin lost a knight for another passer, Minic won in a KBN vs K ending.

game 154, Booot - Integral: Booot threatened the black king side, Integral moved its queen forward on the queen side and Booot blocked its path back. Integral gave a rook for a knight to open the block. In a QRR vs QRN position Booot captured two pawns, then reduced to a winning R vs N ending.

game 168, Integral - Arasan: Integral gave a pawn open a file on the queen side, then gave another pawn and hid its king behind a black pawn. Integral regained one pawn, it kept pressure on the queen side until Arasan gave a knight for a pawn, but Arasan's counter was weak. Integral created a passer on the queen side and exchanged pieces, it queened and mated.

game 178, PlentyChess - Starzix: PlentyChess attacked on the king side, it gave two minor pieces to expose the black king. In a series of exchanges the engines reduced to a RB vs RN position. PlentyChess was two pawns up, Starzix lost material to stop a queening and was mated.

game 198, Patricia - Arasan: Patricia gave two pawns and attacked the king side. Arasan gave a knight and exchanged pieces, the game reached a QRN vs QR position with black two pawns up. Patricia used the extra piece to capture pawns, it pushed a passer to win. 

Standings with 5 rounds to go: PlentyChess +11, Integral +10, Booot Starzix +6, Arasan +5, Clover +4, Renegade BlackMarlin Altair 0, DeepSjeng Tucano ScorpioNN Patricia -5, Minic sirius -7, Stash -8. PlentyChess and Integral have a significant lead and will probably finish in the first two places. There are 4 engines in the race for the other 3 qualification spots, and anything can happen.

Standings with 2 rounds to go: Integral +12, PlentyChess +11, Booot +8, Starzix +7, Arasan +5, Clover +4, Renegade 0, BlackMarlin Altair -1, Tucano -4, Minic DeepSjeng -6, ScorpioNN sirius Patricia -7, Stash -8. Booot and Starzix will probably qualify in places 3-4. Clover still has a chance of qualifying instead of Arasan, it has a game against Minic as white while Arasan will face Starzix as white.

Clover beat Minic, and there is a tie with Arasan with one round to go.

Arasan only drew against Starzix, there is a tie for 5th place between Arasan and Clover.

 

Season 27 superfinal statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins

Final draw rate was 47%.

Game termination

The three most common game termination causes were:

44% - TCEC draw rule

34% - SyzygyTB
19% - Mate

There were no crashes in the stage.

Moves per game

Median= 78.8
Average= 81.7

There were 16 games longer than 100 moves, the longest was 167 moves (Stockfish - Leela, game 32, draw).

Time per game (hours) 

Median= 4:25
Average= 4:22

Openings

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

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

Reverse pairs, wins 

Reverse pairs, same moves

Pairs of reverse games diverged slower than usual, 14% diverged immediately out of book, 40% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 21 plys (Leela - Stockfish games 3 and 4, Nimzo-Indian Rubinstein variation, Stockfish won as white).

Season 27 superfinal games 91-100, season summary

Stockfish is the winner of the season 27 superfinal. The final score is 35-18 with 47 draws. In the last 10 games Stockfish won 3 more game pairs, extending its lead to 17 wins. Game 94 was an example where Stockfish saw a win and Leela's eval was close to 0, such huge eval differences are quite rare in the recent superfinals. Leela had a promising eval advantage in game 98 but Stockfish managed to reduce to a drawn ending. 

Stockfish won the first two game pairs, but then Leela won 2 of the next 3 game pairs. The reverse games in the two Leela wins ended in a Q vs R endgame fortress, in one of them Stockfish thought it was winning for a while. Stockfish led 3-2 at this stage, it seemed possible the match would be competitive. Stockfish won two more pairs, in one of them Leela had high evals but missed the win in the reverse. Leela won another game pair and the score was 5-3 after 11 game pairs, then Stockfish won 3 pairs in a row and extended the gap to +5. After 16 pairs there were 11 decisive pairs and none had two white wins, then there were two pairs with two white wins and one with a Leela win that reduced to gap to +4. This was Leela's last pair win in the match, Stockfish won 13 more to finish with a +17 gap. There were 14 pairs with two white wins, so Leela won more games but couldn't hold the reverse. In many games Stockfish spent a lot of time in the beginning of the game, more than 40 minutes for one move in some cases. It ran out of time and played on increments as these games continued, sometimes finding a complicated win that neither Leela nor the spectators believed was possible. This season Stockfish again displayed its superiority in converting difficult endgames.

Season 27 leagues started with the entrance league, with 16 engines and 5 advancing. The newcomer Ceres led the league easily, Devre (another newcomer) and BlackMarlin also advanced with almost no game pair loss. For BlackMarlin this was a little surprising based on its predicted strength. Three engines were in the race for the last two qualification spots, in the last round Halogen lost it game, PlentyChess (newcomer as well) and akimbo finished in 4th and 5th places. In league 2 Ceres again won easily and without loss, PlentyChess finished a close second with one loss. There were 5 engines with a chance of qualifying, in the last RR Devre pulled away from the group but was caught again. In the last round Devre held on to 3rd place and Uralochka finished in 4th, tied with Devre and with a small lead over the chasing engines. In league 1 there were three engines in the lead: Obsidian, Caissa and Ceres. After two RRs the three leaders were still close to each other, in RR3 Obsidian pulled away and it continued to lead until the end. Caissa had a weak RR3 and it allowed Ceres to tie the score. However in RR4 Ceres lost 3 times, Caissa also lost a game but it performed better than Ceres and managed to qualify from second place. Ceres finished in third place, the end of its first TCEC season.

In the premier division Stockfish led from the start and finished first. It won 22/28 game pairs without loss, including 3 wins against Leela and 4 draws against Obsidian. Leela was second but Obsidian and Berserk were not too far behind. In DRR3 Leela beat Obsidian and Berserk and opened a gap to finish in second place and qualify for the superfinal. Obsidian was third after DRR3 with Berserk and KomodoDragon chasing. In DRR4 Obsidian had 3 game pair losses, including against KomodoDragon and Ethereal, and only one win. Berserk was solid with one loss and 3 wins and it managed to finish third ahead of Obsidian. KomodoDragon had one win and one loss, only enough for fifth place.

For the last few seasons I have been neglecting the personal section of this season summary. The war in Gaza that started on October 7th 2023 is still ongoing, perhaps the shock I had then makes it hard for me to look back, and when the season ends I just leave the blog until the next league season. Most of the people kidnapped were returned, either dead or alive, but as of June 2025 there are still 50 held in Gaza, about 20 of which are assumed to be alive. Related events in Lebanon, Syria, Yemen and lately Iran make the war in Gaza seem small at times, but it is devastating to the people in Gaza as well as internally for Israel. My concern is for the safety of my family and my country, I have less attention for other things such as the war in Ukraine that is still raging after more than 3 years (Russia using ammunition from Iran and soldiers from North Korea, what???), or an almost war between nuclear powers Pakistan and India.

Still, I hope for a better future, and go TCEC!!

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Games 91-92 started with a sideline in the KID, Steiner attack variation. All pieces and pawns were on the board, the white king was in the center and the white king side pieces were not developed. In game 91 Leela castled long and exchanged a pair of bishops on the king side. Stockfish's eval came down, the white queen moved forward on the king side but the black king was safe. Stockfish captured a pawn and created a passer in the center. Leela captured a pawn and then a rook with a knight, but the knight was trapped. Before capturing the knight Stockfish moved a bishop to protect its passer. Leela captured a pawn and tried to expose the black king, Stockfish hid its king behind a white pawn. Then in a series of exchanges the engines reduced to a QR vs QBN position, the black passer was gone and Leela was up two pawns. Evals were low, after exchanging queens the game was adjudicated.

In game 92 Stockfish castled long, the black queen moved forward on the queen side and Leela's eval was unusually high for the first move, over 1.5. Stockfish immediately pushed the g pawn and Leela pushed the b pawn. The engines exchanged bishops on the king side and the white queen was on h6, Leela's eval came down while Stockfish's eval increased. Stockfish ignored Leela's threats on the queen side and prepared a king side attack. On move 17 Leela's eval jumped, Stockfish's g5 pawn attacked a knight defender on f6. 

Leela went on the attack despite the high evals. It gave the knight for a pawn and then gave the second knight to open the b file and create an advanced passer. The white king was in the corner and the black passer reached c2, but then it was Stockfish's turn to attack. Leela gave a rook for a knight to protect its king, Stockfish had time to block the black passer with its queen. After a series of exchanges the game reached a QRB vs QR position and the black c7 passer was gone. Stockfish kept the black pieces away from its king, on move 43 the engines exchanged rooks. 

Stockfish soon saw the win in its PV. It used checks by the queen to capture a few pawns and then forced a queen exchange. The game ended in a tablebase win. Stockfish wins the game pair, it leads 33-18.

Games 93-94 started with a 22-ply sideline in the Sicilian, Scheveningen, classical variation. There was one pawn exchange and all pieces were on the board, white had a space advantage. In game 93 the engines opened the d file, then in a series of exchanges the queens were off as well as minor pieces, Stockfish created a passer in the center. From move 24 the engines played out long PV agreements and evals came down. Leela captured a pawn and created a passer, the game reached a RBN vs RBN position. Stockfish pushed the passer to e2, Leela captured the passer and Stockfish captured the white passer. Both engines created a new passer, Leela captured the black passer on the 2nd rank again. Leela captured the last black pawn and was two pawns up, however evals were close to 0. The game was adjudicated after rooks were exchanged. 

In game 94 Stockfish pushed pawns on the queen side, the engines exchanged pawns, knights, bishops and queens, and opened the d file. The engines played out a long PV agreement and the game reached a RRB vs RBN position with black two pawns up. Leela had a passer on the queen side and its eval was low, Stockfish's eval was around 1.5. 

Stockfish's eval came down and moved back up, it captured the c5 pawn, the engines pushed pawns on the king side and then Stockfish moved a rook to the back rank. The engines cleared the queen side pawns, then Stockfish moved its other rook to the back rank. On move 57 Stockfish's eval jumped, the engines exchanged a pair of rooks. Stockfish was again on increments and Leela's eval did not move. Stockfish exchanged bishops and Leela's eval dropped even further. On move 64 Leela gave a pawn, Stockfish saw the win in its PV. In the 8-man position left, the contrast with Leela's eval was incredible.

Leela's eval started to react only on move 71. The white king and rook hunted the black knight, on move 79 the knight was close to being trapped and Leela gave it up. The game ended in a tablebase win. Stockfish wins the game pair, it leads 34-18.

Games 95-96 started with the Modern defense, Averbach system, played in high level human chess. White had a space advantage, all pieces and pawns were on the board and both kings were uncastled. In game 95 pawn exchanges in the center opened the e file, the engines castled in opposite directions and Leela captured a pawn on the king side. Pawn exchanges opened more files in the center, the game reached a RRN vs RRN position. Leela doubled rooks on the d file, Stockfish's eval came down and a pair of rooks was exchanged. The engines shuffled and Leela's eval also came down. There were a few pawn exchanges and knights were exchanged as well, the game was adjudicated when Leela's eval was low enough for the draw rule. In game 96 there were no exchanges after the start and both engines castled short. The engines blocked the center and a pawn exchange opened the a file. Evals came down as the engines exchanged all rooks as well as queens. The engines shuffled and there were a few pawns exchanges, the game was adjudicated after two more minor piece exchanges.

Games 97-98 started with a 17-ply sideline in the Alekhine defense, Marcozy variation. One pair of knights was exchanged, all pawns were on the board, black had a passer in the center and an eval advantage. In game 97 Leela blocked the black passer with bishops, Stockfish pushed pawns on both sides of the board. The black queen moved forward on the king side and the white king moved without castling. Stockfish's (negative) eval increased and the black queen retreated.  Stockfish pushed the g pawn to g3 and moved the king side rook forward to capture a pawn. Leela captured the g3 pawn, Stockfish gave the rook for a bishop yet Leela's eval also increased. In a pawn trade the white queen moved forward on the king side and Leela created a passer there, Stockfish castled its king long. In a series of exchanges the game reached a RRN vs RBB position, Stockfish captured the white passer and was a pawn up.

Pawn exchanges opened the queen side and Stockfish created a second passer. The black king moved forward and Stockfish pushed a passer to d3. Stockfish gave its rook for the knight and captured another pawn. 

Stockfish saw the win in its PV, it had a skewer attack on the two white rooks but refused to exchange. Stockfish pushed the second passer to a6, the white king moved to help block the white passers and the black king moved forward to support them. Leela lost a rook for one passer to avoid mate, Stockfish captured the remaining white pawns and the game ended in a tablebase win. 

In game 98 the start was similar but not identical to game 97, Stockfish blocked the black passer and Leela pushed pawns on the king side. Stockfish thought for 41 minutes on its 4th move, yet Leela chose a different continuation. The engines played out a long PV agreement, Stockfish captured a pawn on the king side, there was a minor piece exchange on the queen side and the white king moved without castling. Leela regained the pawn and castled long, the engines opened files on the king side and exchanged a pair of rooks. Stockfish's (negative) eval increased, Leela refused to exchange rooks, instead it captured two pawns and exchanged the rook for a bishop, resulting in a QRN vs QBB position with black two pawns up. Leela's (negative) eval started to increase, Leela gave a pawn on the queen side but when it didn't take back Stockfish's eval dropped. The engines exchanged queens and Leela's eval dropped as well. The game reached a B vs R ending, Leela was up two pawns with connected passers on the queen side. Leela pushed the passers forward, Stockfish blocked with its king in front and its rook behind the pawns and there was nothing Leela could do. The engines shuffled until Leela lowered its eval for the draw rule on move 93. Stockfish wins the game pair, it leads 35-18.

Games 99-100 started with a 22-ply sideline in the KID orthodox variation. The center was blocked, all pieces and pawns were on the board. In game 99 the engines exchanged pawns and a pair of knights on the queen side. Leela's eval increased, the engines opened the a file and exchanged a pair of rooks. The engines shuffled for a while and Leela's eval came down. The white king walked to the queen side and the shuffle continued until the engines exchanged rooks on move 59. The engines opened the h file, Leela's eval came down slowly. Stockfish captured a pawn and the black queen moved forward. Leela regained the pawn and captured a knight, Stockfish ended the game in a perpetual check. In game 100 Stockfish pushed pawns on the queen side until it was locked with white pawns on a6 and c6. Leela pushed pawns on the king side, the engines opened the h file but completed a diagonal pawn wall with a black pawn on h3. The engines exchanged a pair of rooks and started to shuffle. Stockfish extended the shuffle with a pawn move, evals came down. On move 126 Stockfish gave a knight for two pawns on the king side, after another shuffle the engines started to exchange pieces. The game reached a B vs N ending, Stockfish was two pawns up but evals were low and the game was adjudicated.

Season 27 superfinal games 81-90

After 90 games Stockfish leads 32-18 with 40 draws. Stockfish won 3 game pairs and extended its lead to 14 wins. The 3 game pair wins were all long endgames where Stockfish saw the win many moves ahead and Leela was still unsure, and Stockfish played with minimal time available. Since there are only 10 games left Stockfish will win the match. Leela hasn't won a pair in the last 26 pairs. 

Games 81-82 started with a 20-ply sideline in the Sicilian Richter-Rauzer variation. The engines castled in opposite directions, there was one pawn exchange and all pieces were on the board. In game 81 the engines exchanged minor pieces, a pawn exchange opened the d file. The black queen moved forward on the king side and came back, both engines moved their major pieces to the center. Evals increased for a while, Leela's eval was over 1.5 on move 25. Stockfish thought Leela's move was a mistake and its eval dropped. In a series of exchanges the engines reduced to a QN vs QN position, Leela's eval came down as well. The engines traded pawns and created a white passer on the queen side and a black passer on the king side. Both passers raced forward, both were stopped. Leela captured a pawn but evals were low and the game was adjudicated.

In game 82 the engines repeated game 81 for 13 plys, the d file was open. Evals increased while Leela doubled rooks on the d file. A white knight blocked the file but in a series of exchanges the knight was exchanged as well as a pair of rooks. The game reached a QRB vs QRN position on move 24, the engines opened the f file as well. 

Stockfish moved its major pieces forward, Leela pushed the h pawn to avoid back rank threats. Stockfish moved its rook to the back rank and exchanged rooks. The engines traded pawns and created two white passers on the queen side and two black passers on the king side. Both engines pushed a passer forward, Stockfish captured a pawn in the center and it seemed Leela was winning the race. Leela captured the white passer and its passer was on the 2nd rank, but Stockfish captured the black knight with check, it saw the win in its PV.

It didn't seem possible for Stockfish to stop the queening as well as protect its bishop, but Stockfish was confident it could. The first set of checks ended with the white queen on g2 and Stockfish protected its bishop with the b pawn. Leela didn't have a check, next move Stockfish connected its bishop and queen on the long diagonal to prevent a queening, giving Leela a pawn. Leela gave a few checks and the white king moved forward. Stockfish pushed the black king back and the white queen moved to the 7th rank. It allowed the queening in the end, before mating. Stockfish wins the game pair, it leads 28-16.

Games 83-84 started with a rare 20-ply sideline in the Pirc defense, classical variation. All pawns and pieces were on the board, white had a space advantage. In game 83 there was a pawn exchange in the center, then a pair of knights were exchanged. Evals came down, on move 21 Leela gave a knight for a pawn and created connected passers on the queen side. Leela captured another pawn on the queen side, then a third pawn to open the d file. In a series of exchanges the engines reduced to a RB vs RRB position, Leela was down a rook but up 3 pawns. For a long while the engines mainly shuffled and made some pawn moves. On move 72 Stockfish gave a pawn, on move 81 Stockfish gave the bishop for one of the white passers. The game was adjudicated on move 99 when Leela lowered its eval for the draw rule. 

In game 84  the engines started similarly, with a pawn exchange in the center and a knight exchange, though with slightly different moves. Evals were mostly stable, the engines shuffled for a while. Stockfish pushed pawns on the king side, on move 32 Leela gave a pawn to open the center. The d file opened and the black queen moved forward. Leela regained the pawn, Stockfish's eval started to increase. In a long PV agreement there was a series of exchanges that reduced to a RR vs RB position with black a pawn up. 

Stockfish was down to increments and Leela's eval was low, it was not clear whether Stockfish's eval was real but it kept increasing. Leela created a passer on the queen side, Stockfish moved its rooks forward and captured the passer. Leela seemed to have a fortress on the king side, with the king and rook protecting the f7 pawn and the bishop on the long diagonal holding back the white king and pawns. For a very long time Stockfish moved its king and rooks to limit the black bishop. For a while Leela's eval dropped close to 0, then came back up but was still low. On move 74 Stockfish finally managed to force the black bishop away from the long diagonal. It saw the win in its PV.

Stockfish made sure the bishop stays away, on move 85 it pushed the f pawn and exchanged pawns. Then it pushed the g pawn and the black king became trapped. The game ended in a tablebase win. Stockfish wins the game pair, it leads 29-16.

Games 85-86 started with an 18-ply rare sideline in the English opening. There was one pawn exchange and all pieces were on the board, white had more space and the white king was still uncastled. In game 85 Leela exchanged minor pieces and castled its king. Leela managed to get a protected bishop to c6, evals increased slowly. On move 22 a pawn exchange on the king side weakened the black king support, a minor piece trade got the white bishop to e6 with check. The white queen attacked and Stockfish exchanged queens.

Stockfish exchanged bishops, creating a white advanced passer on e6. The black king moved to the center and captured the passer. A pawn exchange on the queen side created a black passer on the queen side, Stockfish gave a rook for a knight and reduced to a RR vs RN position on move 41.

Leela moved a rook forward and the engines traded pawns. The second white rook moved forward and Leela captured two pawns, it had 3 passers and Stockfish had 2. Both engines pushed passers forward slowly, on move 78 one white passer reached the 7th rank. Leela gave a rook and queened the passer, Stockfish had a passer on the 2nd rank while Leela queened a second passer, the game ended in mate.

In game 86 the engines repeated game 85 for 21 plys with transposition, Stockfish castled its king and moved a bishop to c6. Leela pushed pawns on the queen side, trapped the white bishop and created a passer. In a series of exchanges the white c6 bishop was exchanged as well as the queens. The game reached a RRB vs RRB position on move 27, Stockfish had a blocked passer on c7. 

Stockfish's eval slowly increased while Leela's eval stayed stable around 1. Leela captured the white passer and Stockfish opened the d file. The engines avoided exchanging rooks, there was another pawn exchange and Leela doubled rooks on the c file. Stockfish blocked the black passer, the white king moved forward and a pair of rooks was exchanged. On move 58 Leela's eval started to slowly increase, the white king kept moving forward until it reached d8, attacking the black bishop. 

Leela tried to keep its bishop, it exchanged rooks and gave pawns to save it. The game reached an opposite color bishop ending, Stockfish had a passer on the queen side and it kept the black king away. Leela captured two pawns on the king side but lost its bishop for the passer, the game ended in a tablebase win. There were two white wins in this pair, Stockfish leads 30-17.

Games 87-88 started with a line in the French Winawer, advance variation played in high level human chess. The center was blocked, all pieces and pawns were on the board and both kings were uncastled. In game 87 Stockfish thought for 42 minutes on its second move, the engines pushed pawns on the queen side, Stockfish exchanged a pair of bishops and the white king moved without castling. The engines locked the queen side, evals slowly increased as Stockfish castled long and the white king walked to the queen side. Stockfish's eval came back down a little, Leela moved its major pieces to the king side, it captured a pawn and exchanged queens and a pair of rooks. 

The black king walked back to the king side, Leela moved its knights to the queen side and its eval drifted down. On move 46 Leela pushed the g pawn to open the king side and evals jumped. After a minor piece exchange Leela created a passer on f6, the white rook moved forward and the game reached a RB vs RN position. 

Stockfish captured the white passer, Leela captured the black b and d pawns and created two more passers. Stockfish captured the white d pawn and Leela captured the black h pawn. Leela pushed the h passer and Stockfish lost material to stop it, the game ended in mate.

In game 88 Leela made a different choice on its second move, there was a bishop exchange but the white king did not move. There was a pawn exchange on the king side, the queen side stayed active. Leela walked its king to the queen side, the engines exchanged pawns and a pair of knights in the center and evals increased. Leela moved its queen forward on the queen side and Stockfish blocked its retreat. A series of exchanges opened the c file, Stockfish created a passer on the d file and Leela had one on the a file. On move 36 the game reached a QRB vs QRN position. 

The white king was under threat but safe enough. Stockfish moved its major pieces forward on the king side and captured 3 pawns. Leela captured one pawn on the queen side but the white passers were much more dangerous than the black ones. Both minor pieces were captured, Stockfish saw the win in its PV. Leela captured a white passer on the 7th rank, there were more exchanges and the game ended in a tablebase win. There were two white wins in this pair, Stockfish leads 31-18.

Games 89-90 started with a 20-ply sideline in the open Ruy Lopez, Bernstein variation. There was one pawn exchange, all pieces were on the board and the black king was still uncastled. In game 89 Stockfish captured a pawn in the center, Leela used a pin to captured a pawn on the queen side. Leela opened the a file, the engines exchanged a pair of rooks and minor pieces. Evals came down, Leela was a pawn up but Stockfish had a bishop pair advantage. The game reached a QNN vs QBB position, in another series of exchanges the engines reduced to a N vs B ending on move 35. Leela's eval was too high for the draw rule, the game continued for 30 moves before adjudication.

In game 90 the engines exchanged pawns on the queen side and a pair of bishops. Stockfish pushed the e pawn and exchanged it, the black king moved without castling. After move 17 Stockfish's eval started to increase while Leela's eval drifted down. Stockfish doubled queen and rook on the a file, a series of exchanges started on move 23 and Leela's eval jumped. The engines exchanged knights and rooks and opened the a and b files.

The white queen moved to the back rank and pinned the bishop. All minor pieces were exchanged and the game reached a QR vs QR position with white a pawn up. Stockfish avoided exchanges and arranged its pawns, its eval increasing quickly while Leela's eval stayed stable. On move 46 the rooks were exchanged. 

Stockfish's eval was very high, again it was down to increments. Leela's eval did not increase, Stockfish repeated checks, n move 63 there was a pawn exchange on the king side. Leela chased the white king across the board and Leela's eval started to increase. On move 99 the white king reached e6, Stockfish saw the win in its PV. There were a few pawn trades and the game ended in a tablebase win. Stockfish wins the game pair, it leads 32-18.

Season 27 superfinal games 71-80

After 80 games Stockfish leads 27-16 with 37 draws. All the last 5 game pairs were drawn, 4 had two white wins. Stockfish continues to lead by 11 wins and there are 10 pairs left in the match. Leela's non-win streak is now 21.

Games 71-72 started with a 20-ply sideline in the King's Indian defense played in human chess. All pieces and pawns were on the board. In game 71 the engines exchanged minor pieces on the king side and then opened the e file. Evals slowly increased, there was a pawn exchange on the queen side. For a while Stockfish blocked the center with minor pieces, eventually Leela exchanged a pair of bishops and a pair of rooks. 

After a few shuffling moves Leela moved its rook to the e file and its queen moved forward on the queen side. A knight exchange created a white passer on e6 and reduced to a QRB vs QRN position. Stockfish pushed pawns and locked the king side, Leela exchanged queens and its passer reached d7.

Stockfish captured the white d passer, the engines traded pawns and Stockfish created a passer on the queen side while Leela had a pawn majority on the king side. Leela captured a pawn on the king side and pushed its passers, Stockfish had no good counter, it lost more material and the game ended in a tablebase win.

In game 72 the engines exchanged minor pieces on the king side and opened the e file as before, the continuation was a little different though there was a pawn exchange on the queen side. Stockfish's eval slowly increased, Leela's eval remained stable. The engines exchanged a pair of rooks, Stockfish captured a pawn on the queen side and Leela avoided a queen exchange. Stockfish created a passer on the queen side through a knight exchange, the game reached a QRB vs QRB position.

Stockfish moved the bishop to c4 to keep all its queen side pawns protected. Leela avoided exchanges, its eval increased a little and the engines shuffled for a while. Leela blocked the queen side and the b passer, on move 49 the queens were exchanged.

Stockfish used its king as an additional piece, first to support a pawn exchange on the king side that opened the f file, then to support a pawn exchange on the queen side that opened the c file. After a pawn trade Stockfish created a passer on the king side. Leela gave the knight for the b5 passer, Stockfish queened the king side passer to win. There were two white wins in this pair, Stockfish leads 24-13.

Games 73-74 started with a 24-ply sideline in the Ruy Lopez, Chigorin defense variation played in human chess. The center was blocked, all pieces and pawns were on the board. In game 73 the engines opened the b file and Stockfish created doubled passers on the a file. Then a minor piece exchange created moved one black passer to b3. Evals increased a little, Leela captured the black b passer and the engines exchanged a pair of rooks. Leela gave back the pawn and created a passer in the center. 

The engines mostly shuffled for a long time, their evals not changing a lot. The king side was locked, on move 63 the remaining rooks were exchanged. Evals started to increase again, Leela moved the queen forward and on move 79 the queens were exchanged. The game reached a BN vs BN position. 

Both knights captured pawns, Stockfish captured the b5, f3 and g4 pawns, but Leela captured the h6 pawn which was more important. Leela had two advanced passers, Stockfish lost its knight and the king stopped one passer. Leela gave the bishop to stop the black a passer, then queened its remaining passer. The game ended in a tablebase win.

In game 74 the engines played a while without exchanges, on move 22 the pawn exchanges started on the queen side, opening the a and b files. Both engines created a passer, the engines exchanged a pair of rooks. On move 38 Leela pushed the f pawn, this led to the opening of the g file. Stockfish's eval jumped over 2 while Leela's eval was low, it didn't expect Stockfish to capture the black passer on the 40th move.

Leela's eval jumped a few moves too late. The engines exchanged a pair of bishops and Stockfish moved its major pieces to the king side. The exchanges continued and the game reached a knight ending on move 60, with white two pawns up. Stockfish pushed two passers forward, when the white king moved to support them Leela could not avoid a queening. The game ended in mate. There were two white wins in this pair, Stockfish leads 25-14.

Games 75-76 started with a sideline in the Caro-Kann, two knights attack variation. In game 75 there was a pawn exchange on the queen side, both engines castled their kings and Leela had strong pawns in the center. The engines exchanged a pair of bishops, the white d pawn became a passer. On move 24 evals started to increase, a pawn exchange opened the f file. The queens moved to the king side, a series of exchanges opened the h file and exposed the black king, Leela was a pawn up. The white king had minimal pawn support but the g pawn was also a passer. The queens were exchanged on move 43.

Stockfish regained the pawn and exchanged a pair of rooks, reducing to a RBN vs RBN position. Leela captured a pawn again and then gave the g passer. The kings moved forward and after a while the remaining rooks were exchanged. Leela captured a pawn and the a6 pawn became an unstoppable passer. Stockfish pushed the b pawn but Leela captured it, Leela queened and mated. 

In game 76 evals increased steadily from the start. The engines exchanged pawns on the king side and castled their kings. Pawn exchanges on the queen side opened the a and c files, Leela created a passer there. The engines exchanged a pair of bishops, Stockfish pushed the h pawn and opened the h file. The engines exchanged a pair of rooks, then all remaining minor pieces. Stockfish created a passer in the center and the game reached a QR vs QR position. 

Leela couldn't protect both the b and d pawns, the white queen moved forward and captured the d5 pawn. The engines exchanged rooks and traded pawns, Stockfish pushed its passer to e6 and saw the win in its PV. The white king moved forward and captured another pawn, the queens were exchanged and the game ended in a tablebase win. There were two white wins in this pair, Stockfish leads 26-15.

Games 77-78 started with a sideline in the Dutch defense, Queen's knight variation. All pieces and pawns were on the board, both kings were castled. In game 77 there was a pawn exchange in the center, evals came down quickly and the engines exchanged a few minor pieces. The e file opened and there were more exchanges, the game reached a queen ending and was adjudicated on move 44. In game 78 there were no exchanges right after the start, a few moves later there were pawn exchanges on the queen side. The black queen moved forward on the king side and there was a pawn exchange there. Evals started to come down, the black queen retreated and the engines shuffled for a while. On move 39 there was a minor piece exchange, first pieces off the board. Then queens were off in a series of exchanges, both engines had a passer and Leela had a bishop pair advantage. Stockfish captured a pawn and the game reached a RRN vs RRB position. Stockfish captured more pawns, but Leela ended the game in perpetual check and a repetition.

Games 79-80 started with a 22-ply rare sideline of the Benoni defense, Taimanov variation. There was one pawn exchange and all pieces were on the board. In game 79 there was a minor piece exchange on the king side, evals slowly increased. The black queen moved forward on the queen side, came back, moved forward on the king side and came back again. On move 30 Stockfish created a pawn majority on the queen side. Leela doubled rooks on the half open g file, Stockfish doubled rooks on the c file, opened the b file and created a passer.

Leela moved a bishop to c6 to disconnect the rooks from the c4 passer. Stockfish moved a rook forward on the b file to support the pawn, the engines exchanged a pair of rooks. Stockfish gave a rook for the blocking bishop and a pawn, still holding on to its passer. The game reached a QRN vs QBN position, Leela captured the black passer and Stockfish created two new passers. On move 61 queens were exchanged. 

Leela captured the two black passers on the queen side, Stockfish managed to regain a pawn after exchanging knights but the game ended in a tablebase win.

In game 80 the engines exchanged bishops in the center and opened the c file. More minor pieces were exchanged and Stockfish captured a pawn. Evals increased, Leela doubled rooks on the c file and Stockfish pushed pawns in the center. On move 28 Stockfish gave a knight for a pawn and created connected passers in the center. 

Leela captured a pawn on the queen side, Stockfish pushed the e4 pawn, after exchanging queens Stockish had 3 connected passers in the center. Leela lost a rook for a passer, it captured the other two  passers and Stockfish saw the win in its PV. The game reached a R vs N ending, black with two pawns up. The white king moved forward and Stockfish captured pawns, the game ended in a tablebase win. There were two white wins in this pair, Stockfish leads 27-16.

Season 27 superfinal games 61-70

After 70 games Stockfish leads 23-12 with 35 draws. Stockfish won two game pairs and its lead is 11 wins. Leela hasn't won a game pair in the last 16 pairs, and there are only 15 pairs left in the match.

Games 61-62 started with a sideline in the Queen's gambit accepted, central variation. Black was up a pawn with a passer in the center. In game 61 Leela exchanged both its bishops for knights causing two black doubled pawns. Leela captured the black passer, both queens moved forward and then were exchanged. The game reached a RN vs RB position, Stockfish's eval came down while Leela remained stable. The engines shuffled for a long with a few pawn moves, after move 88 the started to exchange pawns and pieces and Leela's eval came down enough for adjudication. In game 62 Stockfish exchanged minor pieces and captured the passer. After more exchanges the game reached a QRN vs QRB position on move 18. Evals came down, another series of exchanges reduced to a rook ending with white a pawn up. Evals were low enough for the draw rule and the game was adjudicated. 

Games 63-64 started with a rare sideline in the French Tarrasch, pawn center variation. The center was locked, all pieces and pawns were on the board. In game 63 Leela pushed pawns on the king side and castled short, Stockfish pushed pawns on the queen side and opened the b file. The engines exchanged a pair of rooks and Stockfish castled short as well. Evals were stable as the engines mostly shuffled, for a few moves Leela's eval increased above 1.5. Stockfish captured a pawn and created a passer on the queen side, Leela's eval came back down. Leela opened the king side, Stockfish gave a knight for two pawns and exchanged queens.

The engines shuffled again for a while with stable evals, Leela moved a rook to the 7th rank. On move 52 the engines traded minor pieces, evals started to increase. Stockfish pushed a passer to h3, then gave a rook for a bishop and reduced to a RNN vs BB position with black 3 pawns up. 

Stockfish pushed a second passer to a3, Leela blocked with a knight, then exchanged the other knight for a bishop. Stockfish captured a pawn on the king side and pushed its passers there to g3 and h2 but there the white king blocked them. Leela gradually captured pawns and the game ended in a tablebase win.

In game 64 again Stockfish pushed pawns on the king side and Leela pushed pawns on the queen side, the piece moves were a little different and evals increased early. Stockfish castled short and the engines exchanged a pair of rooks. The black queen moved forward on the b file, Leela captured a pawn and created an advanced passer. Stockfish pushed the f pawn, Leela gave a knight for the pawn to keep the king side closed.

Stockfish moved major pieces to the a file and Leela castled its king. Leela lost the passer and traded queen for a rook and knight. Leela captured a pawn and created another passer on the queen side, it tried to block the opening in the pawn wall with its remaining pieces. On move 45 the engines exchanged a pair of bishops and the game reached a QNN vs RBN position. 

Leela couldn't hold the block on the queen side, after a series of exchanges the engines reduced to a knight vs pawns endgame. The white king moved forward and captured pawns, Stockfish queened a passer and mated. There were two white wins in this pair, Stockfish leads 21-12.

Games 65-66 started with a 22-ply sideline in the Nimzo-Indian defense, Saemisch variation. The engines castled in opposite directions, all pawns were on the board and there was one minor piece exchange. In game 65 the engines played behind their pawn lines and blocked the queen side. There was a pawn exchange in the center and another on the king side, Leela gave a pawn and opened the e file. Stockfish's eval came down, the major pieces moved to the king side and a minor piece exchange opened the f file. The engines exchanged queens and Leela's eval came down as well. The exchanges continued and the game was adjudicated on move 45. In game 66 Stockfish thought for 45 minutes on its second move. The engines blocked the queen side and exchanged minor pieces on the king side. Leela captured a pawn on the queen side and created a passer, Stockfish locked the center and exchanged bishops. Stockfish regained the pawn, it avoided a queen exchange for a few moves but then agreed. In a RRN vs RRN position the engines started to shuffle, Stockfish's eval came down while Leela's eval was not low enough for the draw rule. The engines exchanged knights, the game was adjudicated on move 99. 

Games 67-68 started with a sideline in the Ruy Lopez exchange, Bronstein variation. The engines castled in opposite directions, all pawns were on the board and there was one minor piece exchange. In game 67 Stockfish thought for 45 minutes on its first move, which was not what Leela expected. There was one pawn exchange on the king side, Leela pushed pawns on the queen side and a pawn exchange opened the b file. In a series of exchanges the queens were off, evals slowly came down. The pawns stabilized and the game reached a RRN vs RRB position. There was a long shuffle, the game was adjudicated on move 85 after a series of exchanges.

In game 68 Leela played the first move it expected in game 67. Stockfish pushed pawns on the queen side, there was a minor piece exchange on the king side. Evals started to increase, a pawn exchange opened the d file, Stockfish moved its queen forward on the queen side and captured a pawn. The black king felt the danger and walked to the king side. The white queen retreated, a pawn exchange opened the b file, Leela regained the pawn and the game reached a RBN vs RBN position. Stockfish pushed a passer to a7 and Leela blocked with the rook. 

Stockfish moved pieces forward on the queen side while the black king walked back there, Stockfish captured a pawn, Leela replaced the rook with its king as a blocker on a8. Leela pushed the c passer until it reached c2 and the white king blocked it. In a series of exchanges most pieces were off as well as the two passers and only knights remained. Stockfish was up a pawn, it captured a second pawn and the game ended in a tablebase win. Stockfish wins the game pair, it leads 22-12.

Games 69-70 started with a 22-ply rare sideline in the Sicilian Najdorf variation played in human chess. There was one pawn exchange, all pieces were on the board, white castled long and the black king was uncastled. In game 69 the engines exchanged a pair of knights, Stockfish threatened the white king on the queen side and kept its king in the center. On move 21 evals dropped, Stockfish opened the center and the black queen moved forward. Leela countered and forced the black king to move, after a series of exchanges the game reached a RR vs Q ending. Both kings were exposed, evals were low and the game was adjudicated.

In game 70 after exchanging knights Leela did not threaten the white king immediately. Stockfish captured the g7 pawn with its queen and Leela captured the g2 with a rook, the engines exchanged a pair of rooks. Leela moved its other rook, so there was no option of castling the king.

Stockfish moved a rook to the open g file, its eval started to increase. Stockfish opened the center with a pawn exchange, the white queen moved to the king side as well. The black king felt in danger and Leela moved it to the queen side. The engines opened the queen side and after a series of exchanges the game reached a QN vs QN position. Stockfish's eval was close to 4 while Leela's eval was still low. 

The black queen moved to capture the white h passer. This exposed the black king to attacks, Stockfish gave many repeating checks and captured the a pawn. On move 82 Stockfish managed to get its knight to d6, by this time Leela's eval was already increasing. Stockfish saw the win in its PV, it avoided a queen exchange, Leela lost material and the game ended in mate. Stockfish wins the game pair, it leads 23-12.