Openings analysis, seasons 6-16 late stages

About two years ago I did some statistical analysis of the openings that were chosen for the late stages of TCEC. My focus was to try to measure the size of the "TCEC opening space", an undefined and elusive concept. More details can be found in the previous report. I repeat this analysis here with 2.5x more games. I added information about the draw rate (dr) and score (sc) of the openings where:

dr = draw rate (percent) = (number of draws) / (number of games) * 100
sc = score (number between 0 and 1) = average score for white =
  = (number of white wins + 0.5*number of draws) / (number of games)

The games I used for the analysis:

• 1246 games from seasons 6-10, as detailed in the previous report.
• Season 11 premier division - 280 games. The first two RRs in this division were without book and were not used for the analysis.
• Season 11 superfinal - 100 games
• Season 12 premier division - 168 games. Chiron crashed frequently in the division and was disqualified, its games were not used in the analysis.
• Season 12 superfinal - 100 games
• Season 13 premier division - 224 games.
• Season 13 superfinal - 100 games
• Season 14 premier division - 168 games.
• Season 14 superfinal - 100 games
• Season 15 premier division - 168 games.
• Season 15 superfinal - 100 games
• Season 16 premier division - 168 games.
• Season 16 superfinal - 100 games

Total is 3022 games, 1511 game pairs.

The total win statistics are: dr = 68.8%, sc = 0.59

ECO, first letter

 
Entropy =  4.92

ECO, full code

There are 500 different ECO codes. The entropy of the ECO codes in the list is 280.1, covering 390 different codes out of the possible 500. The most frequent ECO codes are

• B90 50 times, dr=62.0%, sc=0.65, Sicilian Najdorf
• B12 38 times, dr=71.1%, sc=0.57, Caro-Kann defense
• B06 36 times, dr=58.3%, sc=0.63, Robatsch (modern) defense
• C11 33 times, dr=66.7%, sc=0.58, French defense
• B01 32 times, dr=81.3%, sc=0.53, Scandinavian defense
• A57 30 times, dr=76.7%, sc=0.62, Benko gambit 

ECO codes with the lowest draw rates and at least 10 games:

• B51 10 times, dr=20.0%, sc=0.70, Sicilian, Canal-Sokolsky attack
• E99 11 times, dr=36.4%, sc=0.45, King's Indian, orthodox, Aronin-Taimanov, main line
• A00 14 times, dr=42.9%, sc=0.64, Polish opening
• C02 20 times, dr=45.0%, sc=0.68, French advance

 ECO codes with the highest draw rates and at least 10 games:

• A25 10 times, dr=100%, sc=0.50, English, Sicilian reversed
• D43 10 times, dr=100%, sc=0.50, QGD semi-Slav
• B89 12 times, dr=91.7%, sc=0.54, Sicilian, Sozin
• A20 18 times, dr=88.9%, sc=0.56, English
• D10 18 times, dr=88.9%, sc=0.56, QGD Slav defense

 ECO codes with the lowest scores and at least 10 games:

• A13 13 times, dr=69.2%, sc=0.42, English
• C34 19 times, dr=78.9%, sc=0.45, King's Gambit accepted
• C33 10 times, dr=70.0%, sc=0.45, King's Gambit accepted
• E99 11 times, dr=36.4%, sc=0.45, King's Indian, orthodox, Aronin-Taimanov, main line
• A36 14 times, dr=78.6%, sc=0.46, English symmetric

 ECO codes with the highest scores and at least 10 games:

• C57 10 times, dr=50.0%, sc=0.75, Two Knights defense
• B78 11 times, dr=54.5%, sc=0.73, Sicilian, dragon, Yugoslav attack
• A16 12 times, dr=58.3%, sc=0.71, English
• A52 10 times, dr=60.0%, sc=0.70, Budapest defense
• B51 10 times, dr=20.0%, sc=0.70, Sicilian, Canal-Sokolsky attack
• B95 10 times, dr=60.0%, sc=0.70, Sicilian Najdorf

Book sequences

If we look at the full book sequences, there are 1452 distinct sequences out of 1511 game pairs, with entropy 1428.4. There are 47 book sequences that appeared in 2 game pairs, 6 book sequences appeared in 3 game pairs.

I truncated the book sequences at fixed lengths to measure the expansion as the length increases. For short lengths I also list the most frequent sequences.

After 2 plys the entropy is only 13.42, a total of 47 sequences for 1506 game pairs. The leading sequences are:

• 1. d4 Nf6, 25.9%, dr=68.6%, sc=0.58
• 1. e4 c5, 18.7%, dr=69.0%, sc=0.60
• 1. e4 e5, 10.9%, dr=70.4%, sc=0.57
• 1. d4 d5, 8.3%, dr=72.0%, sc=0.58
• 1. e4 e6, 6.6%, dr=61.6%, sc=0.63

After 4 plys the entropy is 53.7, a total of 203 sequences for 1503 game pairs. The leading sequences are:

• 1. d4 Nf6 2. c4 e6, 9.7%, dr=72.6%, sc=0.57
• 1. d4 Nf6 2. c4 g6, 8.0%, dr=66.3%, sc=0.58
• 1. e4 c5 2. Nf3 d6, 7.6%, dr=66.2%, sc=0.62
• 1. e4 e5 2. Nf3 Nc6, 7.5%, dr=67.3%, sc=0.59
• 1. e4 e6 2. d4 d5, 5.9%, dr=61.2%, sc=0.64

After 6 plys the entropy is 163.9, a total of 440 sequences for 1487 game pairs. The leading sequences are:

• 1. e4 c5 2. Nf3 d6 3. d4 cxd4, 6.8%, dr=68.8%, sc=0.61
• 1. d4 Nf6 2. c4 g6 3. Nc3 Bg7, 5.7%, dr=64.7%, sc=0.56
• 1. e4 c5 2. Nf3 Nc6 3. d4 cxd4, 3.6%, dr=75.5%, sc=0.57
• 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6, 3.5%, dr=71.1%, sc=0.61
• 1. e4 c5 2. Nf3 e6 3. d4 cxd4, 3.2%, dr=71.9%, sc=0.61
• 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4, 3.0%, dr=70.0%, sc=0.56

After 8 plys the entropy is 313.0, a total of 637 sequences for 1445 game pairs.
After 10 plys the entropy is 492.3, a total of 803 sequences for 1399 game pairs.
After 12 plys the entropy is 729.9, a total of 936 sequences for 1355 game pairs.
After 16 plys the entropy is 1095.7, a total of 1156 sequences for 1252 game pairs.

Season 16 superfinal games 91-100

Stockfish won the season 16 superfinal The final score is 14-5 with 81 draws. It was clear that Stockfish was going to win, AllieStein managed to win a game in the last game pair and then blundered in the reverse.

The superfinal was quite one-sided. Stockfish returns as a champion after losing in the previous superfinal to Leela. Stockfish barely made it through the premier division after crashing twice due to a software bug. Despite the crashes it finished first in the division.  AllieStein played well in the premier division but was clearly not prepared for a head-to-head match with Stockfish. In the premier division Stockfish beat AllieStein in 3 of 6 games, AllieStein's performance was better in the superfinal but still it blundered away too many games.

We did not get a rematch of Stockfish and Leela after Leela finished third in the premier division and did not qualify for the superfinal. Leela was the only engine to have a positive score against Stockfish, I'm sure that the superfinal would have been more competitive with Leela instead of AllieStein, perhaps Leela would have won. Leela needs to improve its skiils in multi-engine competitions. Stockfish is consistently winning the premier division of the last few seasons, it appears to be a better all-around player than Leela.

Season 16 is over. It was another great season for me in terms of viewers, so thank you all !!  This last post took some time to complete, I was less in a hurry once the result of the match was obvious and I started my TCEC cup break a little early. My coverage of the season was interrupted just before the premier division and the season felt like a race to catch up since then. I'm glad it's finally over. I saw myself referenced in a chat command about the book sequences of the superfinals, and I feel obliged to repeat the analysis I ran about two years ago. I'm working on this now and will post the results soon.

TCEC is getting more coverage than a few years ago. Guy Haworth and Nelson Hernandez (Cato !) publish an article that summarizes each season - with a kind reference to this blog. Chess GM Matthew Sadler published reports of the superfinals in seasons 14 and 15. These articles can be found on the TCEC main site under the "TCEC Articles" tab. Kingscrusher has posted video reports of selected TCEC games for the last few seasons, mainly following the NN engines rise to the top. There is also a wiki page for TCEC with pages for individual seasons starting with season 14.

I'll be back for season 17, Go TCEC !!

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Games 91-92 started with a King's Gambit variation. In game 91 Stockfish kept connected pawns on the king side facing the white king. The black king was exposed and AllieStein used its bishops to threaten the king side along diagonals. A long series of exchanges resulted in an opposite color bishop ending, Stockfish refused to lower its eval and the engines continued to play until move 122. In game 92 the black king walked to the king side without castling. Stockfish opened a file in the center and the engines exchanged all the rooks. The game reached a queen ending, Stockfish chased the black king giving checks with its queen. The game ended in a tablebase draw.

Games 93-94 started with a 20-ply book sequence in the QGD opening exchange variation, where the engines castled in opposite directions. In game 93 the engines exchanged pieces and pawns in the center, then Stockfish gave a knight for two pawns and created connected passers on the queen side. Evals were negative from the start, Stockfish's evals increased over 2 while it moved its major pieces to support the passers and face the white king.

AllieStein was relatively calm with eval under 1. It blocked the passers while Stockfish increased the pressure on the open b file. AllieStein realized it was in danger but it was too late.

Stockfish moved a rook to the 2nd rank threatening mate. AlllieStein tried to counter with a weak attack on the black king without results. Stockfish had too many attacking options and the game was quickly adjudicated.

In game 94 Stockfish gave a pawn and opened the king side, its rooks threatened the black king. AllieStein played defensively, its eval slowly coming down. Stockfish traded RN for Q, the engines slowly exchanged pieces, AllieStein sacrificed a knight and the game reached a Q vs R ending. AllieStein was two pawns up, Stockfish's eval jumped but the black king could not be attacked by its queen. The engines shuffled and the game ended in a 50-move draw.

In game 95 Stockfish's eval was 0 almost the entire game. Both engines castled long, then they opened the king side. There were many early exchanges and only RNN vs RBN remained on move 27. The engines mainly shuffled with an occasional pawn move for a long time, AllieStein used all its time on one move as it does sometimes. After move 100 the engines started exchanging pawns and by move 119 the game reached a RN vs RB position. The game ended in a tablebase draw. In game 96 both engines kept their king in the center. There were no pawn exchanges after the start, after several pieces were exchanged the game reached a QRN vs QRN position on move 34.The engines shuffled for a while and then exchanged queens. It took 50 more moves, with both engines promoting a pawn to a queen, before AllieStein lowered its eval for the draw rule (the draw rule bug prevented the game from ending about 15 moves earlier).

In game 97 AllieStein kept its king in the center and pushed pawns on the king side. Stockfish pushed pawns on the queen side and its eval came down to 0. AllieStein used an open file on the queen side to move its queen to the 7th rank, Stockfish sacrificed a knight and forced a repetition draw by attacking the white queen. In game 98 AllieStein pushed pawns on the king side, leaving its king without pawn support in an open file. Stockfish castled long though there was an open file on the queen side as well. AllieStein gave a rook for a bishop and closed the king side file, evals turned negative. After a short shuffling period the engines exchanged queens, AllieStein's eval was over 4. Evals remained constant through another shuffle, then AllieStein captured a pawn and its eval jumped over 8. The shuffling continued and evals came slowly down, then the engines reduced to a RB vs BN position with black two pawns up. AllieStein continued to think it was winning, the game ended in a 50-move draw on move 229.

Games 99-100 started with a 23-ply book sequence in the Sicilian, Accelerated Dragon variation, where the engines castled in opposite directions. In game 99 AllieStein's eval was over 2 almost from the start. Stockfish gave a rook for a bishop and opened the queen side. The attack on the white king was weak, AllieStein used the open file to exchange queens and a pair of rooks. The game reached a RBN vs BBN position on move 30.

The engines exchanged pawns and more files opened, the white rook became stronger with more space to move. AllieStein's eval jumped over 4 and continued to increase, Stockfish's eval stayed below 2, perhaps it thought its bishop pair was strong enough. The engines mostly shuffled for a while, then AllieStein forced a trade of one of the black bishops. Stockfish chose to take a knight for it but its eval jumped to around 3.

The end game was slow, AllieStein captured and exchanged pawns when it could and evals continued to increase. On move 80 AllieStein captured a pawn and created a queen side passer.

AllieStein was not in a hurry, it seemed it was not trying to win. Stockfish's eval increased when its king was blocked away from the queen side. AllieStein finally started to move its passer forward and the game was adjudicated.

In game 100 Stockfish gave two pawns and opened the king side, AllieStein gave a rook for a knight and weakened the white center. Evals were over 1 for a while, they came down after Stockfish's attack died down. The black king was still quite exposed but both engines thought it was safe enough.

Evals stayed low for a while, not a lot happened until AllieStein decided to push pawns on the king side and then move its king up the board. AllieStein played a few moves from its PV without thinking, suddenly Stockfish's eval jumped over 2 and it started giving checks with the black king in the center. AllieStein pushed a pawn to the 3rd rank and thought that the threat of promotion was enough compensation.

AllieStein soon realized its king was in a mating net. Stockfish captured the passer and then continued to give checks with the queen attacking from all directions. The game was adjudicated before Stockfish started to win material.

Season 16 superfinal statistics

A summary statistics table of previous stages and seasons. 

Draw rate, wins

 
Final draw rate was 81%.


Game termination

The three most common game termination causes were:

26% - SyzygyTB
21% - TCEC draw rule
20% - 3-Fold repetition


There were no crashes in the stage. One game ended with mate on the board, very unusual for a superfinal.

Moves per game

Median= 82
Average= 89

The games are longer when NN engines are involved, due to different scoring methods that delay the application of the win and draw rules. There were 32 games longer than 100 moves, the longest was 242 moves (Stockfish - AllieStein, game 54, draw).

Time per game (hours)

 
Median= 4:09
Average= 3:53

Openings

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


The engines had almost no freedom to choose the opening variant, 94% of the game pairs repeated the same ECO code, 92% repeated the opening variant. In 96% of the game pairs the ECO first letter was repeated twice. A notable exception was the first game pair which was without book.

Reverse pairs, wins

 

Reverse pairs, same moves

 
Pairs of reverse games diverged very quickly, 34% diverged immediately out of book, 68% of the pairs diverged at most after 1 move. The longest repeated sequence of moves was 16 plys (AllieStein - Stockfish games 15 and 16, Robatsch defense, pseudo-Austrian attack variation, two draws)

Season 16 superfinal games 81-90

After 90 games Stockfish leads 12-4 with 74 draws. The last 10 games were all draws, Stockfish continues to lead with a gap of 8 points.

There were almost no exchanges after the start of game 81, Stockfish's eval was 0 and AllieStein's eval was under 1. In a series of exchanges Stockfish traded RB for Q and then it started to chase the white king with checks. AllieStein gave back the material and the game reached a knight ending. The engines continued to play, the game ended in a tablebase draw. In game 82 the king side opened early and Stockfish preferred to castle long. AllieStein's eval turned negative, there was a long period of mainly shuffling and then a long series of exchanges that left a BNN vs BNN position. Both evals came down, the engines played until AllieStein's eval was low enough for the draw rule.

Games 83-84 started with a 20-ply book sequence in the Sicilian Najdorf opening, Adams attack variation. In game 83 the engines castled in opposite directions, Stockfish's eval was 0 almost from the start. Stockfish gave a rook for a knight and pawns, opening the queen side. AllieStein moved its rook and to the 7th rank, then its queen moved forward. This left the white king exposed, Stockfish started giving checks with its queen. Eventually the game ended in a check repetition. In game 84 the engines first exchanged pawns and pieces in the center and then castled in opposite directions. Stockfish gave a pawn and then the engines exchanged all rooks, only QB vs QB remained on move 33. The engines exchanged a few pawns and pushed passers forward, then Stockfish forced a repetition draw.

AllieStein started game 85 with an eval over 1. The engines gradually exchanged pieces and pawns, on move 33 only QBB vs QBB remained with pawns only on the king side. After a long shuffle the engines exchanged down to a same color bishop ending. AllieStein was a pawn up and it wouldn't lower its eval. Pawn moves kept the game going until a 50-move draw on move 193. In game 86 queens were exchanged early, the engines opened the queen side and removed all knights. Stockfish was a pawn up with an advanced passer on the queen side, AllieStein's bishops controlled the center and it moved a rook to the 2nd rank. AllieStein captured the passer, Stockfish gave a rook for a bishop and the game reached a RBB vs RRB position with white two pawns up and evals at 0. The black king was exposed and AllieStein started giving checks. The game should have ended by the draw rule, in the end it was a draw by repetition.

Game 87 was a miniature that ended in a repetition draw on move 17. In game 88 all the pawns were on the board and the engines played behind their pawn lines. The engines started to shuffle after the first pawn exchange, Stockfish avoided a 50-move draw and opened the queen side. The engines exchanged pieces until only QR vs QB were left with black a pawn up, the game was adjudicated by the draw rule.

Queens were off early in game 89, forcing the black king to move. Alliestein captured a pawn and opened the king side, it kept its king uncastled as well. The game reached a RRN vs RRN position on move 35, AllieStein's eval came slowly down. The engines continued to exchange pieces and pawns, the game ended in a tablebase draw. In game 90 there were several early exchanges that opened the queen side, Stockfish went two pawns up yet evals were close to 0. Queens were exchanged, AllieStein's pieces were more developed and it pushed pawns on the queen side while Stockfish improved its position. After trading all the queen side pawns Stockfish pushed pawns in the center. There was a long series of exchanges and only N vs B remained with equal material and pawns only on the king side. The game was adjudicated when evals were low enough for the draw rule.

Season 16 superfinal games 71-80

After 80 games Stockfish leads 12-4 with 64 draws. The gap stays at 8 points with 20 games to go. AllieStein finally won a game after 6 losses in the last 40 games.
There were crashes in games 71 and 75, the games were later resumed.

In game 71 Stockfish pushed pawns on the king side and kept its king in the center. The engines opened the queen side and the black king walked to the king side even though there was no pawn protection there. After a few exchanges Stockfish blocked the entry points and the engines started to shuffle. AllieStein could not find a way in, the game ended in a 50-move draw. Game 72 started similarly, AllieStein kept its king in the center and pushed pawns on the king side, its eval turned negative. Stockfish countered on the queen side, it went a pawn up and its eval was 0. AllieStein traded a bishop and knight for a rook, then a series of exchanges led to a RB vs R position, black two pawns up. Stockfish gave its bishop for pawns, the rook ending was a draw and the game was adjudicated when AllieStein lowered its eval.

In game 73 Stockfish's eval was 0 from the start. The engines opened two files, after exchanging a pair of rooks each engine controlled one file. Neither engine attempted to attack and the engines started to shuffle. The pawns stabilized and shuffling continued until a 50 move draw. In game 74 the engines locked pawns on the queen side without exchanges. AllieStein's eval turned negative in the closed position, it captured a pawn on the queen side and evals started to increase. AllieStein gave back the pawn and created a queen side passer, its eval peaked over 3 as it shifted to the king side and tried to break through. Stockfish guarded the entry points and the engines started to shuffle, AllieStein's eval slowly came down. AllieStein avoided the 50-move draw, then gave another pawn and opened a file on the king side. The engines exchanged a pair of rooks and queens and only RBN vs RNN remained, Stockfish a pawn up. For a short while Stockfish's eval jumped to almost 3, it created two passers on the 7th rank, then gave the bishop and promoted one pawn to a queen. However, AllieStein had a passer on the 2nd rank, and it used this threat to force a repetition draw.

AllieStein's eval was over 1 from the start of game 75. Evals started to jump without a visible reason at first. AllieStein pushed pawns on the king side and moved its king forward, leaving the first two ranks empty for its rooks for quick maneuvering. Stockfish's queen was stuck on the queen side, almost out of the game completely.

Evals continued to climb quickly, the white pawns looked dangerous for the black king. Stockfish gave a rook for a bishop and exchanged queens, the game reached a RRN vs RBB position. The black king was out of danger, AllieStein still had better pieces and a material advantage.

Both engines agreed that the material advantage and position was winning for white. AllieStein created an advanced passer on the king side, its PV showed that its plan was to create more passers by giving a rook for a bishop and pawn. The game was adjudicated on move 47.

In game 76 Stockfish pushed pawns on the king side, AllieStein made sure its king had pawn protection. Stockfish's king was exposed, it went a pawn up and had a bishop pair while AllieStein had a pair of knights. AllieStein pushed a pawn all the way to a2 where it was blocked, then it used almost all its time thinking about one move. The engines mainly shuffled for a long while and evals came down. AllieStein traded Q for RB, the game reached a QR vs RRN position and ended in a tablebase position.

AllieStein had an eval over 1 from the start of game 77, it opened the queen side and went two pawns up. Stockfish moved a knight forward and countered on the king side, its eval was at 0 while AllieStein's eval jumped over 2. AllieStein pushed a passer to the 7th rank, Stockfish captured it there and after a series of exchanges the game reached a QBB vs QRB position with white 2 pawns up. The engines exchanged queens and black had no more pawns. The 8-man position was a draw, AllieStein tried to push its pawns forward but Stockfish prevented their promotion. The game ended in a tablebase draw on move 175. In game 78 both kings were in the center, AllieStein attacked on the queen side and Stockfish on the king side. There were many early exchanges, the black king was forced to move, the white king castled late to escape a mate threat. The game reached a QRB vs QRN position on move 28, queens were then exchanged and the game ended in a tablebase draw on move 47.

In game 79 the engines blocked the center and opened the queen side. After exchanging a pair of rooks Stockfish's eval came down to 0 and the engines mostly shuffled. On move 72 the engines resumed exchanging pieces and the game reached a rook ending, and later a tablebase draw.

In game 80 the engines blocked the center and the queen side. All the pawns remained on the board, the engines slowly pushed the king side pawns until the king side was also blocked. The engines played behind the pawn lines and mostly shuffled, most of the minor pieces were exchanged along open diagonals and evals stayed low. On move 135 the engines exchanged queens and only RRB vs RRB remained, then AllieStein gave a pawn.

Stockfish was careful not to allow the black e pawn to advance. Meanwhile the black king had a path forward on the dark squares. AllieStein hesitated for a while, then decided to walk forward with its king all the way to g3. Stockfish offered the f3 pawn and AllieStein took it.

Stockfish's eval immediately jumped to around 2, AllieStein's eval increased gradually as well. The king side was opened after a few moves and the forward black king was exposed to attacks by the rooks. Stockfish was able to move a rook forward to the 6th rank where the black pawns were unguarded and to capture two.

AllieStein tried to counter by placing its rooks on the 2nd rank but the white king was safe enough and Stockfish pushed the d pawn forward. The pawn promoted to a queen at the cost of a rook, the QR vs RR ending was a win for Stockfish.

Season 16 superfinal games 61-70

After 70 games Stockfish leads 11-3 with 56 draws. Stockfish extends its leads to 8 points with only 30 games left. AllieStein has not won since game 39, it is hard to imagine it can close the gap.
The network crashed in game 70 and it was later resumed.

Games 61-62 started with a variation of the Trompowsky attack where white lets the black queen grab two pawns on the queen side. In game 61 AllieStein walked its king to the king side. Stockfish pushed pawns on the king side, it had to be careful because its own king was exposed and most defenders were on the queen side. Evals dropped to 0, AllieStein ignored an attack on its knight on the queen side and planned a king side attack. It was following its PV automatically and failed to see Stockfish's reply on move 24. Evals immediately jumped and AllieStein realized it was in trouble, Stockfish had an immediate mate threat.

The engines exchanged queens and the kings were no longer in danger. Stockfish was up a rook for a bishop but its queen side pieces had to develop safely. AllieStein used the time to gain a few pawns, the game reached a RBN vs RRB position with apparent material equality but Stockfish had a huge eval advantage.

The d6 pawn was soon captured. Stockfish's rooks did not allow the white king to leave the king side, the black king was an extra piece on top of the material advantage. The game was adjudicated when evals were high enough. This was the first win for black in the match.

In game 62 the black queen escaped to the king side, AllieStein trapped a white bishop. Stockfish captured two pawns for the bishop and won a rook, then AllieStein gave a knight for two pawns. Stockfish was up a rook for 2 pawns, AllieStein compensated with two connected central passers facing an exposed white king, and evals were at 0. Stockfish castled and AllieStein pushed a passer to the 2nd rank. When it pushed the second passer forward Stockfish gave a knight and captured the passers. All remaining pawns were on the king side, after some shuffling the engines exchanged down to a B vs BN position with Stockfish 2 pawns up. The endgame was very long, AllieStein thought it had an advantage when it blocked the white pawns and pushed its single pawn forward. Its eval peaked around (negative) 4.5, but there was no real advantage. The game finally reached a tablebase draw on move 125.

In game 63 the engines mostly played behind their pawn lines, AllieStein's eval was around 2. Stockfish opened a file on the queen side and doubled rooks. The engines exchanged all knights and a pair of rooks, Stockfish's eval dropped to 0 and the game reached a RBB vs RBB position. The engines shuffled, AllieStein's eval came slowly down as it couldn't break the pawn wall. The game was adjudicated when evals were low enough for the draw rule.

There were a few quick exchanges at the start of game 64, evals were over 1. After the engines castled Stockfish pushed pawns on the queen side and its eval started to increase. After a few exchanges the queen side opened and AllieStein was a pawn up, all the black pieces were on the queen side yet AllieStein thought it was safe with an eval of 0. It did not anticipate Stockfish's next move.

Stockfish sacrificed a bishop and opened the king side immediately. AllieStein thought white would first move its queen to give the bishop support. Now Stockfish threatened mate on the h file, AllieStein realized this when it stopped to think a few moves later. It exchanged queens but Stockfish doubled rooks on the 7th rank.

Stockfish captured the black g pawn and pushed the e pawn to the 7th rank, then moved its rooks to the 8th rank. All of the black pieces were busy preventing the pawn from queening, Stockfish pushed another pawn forward, it still had another pawn and its king was free to advance as well. The game was adjudicated quickly. An unexpected win for Stockfish in the French opening, where NN engines are usually better.

There were almost no exchanges after the start of game 65, AllieStein’s eval was over 1. The engines exchanged pawns on the queen side, the first piece was exchanged on move 29. AllieStein gave a rook for a bishop and pawn, Stockfish’s eval came down to 0. After exchanging queens the game reached a RBB vs RRB position, AllieStein two pawns up and with a queen side passer. Stockfish captured the passer on the 7th rank and the engines exchanged bishops. AllieStein’s eval kept the game going, it reached a tablebase draw on move 125. In game 66 the engines exchanged pawns and pieces slowly and evals came down to 0. AllieStein’s eval turned negative, and then it jumped over 2 after the engines opened two files on the queen side. The engines started to shuffle, Stockfish’s eval was a constant 0. After exchanging all rooks the shuffling resumed, AllieStein lowered its eval slowly. The game ended in a 50-move draw.

In game 67 the engines castled in opposite directions. The black pawns on the queen side were gone early, however the white king was safe behind knights and pawns. The engines exchanged queens and then mostly shuffled, the game ended by the draw rule on move 37. In game 68 Stockfish's eval was 0 throughout the game. Stockfish castled long and AllieStein pushed pawns on the queen side, its eval negative under 1. After a long series of exchanges only RRN vs RRN remained, for some unknown reason AllieStein used almost all its time on one move and had only seconds left for the remainder of the game. The engines exchanged knights and captured most pawns, AllieStein wouldn't lower its eval for the draw rule. The game ended in a tablebase draw on move 124.

The engines played behind their pawn lines for the first 20 moves in game 69, then they started to exchange pieces and pawns. AllieStein gave two bishops for a rook and the game reached a 7-man R vs BN ending on move 46. Evals came down to 0 and the game ended in a tablebase draw a few moves later. In game 70 there were a few exchanges after the start, Stockfish concentrated its forces on the queen side. On move 23 both engines created passers on the queen side, then all the pieces moved either to support or to block these passers. The engines shufled for a while, after exchanging a pair of rooks the shuffling continued. The game ended with a 50-move draw.

Season 16 superfinal games 51-60

After 60 games Stockfish leads 9-3 with 48 draws. Stockfish increases its lead to 6 points and it is probably going to win the match. AllieStein had a chance to win a game, it had a huge eval advantage but failed to convert the win.


There were a few exchanges after the start of game 51 and the engines started to shuffle early. After almost 50 moves there were several exchanges and the queen side opened. The engines slowly exchanged pieces until reaching an opposite color bishop ending and the game was adjudicated. In game 52 Stockfish pushed pawns on the king side and its king was quite exposed. After a series of exchanges the game reached a QR vs QB position on move 34, black two pawns up. After a while the pawns stabilized and Stockfish's eval came down to 0. Both kings were exposed and both engines could give checks, the game ended in a check repetition close to the 50-move draw.

There were many exchanges after the start of game 53 and only RBN vs RBN were left on move 23. Stockfish's eval came down to 0, AllieStein's eval remained too high for the draw rule for a long time. The engines slowly exchanged pieces and pawns until reaching a rook ending, the game ended in a tablebase draw on move 106. There were no exchanges at the start of game 54, AllieStein pushed pawns on the king side, it had more space for its pieces and its eval turned negative. The engines exchanged pawns on the king side and then mainly shuffled, Stockfish went a pawn up and its eval was close to 0 yet AllieStein's eval was around 1.5 (negative). AllieStein avoided a 50 move draw, the engines started to exchange pieces and open the position. AllieStein gave a rook for a knight, its bishop pair threatened the white king and evals jumped again. The game reached an unusual QN vs RBB position, AllieStein had an advanced passer that cost Stockfish its knight. At this stage AllieStein's eval was over 6, it peaked close to 8, yet incredibly Stockfish's queen seemed to be holding the defense by itself. One bishop was pinned and AllieStein could get no more than checks. Evals slowly came down, AllieStein lost its last pawn to avoid a 50-move draw. AllieStein continued to play but it lost its chance (if there was one). The game ended in a tablebase draw on move 242.

In game 55 the engines castled in opposite directions, Stockfish's eval was 0 almost from the start. Stockfish opened the queen side and placed its major pieces facing the white king. AllieStein opened the king side and defended its king. A series of exchanges led to a R vs BN imbalance and a QR vs QBN position on move 43. After exchanging queens only two white pawns remained in a 7-man position, AllieStein played on until a tablebase draw.

In game 56 Stockfish castled long and AllieStein pushed its queen side pawns. Evals jumped when AllieStein sacrificed a knight and opened the queen side. Many black pieces and pawns were facing the white king yet Stockfish was confident it could hold off an attack and its eval increased over 2.

Stockfish opened the b file and exchanged a pair of rooks, AllieStein doubled queen and rook in the open file. The black attack looked very dangerous yet Stockfish calmly played on the king side. For a while it seemed AllieStein was not sure how to proceed and evals slowly drifted down. Then AllieStein let go of a pawn in the center and evals jumped again.

Stockfish pushed its pawn to d7 to add a constant threat on the back rank. Then it gave a rook for a knight and pawn and exchanged all bishops. Only QNN vs QR remained, most of AllieStein's attack was over. It was no longer a piece behind but Stockfish still had a material advantage.

AllieStein removed the pawn on d7, Stockfish added two connected passers in the center to the passer on the king side. The white knights controlled the black pawns on the king side and AllieStein realized it had no hope, the game was soon adjudicated.

In game 57 AllieStein pushed two pawns to the 6th rank early, its eval went over 1. Stockfish exchanged queens and its eval dropped to 0, AllieStein's eval climbed over 1.5 and the engines started to shuffle. AllieStein avoided a 50-move draw, after a long series of exchanges only RN vs RB remained with pawns only on the king side. AllieStein was a pawn up but it was a doubled pawn and the king side pawns could not advance. AllieStein's eval kept the game alive, it ended in a tablebase draw on move 175. In game 58 queens were off early and AlllieStein was a pawn up. Stockfish concentrated on the queen side, the engines exchanged pieces and pawns until all the pawns on the queen side were gone and material was equal. The game reached a RBN vs RNN position and the engines started to shuffle, evals were close to 0 and the game was adjudicated quickly.

AllieStein's eval increased over 1 after the start of game 59. Both engines were in no hurry to attack, AllieStein gave a rook for a bishop and pawn, then created a passer in the center. The game reached a QRN vs QRR position, AllieStein's eval was over 1.5 and Stockfish's eval came down to 0. After some shuffling the engines exchanged a pair of rooks and AllieStein's eval came down as well. Both kings were exposed and the engines could give checks, the game ended in a check repetition.

In game 60 AllieStein pushed a pawn to a3 while the white king was on the other side, evals were over 1. Stockfish opened a file in the center and pushed two pawns on the queen side. After several exchanges Stockfish was a pawn up with a passer on the 6th rank.

Stockfish pushed the passer to the 7th rank where AllieStein blocked it with a rook. After exchanging the remaining minor pieces and pawns on the queen side the focus of the game became the white passer. One black rook could not move, AllieStein's only hope was a counterattack on the white king.

For a while there was no progress, then Stockfish offered a pawn on the king side. AllieStein accepted and evals jumped immediately. With the second black rook out of the way Stockfish could now move its rook to the 7th rank.

AllieStein's queen had to protect the b8 rook, Stockfish moved its rook forward and now it could also threaten the black king. AllieStein couldn't defend against all the threats and the game was soon adjudicated.

Season 16 superfinal games 41-50

After 50 games Stockfish leads 7-3 with 40 draws. Stockfish extends its lead to 4 points at the half-way point after two game pair wins. In both games there was a sudden eval jump after a mistake by AllieStein, but not after a no-think instamove, just not evaluating the reply correctly.

There was a change in the running parameters of AllieStein (hash and treesize) starting from game 45. These parameters should have been changed from the start of the superfinal but were not by mistake. It is not clear what effect this paramter change will have, I have not observed a change in AlllieStein's performance, and it lost game 46.

Games 41-42 started with a 20-ply book sequence in the Neo-Gruenfeld defense, Goglidze attack variation, where the engines castled in opposite directions. In game 41 AllieStein pushed a pawn on the king side, it removed all the black pawns there and reached the 7th rank. Stockfish hid its king behind the white pawn and attacked on the queen side. The white king was exposed, Stockfish sacrificed a knight and chased the king. AllieStein gave the material back, the game reached a QRN vs QRN position on move 34. The game was almost adjudicated before the engines exchanged queens and Stockfish got rid of the white passer. AlllieStein went two pawns up but Stockfish was sure it was fine, the 50-move rule forced AllieStein to give a pawn back and the game ended in a tablebase draw on move 167.

In game 42 both engines were more focused on defense and both kings were relatively safe. Evals remained around 1 as the engines exchanges many pieces. AllieStein tried to attack the queen side, evals came down as the black pieces moved forward leaving their king less defended. AllieStein completely missed Stockfish's move 37, though it thought more than 3 minutes.

Evals immediately jumped as Stockfish opened a file on the king side. AllieStein gave a rook for a knight to lower the risk to its king. The game reached a QR vs QB position, both kings were exposed, evals were around 4.

Stockfish cleared the queen side pawns, then started to give checks. The white major pieces threatened a back rank mate, Stockfish only had to be careful not to allow a perpetual check draw on the other side.

Stockfish captured a pawn and created passers on the king side, these together with the mate threat were enough for a win.

Games 43-44 started in the Two Knights defense, Polerio defense variation. White was a pawn up and black had a development advantage. In game 43 Stockfish's eval was 0 almost throughout the game. Stockfish regained the pawn, after exchanging queens AllieStein castled long. Neither engine attacked, the game reached a RRB vs RRN position on move 35. Stockfish had a king side passer, AllieStein had a pawn majority on the queen side. AllieStein thought it had an advantage for a short while, after exchanging a pair of rooks and several pawns evals came down again. The engines played almost 50 moves of a 7-man position before ending in a tablebase draw. In game 44 Stockfish kept its king in the center, its eval came down to 0 quickly while AllieStein's eval turned negative. AllieStein had the initiative though Stockfish was a pawn up, the engines reduced to a QRB vs QRN position. AllieStein pushed a passer to the 2nd rank, Stockfish blocked it and then gave a rook for a knight, created passers of its own and exposed the black king. After exchanging queens the engines continued the B vs R ending for 30 more moves before reaching a tablebase draw.

In game 45 AllieStein pushed its pawns forward and did not castle, it had a space advantage and eval around 0.5, Stockfish's eval was 0. The white king walked to the king side while AllieStein pushed its king side pawns. AllieStein sacrificed a knight and exposed the black king, with the white queen and two advancing passers attacking. The white king was alone, Stockfish moved its queen forward and found a perpetual check draw after a rook sacrifice.

In game 46 both engines waited a while before castling, and the f file was open by the time both engines castled short. Stockfish's eval remained mostly under 1, the engines exchanged most pieces and pawns. By move 32 only QRN vs QRB remained with 3 pawns each.

Stockfish pushed the e pawn one square forward and slowly arranged its pieces so it could push it further to the 7th rank. AllieStein delayed as much as it could but could not stop the pawn from reaching e7. Stockfish's eval increased to around 2, its next plan was to force the black rook out of the queening square. AllieStein's hope was to counter with an attack on the white king. Stockfish thought AllieStein's 44th move was a mistake and AllieStein immediately agreed, both evals jumped.

Nothing could stop the knight move to c7, the black rook had to move and AllieStein lost its bishop after Stockfish queened the pawn. The extra piece was enough for a win, the game was adjudicated a few moves later.

There were almost no exchanges at the start of game 47, AllieStein's eval was over 1. AllieStein pushed pawns on the queen side and drove the black pieces back. The engines opened the queen side and exchanged a pair of knights, AllieStein's eval jumped to around 2 and Stockfish's eval jumped over 1. However, after AllieStein opened the king side and sacrificed a knight for pawns Stockfish's eval dropped back to 0. The game reached a RB vs RBN position, AllieStein was 2 pawns up with 3 connected passers. Stockfish was confident it could hold, indeed the game continued for 60 moves until AllieStein lowered its eval. The game ended in a tablebase draw. In game 48 again there were only a few exchanges and the engines played behind the pawn lines. AllieStein controlled an open file on the queen side, it gave a rook for a bishop and managed to move its queen forward to the white back ranks. This only led to an exchange of queens and a RRB vs RBN position. The game ended in a check repetition.

Stockfish's eval was 0 almost throughout game 49. After a series of exchanges only RBN vs RBN remained on move 27. AllieStein had a pawn majority on the king side, and it managed to create a passer out of this. Stockfish defended easily, evals remained low and the game ended in a tablebase draw. In game 50 the engines gradually exchanged pieces and pawns and evals came down to 0. On move 39 the game reached a rook ending, AllieStein's eval turned negative and it took a long time until its eval came back down. The game ended in a tablebase draw after 118 moves.

Season 16 superfinal games 31-40

After 40 games Stockfish leads 5-3 with 32 draws. The gap between the engines stays 2 points. AllieStein lost another game due to a judgment error made without proper consideration. Its win shows that AllieStein can sometimes understand a long term advantage better than Stockfish.


Games 31-32 started with a 24-ply book sequence, with white a rook up and a knight trapped in the corner, and the black king uncastled after moving. In game 31 Stockfish captured the knight and pushed pawns on the king side facing the white king. Its eval dropped to 0 as it opened the king side, the two black knights gave checks and AllieStein avoided a repetition. To get its king out of trouble AllieStein gave two pawns, Stockfish sacrificed a rook to finish the game in a check repetition.

In game 32 both engines did not castle. AllieStein pushed pawns on the king side and the white king walked to the queen side. After capturing the white knight in the corner AllieStein planned in its PV to capture the pawns on the king side. The plan included a knight sacrifice and allowing Stockfish to push a passer on the queen side. AllieStein went ahead with this and Stockfish played along. The engines' PVs disagreed on move 32, AllieStein made its move with 3 seconds thinking time.

Stockfish's eval jumped over 1.5 and climbed fast. AllieStein bet the game on the value of the three advanced passers in the center. Stockfish's advanced passer together with mate threats and attacks on pieces forced AllieStein to defend. AllieStein only realized it was in trouble on move 39.

After exchanging queens Stockfish captured one of the passers. The threat of the black central pawns was smaller, Stockfish could block them with its bishops. The extra rook was enough for a win, the game was adjudicated a few moves later.

AllieStein started game 33 with an eval under 1. The white king walked to the queen side, AllieStein's eval increased over 2 while Stockfish's eval remained low. AllieStein tried to press on the queen side but nothing came out of it, Stockfish's eval dropped to 0. The queen side pressure was released after several exchanges, Stockfish then gave a rook for a bishop and used a queen and knight combination to threaten the white king. The game reached a QRN vs QBN position and ended in a perpetual check draw. In game 34 Stockfish castled long, its eval went over 1. AllieStein had a bishop pair but in a closed position the two white knights were more useful. The pawn lines stabilized and the engines started to shuffle. Stockfish avoided a 50-move draw and its eval came down. The engines reduced to a N vs B ending and the game ended in a tablebase draw.

The engines castled in opposite directions in game 35. AllieStein's eval increased over 3 as the engines started to exchange pieces, its eval peaked around 4. The game reached a RN vs RB position with white a pawn up. Stockfish's eval came down to 0 and the engines started to shuffle. AllieStein created passers on the queen side and Stockfish had a passer on the king side. Stockfish gave its bishop to stop a white passer, AllieStein gave a rook to stop a black passer, the remaining N vs R ending was a draw. In game 36 AllieStein kept its king uncastled, Stockfish's eval was a little over 1 and did not increase. AllieStein opened the king side and the white king walked back to the center, Stockfish went up a pawn but its eval came down to 0. After a long series of exchanges only RRN vs RRB remained, Stockfish ended the game with a check repetition.

Evals were low from the start of game 37. AllieStein gave two pawns but had a bishop pair, the game reached a RBB vs RNN position on move 22. In the next 35 moves the engines exchanged a pair of pawns, AllieStein captured a black passer and then the engines reduced to a B vs N ending. The game should have ended by the draw rule on move 44, the game eventually ended on move 90. In game 38 Stockfish pushed pawns on the king side and its king became exposed. AllieStein's eval turned negative, it tried to press on the king side but Stockfish kept the files closed. The game reached a rook ending on move 48. Black's extra pawn was not enough, the game was adjudicated 25 moves later.

Games 39-40 started with a 20-ply book sequence in the Frence defense, Boleslavsky variation, where the engines castled in opposite directions. In game 39 AllieStein pushed a pawn to h6, a thorn pawn, its eval over 1.5. Stockfish pushed pawns on the queen side, it was surprised when AllieStein remained passive. Stockfish captured on b2 and the white king hid behind the pawn, AllieStein's eval jumped over 2.5.

AllieStein's eval climbed quickly, the black DS bishop was blocked and the white knight on d6 was a threat for the black pieces. The engines exchanged queens and Stockfish could no longer threaten the white king. Stockfish opened the long diagonal to find space for its bishop and to protect the b2 pawn, the only safe square it found was in the corner.

AllieStein soon captured the two black pawns on the b file. The trapped bishop could not get out of the corner, and the other black bishop on d5 was blocking the white rooks from attacking the back ranks.

AllieStein used its knight to drive the d5 bishop away and the rooks came forward. AllieStein captured a third pawn, the game was adjudicated 10 moves later.

There were many exchanges after the start of game 40, only RRN vs RRB remained on move 27. The pawn lines stabilized and the engines shuffled for a while as evals slowly came down. Stockfish moved both its rooks to the 7th rank and the game ended in a 3-fold repetition.

Season 16 superfinal games 21-30

After 30 games Stockfish leads 4-2 with 24 draws. AllieStein lost another game with a blunder caused by ignoring a winning move by the opponent, as well as not thinking long enough before making a move. It immediately came back with a win, this time showing a better understanding of the position than Stockfish.

The engines castled in opposite directions in the book sequence of games 21-22. AllieStein started game 21 with an eval over 1 and it stayed at that level for a long time. Stockfish pushed pawns on the queen side and opened files facing the white king. After several exchanges only RRB vs RRB remained on move 25, white had a pawn majority on the queen side. AllieStein managed to create a queen side passer, other than that the engines mainly shuffled. The game was adjudicated when AllieStein lowered its eval. AllieStein pushed pawns on the queen side in game 22, this time the engines locked pawns and kept the queen side closed. Stockfish pushed pawns on the king side but couldn't open files there either. The engines mainly shuffled, after the last knight was off Stockfish captured a pawn but could not improve. The game ended in a 50-move draw.

There were no exchanges after the start in game 23, the first exchange occured on move 22. The engines continued to play mostly behind the pawn lines, on move 39 the last knights were exchanged and evals were close to 0. The engines gradually exchanged pieces and pawns, on move 58 only QRB vs QRB remained, white had 2 pawns and black had 1. The engines mostly shuffled and gave checks, the game ended in a 50-move draw. In game 24 there were again no exchanges. The pawns in the center and the queen side were locked, Stockfish's eval gradually increased until it was over 1.5 but its plan was not clear. On move 37 the first pawn was taken, AllieStein pushed a pawn to the 2nd rank while Stockfish gave a knight for pawns and opened the king side, evals dropped to 0. AllieStein traded RB for Q, its king was exposed and the game ended in a check repetition.

In game 25 AllieStein kept its king uncastled, its eval slowly climbed over 1 while Stockfish's eval dropped to 0. The engines opened the king side and the black king was exposed, after many exchanges only QR vs QR remained with AllieStein a pawn up. The white king was also vulnerable and Stockfish started giving checks. Eventually the engines exchanged queens and the game was adjudicated.

Game 26 started similarly, Stockfish kept its king uncastled and pushed pawns on the king side. On move 20 AllieStein captured a knight after thinking less than a second, this opened the h file and Stockfish's eval jumped over 2.

The king side opened and the black king was exposed. AllieStein continued to follow its PV, it totally missed Stockfish's move 25, seeing the mate threat too late.

Stockfish captured the black queen and the game ended in mate on the board a few moves later. A game pair win for Stockfish.

AllieStein's eval started over 1 in game 27 and slowly increased. Stockfish opened a file in the center, most pieces stayed on the board and neither engine seemed ready to attack. The main difference between the engines was that AllieStein had a bishop pair and Stockfish had a knight pair.

The engines shuffled for a while and exchanged all rooks through the open file. AllieStein's eval jumped over 3, after exchanging queens the game reached a BB vs NN position. Stockfish continued to be calm with an eval below 1.

Stockfish's eval started to increase. It allowed AllieStein to capture a pawn on the king side and in return trapped a bishop in the corner. AllieStein's eval shot up and after arranging its pieces it exchanged the trapped bishop with a black knight.

The white king advanced and Stockfish couldn't protect the pawns on both sides. AllieStein captured a second pawn and the game was adjudicated a few moves later.

In game 28 evals started below 1 and gradually came down. Both central files opened, this time AllieStein kept one bishop. The engines used the open files to exchange a pair of rooks and queens as well. The engines continued to exchange pieces until only B vs N remained. AllieStein's eval turned negative but it had no real advantage. The game ended in a 50-move draw. AllieStein comes right back with a game pair win.

Games 29-30 started with a 20-ply book in the QGD opening, Rubinstein variation, with the kings castled in opposite directions. In game 29 there was a long series of exchanges and most pieces were gone. By move 28 only Q vs QB remained, white 3 pawns up for the bishop. AllieStein pushed pawns forward, it captured the bishop and allowed Stockfish to draw with check repetition. In game 30 AllieStein gave a pawn and opened the queen side, the pieces stayed on the board longer. AllieStein regained the pawn and the engines exchanged pieces until reaching a QRN va QRN position, evals coming down to 0. The black king was exposed and Stockfish gave checks, the game should have been stopped twice by the draw rule but the engines played on. The game ended with a check repetition draw.

Season 16 superfinal games 11-20

After 20 games Stockfish leads 3-1 with 16 draws. AllieStein's losses came from two blunders, where it realized its mistake almost immediately. It needs to improve its analysis to avoid these mistakes.


AllieStein had an eval over 1 at the start of game 11. There were very few exchanges, the engines played behind their pawn lines and AllieStein had a space advantage. Stockfish gave a pawn and opened a file on the queen side, evals came down and after a series of exchanges only QN vs QB remained. The queens were exchanged and the engines continued to play 40 more moves before adjudication.

In game 12 there were again almost no exchanges after the start. Evals started below 1 and were more or less stable. AllieStein pushed pawns on the king side, this added space for its pieces while weakening its king. A pawn exchange opened the king side, evals were low.

Stockfish's eval jumped over 2 and AllieStein's eval jumped a move later. The black queen became trapped in front of the pawns and Stockfish traded a rook and a bishop for it. The advancing black pawns looked dangerous but evals were over 5.

AllieStein continued to fight, it pushed one pawn all the way to promotion and gained some material for it. However it was only temporary, Stockfish reduced to a QN vs RBN position with 3 queen side passers and the game was adjudicated.

In game 13 Stockfish walked with its king to the king side without castling. The center was blocked, AllieStein kept its king uncastled, its eval increased over 2 and Stockfish's eval went over 1. The queen side opened, AllieStein pushed pawns on the king side. Stockfish placed its pieces in a defensive structure, after a few exchanges only QBB vs QBN remained and the engines started to shuffle. AllieStein couldn't break the fortress, the game ended on move 137 in a 50-move draw.

In game 14 AllieStein let Stockfish capture two pawns on the king side while it captured two pawns on the queen side. Stockfish eventually castled its king, away from most black pieces. AllieStein kept its king exposed in the center, evals came slowly down.

Stockfish opened files in the center and on the king side, evals came down to 0. All the major pieces were active and the kings were exposed, there was always the possibility of a perpetual check draw. AllieStein was sure Stockfish was about to capture the c3 pawn, it thought 2 seconds and missed Stockfish's reaction with eval over 5.

Analysis shows that if AllieStein takes the bishop on c5 with its pawn it loses the e4 rook and the game reaches a RR vs RN losing endgame. Taking with the queen is mate in 3, running with the king leads to losing the queen and a quick mate. AllieStein chose to block the check with its knight, and after a few exchanges the game was adjudicated as Stockfish was about to capture a rook. A huge blunder by AllieStein.

Both kings remained uncastled in game 15. AllieStein pushed pawns on the king side, it gave two pawns and opened the king side leaving its king exposed. After many exchanges only QBN vs QBB remained, AllieStein got one pawn back and attacked the black king. Stockfish sacrificed a bishop and starting giving checks. There were a few more exchanges but in the end AllieStein couldn't escape the checks and the game was adjudicated on move 104. In game 16 Stockfish pushed pawns on the king side and kept its king uncastled, while AllieStein castled its king. The engines gradually exchanged pieces ane evals were low, Stockfish went a pawn up and created a queen side passer. For a short while evals jumped over 2 but it was a false alarm. AllieStein threatened the exposed white king using the back ranks, the engines reduced to QN vs QB position and Stockfish gave checks until adjudication.

In game 17 there were almost no exchanges after the start. Then in a long series of exchanges almost all the pieces were removed and RNN vs RBN remained on move 30. Stockfish had a queen side passer, it pushed it to the 2nd rank but there AllieStein captured it. The engines exchanged a pair of knights and started to shuffle. Eventually the rooks were exchanged and the game ended in a tablebase draw. Stockfish started game 18 with an eval around 1 that slowly increased. Again there were no exchanges after the start and then a long series of exchanges, by move 33 queens were off and most queen side pawns as well. Evals were over 2 and still increasing. Stockfish managed to capture a bishop for pawns and the game reached a RB vs R position. Stockfish's eval was over 3 yet AllieStein found a fortress that Stockfish couldn't break. The white king stayed in the corner and the white pieces were not strong enough to capture a pawn or attack the black king. The game ended in a 50-move draw.

Game 19 was a miniature that ended in a repetition draw on move 16 after less than 30 minutes. In game 20 there were no exchanges after the start, on move 27 Stockfish opened a file in the center and then captured a rook for a bishop. Evals stayed below 1, AllieStein blocked the open file and the pawns stabilized. On move 42 the last knights were exchanged and the engines started to shuffle. Stockfish's eval was over 1 but it could make no progress, the game ended in a 50-move draw.

Season 16 superfinal games 1-10

After 10 games the score is 1-1 with 8 draws. In the premier division Stockfish beat AllieStein 3-0. However AllieStein updated its net and it appears to be better in the superfinal. Hopefully Stockfish will be stable in the superfinal, I wouldn't want crashes to affect the outcome of the match.

Games 1-2 were played without a book start sequence. Game 1 was a French opening, Steinitz variation. Queens were off early and both engines did not castle. AllieStein went a pawn up and the engines started to shuffle in a closed position. The 50-move draw was avoided twice before the engines lowered their evals for adjudication by the draw rule on move 137. Game 2 was a Semi-Slav defense. The engines opened files on the queen side and exchanged most pieces, only QB vs QN were left on move 24. After exchanging queens AllieStein's eval turned negative, the endgame was stopped by a 50-move draw.

Games 3-4 were a King's Indian defense. In game 3 AllieStein broke the diagonal pawn lines and allowed Stockfish to create a passer in the center. The engines mostly shuffled from move 19, evals increased as AllieStein had more space and Stockfish's king was vulnerable.



AllieStein used the open long diagonal for a constant mate threat, then pushed the a pawn forward to the 6th rank. The black pieces were forced to defend passively. 



AllieStein attacked on the king side, Stockfish gave a rook for a bishop and exchanged pieces until only RR vs RN remained.



The material advantage and passer on the 7th rank were enough for a win. First blood in the superfinal for AllieStein.

In game 4 Stockfish kept the diagonal pawn lines and this allowed AllieStein to create pressure on the king side, its eval turned negative. AllieStein opened the king side, Stockfish countered on the queen side and gave a rook for a bishop. after many exchanges the game reached a QBN vs QR position, the king side attack was mostly over and the white king escaped to the center. The game ended in a perpetual check draw. AllieStein wins the first game pair.

Games 5-6 started with a 19-ply book sequence in the Sicilian, Paulsen variation. In game 5
the engines castled in opposite directions, AllileStein pushed pawns on the king side and thought it had an advantage. Stockfish surprised with a rook sacrifice that opened the queen side, forcing a quick perpetual check draw.

Game 6 started similarly, Stockfish pushed a pawn to h6 and caused the long diagonal to open, weakening the black king. AllieStein countered on the queen side but was not able to break Stockfish's defense or to force a perpetual check draw. Stockfish moved a bishop to g7 in front of the black king, its eval increased over 2.

Stockfish opened the f file and threatened immediate mate. AllieStein's pieces were far on the other side, Stockfish traded its queen for a rook and bishop, removing the last defenders. Only RRB vs QR remained, Stockfish's eval jumped over 14.

Black had to use all its pieces to avoid mate on f8. Stockfish created a passer on the queen side and the game was adjudicated, PVs showed that after exchanging all pieces on f8 black can't stop the passer. Stockfish wins a game pair and equalizes.

Queens were off early in game 7 and Stockfish kept its king in the center. After a series of exchanges only RR vs RBN remained, most of the pawns were gone and both kings were exposed. AllieStein's eval stayed over 1.5 for a long time, it created a king side passer and managed to push it forward while Stockfish captured the remaining white pawns. AllieStein sacrificed its rooks and queened the pawn, this led to a drawn Q vs RB ending. In game 8 AlllieStein castled its king and the position remained closed. Evals came down to 0 after files were opened on both sides, the game reached a RN vs RB position and ended in a tablebase draw.

Games 9-10 were a King's Gambit Accepted variant. There were many exchanges after the start of game 9, evals came down to 0 and the game reached a rook ending on move 31. AllieStein thought it had a small advantage, the game continued for 40 moves until it lowered its eval for adjudication by the draw rule. In game 10 the pieces stayed on the board longer, both kings were uncastled in the center and queens were off early. Stockfish's eval was 0, AllieStein thought it had an advantage. The game reached a RBN vs RBN position on move 42, a N vs B ending on move 61, and ended in a tablebase draw.