Season 22 premier division, final results

 Final standings

Stockfish and KomodoDragon will play in the season 22 superfinal. In RR7+8 both won all their game pairs against bottom5 engines and drew their games within the top3. As a result Stockfish kept its small lead of 0.5 points. Leela still had a small chance of catching up with the leaders but in RR7+8 it drew as white against rofChade and Stoofvlees, and it lost as black against SlowChess (after winning as white). Instead of getting closer Leela lost touch with the leaders and finished 3 points from 2nd place.

ScorpioNN and Igel are relegated to League 1. All the game pairs within the bottom5 engines in RR7+8 were drawn except two, Stoofvlees and SlowChess beat Igel. Combined with the results of the games against Leela, ScorpioNN and Igel only got further behind and could not escape relegation. 

There was a clear divide between the top3 and the bottom5 in the division. The top3 beat the bottom5 in 48/60 game pairs without loss (though there were a few which were drawn with two white wins). The fact that Leela drew 8 such game pairs, compared to 2 each for its rivals, is the main reason Leela finished 3rd. Within the top3 only 1/12 game pairs was decisive and not two draws, in it Stockfish beat KomodoDragon. This explains why Stockfish won the division, and may also hint to the result of the superfinal.

Stockfish and KomodoDragon led the division from the start and we had almost 3 weeks to let this sink in, but still the fact that KomodoDragon is in and Leela is out is a big surprise. At least to me, perhaps those who are following the development of chess engines more closely knew this was going to happen. The last time Leela was not in the superfinal was in season 16. The superfinal of TCEC has been Stockfish - Leela since season 14, except once when AllieStein replaced Leela in season 16. The last time KomodoDragon was in the superfinal was in season 13 (then only Komodo), when the NN revolution only started. Note that Leela may have been the first strong NN engine in TCEC, but now almost all engines in TCEC uses NNUE technology, so it's more a case of "if you can't beat them, join them". 

Finally, I saw on Chessdom and also in the chat that this was the last season Nelson Hernandez (aka Cato the Younger) provided opening books. I checked back in my reports and it seems Cato first organized the TCEC opening books in season 6, the T in TCEC still stood for Thoresen in those days. Cato has had a huge impact on TCEC, always trying to keep the draw rate not too high and not too low, faced with ever improving chess engines. In the last few seasons some of Cato's duties were shared with other opening book authors, I hope that in the future TCEC will be as interesting and as much fun without Cato's openings. I'm sure that the legendary Catobase and Cato's Fault will still have a place in TCEC and I'm looking forward to seeing Cato in the chat as a viewer/commentator.

Interesting games 

game 170, KomodoDragon - SlowChess: The center was blocked and there were only a few exchanges. KomodoDragon had a space advantage, it chose not to castle its king. There was an opening in the pawn wall on the king side, and after SlowChess captured a pawn on the queen side KomodoDragon could also attack there, it had to decide where to go. The pieces went to the queen side, and then KomodoDragon gave a rook for a knight on the king side and created a passer on the 7th rank. SlowChess could only block and wait while more white pieces move to the king side. Eventually SlowChess lost a rook for the passer and it continued to lose material, the game ended in a tablebase win.

game 172, Leela - Igel: Leela went up a pawn early, then a series of exchanges cleared the center and most minor pieces. The game reached a RN vs RB position, Leela two pawns up with a doubled passer. After exchanging rooks Leela slowly pushed its passers forward, Igel captured one but Leela gave its knight and queened the other, game over.

game 175, SlowChess - Stoofvlees: SlowChess created an advanced passer in the center, Stoofvlees blocked it and focused mostly on the king side. The game reached a QR vs QN position with both kings exposed and SlowChess two pawns up. Evals were under 1 for a while but then they started to jump, SlowChess pushed the passer to the 7th rank. Stoofvlees tried to counter with its own passer, but when the white king came forward Stoofvlees was forced to exchange queens. SlowChess was on time to delay the black passer, it queened one passer and finished the game with a spectacular under promotion to a knight of a second passer to a knight, and mate.

game 177, KomodoDragon - rofChade: Evals gradually increased from the start though rofChade was a pawn up. On move 23 KomodoDragon had advanced connected passers in the center which restricted rofChade's movement. After some preparation KomodoDragon pushed a passer to the 7th rank, it was difficult for rofChade to defend and it started losing material. The game ended in mate.

game 178, Stoofvlees - ScorpioNN: The game reached a RB vs RN position with evals under 1. ScorpioNN missed something or did not think far enough, it gave a pawn and Stoofvlees' eval jumped. The engines played a long PV agreement and towards its end ScorpioNN started to see the problem. The engines reduced to a won 7-man rook ending with the white rook on the 7th rank and a passer on the 6th rank. Stoofvlees did not make mistakes and the game ended in a tablebase win.

game 179, Leela - SlowChess: Leela captured a rook for a knight and pawn early, and it pushed a passer to d6. SlowChess captured the passer after a while, the game reached a RR vs RB position. Leela pushed another passer on the d file, eventually SlowChess lost its bishop for the passer. Leela was 3 pawns down but the extra rook was enough for a win. Leela was in no hurry to mate, the game ended in a tablebase win.

game 182, SlowChess - Igel: SlowChess was up a rook for a knight and pawn early, with the queens off the board. The game reached a RN vs BN position and Igel still thought it was ok. SlowChess created a passer and pushed it to the 7th rank, Igel's eval started to increase as well. Igel captured the passer but the black pawns fell one by one and eventually the game ended in a tablebase win.

game 184, KomodoDragon - Stoofvlees: KomodoDragon's eval started to jump on move 18, the engines followed a PV agreed series of exchanges that resulted in a QRN vs QRB position. Stoofvlees thought it was ok, even when it didn't play instantly. On move 31 Stoofvlees finally saw the problem, the engines reduced to a king and pawns ending which was a win for white.

game 187, Igel - ScorpioNN: Evals increased after Igel captured a rook for a bishop. ScorpioNN managed to equalize material but Igel went a pawn up in a QRN vs QRN position. After a while Igel gave its rook for a knight and pawn, and created connected passers in the center. ScorpioNN captured one passer and reduced to a queen ending, the other white passer was enough to win.

game 188, Stockfish - SlowChess: Evals increased from the start, the engines played out a long PV agreement where initially Stockfish gave a knight but attacked the black king forcing it to move. Stockfish got the piece back but was two pawns down, however the black queen side rook was trapped. After some preparation Stockfish reduced to a QR vs QR position and captured two pawns. The game ended in a tablebase win.

game 191, KomodoDragon - Igel: There was only one pawn pair exchanged after the start, KomodoDragon had a space advantage with both bishops placed behind the black pawns. Igel opened the queen side and tried to counter but was weak. The engines started to exchange pieces on move 31, KomodoDragon went a pawn up and reduced to a rook ending. KomodoDragon captured the remaining black pawns and the game ended in a tablebase win.

game 193, Leela - rofChade: The game reached a RB vs R position with black two pawns up. Leela's eval was over 1, which is quite high for Leela. In this case, however, rofChade was able to hold, Leela mainly shuffled until its eval dropped and the game was adjudicated.

game 196, SlowChess - ScorpioNN: The engines exchanged pawns and opened files. ScorpioNN went a pawn up while SlowChess threatened the black king through the open h file. ScorpioNN captured a second pawn but a series of exchanges reduced to a R vs N ending. SlowChess managed to stop the black pawns and the game ended in a tablebase win.

Standings after RR7: KomodoDragon +17, Stockfish +15, Leela +12, rofChade -3, Stoofvlees -6, SlowChess -8, ScorpioNN -13, Igel -14. Top3 as white with 7/8 wins vs bottom5, again it was Leela that failed to win, this time against rofChade. Leela has been very consistent in the division, I don't see how it is going to close the gap to 2nd place in the last RR. ScorpioNN lost 3 games within the bottom5, it is very unlikely that it will get out of the relegation zone at this stage.

game 199, Stockfish - Stoofvleees: Stockfish had an eval advantage that increased from the start. It castled long and Stoofvlees opened the queen side to threaten the white king. Stoofvlees castled short to find safety for its king and Stockfish opened a file there. In a very sharp position the engines exchanged pieces and Stockfish essentially traded its queen for two rooks. The game reached a RRN vs QB position and Stockfish went two pawns up. After securing its king Stockfish opened the g file and mated with its rooks.

game 203, Stoofvlees - SlowChess: Queens were off early, almost all pawns remained on the board and the engines exchanged pieces gradually until only RRB vs RRB were left. Evals started to increase, Stoofvlees created a central passer when SlowChess exchanged a pair of rooks (was that necessary?). SlowChess tried to activate its pieces, it gave a pawn and opened the king side. The black pieces moved forward to attack, and the white passer was free to advance. SlowChess gave the bishop for the passer, Stoofvlees was down to one pawn but that was enough for a tablebase win. There were two white wins in this opening.

game 204, KomodoDragon - ScorpioNN: see featured game below.

game 206, ScorpioNN - Stoofvlees: The engines opened the queen side with pawn exchanges, ScorpioNN had an eval advantage and it traded Q for RN. Evals increased after ScorpioNN managed to get a rook to the back rank, then captured a pawn and created a queen side passer. Stoofvlees tried to attack the white king but was too weak and had to defend its own king when ScorpioNN moved a second rook forward. Stoofvlees started to lose pieces, ScorpioNN queened its passer and mated. There were two white wins in this opening.

game 207, SlowChess - Leela: SlowChess had an eval advantage from the start, the engines exchanged pieces until only QRN vs QRB remained. SlowChess had a strong passer in the center, while Leela pushed a passer on the queen side without support. The engines exchanged queens and SlowChess captured the bishop for its passer, it was on time to block the black passer. Eventually SlowChess captured the passer but it was down to its last pawn. SlowChess protected its pawn and opened a clear path for it, Leela couldn't stop the queening, game over. There were two white wins in this opening.

A crucial blow for Leela's dream of a superfinal, effectively 2 points away from 2nd place with 4 games left to play. Stockfish has 3 more games as white against the bottom5, Leela needs a very unexpected miracle to advance.

game 208, Stockfish - Igel: Stockfish's eval started to increase after it went a pawn up and created a passer on the queen side. The engines exchanged pieces until only RR vs RR remained, Igel captured the passer and Stockfish was still a pawn up. Igel's eval reacted slowly, Stockfish exchanged a pair of rooks and then cleared the queen side. There were two connected white passers on the queen side and one black passer on the king side. The engines traded a pair of passers but the remaining white passer secured the win.

game 209, Stockfish - rofChade: rofChade had a tripled pawn on the queen side, evals slowly increased. On move 25 Stockfish created a central passer, the engines reduced to a RRN vs RRB position. A few pawn exchanges cleared the board and Stockfish added a second passer in the center. rofChade gave its bishop to stop one passer, it took Stockfish a while but eventually it exchanged a pair of rooks and captured all the black pawns. Then it queened a passer and mated.

game 211, Leela - ScorpioNN: Leela captured a pawn and its eval started to increase. On move 28 the engines started a long PV agreement in a QRB vs QRB position, ScorpioNN regained the pawn and Leela exposed the black king to attack. A second PV agreement led to a queen ending, Leela was a pawn up in a 7-man position. ScorpioNN delayed as much as it could, the game ended in a tablebase win 25 moves later.

Sandings with 3 round to go: KomodoDragon Stockfish +18, Leela +12, rofChade -4, Stoofvlees -7, SlowChess -8, ScorpioNN -14, Igel -15. The superfinal and the relegating engines are determined.

game 215, ScorpioNN - Igel: The engines opened files on the queen side and most pieces moved there. Igel gave a rook for a bishop, perhaps it thought its bishop pair gave it compensation. Indeed, ScorpioNN chose to give the material back and remove one of the black bishops, evals increased in a QN vs QB position. ScorpioNN exchanged queens, the black bishop was passive defending two pawns. ScorpioNN captured one pawn, then created a passer, Igel's defense collapsed. ScorpioNN captured two more pawns and the game ended in a tablebase win. There were two white wins in this opening.

game 218, Stockfish - ScorpioNN: ScorpioNN moved its king, Stockfish opened the king side and castled long. For a while ScorpioNN thought it was ok while Stockfish's eval increased and the engines exchanged pieces. Stockfish created a queen side passer in a QNN vs QBN position, ScorpioNN captured two pawns but its queen had to run to stop the queening. The black king became vulnerable, ScorpioNN chose to allow a queening for a knight. Stockfish was down 3 pawns in a QQN vs QBN position, the power of the two white queens was too great and the black passers were too slow to avoid mate.

game 222, Stoofvlees - Igel: Evals stayed under 1 for a long time. On move 45 Igel gave a queen for two rooks and the game reached a QB vs RRB position. The engines shuffled or 25 moves, Stoofvlees pushed pawns on the king side and evals started to increase. Progress was very slow, it seemed the engines were shuffling again but evals went higher. The black pieces protected each other but eventually Stoofvlees managed to capture all the black pawns. Igel couldn't handle 3 white passers moving forward, Stoofvlees found a way to reduce to a tablebase win.

game 224, ScorpioNN - SlowChess: Evals increased from the start, SlowChess couldn't find a safe place for its king and its king side pieces were trapped. SlowChess traded a knight for a bishop to activate its king side rook, this created an advanced passer for ScoripoNN on the king side. While SlowChess blocked the white passer ScorpioNN shifted to the queen side and put QRR on an open file. As a result of this strong attack SlowChess lost material until the game ended in a tablebase win. There were two white wins in this opening.

Featured game: KomodoDragon - ScorpioNN
Premier division, game 204
Link to game on TCEC

KomodoDragon had an eval advantage from the start but it seemed ScorpioNN was holding. The engines exchanged pieces until only RB vs RB remained and evals were below 1. On move 46 KomodoDragon expected a bishop move, ScorpioNN reported that move in its PV but instead it moved its rook.

I don't know if that was a PV reporting bug or an actual bug, but KomodoDragon's eval jumped immediately as it exchanged rooks. ScorpioNN's eval did not react immediately, indeed usually an opposite color bishop ending with equal material is a draw. KomodoDragon saw that this case was different. It placed its bishop on the long diagonal to block the black passers on the queen side. ScorpioNN had to block the white passers on the king side and KomodoDragon pushed a passer on the queen side to the 7th rank.

ScorpioNN was close to zugzwang, the pawns couldn't move, a king move would allow white to move Kg4 and push pawns, and the bishop had to watch the a8 square. KomodoDragon was also threatening to advance with its white king and g pawn. ScorpioNN saw no way out, it gave two pawns and was then forced to allow KomodoDragon to push pawns. The black bishop moved away from the long diagonal and KomodoDragon queened to win.