Stockfish wins the superfinal of season 21, the final score is 19-7 with 74 draws. In the last 10 games there was one game pair with two white wins and then Stockfish won 3 more game pairs and extended its lead.
The openings of the superfinal were not ordered by their expected bias as in season 20. The order was not random probably, for example the 3 game pairs with black advantage were consecutive. This season the openings were prepared by Jeroen Noomen and GM Matthew Sadler, each responsible for half of the openings. Stockfish led from the start, the gap was small at first and was only +3 after 50 games. Then Stockfish won 6 game pairs in the next 20 games, Leela won only one and the gap increased to +8. Leela won a game pair in the next 10 games, but in the last 20 games Stockfish extended its lead with 5 more game pair wins. Only two openings resulted in two white wins.
There were many games that Stockfish won, where the eval turning point followed an "instamove" in which Leela spent very little time thinking and used its prepared PV to play. Usually Leela was surprised by Stockfish's reply, it spent a lot of time thinking on its next move and its eval jumped as well. I don't know what would have happened if Leela thought more on the crucial move, but improving its time management or forward search may make it better.
This season there were a total of 46 engines participating. The lower leagues of the season were short 1DRR events that flew by as always. Booot and Nirvana returned to TCEC after not participating for a few seasons. Nirvana climbed to league 4 and then was relegated back. Booot together with ClassicAra made it to league 2, there Booot stayed and ClassicAra was relegated to league 3. Koivisto, a new non-crashing version, also started in qualification and ended in league 3. Halogen started in league 4 and ended in league 2. League 1 was a more serious 2DRR affair, none of the lower league engines could get there. The league 2 qualifiers were veteran engines Nemorino and Pedone, Nemorino was then relegated back. The second relegated engine from league 1 was rofChade, a bit surprising since it qualified for the premier division in season 20. The qualifiers for the premier division were Ethereal, same as in season 20, and Igel, first time appearance.
The premier division was a 4DRR event. Stockfish and Leela took the lead early and qualified for the superfinal. Stockfish won the premier division despite the fact that Leela beat it in one game pair. Leela was the only engine that did not lose a single game pair in the division. KomodoDragon continued its success of season 20 and finished in 3rd place, not too far behind. Ethereal and Igel were relegated back to league 1.
A new addition in the superfinal of this season was the live commentary of some of the games by GM Matthew Sadler, author of half of the opening. This is something that was missing in TCEC from the start, a real expert that can analyze the games as they are played and share his opinions. GM Sadler has a lot of respect for the engines, in his commentary he refers to the plans they have in their PV, and gives his understanding of the game in terms a layman like me can understand. I listened in to only a few of these live streams, I get overloaded during the superfinal since I write a summary of every game, and I can't keep up. I use the archive to follow the games and don't have a lot of time for the live ones. Now that the season is over I will go back and look at a few selected videos for games I thought were interesting.
During the season I heard that Guy Haworth had died, I mentioned this in my league 1 summary. Guy Haworth wrote the season summaries that appear in the TCEC articles tab, together with Nelson Hernandez (Cato). He was a reader of this blog, and left me a few comments and corrected my errors. We communicated briefly during season 20, sadly he died before we had a chance to discuss this season.
A final word on the Covid pandemic. It's been 6 months since I wrote the summary of season 20, Covid is still here. The virus keeps finding ways to improve, the delta variant is spreading fast, much faster than the original. Us humans have to keep ourselves as safe as possible, especially those of us who are not so young anymore. My message from the last two seasons is still valid:
"Please take this seriously, avoid crowded places and unnecessary
contacts. Keep yourselves and your family safe. Governments may give bad
advice or act slowly, but our personal health depends mostly on our
personal behavior."
To this I can add: if you can, get vaccinated. The vaccines are safe and they lower the threat of getting infected significantly. Apparently the vaccines are less effective against infection by the delta variant, but still they lower the chance of a severe disease or worse. Getting vaccinated is important for you as well as your loved ones, even if you are young and Covid is less of a threat to you. Please, get vaccinated if you can.
That's all from me this season, hope to be here for the next one.
Go TCEC!!
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Games 91-92 started with a 26-ply book in the KID Orthodox variation, that diverged from recent GM games at the 26th ply. In game 91 Leela pushed a pawn to a6 and Stockfish exchanged it. Stockfish's eval was over 1.5, the engines shuffled for a long time with one minor piece exchange that created an advanced passer for Leela on the queen side. On move 46 Stockfish opened a file on the king side and went a pawn up, creating a central passer. Stockfish gave the pawn back on the queen side where Leela added a second passer. On move 52 the queens were exchanged.
Stockfish pushed the h pawn forward, connecting a second passer when Leela captured the h pawn. Leela blocked the black passers and Stockfish didn't have the strength to support them. Stockfish exchanged a pair of rooks and captured one of the queen side passers, it tried to block the second one.
The black knight and bishop couldn't support each other and the remaining pieces were too far away. Leela's rook drove the defenders away and pushed the passer to the 7th rank. Stockfish managed to capture the passer but lost its rook. The h pawn was unstoppable, Leela queened and then mated.
In game 92 Stockfish pushed the a pawn forward, when it reached a6 Leela played b6 instead of taking it. There was one pawn exchange on the king side, no exchanges besides that. Stockfish's eval was over 2.5, but it seemed to be shuffling from move 21. The white king walked to the queen side, evals slowly drifted down. On move 56 evals started to increase again, Stockfish waited for the right moment and on move 68 it pushed h4.
Stockfish opened the h file and the exchanges began. The black king became exposed, and after clearing most pawns from the king side the white g pawn became a dangerous passer. Leela preferred to give a rook for a bishop to capture the passer.
Material seemed balanced but Leela couldn't prevent the white queen moving forward. Stockfish captured two black pawns, it gave the rook but captured the bishop. Material was equal again but two advanced passers on the queen side were strong enough to secure a win. There were two white wins in the game pair, Stockfish leads 16-7.
In game 93 there were many early exchanges on the queen side and only RRN vs RRN remained on move 20 with white a pawn up. The engines gradually exchanged pawns and evals came down. Leela had two advanced passers on the queen side, Stockfish countered by doubling rooks on the 2nd rank and threatening the white king. Leela exchanged a pair of rooks and gave up one passer to secure its king, the 7-man position was a draw and the game was adjudicated.
The engines repeated 21-plys of the previous game in game 94 up to transpositions. Stockfish's eval was over 1, the queens stayed on the board longer than in the previous game. From move 20 the engines played out a PV agreement, Stockfish gave a pawn in the center while its knight moved to the central e5, Leela moved a rook to the 2nd rank. Stockfish regained the pawn on the queen side and created an advanced passer, Leela doubled rooks on the 2nd rank and threatened the white king. Leela was surprised by Stockfish's move 29, it thought for 13 minutes and its eval jumped to around 1. Stockfish moved its queen forward on the king side, captured a pawn and then exchanged queens.
Stockfish played the ending very patiently, alternating between harassing the black king and slowly pushing its own passers forward. Leela defended the best it could, by move 80 it only managed to move its passer to b4 while Stockfish had a passer on h7. Leela traded pawns and this left a 7-man position with one last white pawn. The game ended in a tablebase win. Stockfish wins the game pair, it leads 17-7.
In game 95 the center was blocked and the engines opened two files on the queen side. After a few exchanges in the center all rooks moved to the queen side. The engines played out a long PV agreement, evals came down and all rooks were exchanged. On move 39 the game reached a QN vs QB position, both kings were exposed to checks. Leela wouldn't lower its eval, a few pawn trades extended the game which was finally adjudicated on move 95.
In game 96 there were two pawn exchanges after the start, one on each side, but no files were opened. The engines mostly agreed in their PVs and evals did not change a lot. On move 26 Stockfish captured a pawn on the king side and created a passer there. Leela did not want to open files close to its king and it allowed Stockfish to push a second passer forward. Leela captured a pawn on the queen side and created a passer of its own. On move 35 the engines exchanged queens.
Leela couldn't take the bishop because of immediate mate. Instead it captured the knight on e6, this started a series of exchanges that opened the king side and led to a R vs N position on move 69. The rook was much stronger than the knight in an open position, Stockfish managed to queen a passer and win. Stockfish wins the game pair, it leads 18-7.
In game 97 there were no exchanges after the start and the engines played behind the pawn lines, the black king walked to the king side without castling. On move 19 Leela gave a pawn and opened the center. Stockfish managed to connect its rooks on the back rank, Leela regained the pawn and created a passer on the queen side. After a few pawn moves and a minor piece exchange the engines started to shuffle. On move 51 Stockfish's eval dropped to 0, it gave a pawn and captured a rook with its bishop. Leela had an advanced passer on the king side, it chose not to retake and instead to attack the black king. Eventually Leela captured back a rook, but then Stockfish ended the game with a repetition draw.
In game 98 Stockfish exchanged both bishops for a bishop and a knight early. Stockfish's eval was over 2 and increasing, the black queen came forward and was a target for attacks. Leela castled its king and found a way for the queen to retreat. Stockfish pushed pawns on the king side, it gave a pawn to create an opening in the pawn wall protecting the black king.
All the white pieces moved to the king side, Leela surrounded its king with pieces and tried to hold on. Stockfish moved its queen slowly, in small steps, through the h file opening and all the way to h7. Leela could only watch and wait, while making sure its king had a path to get out of the corner.
Stockfish planned its attack very carefully, Leela saw the same sequence of moves in its PV. There was a series of exchanges that resulted in a QR vs QN position, then Stockfish just reduced to a king and pawns ending. It was a pawn up, Leela couldn't prevent a queening and mate was just a matter of time. Stockfish wins the game pair, it leads 19-7.
In game 99 Stockfish gave a pawn in the center and the engines opened a file. Stockfish castled long and pushed pawns on the king side. Evals did not change a lot as the engines exchanged minor pieces and Leela kept the king side files closed. After exchanging a pair of rooks the white queen moved forward, evals came down. Leela captured two pawns, Stockfish countered by attacking the white king and reducing to a QB vs QB position. Leela pushed a passer forward, Stockfish gave its bishop and ended the game in a perpetual check. In game 100 Stockfish as white gave a pawn with an open file in the center. This time both engines castled short, evals came slowly down. The pawns stabilized, after some shuffling Stockfish regained the pawn and evals were close to 0. The engines reduced to a RB vs RB position, Stockfish took the bishop and Leela preferred a perpetual check draw over retaking the bishop.
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