Final results of stage 2:
Houdini and Komodo move on to the superfinal of season 10. Stockfish finishes a close 3rd only half a point down. Andscacs and Booot finish in 7-8th, will therefore be playing in division 1 in season 11. Fire, Chiron and Ginkgo will join the top 3 and will play directly in the premier league, together with the two qualifiers from division 1 (The new format for season 11 was published on Chessdom).
Komodo finished strong with 5/7 in the last RR. Houdini had 7 straight draws, enough to hold off Stockfish with only 4.5/7. Stockfish is the only engine with no loss in stage 2 (as well as stage 1). It managed to beat Komodo once and Fire twice but failed to beat Chiron in four games. This is the first TCEC season that I've watched (since season 4) where Stockfish has not qualified to the superfinal. Better luck next season.
Some of the game highlights:
Komodo - Chiron: Komodo's eval gradually increased after the opening. Chiron tried to create a wall across the board, Komodo waited for the right moment to open the queen side and attack through the open files. Komodo used the fact that the black king was exposed to win two pawns, enough for a win. A good start for Komodo in the last RR. It needs all the wins it can get.
Andscacs - Stockfish: Andscacs had an eval advantage, the engines didn't seem to have a plan and Stockfish soon lowered its eval to 0. As the engines continued to shuffle mostly Stockfish started to imagine it had an advantage. The position remained closed for almost 60 moves, then after several exchanges Stockfish gave a rook for a bishop and pawns, and its eval was approaching 1. The pieces remaining were RRN vs RBB, and the engines exchanged down to a N vs B ending, black a pawn up. Despite having tablebases Stockfish could not find a winning line. The game continued for more than 100 moves before adjudication. The longest game of the stage so far. Stockfish now 0.5 points behind Komodo and in 3rd place.
Fire - Houdini: Fire had an eval advantage for a while, after a series of exchanges only RN vs Q were left. Both engines could not improve their position and the game was adjudicated a draw. At the end of round 22 Houdini is 1 point ahead of Komodo, Stockfish 0.5 points behind Komodo.
Fire - Komodo: Komodo let its queen get trapped in the center and traded it for BN and pawns. Despite the apparent material imbalance the evals were close to 0. Komodo's knights became very active on the king side making many fork threats. Fire was forced to give its queen for RN, leading to a RRN vs RBN drawn position. All round 23 games were draws, no changes in the table.
Komodo - Booot: There were a lot of fireworks after the opening. Komodo sacrificed a rook and opened the king side with a mating threat, Booot was barely able to defend. After many exchanges only QR vs QR were left with Komodo a pawn up and evals around 0.7. Komodo outplayed Booot in the endgame, eventually exchanging queens into a won rook endgame. A second win for Komodo in the RR, it is a point ahead of Stockfish with only 4 games each left.
Andscacs - Fire: Fire equalized quickly after the opening, and then evals became negative. Andscacs was two pawns up but its king side pieces were not developed and its king was exposed in the center. The game reached a BN vs RB position with Fire evals at around 1. Andscacs traded two advanced passers for a bishop, and then Fire's better endgame (using tablebases) was sufficient for a win. Andscacs' chances of being at least 6th are small.
Andscacs - Komodo: Andscacs thought it had a significant advantage for a long time, Komodo's eval stayed low. After Komodo created a passer in the center and put all its major pieces on a file on the queen side evals became negative. Afte exchanging queens with only RRN vs RRN remaining Komodo's pawn on the 2nd rank was much stronger than Andscacs' pawn advantage. It was only a matter of time for Komodo to convert a win. Third win for Komodo in the RR, it's getting closer to the superfinal. Two losses in a row for Andscacs, both in white pieces.
Fire - Ginkgo: The opening was balanced with a small advantage for white. Fire played the opening better and its eval gradually increased. When the position opened up and many pieces were exchanged Fire won a bishop for two pawns and evals were over 2 in a RBB vs RN position. Ginkgo tried to advance pawns on the king side, Fire stopped the pawns and was quickly winning.
Stockfish - Booot: Stockfish's eval climbed above 1 right after the opening. Before long it was a pawn up with an advanced passer on the 7th rank. Booot exchanged down to a RB vs RB position but the white passer was enough for a win. After round 25 Komodo and Houdini lead, Stockfish is 1 point behind. Booot in 7th is 0.5 point behind 6th place and 0.5 points ahead of Andscacs in 8th. Only 3 games per engine left.
Komodo - Stockfish: Stockfish equalized quickly and exchanged pieces until only QBB vs QBN remained. After exchanging queens the game reached an opposite color bishops ending and a draw. With two games left Stockfish needs a miracle to get to the superfinal. All the games in round 26 were draws, no change in the table and only 2 games left.
Fire - Booot: Fire had an eval advantage that gradually increased after the opening. After many exchanges only RRN vs RRN were left, Fire was a pawn up with connected passers on the queen side and evals over 1. Booot gave a knight to try to stop the white pawns, Fire had no problem winning the endgame. With this loss Andscacs and Booot will almost certainly be ranked 7-8. They are both automatic tiebreak losers because of crashes, so they need a crash in the Chiron - Ginkgo game to have a chance.
Komodo - Houdini: Stockfish was trailing by a point and needed a decisive result in this game to have some chance of qualifying to the superfinal. Komodo had an eval advantage from the opening. Houdini closed the position and avoided exchanges, keeping the evals low. There was only one exchange (B for N) in the first 40 moves of the game. Houdini had doubled pawns and Komodo had a better center, but nothing more. When the engines opened up the center the evals came down, and even turned negative for a while, but there was nothing in the position. The engines exchanged down to a RR vs RN position, and with both kings exposed to checks the game was soon adjudicated. As a result of this draw Stockfish is out of the superfinal, Komodo and Houdini are in.
Stockfish - Fire: The opening favored Stockfish and its eval reached 1 quickly. There was an eval jump to over 2 when Stockfish initiated a series of exchanges that led to a RBN vs RR position. Fire's rooks had little room to move with many pawns on the board. After a pair of rooks was exchanged Stockfish's eval was already over 5, it created a passer that would cost Fire its remaining rook and the game. The win comes too late for Stockfish, already with no chance of qualifying for the superfinal.
Chiron - Ginkgo: Chiron had an eval advantage after the opening. The position was static for a while with the engines shuffling. After all the knights were exchanged Chiron's bishops became very active on the king side, evals increasing over 1. Chiron opened up the king side, forcing a bishop for rook exchange. Then Chiron traded the material advantage to get a winning rook ending. This game closes the stage.
Featured game: Houdini - Stockfish
Stage 2, round 27
Link to game on TCEC
Stockfish was trailing Houdini by a point with two games remaining. It needed at least a draw to keep some chance of qualifying. Houdini had a small eval advantage after the opening, Stockfish remained relaxed. Houdini castled long and advanced its king side pawns, Stockfish's king remained uncastled and it advanced pawns on the queen side. It wasn't clear where the black king could go, Stockfish chose to castle into the white pawn storm.
This looked very dangerous for black, and Houdini pushed the king side pawns closer to the black king. Stockfish remained calm, advancing on the queen side and careful not to move anything on the king side. It did not want to open files or create weaknesses around its king. Instead Stockfish began exchanging pieces. After queens were off a few files were opened and the evals increased a little. Eventually the position was simplified to a double rook ending, Houdini a pawn up.
Houdini still had an advantage, even one pawn can be significant with all the rooks on the board. However Stockfish was able to exchange one pair of rooks, still Houdini with a pawn advantage. For a short while Houdini's eval was higher than what it had been all game.
Houdini's excitement was short lived, its eval quickly dropped down to 0. Both engines raced their pawns forward, Stockfish was faster and Houdini had to trade pawns to avoid queening. The remaining 2 pawns against 1 rook ending was an easy draw. Stockfish managed to escape a difficult position, keeping its superfinal hopes alive for at least one more game.