Stockfish and Leela will play in the season 18 superfinal. Stockfish took the lead in RR3 and never looked back. Leela kept winning in a steady pace to end up in 2nd place. It finally won a game against a top 4 engine, though it was a result of a Stoofvlees blunder. AllieStein stayed in the race until the last two rounds. It had a potential tiebreak advantage over Leela but it couldn't find wins when it needed them, instead it lost to Komodo and couldn't recover. Stoofvlees made a late comeback in the last RR, after losing twice in RR5. Its +4 score after RR2 seems to be a statistical outlier.
Fire and rofChade are relegated back to league 1. There were 4 leagues this season, and 7 of the 8 engines that promoted at the end of a league were then relegated back in the next league. Only Booot managed to survive its promotion to league 1.
Game 114, Stockfish - Fire: Fire didn't castle and moved its king early, Stockfish's eval increased over 1 as it gathered forces for a king side attack. Fire protected its king and Stockfish shifted to the center and created a passer. It gave a rook for a knight and used a mate threat to reduce to a QRN vs QRR position, with two pawns up. Fire had to block the passer with a rook, this was enough for a win though it took Stocfish a while.
Game 115, AllieStein - Ethereal: AllieStein pushed a pawn to h6 and attacked the black king, while its king remained uncastled. Ethereal exchanged queens and captured two pawns, yet evals increased quickly. The black king was trapped in the corner, Ethereal relieved the pressure by exchanging pieces until only R vs B remained. The white pawns were out of the bishop's reach, AllieStein captured pawns until getting a tablebase win.
Game 117, rofChade - Stoofvlees: Stoofvlees made a few moves in the opening that were not optimal, rofChade went a pawn up and evals were around 1. Stoofvlees pushed pawns on the king side, it then gave a second pawn and attempted to attack the white king. rofChade gave the pawns back and was confident in its defense despite the two black rooks on the 2nd rank. Then Stoofvlees blundered badly, it went ahead with the attack and missed the threat against its king. It saw the mate coming 4 moves later, too late. rofChade gets its first win in the division, a real blow for Stoofvlees' superfinal chances.
Game 121, Stockfish - rofChade: Stockfish had an eval of 1 from the start. rofChade had problems developing the queen side while Stockfish attacked on the king side, evals increased quickly. Stockfish gave a rook for a bishop and pawn, creating a pawn majority on the queen side and a threat to the black king on the long diagonal. After exchanging queens Stockfish created passers on both sides and rofChade's defense collapsed. Stockfish started to win material and the game was adjudicated.
Game 123, Komodo - Fire: Komodo pushed pawns on the king side and didn't castle its king. The g file opened and one white pawn reached h6, Komodo's eval was over 1. Fire had no real counter, evals slowly increased as Komodo moved both its rooks and its queen to the g file. Fire had to give material to save its king and the game was adjudicated.
Game 129, AllieStein - rofChade: rofChade was up a rook for a bishop exchange early in the game, though AllieStein had a small eval advantage. AllieStein had a strong bishop pair that limited the black pieces. AllieStein castled long, when it was ready it opened the king side with its pawns. For a while the engines seemed to be shuffling, though AllieStein's eval continued to increase. Eventually rofChade gave back the rook to get rid of one of the white bishops. AllieStein pushed a passer to the 7th rank and rofChade gave a bishop to stop it. AllieStein had enough pawns to win in a RB vs R ending.
Game 131, Stoofvlees - Leela: Stoofvlees had an eval advantage in a closed position, Leela defended well. The position opened and the engines reduced to a RN vs RB position with low evals. Suddenly Leela's eval jumped over (negative) 3, Stoofvlees blundered and Leela captured the knight a few moves later. Stoofvlees was 3 pawns up but its pawns were isolated and it couldn't defend them all. Leela kept one pawn safe, it slowly captured black pawns until reaching a tablebase win.
Game 134, Leela - Ethereal: The engines castled in opposite directions, two pawns were exchanged on the queen side and Leela pushed a pawn to h6 on the king side. Evals increased slowly while the engines exchanged pieces and pawns. Leela pushed pawns on the king side, after a series of exchanges only QRN vs QRB remained and Leela had an advanced passer in the center. The engines exchanged queens and the white king moved forward to support the passer. Ethereal gave a rook for a knight to get rid of the passer and the R vs B ending was a win for Leela.
Game 136, AllieStein - Komodo: There were many exchanges after the start and the game reached a RRB vs RRB position on move 22, with AllieStein a pawn up. AllieStein had a 3 to 1 pawn majority on the queen side, after exchanging a pair of rooks its eval jumped quickly to double digits. AllieStein knew it was winning but getting there took 40 moves. First it exchanged pawns on the queen side and created connected passers. Komodo concentrated on blocking the passers, AllieStein captured two pawns on the king side and then reduced to a winning rook ending.
Scores after 35 rounds: Stockfish +9, Leela +7, AllieStein +6, Stoofvlees +2, Komodo -1, Ethereal -4, rofChade -9, Fire -10. Stockfish and Leela continue to lead with two wins each. AllieStein had its best RR so far with 3 wins, it is still in the race. Stoofvlees is practically out after losing twice, including a huge upset by rofChade. No news at the bottom other than now Fire is last. The only question is which engine will beat Fire and rofChade, and how this will affect the race at the top of the table. So far the reverse games have been less exciting, we'll see how the last RR goes.
Game 141, rofChade - Leela: The engines shuffled from move 28, with pawn moves that reset the 50-move counter. On move 158 the engines exchanged a pair of rooks, on move 221 the queens were exchanged and only RB vs RB remained. Leela may have missed a win, rofChade's eval was over (negaitve) 2 for a while. However evals came down as the game continued, adjudication finally came on move 304.
Game 145, Stoofvlees - rofChade: The engines opened the king side, both kings were exposed and the black king was especially vulnerable on the long diagonal. Stoofvlees gave a rook for a bishop and created an advanced passer in the center. Evals increased quickly while the engines exchanged pieces until only BB vs RN remained. Stoofvlees went 3 pawns up, it promoted a pawn before the game was over.
Scores after 38 rounds: Stockfish +9, Leela +7, AllieStein +6, Stoofvlees +3, Komodo -1, Ethereal -4, rofChade Fire -10. Only one decisive game in 3 rounds. AllieStein couldn't get anyting playing white against Fire. If it wins a game it will have a tiebreak advantage over Leela, so the superfinal race is still open.
Game 154, Stoofvlees - Fire: The black queen moved forward, Stoofvlees used its absence to place a pawn on f6 before exchanging queens. Evals increased as the engines exchanged pieces, they were over 3 when only BN vs BN remained. Material was equal, Stoofvlees moved its king forward and Fire couldn't stop it and protect all its pawns. Stoofvlees captured the white king side pawns and created passers, enough for a win.
Game 159, Leela - Stoofvlees: The game reached a BB vs R ending on move 31, evals over 1.5. Stoofvlees had a passer on the 2nd rank, it took Leela a few moves to get rid of it. Analysis engines were sure Leela was winning, and that move 43 was a mistake. Leela did not find a way to win, the engines shuffled with a few pawn moves in between. The game was adjudicated on move 143.
AllieStein only managed a draw playing black against rofChade, while Leela missed a win against Stoofvlees. No change at the top, only two more rounds to play.
Game 164, Komodo - AllieStein: See featured game below.
At precisely the wrong moment AllieStein lost a game. One round to go there is still a theoretical possibility that AllieStein will finish ahead of Leela, AllieStein has to win in black against Stoofvlees and Leela has to lose in white to Fire.
AllieStein only managed a draw against Stoofvlees, and Leela qualified for the superfinal before its last game. Leela was close to a win against Fire but the game ended in a draw. In any case AllieStein wouldn't have qualified even if it had won its last game.
Featured game: Komodo - AllieStein
Premier division, game 164
Link to game on TCEC
Premier division, game 164
Link to game on TCEC
Komodo had an eval advantage of around 1 from the opening. AllieStein tried to attack on the king side, its queen moved forward and captured a pawn, while its king remained uncastled in the center. Komodo opened a file in the center, its pieces were ready to attack the black king. AllieStein's queen came back quickly, evals were over 2 already on move 19.
Komodo targeted the pinned black knight, AllieStein couldn't castle because the king was a crucial defender. The black pieces surrounded their king, with very little room to move. AllieStein's eval was over 10 on move 25.
Komodo attacked through the center, it gave a rook for a bishop and exposed the black king. Komodo was behind in material but the black king was in front of its defenders, facing 4 white pieces and with nowhere to hide.
The game was adjudicated, both PVs showed how AllieStein loses material within a few moves. There were two white wins in this opening, though the games were very different. I don't think anyone expected Komodo to beat AllieStein this fast, if at all.