Season 20 premier division, after RR6

Standings after RR6

Stockfish and Leela continue to lead. In the 3rd DRR Leela had 6 game pair wins, including the one against Stockfish. Stockfish had only 5 game pair wins and one loss. As a result Leela is only 0.5 points behind and the race is on for 1st place. It is clear that these will be the finalists in any case.

The gaps between the engines in places 3-5 have increased a little. KomodoDragon had a great score of 5 game pair wins and one loss in this DRR, its 3rd place appears more firm.

ScorpioNN and Ethereal continue their race to survive in the division. ScorpioNN is slightly ahead but it is far from safe. There were two white wins in their direct encounter this DRR.

Interesting games

Game 125, AllieStein - Stockfish: The game reached a double rook ending and Stockfish's eval was 0. On move 34 Stockfish's eval jumped over 6 after thinking for six and a half minutes, despite the fact that AllieStein played the move Stockfish expected. The eval went over 8 for the next two moves, then dropped back to 0 after AllieStein's move 37. There may have been a deep win for white that AllieStein missed here. The engines reduced to a drawn rook ending.

Game 128, ScorpioNN - Ethereal: Evals constantly increased as the engines exchanged pieces. The game reached a RBB vs RBN position, ScorpioNN's eval advantage was probably due to the bishop pair. After exchanging the rooks ScorpioNN captured a pawn, then used its queen side pawn majority to create a passer. Ethereal had to block and ScorpioNN had time to move its king forward and to capture all the remaining black pawns. The game ended in a tablebase position.

Game 131, rofChade - Stoofvlees: Stoofvlees gave its queen for two knights early. For a while Stoofvlees thought its attack on the white king gave it compensation, but when it sacrificed a knight there were not enough pieces left for the attack. rofChade shifted to the king side and attacked the black king, Stoofvlees was not prepared for defense and it got mated.

Game 133, AllieStein - Leela: AllieStein was sure it was winning in a double bishop ending with a passer on the 6th rank. Leela managed to prevent the passer's advance, the engines shuflled for 130 moves before AllieStein realized it cannot win and lowered its eval. Leela captured the passer on the 7th rank and the game was adjudicated on move 204. Did AllieStein miss a win? Perhaps it should have avoided some of the early exchanges.

Game 135, ScorpioNN - rofChade: The engines shuffled for a while in a RRN vs RRB position. After exchanging a pair of rooks ScorpioNN started to capture the black pawns until they were all gone. ScorpioNN had connected passers in the center that gave it the win. 

Game 137, KomodoDragon - AllieStein: KomodoDragon started an attack on the king side with a bishop sacrifice. After a series of exchanges only R vs BN remained on move 25. The engines traded pawns until there were only two white pawns left in a 7-man position. KomodoDragon managed to convert by slowly pushing a pawn to the 7th rank, then forcing AllieStein to lose a piece when the second pawn moved forward.

Game 140, Leela - Stoofvlees: Leela had an advanced passer on d6. It gave two pawns and cleared the squares surrounding its passer, then moved its rook and queen to the 7th rank. Stoofvlees exchanged queens and Leela thought that was a mistake. Leela pushed its passer with two rooks on the 7th rank, Stoofvlees tried to counter with pawns on the other side but was too late. Leela captured a rook for the passer and mate followed.

Scores after RR5: Stockfish +13, Leela +11, KomodoDragon +7, AllieStein +2, Stoofvlees -2, ScorpioNN -7, Ethereal -9, rofChade -15. 

Game 141, AllieStein - Stoofvlees: Evals slowly increased though material was equal, on move 28 AllieStein captured a pawn and created an advanced passer in the center. The black pawns were all isolated, before long AllieStein captured them all. The engines reduced to a double knight ending, the 3 white pawns ensured AllieStein would win though the game continued for almost 50 more moves.

Game 149, AllieStein - ScorpioNN: ScorpioNN blundered in what appeared to be a drawn position. It chose to reduce to a king and pawns position and realized it was lost two moves too late.

Game 151, Leela - KomodoDragon: Evals were around 0.5 and the engines shuffled for a long while. Things started to go wrong for KomodoDragon when it pushed a pawn on move 63. Evals increased slowly at first as the engines opened the king side and Leela pushed pawns on the queen side. KomodoDragon went up a pawn, Leela hid its king behind a black pawn and created a passer on the queen side. Leela then reduced to a RN vs RB position, it lost its passer but captured 3 black pawns. Leela pushed its remaining pawns forward and forced a queening to win the game.

Game 153, Stockfish - AllieStein: AllieStein kept its king in the center with open files on both sides. AllieStein didn't see the danger until its king was exposed and forced to move. Stockfish lost some material in a counterattack, the game reached a QRB vs QRR position with white two pawns up. The black king found safety in the corner while Stockfish slowly pushed passers on the other side. AllieStein could not stop the pawns and when it ran out of checks Stockfish queened, with mate following.

Game 155, KomodoDragon - Stoofvlees: KomodoDragon's eval jumped over 2 early as it attacked on the king side. Stoofvlees castled long so its king could escape but it lost a bishop. Stoofvlees had some compensation since it pinned a knight and the threatened white queen had to defend or lose it. KomodoDragon found a way to free the pin without losing material. Stoofvlees tried a desperate attack on the white king, but couldn't avoid mate.

Game 156, Ethereal - ScorpioNN: The black king moved early and hid behind a white pawn. Ethereal sacrificed a knight and opened a file on the king side, its eval jumping to 4. Ethereal soon had a strong attack on the black king, scorpioNN gave a rook for a bishop to reduce the number of pieces attacking. However the black king was targeted by all major white pieces, a series of exchanges led to a Q vs N ending and a win for Ethereal. Double white wins in this opening.

Game 160, Leela - Stockfish: Stockfish gave a rook for a knight early in the game, this weakened the white queen side where Leela's king was located. The black king remained uncastled, however both engines did not have an effective attack. Evals increased as the engines exchanged pieces, the game reached a RN vs BN position. The endgame was slow, after 15 moves the engines reduced to R vs N ending, Leela created an unstoppable passer after another 15 moves. Mate followed not long afterwards.

Game 161, Leela - AllieStein: see featured game below.

Game 162, Stockfish - Stoofvlees: After some preparation Stockfish broke through the center. After a series of exchanges Stockfish was a pawn up and the center was clear, the black king exposed to attack by the white major pieces. The game reduced to a QRR vs QRR position and Stockfish took over the 7th rank with two rooks. Stoofvlees started to lose material and mate came in a few moves.

Featured game: Leela - AllieStein
Premier division, game 161
Link to game on TCEC

Evals were under 1 after the start, Leela pushed pawns on the queen side which was mostly blocked. AllieStein moved its queen forward on the king side and pushed pawns facing the white king. On move 18 AllieStein exchanged a forward white bishop with a knight, which created a passer for Leela on the 6th rank. There was a 20-move PV agreement, at the end of which was a QBN vs QR position. However AllieStein changed its mind and sacrified a bishop to open the king side instead. It thought it had a strong attack on the white king, Leela was certain it was safe and its eval jumped over 2.

Leela played f3 to prevent the black knight move to g4, while on the other side Leela moved a knight to b5 and suddenly the isolated passer became a serious threat. AllieStein ignored the threat to its rook on a7, it continued to add more pieces to the attack and its eval remained under 1. Leela captured the rook, AllieStein expected something else and suddenly its eval changed to a mate prediction for white.

AllieStein realized its attack wasn't fast enough and it was forced to keep an eye on the white passer. Leela's counter was very quick. The g file opened and Leela exchanged a pair of rooks. Then the d file opened, the white queen came forward and it mated together with a knight.