Stockfish remains in the lead with a +3 score in this RR. Leela had a great RR with 4 wins, and despite losing a game to Stockfish (first loss in the division) it extends the gap to 1 point from 3rd place. Komodo and Houdini are still in the race, they need wins and/or luck to overtake Leela.
KomodoMCTS continues to survive and not crash. Ethereal scored -4 in the RR and drops to the bottom of the table joining Andscacs. Fire is 1 point ahead of the relegation zone and is not in the clear yet.
A few interesting games
Andscacs - Houdini: Houdini's eval was negative from the start. Andscacs opened a file on the queen side and placed a rook on the 7th rank, Houdini sacrificed a knight for pawns and created a pair of connected passers. The engines exchanged pieces and Andscacs gave back the knight to remove one of the passers. This left a double bishop ending with Houdini a pawn up. The white king walked to the queen side to stop the passer, the black king captured a pawn on the king side and secured the win for Houdini.
Stockfish - Houdini: Stockfish's eval was close to 1 from the start. Houdini pushed pawns on the king side, leaving its king without pawn support. Stockfish pushed pawns on the queen side, all pawns remained on the board until move 33 when Stockfish opened the queen side. Evals were over 2, Houdini opened the king side and created a little space for its pieces, exposing the king to attacks. Stockfish gave a rook for a bishop, but with all its pieces targeting the black king Houdini could not hold. The game was adjudicated with PVs showing how Stockfish can reduce to a winning endgame.
Leela - Fire: Leela's eval was over 1 and increasing from the start. Fire opened a file on the queen side and controlled it with major pieces, Leela covered its back ranks and did not allow Fire to attack from there. Meanwhile the black pawns blocked one of Fire's bishops, and Leela pushed pawns on the king side and trapped the second bishop in the corner. Fire was paralyzed, though it took a while to recognize it was losing. Leela had all the time in the world first to exchange queens and then to walk with the king to the queen side and drive away the black rook. In despair Fire gave a bishop to break the blockade, a white passer forced Fire to lose more material and the game.
Ethereal - Leela: Leela's eval was negative from the start, it kept its king in the center and blockaded the center and king side with pawns, its eval gradually increased. A pawn exchange opened a hole on the queen side, the black king walked to safety on the king side and Leela moved pieces to the queen side. Another pawn exchange created a queen side passer for Leela and Ethereal's eval started to increase as well. Leela pushed the passer to the 3rd rank and slowly increased the pressure, until Ethereal gave a rook for a knight to capture the passer. Leela reduced to a winning R vs B ending.
Komodo - Fire: After several early exchanges queens were off, Komodo had a bishop pair advantage and an eval over 1. Fire reduced to an opposite color bishop ending with Komodo a pawn up. The white king was better placed than the black king, allowing Komodo to capture a second pawn. Komodo was able to convert this advantage to a win.
Stockfish - Ethereal: Stockfish's eval was over 1 a few moves after book though material was equal. As the board cleared up it became evident that Ethereal's pawn structure was weak. Stockfish focused on the backward d6 pawn and Ethereal put both rooks behind it to defend. In a RRN vs RRN position the h6 pawn became a second target. Ethereal's pieces were not fast enough to defend both pawns and Stockfish captured the h6 pawn. The game reduced to a knight ending, Stockfish captured a second pawn and the game was adjudicated.
Leela - Andscacs: Andscacs pushed its king side pawns in front of a castled king. Leela kept its king in the center, then pushed a pawn to h6 with its eval jumping over 2.5. Leela attacked the king side pawns and weakened their structure, Andscacs remained calm and was sure in its defense. Leela's king walked to the queen side, its eval increasing though it seemed Andscacs was holding. The game reached a RN vs RB position, it took Leela a long time to find a winning path. It captured a pawn and reduced to a winning rook ending. A double win for Leela for this opening.
Leela - KomodoMCTS: Leela had an eval around 1 from the start. The engines opened the queen side, KomodoMCTS had an isolated pawn in the center. Leela's eval jumped over 4 when it exchanged a bishop for a knight and created a pawn majority on the king side. The engines shuffled for a long time, Leela reduced to a RN vs RB position on move 78. It delayed the king side push to move 104, this created a passer that cost KomodoMCTS a bishop and the game was adjudicated.
Ethereal - Komodo: Ethereal started with a small eval advantage, Komodo equalized and evals came down to 0 despite Ethereal being a pawn up. The engines exchanged down to QRB vs QRN position, but one move before adjudication by draw rule evals became negative. Ethereal exchanged queens and Komodo regained the pawn, evals stayed below 1. Ethereal pushed a pawn and queened it, giving its other pieces and leaving a Q vs RN position Komodo 2 pawns up. Evals remained low for a while, then Ethereal blundered and evals jumped. Komodo connected its pawns and its king, surrounded by its pieces. Two connected passers started to march and the game was adjudicated.
Houdini - Ethereal: Houdini had an eval advantage that gradually increased. There were almost no exchanges in the first 40 moves, Houdini's eval was over 3 as it increased the pressure on the queen side pawns in a closed position. The black pieces were busy defending the queen side, when Houdini opened the king side it won a knight and Ethereal's defense collapsed. The game was adjudicated before Ethereal lost more material.
Stockfish - Leela: See featured game below. First loss to Leela in the division.
Featured game: Stockfish - Leela
Premier division, round 28
Link to game on TCEC
Stockfish had a small eval advantage from the start, but it remained around 0.5 for the first 30 moves. Both kings were safe, there was one open file on the queen side that Leela controlled, the engines gradually exchanged pieces. On move 33 Stockfish offered a pawn but did not expect Leela to take. When Leela calmly took the pawn Stockfish's eval jumped over 2.
The PV showed that Leela saw the immediate tactic, it was losing a rook for a knight and pawns. However, it thought it had a perpetual check draw and missed Stockfish's 38.Bxb5 move. When it saw what happened Leela's eval jumped over 3. After several check moves the engines reduced to a QR vs QN position.
Stockfish captured the black b pawn and the pawn on the a file became a dangerous passer, though it was still far away from promoting. Leela countered with central passers of its own, Stockfish attacked the back ranks and threatened mate.
Leela's last resort was checks against the white king. The black queen chased the white king for more than 15 moves, while evals continued to increase. The game was adjudicated when the king approached the a8 corner, the support of the white pieces guaranteed a stop to the checks and a win for Stockfish.
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