Crosstable after RR4
Stockfish maintained its 3.5 point lead at the top of the table. Houdini is in 2nd, extending its lead over Komodo to 1.5 points after beating it for the second time in the division. Chiron won its first game, it is still in the relegation zone together with Ginkgo. Andscacs and Ethereal are a point ahead, Fire is 2.5 points clear of Ethereal after Ethereal lost 3 games in RR4.
A few interesting games
Houdini - Chiron: Houdini's eval gradually increased after the opening. Houdini captured a pawn and created an advanced passer in the center. Chiron had to block the passer, defened its pieces and protect its king against a potential attack on the long diagonal. Chiron's defense collapsed after Houdini opened a file on the king side. Houdini reduced to a QRB vs QRN position and finished with a bishop sacrifice, leading to a won endgame.
Stockfish - Houdini: Stockfish was a rook for bishop up in a closed RN vs BN position, Houdini kept the pawn line strong and held the draw.
Ginkgo - Ethereal: For 50 moves evals were close to 0, then they suddenly jumped over 1. The engines exchanged most pieces and only RB vs RB remained and Ginkgo advanced a passer to the 7th rank. Ethereal was a pawn up but had to prevent Ginkgo from promoting the pawn, both engines couldn't improve and the game ended in a draw.
Houdini - Komodo: See featured game below. This was the second win for Houdini against Komodo in the division.
Houdini - Ginkgo: Houdini gave a rook for a bishop but had an advanced passer in the center. Ginkgo realized it was in trouble too late, its king was exposed and it had to block the passer. Ginkgo's defense collapsed and the game was adjudicated before Houdini won more material.
Komodo - Fire: Komodo had a space advantage and eval over 1, Fire seemed to be holding. The engines exchanged pieces until only N vs B remained, then Fire blundered and Komodo's eval jumped over 3. The winning sequence was not trivial and very long, probably based on the fact that the black bishop had no targets. Fire saw it was lost and the game ended without demonstrating exactly how Komodo can win.
Stockfish - Andscacs: There were many early exchanges and only RR vs RN remained on move 25. Andscacs was a pawn up and it had a pawn majority on the queen side, Stockfish had a pawn majority on the king side. Eventually Stockfish forced a rook exchange to stop a king side passer and the game reached a tablebase R vs N win for white. A double win for Stockfish in this opening
Chiron - Ethereal: Ethereal gave a pawn and tried to develop a king side attack, but nothing came out of it. The engines shuffled essentially until move 82 when Ethereal captured a pawn and gave a rook for a bishop. Evals jumped to around 2, Chiron hid its king behind a black pawn and started advancing its central passers. There was another long shuffle, then the engines reduced to a QR vs QB position and evals continued to increase. 30 moves later both engines were sure of Chiron's win, PVs showed different possible lines, both quite long. This was the first win for Chiron in the division.
Ethereal - Stockfish: Stockfish took over the game early, it attacked the king side through the half open g file. Ethereal's pieces were tied down to defend the king side and Stockfish switched to the queen side. It won a pawn and reduced to a RRB vs RRB position. Stockfish had an advanced passer in the center, the game was adjudicated before Ethereal lost material. Stockfish won both games in this opening.
Fire - Ginkgo: There were many early exchanges, only QBB vs QNN remained on move 30. Evals increased gradually, Fire exchanged a bishop for a knight and then managed to move its queen behind Ginkgo's pawns. The black king was exposed to attacks and Fire used this to reduce to a won queen ending.
Komodo - Ethereal: Komodo had space advantage on the king side, evals were close to 1 though it was a pawn down. The engines essentially shuffled until move 98, then finally Komodo started its king side attack, perhaps following a blunder by Ethereal. Komodo went up a rook for a bishop and opened the king side, then drove the black king to the center. Again the game ended long before the win was explicit.
Stockfish - Chiron: The engines castled in opposite directions, Stockfish pushed a pawn on the king side and weakened Chiron's king position. Evals increased quickly, the game reached a QN vs QB position where the black king was weak in the corner and the bishop had no pawn targets and couldn't support the black pawns. The game was quickly adjudicated. Stockfish won both sides of this opening.
Andscacs - Fire: Evals turned negative as Fire prepared a queen side attack in a closed position. However, when Fire opened the queen side evals dropped from 2 to 0. The game ended in a perpetual check.
Featured game: Houdini - Komodo
Premier division, round 24
Link to game on TCEC
The game started with evals close to 0. On move 15 Komodo allowed Houdini to block the center with a d5 pawn. Evals
increased gradually as Houdini pushed pawns on the king side and had a space advantage. Komodo's pieces had less and less room to move.
Komodo tried to counter on the queen side and opened a file. Houdini blocked the file with an outpost knight on c6. Houdini continued to push its king side pawns, and when the pawn line reached g6 the black LS bishop was trapped.
Houdini concentrated its pieces on the queen side while threatening to open the king side with its pawns. Komodo had to keep an eye on both sides and its pieces were overextended. Eventually it allowed Houdini to advance a passer in the center, then gave a piece to stop it.
Houdini was up a piece and Komodo's king was trapped in the corner. This was enough for a
win though the game ended before the win was evident.