Tuesday, April 16, 2019

Season 15 premier division after RR2

Crosstable after RR2

After the reverse games of RR2 the table is getting clearer. Stockfish and Leela are leading, together they have won 7 games of the 12 decisive games so far. At the bottom we find Ethereal and Fire with 8 combined losses. The new NN engine AllieStein is strong enough for this division, so far it lost 3 games and won 2. Komodo has 14 straight draws, its younger family member KomodoMCTS has a better score with 2 wins and a loss. Houdini is still strong despite the fact that it hasn't been updated for a few seasons.

There were two consecutive network crashes, the GPU server was rebooted and the games were later resumed.

A few interesting games

Stockfish - KomodoMCTS: See featured game below.

Leela - AllieStein: Evals were over 1 from the start. The engines concentrated forces on the queen side, after opening the files many pieces were exchanged. By move 30 only QRN vs QRN were left, evals over 2.5. The black knight was pinned and AllieStein used a few moves to get it free. Leela refused offers to exchange queens, then unexpectedly KomodoMCTS blundered into a knight fork and Leela won a piece. The game continued for 35 more moves but the outcome was obvious.

Ethereal - Leela: In this game the network crashed and the game was later resumed. Leela had an negative eval under 1 in closed position with many pawns. Leela gave a pawn but Ethereal's pawn structure was weak with several isolated pawns. The engines seemed to be shuffling for a while, then Ethereal tried to take the initiative and it gave a rook for a knight and pawn. Ethreal had two connected passers on the queen side in a QRB vs QRR position, Leela thought it was safe and its eval jumped over 2. Leela opened the king side and attacked the white king. Ethereal gave a few checks but eventually Leela exchanged down to a winning B vs R endgame. 

Stockfish - Fire: Stockfish was better after the opening with an eval over 1. Evals gradually increased though material was equal, Stockfish arranged its pieces patiently until it was ready to strike. In a long series of exchanges the engines reduced to a RN vs R position. Fire was up a pawn but it was not enough to hold, the game was adjudicated with with one pawn left for each engine.

Ethereal - KomodoMCTS: Evals were low for 35 moves, then the (negative) evals started to increase to about 1. Ethereal had two weak pawns and KomodoMCTS threatened both. After reducing to a QR vs QR position KomodoMCTS captured a pawn, after exchanging queens it captured a second pawn. The rook endgame was a win for black.

AllieStein - Fire: AllieStein's eval started to jump on move 22 with all pieces on the board. The center and queen side pawns were locked, most of the black pieces were on the queen side and the black king had only pawn defenders. AllieStein pushed pawns on the king side and had a big space advantage, Fire could hardly move. Eventually AllieStein opened the king side and went a pawn up. Fire exchanged pieces to avoid mate, AllieStein captured another pawn and it had three advanced passers. The game was adjudicated 25 moves later in a double rook ending. AllieStein won this opening from both sides.

Stockfish - AllieStein: Stockfish had an eval advantage of about 1 from the start, it had more space and its pieces were more developed. AllieStein gave a pawn and opened the queen side, evals remained more or less constant. When AllieStein gave a second pawn evals climbed for a while but came back down to 1. Evals jumped over 4 as AllieStein tried to attack. Stockfish's king escaped a few checks, and then Stockfish countered with an attack on the black king. AllieStein couldn't escape without losing material and the game was adjudicated.

Featured game: Stockfish - KomodoMCTS
Premier division, game 37
Link to game on TCEC

Stockfish had a small eval advantage from the start. Its eval jumped over 1.5 after the black queen moved to the queen side early in the game. KomodoMCTS didn't think it was in danger after Stockfish opened a file on the king side.

Evals increased very slowly, Stockfish had strong central pawns and a bishop pair. The black queen side pawns were vulnerable, Stockfish had targets on both sides of the board. Its king was exposed so it had to be careful. KomodoMCTS was under a lot of pressure and was busy defending.

KomodoMCTS tried to counterattack, it gave a bishop for 3 pawns and opened the center. After a few queen checks the attack was over, evals jumped very quickly and Stockfish could see the win.

The white pieces were very strong with no pawns in the center to stop them. Stockfish had too many attacking options and it started to win material when the game was adjudicated.

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