Computer chess

Stockfish takes 1-point lead in TCEC Premier Division

After a record-setting Season 22, defending champion Stockfish once again dominated its rivals in TCEC Season 23’s Premier Division, taking a 1-point lead at the half-way mark. The high-bias book – reaching as high as +2 opening evals at book exit – meant it was always hairy for the engines defending inferior positions, but Stockfish time and again drew with Black while winning with White. It won the opening against all its rivals bar rofChade in the first round, and repeated that 1.5-0.5 victory in the second round against everyone except Lc0 and SlowChess. Yes, this means Stockfish has already won three openings against the other two members of the Big Three. Surprisingly enough, both Lc0 and Komodo Dragon did better against the bottom half of the field than Stockfish – both engines have failed to win “only” one opening against the engines placed 4th-8th, while Stockfish has failed to win twice. Nonetheless, the head-to-head wins mean Stockfish is a full point ahead of the field. Lc0 is in second place after a strong second round – in fact, Lc0 “won” the round by defeating every other engine while drawing with Stockfish, a performance that let it narrow the gap with Stockfish by half a point. Lc0’s head-to-head win against Komodo Dragon means Lc0 has a 1.5-point lead over Komodo Dragon going into the second half of the division. The race for the top spots is not settled, but it would take a major shock for Stockfish to fail to qualify for the superfinal, leaving Lc0 and Komodo Dragon to fight for second place.

TCEC Season 23 so far: Ethereal trailblazes TCEC League 1 / Minic convincingly wins TCEC League 2

A pivotal moment in the first round. Leela’s 23…Qxa2? allowed 24. Qxd6 Qxe2 25. Qc7, giving White a dangerous passed pawn. Both engines saw 25…Ng4 attacking the c3-bishop and e3-knight, but Stockfish’s 26. d6, ignoring the threats and pushing the pawn, caught Leela by surprise. Stockfish reached an endgame with a rook for bishop & two pawns. Opposite-color bishops gave Leela some hope, but Black’s four pawn islands proved impossible to defend.

Away from the top boards, Ethereal has strongly established itself in 4th. Although (like everyone else) it was crushed by the Big Three, it won two openings against both Berserk and rofChade, while also beating Stoofvlees once. With 15/28, it is the only engine outside the Big Three with a >50% score. 5th-placed Stoofvlees also won some openings against SlowChess and rofChade to stand a point behind Ethereal and 2.5 points clear of sixth-placed SlowChess. Barring a minor miracle, we’ll be seeing either Ethereal or Stoofvlees in the infrafinal.

That leaves three engines fighting to survive relegation. At the half-way mark, SlowChess is in the lead, but is only half a point ahead of Berserk. Berserk is in the relegation zone, but it is the only one of the bottom three engines to have won an opening against another bottom three engine, defeating rofChade in the first round. rofChade is last, a point away from safety. Still, it scored a rare win against Komodo Dragon in the first round. Although it also lost the reverse, it is rare for the Big Three to lose to anyone other than themselves. rofChade might make it yet.
The second half is estimated to begin in a couple of hours as of time of writing, around 6am UTC 9 October, with rofChade wielding the white pieces against SlowChess. Catch all live games on the website: and TCEC Twitch TV

Article by Low

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