The machine-learning chess engine Lc0 won the Chess.com Computer Chess Championship last weekend, making history as the first neural-network project to take the title. Lc0, which taught itself how to play chess, is now at the game's pinnacle as the champion computer engine.

Could this be a decisive moment in the story of computer chess, when the neural networks leaped past traditional chess engines on their way to dominance? Only time will tell, but Lc0 put on quite a show in winning CCC 7: Blitz Bonanza with a score of 167.5/300 in the finals.

Lc0 placed ahead of runner-up Stockfish (162/300) in the blitz finals, the first time in eight Computer Chess Championships that Stockfish didn't win the tournament (CCC 1-7 and the previous-format event in 2017).

The four-engine finals were packed with neural networks, as Lc0 variants Leelenstein (144/300) and Antifish (126.5/300) placed third and fourth. Computer Chess Championship rules were updated after the tournament to allow no more than two finalists that share a significant code base.

The open-source Lc0 project was inspired by Google/DeepMind's AlphaZero, a neural-network engine that made headlines by beating previous versions of Stockfish in private matches.

Lc0 also won its mini-match against Stockfish in the finals, +10 -8 =82, which is the first time that Stockfish has ever lost a head-to-head matchup with any engine in Computer Chess Championship history.

Can Lc0 defend its title in a longer time control? CCC 8: Deep Dive is live now, featuring 24 of the world's top chess engines playing at a rapid time control of 15 minutes plus a five-second increment per move.

You can vote on each game and follow the always-running Computer Chess Championship:

The CCC 8 field returns the same 24 engines from CCC 7.

Stage one of CCC 8 is a 24-player round-robin, where each engine will play every other engine two times as White and two times as Black. The top four engines from stage one will advance to a 50x-round-robin final stage.

CCC 8: Deep Dive Information:

Engines: 24

Time control: 15 minutes + 5-second increment

Format: 4x round-robin, escalation order (each engine plays every other engine two times as White and two times as Black) in stage one

Games: 1,404 total; 1,104 in stage one and 300 in the finals

Start date: April 13

Expected duration: 42 days total; 33 days for stage one (~May 16), 9 days for finals (~May 25)

Opening book: None in stage one, book chosen by Chess.com tournament staff in finals

Endgame tablebases: On

Top four engines in stage one advance to 50x round-robin finals (No more than two finalists can share code; any qualifying engine that shares code after the first two will be disqualified and the next-highest-scoring engine will take its place.)

CCC 8: Deep Dive Contestants and Escalation Order:

1. Lc0*

2. Stockfish

3. Fizbo

4. Komodo

5. Laser

6. Shredder

7. Leelenstein*

8. BlackMamba

9. Schooner

10. Fire

11. Xiphos

12. Andscacs

13. Antifish*

14. Rofchade

15. Arasan

16. Houdini

17. Protector

18. Senpai

19. Allie*

20. Wasp

21. Texel

22. Bobcat

23. Komodo Monte Carlo

24. Ethereal

*Denotes a neural-network engine.

CCC 7: Blitz Bonanza Crosstable:

CCC 7 Finals Crosstable. Click on the image for a larger version.

CCC 7: Finals PGN Download and Selected Games:

Lc0 does heavy damage to Stockfish on the h-file in a game that could be in a textbook for humans on how to defeat the Pirc Defense. The endgame shows the substantial power of a queen and three connected passed pawns as the mighty fish could only delay its own demise.

Lc0 put on another endgame clinic in a grind-it-out victory over a fellow neural-network engine, Antifish. Lc0 needed 287 moves to finally prove its winning advantage, outmaneuvering Antifish in a complex rook, pawn and knight ending.

The mate-in-three method chosen by Lc0 at the very end might look alien to human players, even though it appears in the endgame that every chess beginner learns: rook-and-king vs king. It may be that humanity can learn about chess from Leela in even the simplest positions.



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Can Lc0 defend its title in the Computer Chess Championship? Let us know in the comments, and be sure to vote on the games at the CCC main site.