Chess Terms
Leela Chess Zero

Leela Chess Zero

Chess engines using the Alpha-Beta search algorithm were the norm and the only option for a long time. The brute force of these engines defeated the strongest human players and brought chess to new heights. It looked like nothing would ever be able to compete with them.

Then a neural network-based chess program, AlphaZero, stepped onto the scene and changed the game forever. Unfortunately, nobody can purchase or license AlphaZero, but chess fans rejoiced when the Leela Chess Zero project was announced—having access to a neural network engine was a dream come true for many. 

Let's learn about Leela Chess Zero. Here is what you need to know:


What Is Leela Chess Zero?

Leela Chess Zero (also known as Lc0, LCZero, and Leela) is an open-source neural network (NN)-based chess engine. The Lc0 project was announced in early 2018, and Gary Linscott (a developer for Stockfish) has led the development. Because of its free and open-source nature, it can be run on many platforms, including Windows, Mac, Linux, Android, and Ubuntu. Lc0 is the strongest NN engine available to the public.

Leela chess zero Lc0
Leela Chess Zero's logo. Image: lczero.org.

Lc0 is strongly inspired by DeepMind's AlphaZero project and learned the game in the same fashion. Unlike conventional chess engines, Leela was only given the rules of the game of chess and became incredibly strong by using reinforcement learning from repeated self-play—as of 2020 it has played over 300 million games against itself.

According to the September 2020 Computer Chess Rating List (CCRL), Leela is the second-highest rated chess engine in the world with a rating of 3462, only slightly behind Stockfish.

Leela Chess Zero Accomplishments

Since stepping onto the scene in 2018, Leela has had increasingly impressive results in a very short time. After a few months it was at grandmaster strength, and in September 2018 Leela placed third out of 24 powerful engines in the 2018 Chess.com Computer Chess Championship tournament.

In December 2018 Leela placed second in season 14 of the Top Chess Engine Championship (TCEC). It lost to Stockfish in the Superfinal by a score of 50.5 - 49.5, but the Lc0-Stockfish rivalry was only beginning.

Leela chess zero
The Lc0-Stockfish rivalry began in 2018 and is ongoing. Image: Chess.com.

In February 2019 Leela defeated Houdini in the second TCEC cup final to earn its first major tournament victory—the first NN engine to win. In May 2019 Leela won the third TCEC cup after defeating Stockfish in the final. It also won the Superfinal of the 15th TCEC season, again defeating Stockfish.

In TCEC's 17th season, held from January-April 2020, Leela again won the championship after it defeated Stockfish in the final. In April 2020 Leela won the 13th Chess.com Computer Chess Championship, defeating Stockfish 106-94 in the 200-game final.

Leela Chess Zero Games

Leela's games sometimes seem like they are being played by an otherworldly entity. The way it evaluates positions is significantly different than how a traditional or conventional engine does, which can lead to incredibly creative and almost alien-like play.

Leela Chess Zero Lc0
Leela's play can seem almost other-worldly. Image: lczero.org.

Leela values things like space and piece activity differently than conventional engines, which can be seen in the following game where Leela uses space and a pawn storm in a marvelous fashion.

Here is a wonderful video by NM Sam Copeland that discusses the above game in great detail:

In this second game example, we see Leela launch a magnificent attack from a dangerous opening gambit. The piece sacrifice on move 16 is mind-blowing and almost alien. Here is the game with annotations by IM Danny Rensch followed by his highly instructional and entertaining video:


Conclusion

You now know what Leela Chess Zero is, what it has accomplished so far, and more. Head over to Chess.com/CCC and watch top engines play at any time on any day!