Top Chess Engine Championship

The TCEC competition is divided into seasons, where each season happens over a course of a few months, with matches played round-the-clock and broadcast live over the internet. Each season is divided into several tournaments, a Leagues Season, a Cup, a Swiss tournament, and a Fischer Random Chess tournament.

Prior to season 21, there was originally one tournament in each season. This tournament consisted of several qualifying stages and one "superfinal", and the winner of the superfinal is called the "TCEC Grand Champion" until the next season. Prior to season 11, the tournament used a cup format, while starting in Season 11, the tournament used a division system. Starting in season 13, there was also a cup tournament consisting of the top 32 engines in the main tournament, resulting in a 5-round single elimination tournament.[8]

Pondering is set to off. All engines run on mostly the same hardware[9] and use the same opening book, which is set by the organizers and changed in every stage. Large pages are disabled, but access to various endgame tablebases is permitted. Engines are allowed updates between stages; if there is a critical play-limiting bug, they are also allowed to be updated once during the stage. In previous seasons, if an engine crashes 3 times in one event, it is disqualified to avoid distorting the results for the other engines; however starting in TCEC Season 20, an engine is allowed to crash as many times as possible without being disqualified from the current event; however, the engine will still be disqualified from future events unless the crash is fixed.[10] TCEC generates an Elo rating list from the matches played during the tournament. An initial rating is given to any new participant based on its rating in other chess engine rating lists.

There is no definite criterion for entering into the competition, other than inviting the top participants under active development from various rating lists which can run on their Linux platform. Originally, TCEC used Windows instead of Linux. In addition, either XBoard or UCI protocol are required to participate.

Usually chess engines that support multiprocessor mode are preferred (8-cores or higher), and engines in active development are given preference. Since TCEC 12, engines like LCZero which use GPUs for neural processing were supported.

Initially, the list of participants was personally chosen by Thoresen before the start of a season. His stated goal was to include "every major engine that is not a direct clone".[11] In TCEC 13, DeusX was banned due to being a clone of Leela, and in TCEC 20, Houdini, Fire, Rybka (engine in Fritz up to TCEC 16), and Critter were banned due to allegations of plagiarism.

Starting in season 21, each season has been expanded to include the Cup, a Fischer Random Chess tournament, and a Swiss tournament, and thus the original tournament has been renamed to the Leagues Season.[12]

The structure of the TCEC VSOB varies from event to event. Most of them have been in a round-robin format.

However, the latest VSOB event, VSOB 21, has a different format, where each opening gets tested to see how unbalanced the position is, and then assigned to a pair of engines depending on the strength differential between the pair of engines: equal positions were assigned to a pair of engines where one engine was vastly stronger than the other, while heavily unequal positions were assigned to a pair of engines about roughly equal strength.

The tables display the results of each TCEC Season that was a multi-stage tournament.

The tables display the results of each TCEC Season that was a league system.

¹ Originally named "nTCEC Season 1".

² Originally named "nTCEC Season 2".

³ Season 7 did not use endgame table bases at all and Stage two did not use opening books either.

After season 20, each season was expanded to include the Swiss, the Cup, and the FRC tournament, and so the original event is now called the Leagues Season.[13]

TCEC allows viewers to submit chess openings to TCEC, upon which the openings will be played by various engines in a series of exhibition games.

¹ Double round robin tournament.

This table includes Main/Leagues, Cup, FRC and Swiss results.[15]