In a study analyzing millions of chess games, researchers identified ten distinct clusters of chess openings, developed a method to determine player skill and opening game difficulty, and found potential applications for their classification system in other strategy games.
Using real data from an online chess platform, scientists of the Complexity Science Hub and the Centro Ricerche Enrico Fermi (CREF) studied similarities of different chess openings. Based on these similarities, they developed a new classification method that can complement the standard classification.
“To find out how similar chess openings actually are to each other – meaning in real game behavior – we drew on the wisdom of the crowd,” Giordano De Marzo of the Complexity Science Hub and the Centro Ricerche Enrico Fermi (CREF) explains. The researchers analyzed 3,746,135 chess games, 18,253 players, and 988 different openings from the chess platform Lichess and observed who plays which opening games.
Did You Know?
- It is possible to checkmate an opponent in chess in two moves.
- Mathematically, there are more possible chess games than there are atoms in the observable universe. This is the Shannon number, which represents all possible move variations in chess. It is estimated there are between 10111 and 10123 positions (including illegal moves) in chess.
If several players choose two specific opening games over and over again, it stands to reason that they will be similar. Opening games that are so popular that they occur together with most others were excluded. “We also only included players in our analyses that had a rating above 2,000 on the platform Lichess. Total novices could randomly play any opening games, which would skew our analyses,” explains Vito D.P. Servedio of the Complexity Science Hub.
The new method identified ten clusters of chess openings represented with different colors. Openings that are close to each other on this network appear often together in the repertoire of players. Credit: © Complexity Science Hub
Ten Clusters Clearly Delineated
In this way, the researchers found that certain opening games group together. Ten different clusters clearly stood out according to actual similarities in playing behavior. “And these clusters don’t necessarily coincide with the common classification of chess openings,” says De Marzo.
For example, certain opening games from different classes were played repeatedly by the same players. Therefore, although these strategies are classified in different classes, they must have some similarity. So, they are all in the same cluster. Each cluster thus represents a certain style of play – for example, rather defensive or very offensive. Moreover, the method of classification that the researchers have developed here can be applied not only to chess, but to similar games such as Go or Stratego.
Who Plays Chess
- Currently, Magnus Carlsen from Norway (born in 1990) is ranked as the best chess player worldwide (rating: 2853; according to FIDE).
- According to the Federation Internationale des Echecs (FIDE) there are currently 1785 grandmasters worldwide (ten of them in Austria)
- Of course, nobody knows how many people play chess worldwide. To give an approximate impression: FIDE currently has 160,684 active players registered. Estimates say that around 600 million adults worldwide play chess regularly.
Complement the Standard Classification
The opening phase in chess is usually less than 20 moves. Depending on which pieces are moved first, one speaks of an open, half-open, closed or irregular opening. The standard classification, the so-called ECO Code (Encyclopaedia of Chess Openings), divides them into five main groups: A, B, C, D, and E.
“Since this has evolved historically, it contains very useful information. Our clustering represents a new order that is close to the used one and can add to it by showing players how similar openings actually are to each other,” Servedio explains. After all, something that grows historically cannot be reordered from scratch. “You can’t say A20 now becomes B3. That would be like trying to exchange words in a language,” adds De Marzo.
July 20 is World Chess Day. It marks the date of the founding of the International Chess Federation (FIDE) in Paris in 1924.
Rate Players and Opening Games
In addition, their method also allowed the researchers to determine how good a player and how difficult a particular opening game is. The basic assumption: if a particular opening game is played by many people, it is likely to be rather easy. So, they examined which opening games were played the most and who played them. This gave the researchers a measure of how difficult an opening game is (= complexity) and a measure of how good a player is (= fitness). Matching these with the players’ rating on the chess platform itself showed a significant correlation.
“On the one hand, this underlines the significance of our two newly introduced measures, but also the accuracy of our analysis,” explains Servedio. To ensure the relevance and validity of these results from a chess theory perspective, the researchers sought the expertise of a renowned chess grandmaster who wishes to remain anonymous.
Reference: “Quantifying the complexity and similarity of chess openings using online chess community data” by Giordano De Marzo and Vito D. P. Servedio, 1 April 2023, Scientific Reports.
DOI: 10.1038/s41598-023-31658-w
