# Round tournament

As a round tournament , also everyone against everyone or league system ( English Round Robin), a tournament form or a league mode is referred to, in which each tournament participant competes the same number of times against all other tournament participants.

This system is u. a. used in most sports leagues . According to a fixed schedule , each team plays against each other team once at home and once away (exact name: double round robin, i.e. double round tournament, as each team scores each other twice).

## Designations

### Single round

In a single round, each team competes exactly once against each opponent . No return matches will be played.

Various types of sport, based on the wording simple round with a first and second leg, also designate a competition mode consisting of a first and second leg as a single round.

So that every participant has the same number of home rights, the number of participants in a single round is often odd. In the one-round group stage of the UEFA Cup until 2009 , each group therefore had five participants. If the number of participants is even, half have home rights once more, while the other half play away once more. Exceptions to this are events such as the European Football Championship , where there is usually only one host and the number of participants in the group is therefore irrelevant for home law.

### Double round

A double round consists of two single rounds . So that one does not have to pause at every round, the number of participants in a double round tournament is usually even.

In some sports (e.g. ice hockey ) the term refers to two single rounds with a return game. Then each team competes four times against each opponent in a double round , in two home games and two away games. This can be used to calculate the number of games per team in a double round by calculating the number of opponents  × 4.

### Other names

Similar to the double round, other multiples of single rounds are also possible. The definition of single round can be different, analogous to the above. The Hungarian Football League plays a triple round with twelve teams: everyone plays three times against each opponent (33 games). In ice hockey, this system is known as the one and a half- fold round , so the Regionalliga Ost 2019/20 with nine teams plays three times against each other (24 games). Triple rounds, on the other hand, refer to three rounds with first and second legs, see e.g. B. the 1993/94 season of the 2nd ice hockey Bundesliga .

## rating

The round-robin tournament, especially the double-round tournament, is generally considered to be the fairest system; in fact, it theoretically provides a correct, continuous ranking from first to last.

In a purely round-robin tournament, the two best-placed teams don't usually meet in the last round. Therefore, the decision about winning the title is very often made before the last game round, so that the last game no longer arouses interest, which is undesirable from the organizer's point of view. If the decision about the title is actually only made in the last round of the game, a so-called “remote duel” is the decisive factor and not a direct comparison. In this way, kingmaker constellations arise, but also the possibility of fraudulent agreements (so-called collusion , see Bundesliga scandal ).

## Fine evaluation

After completing all rounds of the game, it is possible that two participants are tied so that tie-breakers are applied:

• various forms of fine evaluation
• Points from direct encounters, goal difference, number of goals scored, number of away goals, etc.
• own play-off games that are played after the regular game rounds. The play-off games are again held according to the knockout system, so that this results in a mixed tournament format overall.

## execution

Course of a one-round round-robin tournament with 10 participating teams

If the number of participants is, there are n · ( n −1) games in a double round tournament . A one-round tournament or a pure round-robin tournament requires games. When it happens, games can be played simultaneously in each of the rounds , provided there are enough playgrounds. If is odd, there are rounds with games each and an opponent with no game in that one round. It follows from Baranyai's theorem that it is actually possible to create such a game plan with any number of participants. ${\ displaystyle n}$${\ displaystyle {\ begin {matrix} {\ frac {n} {2}} \ end {matrix}} (n-1)}$${\ displaystyle n}$${\ displaystyle (n-1)}$${\ displaystyle {\ begin {matrix} {\ frac {n} {2}} \ end {matrix}}}$${\ displaystyle n}$${\ displaystyle n}$${\ displaystyle {\ begin {matrix} {\ frac {n-1} {2}} \ end {matrix}}}$

• The usual approach for a round robin is to assign a number to each participant and then the matches of each round of so-called mating panels (engl. Berger pairing tables) can be seen (see example in the links).
• For board games in which the participants sit opposite each other at a row of tables, the slide system is a simply functioning procedure for holding a round-robin tournament.

## Modifications

In many cases a combination of a knockout system and a round robin tournament is used. See also tournament form .

Speed ​​Trial (shortened round-robin tournament)

If there is not enough time to hold all rounds with a large number of participants, the Swiss system is usually used . The Swiss system has the disadvantage that the pairings for the next round can only be drawn after the last game of the previous round has been completed. An alternative to this is the Speed ​​Trial (shortened round-robin tournament). At the beginning of the tournament, a predetermined number of rounds are drawn from all participants, whereby two participants are not allowed to play against each other more than once, for example 5 rounds of 12 games each with 24 participants (instead of 23 rounds). Compared to the Swiss system, Speed ​​Trial is not suitable for producing the best player as the tournament winner. Speed ​​Trial can, however, be used sensibly as a preliminary round to determine the final round participants. Speed ​​Trial takes place at various regional backgammon tournaments, e.g. B. in Hanover, Hamburg, Berlin or Dortmund, as well as at flyball tournaments.