The Swiss system is used for competitions in which there are too many entrants for a full round-robin (all-play-all) to be feasible, and eliminating any competitors before the end of the tournament is undesirable.
In the first round, competitors are paired either randomly or according to some pattern that has been found to serve a given game or sport well.
If it is desired for top-ranked participants to meet in the last rounds, the pattern must start them in different brackets, just the same as is done in seeding of pre-ranked players for a single elimination tournament.
In chess, a specific pairing rule, called "Dutch system" by FIDE, is often implied when the term "Swiss" is used.
The Monrad system for pairing is commonly used in chess in Denmark and Norway, as well as in other sports worldwide.
Modifications are then made to prevent competitors from meeting each other twice, and to balance colors (in chess).
If the Dutch system is used, players or teams in the qualifier may be incentivized to not do their best, as doing so might make them play against the 1st seed on the first round, decreasing their chances of having a good score.
Assuming no drawn games, determining a clear winner (and, incidentally, a clear loser) would require the same number of rounds as that of a knockout tournament, which is the binary logarithm of the number of players rounded up.
If fewer than this minimum number of rounds are played, two or more players could finish the tournament with a perfect score, having won all their games but never having faced each other.
Due to the fact that players should meet each other at most once and pairings are chosen dependent on the results, there is a natural upper bound on the number of rounds of a Swiss-system tournament, which is equal to half of the number of players rounded up.
Second, while the outcome of the final game has no bearing on first place, the first-place player can decide who wins second or third prize.
In the 1995 All-Stars Tournament in Scrabble, tournament directors paired David Gibson, who had by then clinched first place, with the highest-ranked player who could not win a prize so that the second- and third-ranked players could compete between themselves for the final placements.
For example, if a tennis tournament had sixty-four players, but only eight courts available, then not all matches in a round can be played at the same time.
Note that the waves format is not strictly necessary, as instead a match could commence as soon as another in the same round ends, but the principle is largely the same.
This method pairs top players more quickly than the standard method in the opening rounds[10] and has the effect of reducing the number of players with perfect scores more rapidly (by approximately a factor of 2 after two rounds).
[11] For the first two rounds, players who started in the top half have one point added to their score for pairing purposes only.
After the second round, the standard pairing method is used (without the added point for the players who started in the top half).
As a comparison between the standard Swiss system and the accelerated pairings, consider a tournament with eight players, ranked #1 through #8.
In a large field it is usually easy to match high-scoring teams who have not previously met.
Players are not required to play in every round; they may enter or drop out of the tournament at any time.
The Keizer system also maximizes the interest of the games by seeking to pairing opponents of similar playing strength.
In "Round 1" of a chess tournament paired using the Swiss System, players usually are seeded according to their known playing strength, often a rating assigned to them by their local club, their national federation, or the world chess federation (FIDE).
Win, lose or draw, all players proceed to the next round where winners are paired against opponents with equal performance scores (e.g.
The rules for Swiss System chess events also try to ensure that each player plays an equal number of games with white and black.
[1] The first national event in the United States to use the Swiss system was in Corpus Christi, Texas in 1945; and the first Chess Olympiad using it was held in Haifa in 1976.
[14] In chess, the terms Swiss and Monrad are both used and denote systems with different pairing algorithms.
Swiss-system tournaments must start with very unequal matches in the early rounds—"slaughter pairing" is the name of one initial pattern used—if the Swiss pairing rules applied subsequently are to allow the top players to meet in the latest rounds.