Analysis, Advantages, and Disadvantages
Determining a clear winner (and, incidentally, a clear loser) usually requires the same number of rounds as a knockout tournament, that is the binary logarithm of the number of players rounded up. Therefore three rounds can handle eight players, four rounds can handle sixteen players and so on. If fewer than this minimum number of rounds are played, it can happen that two or more players finish the tournament with a perfect score, having won all their games but never faced each other.
Compared to a knockout tournament the Swiss system has the inherent advantage of not eliminating anyone. That means that a player can enter such a tournament knowing that he will be able to play in all rounds, regardless of how well he does. The worst that can happen in this respect is being the player left over when there is an odd number of players. The player left over receives a bye, meaning the player does not play that particular round but receives a point. The player is reintroduced in the next round and will not receive another bye.
Another advantage compared to knockout tournaments is that the final ranking gives some indication of relative strength for all contestants, not just for the winner of the tournament. As an example, the losing finalist in a knockout tournament may not be the second best contestant; that might have been any of the contestants eliminated by the eventual tournament winner in earlier rounds.
In a Swiss system tournament, sometimes a player may have picked up such a great lead that by the last round he is assured of winning the tournament even if he loses the last game. This leads to two disadvantages. First, a Swiss system tournament does not always end with the exciting climax of the knockout's final. Second, this unmotivated first-place player may lose their final game, thus affecting the standings of other players. One fairly common fix for this issue is to hold single elimination rounds among the top scorers. In Scrabble tournaments a player with such a strong lead will often be paired against the highest-placed player who cannot possibly finish in the prize-winning zone; this process is known as Gibsonization (also known as the Gibson Rule) after it was first applied to the U.S. Scrabble Champion David Gibson in the 1995 All-Stars tournament. He is the all-time top money winner in the history of Scrabble, and earned a particular reputation by clinching victory in major events before the final round. Because of this, players are said to be Gibsonized: after winning, they are paired with lower-ranked players to avoid affecting the ranking of runners-up.
An additional disadvantage is that, while the players finishing near the top are typically those with the best performances, and those finishing near the bottom are those with the worst performances, the players in the middle tend to be jumbled with little meaningful order. For example, at a recent edition of the European Chess Championship, players scoring 5½/11 had performance ratings ranging from to 2189 to 2559; such a difference suggests that the stronger-performing player would score more than 90% against the weaker-performing one. One player with a 2441 performance rating scored two and a half points better than one performing at 2518.
The system has been used for pool trialing particularly in England. The way to overcome there being multiple players with the same perfect score is to eliminate players after a certain amount of losses. So if you lose three you are out. This will then leave a final match where only one person will end with a perfect score and automatically qualify. This will then leave the right amount of people to play a round robin even so to find the final amount of entrants.
Compared with a round-robin tournament, a Swiss can handle many players without requiring an impractical number of rounds. An elimination tournament is better suited to a situation in which only a limited number of games may be played at once, e.g. tennis. In a Swiss system, all players can be playing a round at the same time.
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