Double-elimination tournament
From Free net encyclopedia
Image:NSB-doubleelim-draw-2004.png A double-elimination tournament is a competition in which a participant ceases to be eligible to win the tournament's championship upon having lost two games or matches. It stands in contrast to a single-elimination tournament, in which only one defeat results in elimination.
A double-elimination tournament is broken into two sets of brackets, the Winners Bracket and Losers Bracket (W and L Brackets for short; also sometimes Upper Bracket and Lower Bracket, respectively). After the first round, the winners proceed into the W Bracket and the losers proceed into the L Bracket. The W Bracket is conducted in the same manner as a single-elimination tournament, except of course that the losers of each round "drop down" into the L Bracket.
As with single-elimination tournaments, most often the number of competitors is equal to a power of 2 (4, 8, 16, etc) so that there are an even number of competitors at every round.
Conducting the tournament
Each round of the L Bracket is conducted in two stages, the first stage consisting of the winners of the previous stage (or losers of the very first round of competition), the second stage consisting of the winners of the first stage against the losers of that same round of the W Bracket. This is to allow the losers of each stage of the W Bracket to "filter down" into the L Bracket.
For example, in an 8-competitor double-elimination tournament, the losers of the first round enter the first stage of the L Bracket semifinals and compete against each other. The losers are eliminated, the winners proceed to the second stage to face the losers of the W Bracket semifinals. The winners of the second stage proceed to the first stage of the L Bracket finals; the winner thereof faces the loser of the W Bracket finals; the winner of that match is the winner of the L Bracket.
The winner of the W Bracket (who will have been undefeated thus far) and the winner of the L Bracket (who will have been defeated only once thus far) will then face each other. If the L Bracket winner wins, then each competitor will have lost only once, thus neither team will have been eliminated, thus those competitors face each other again, the loser being eliminated and the last remaining competitor winning the entire tournament.
Pros and Cons
The double-elimination format has some advantages over the single-elimination format, most notably the fact that third and fourth places can be determined without the use of a consolation or "classification" match involving two contestants who have already been eliminated from winning the championship. A common criticism of the double-elimination format is that sometimes the last competitor to remain undefeated (i.e. the winner of the Winners Bracket) can actually lose only once and still be eliminated. However, that competitor does draw two byes during the course of the tournament, which compensates for that fact, and furthermore many tournaments require the last two remaining competitors to compete again if the undefeated team is defeated for the first time in the finals. This variation is often referred as "full double elimination".
A disadvantage compared to the single-elimination format is that a considerably greater number of matches have to be conducted: since each player has to lose twice and since the tournament ends when only one player remains, in tournament for N competitiors there will be 2*N-1 (or 2*N-2 in case the winner was undefeated during the tourney) games; a plausible alternative is a single-elimination format where each match is a best-of-5 or best-of-7 series. This format still allows a competitor to lose (perhaps multiple times) while still remaining eligible to win the tournament. Of course, having multiple games in each series also requires considerably more games to be conducted.
Another (minor) disadvantage is that the double-elimination format is more difficult to understand and explain. However, once it is understood, then this becomes a moot point.
The most well-known athletic event that employs a double-elimination format is the College World Series in baseball. It is also extensively used in computer gaming tournaments, most famously by the Cyberathlete Professional League.