Swiss tournament system - an introduction

What is it?

I'll start with a quote from wikipedia, as it sums it up perfectly:

A Swiss-system tournament is a non-eliminating tournament format that features a fixed number of rounds of competition, but considerably fewer than for a round-robin tournament; thus each competitor (team or individual) does not play all the other competitors. Competitors meet one-on-one in each round and are paired using a set of rules designed to ensure that each competitor plays opponents with a similar running score, but does not play the same opponent more than once. The winner is the competitor with the highest aggregate points earned in all rounds. With an even number of participants, all competitors play in each round.

Sounds easy enough right? It's kinda like a round-robin, but you don't end up playing every other player in the group.

Why and when to use it

There is a couple of things to consider before you start using the swiss system. 

Setting the correct number of rounds

How many rounds should be played? It depends, but there is a limit as to have many you MUST have, and how many you CAN have at the most. In between those values you should consider how much time you have available to play.

The min/max amount of rounds can be viewed as:

MIN = binary logarithm of the number of participants rounded up (ex: 3 rounds for 8 players, 4 rounds for 16 players, 5 rounds for 32 players and so on).

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.

MAX = half of number of participants rounded up (ex: 4 rounds for 8 players, 8 rounds for 16 players, 16 rounds for 32 players and so on). 

So, you'll need to know your max amount of players (practically; available tables times two), then find out how much time you have available, and then see how many rounds you can fit in that time.

F.ex: We have 8 tables available, that will leave you with a maximum of 16 participants. At least you need 4 rounds, at the most 8. If each round (match) is estimated to take 1 hour, the event could be finished in 4 hours. If you have 8 hours available, play all 8 rounds if you want.

Specify how many rounds

The number of rounds you want to play can be set when you are doing the draw. In the dialog that pops up when you are about to draw the schedule, enter the number of rounds you want to play.

No eliminations

What does this mean? Well, if you're used to single elimination or double elimination brackets, the prospect of no elimination will sound odd. It simply means that all players will be playing in every round of the event until it is finished.

The winner is determined by standings after the final round.

If keeping all the players in the venue all through the tournament sounds like a good idea, the swiss tournament system is definitely for you. Players should also be happy with more table time and match opportunities regardless of if they win or lose.

Make sure you have enough available tables 

The amount of tables you need is half the number of participants in the tournament, so for 16 participants, you'll need 8 tables at the same time (throughout the event/every round!). If you don't have enough tables, you will end up waiting for the duration of the second stint before you can start the next round (as the draw is made after all matches have finished). This again means that without sufficient tables available, you'll end up doubling the amount of time the event will take.

Let's face it, you never want to have players waiting around for too long, so make sure you have enough tables.

Monrad system - what is it?

There are different kinds of swiss systems. They differ in the way seeding is done, and in the way matchups are made for each round. 
For our first swiss system implementation we elected to go for the Monrad system. The Monrad method is a bit more cut-throat than standard Swiss pairing, since high-ranking players are paired against each other earlier in the event.

In a Monrad event, players are ranked, first by points and then by their Buchholz value, Buchholz Cut and then by framescore. Once players are sorted by rank (happens after all matches in the round is finished), they are paired from top to bottom. The player in first place is paired against the player in second place, third place is paired against fourth place, and so on. If a player has met the next on the list before, it will skip to the next one. For odd numbered participants there will also be a bye/walkover.

Buchholz and Buchholz Cut

This is a tie-breaking system, which will separate otherwise equal positions based upon the opponents they have met.
The Buchholz value is calculated like this:

Your Buchholz value is the sum of wins you have (half a point if you have a bye/walkover). Then we take this number and multiply it with the sum of the Buchholz values of your opponents. 
F.ex: I have 3 wins and my opponents have 2, 2 and 1, which adds up to 5. My Buchholz value becomes 3 * 5 = 15.

The Buchholz Cut is the same calculation but we remove the weakest opponent (1), so the Buchholz Cut value will be 3 * 4 = 12.

Advantages

• Equal playing time for all participants, no eliminations.
• Fair matchups (players of similar strength will be matched against eachother).
• Duration of the tournament is predictable.
• Scales very well with number of participants (as long as you have enough tables..).
• Another quote from wikipedia:
  

  Another advantage compared to knockout tournaments is that the final ranking gives some indication of the relative strengths of all contestants, not just of the tournament winner. By contrast, in a knockout tournament the second-best contestant is not necessarily the losing finalist; they could be any of the contestants defeated by the eventual tournament winner in earlier rounds.