About the swiss system

The Swiss system determines how tournaments are run. This algorithm is responsible for fair pairing of players and generation of the final classification. Most chess and card tournaments are run according to this system. This section explains how this algorithm works with simple examples.

Basic information

The tournament is divided into rounds, the number of which depends on the number of participants in the tournament. The number of rounds is usually determined by the following relationship: floor of log(number_of_players), i.e. for 4 players - 2 rounds; 5-8 players - 3 rounds; 9-16 players - 4 rounds, etc. (although it is not a rule and you can increase/decrease the number of rounds depending on the time you have).

In each round, players are paired up and play against each other. In the case of an odd number of players, someone necessarily has to pause (no opponent). After the end of the round, the score is calculated according to the following scheme:

• 3 points for a win
• for a draw 1 point
• for loss 0 pts
• pausing person 3 pts

The above scheme is also only an example and there are no contraindications to use a different scoring system. The pauser is considered to be playing against an additional virtual opponent who always loses. So pausing counts as winning against the weakest player in the tournament.

After one round is completed and the points have been counted, the next round begins and so on until the end of the competition and the publication of the final classification.

The main assumptions of the Swiss system:

• Players with similar scores are paired up
• Two players can only play against each other once

An example of a tournament organized in the Swiss system

Round 1

Let's assume that there are 7 players in the tournament marked as: A, B,... G. Suggesting the previous pattern, 3 rounds will be played. In the first round, the pairing is completely random:

A - E
B - F
C - G
D - [pause]

The winners were: A, B, G and D (as he paused).

Round 2

The winners play with the winners and the losers with the losers - according to the principle that pairs are matched on the principle of similar number of points.

A (3 points) - B (3 points)
G (3 points) - D (3 points)
E (0 points) - F (0 points)
C (0 points) - [pause]

In this turn, A, D, E and C won.

Round 3, last

A (6 pkt) - D (6 pkt)
B (3 pkt) - G (3 pkt)
E (3 pkt) - C (3 pkt)
F (0 pkt) - [pause]

Winners: B, C, F; Draw: AD.

Final classification

Before publishing the results, you need to recalculate the two columns of small points (in fact, you need to recalculate it after each round). The first column of small points is equal to the points of the opponents we beat x3 and the points of the opponents we tied x1. The second column is the total points of the opponents we lost to.

A: 7 pts; defeated E, B, tied with z D => 3*3 + 3*6 + 1*6 = 33 m.pts
B: 6 pts; defeated F, G => 3*3 + 3*3 = 18 m.pts
C: 6 pts; defeated E => 3*3 = 9 m.pts
D: 7 pts; defeated G => 3*3 = 9 m.pts
E: 3 pts; defeated F => 3*3 = 9 m.pts
F: 3 pts; lost everything => 0 m.pts
G: 3 pts; defeated C => 3*6 => 18 m.pts

Now we need to sort the players by big points (main criterion) and small points (less important criterion). So the final classification is as follows:

1. A	7	33	0
2. D	7	9	0
3. B	6	18	7
4. C	6	9	3
5. G	3	18	13
6. E	3	9	13
7. F	3	0	9

Example no 2

6 players: A, B,... F. 3 Rounds.

Round 1

A - D
B - E
C - F

A, B and C won.

Round 2

A (3 points) - B (3 points)
C (3 points) - D (0 points)
E (0 points) - F (0 points)

A, D and E won.

Round 3, last

When generating the following pairs, you need to pay attention to the 2 golden rules: 1. Players who have already played together may not play together, and 2. pairs should have as close as possible the number of points, while not breaking the first rule.

A (6 points) - E (3 points)
B (3 points) - C (3 points)
D (3 points) - F (0 points)

A, B and D won

Final classification

In this case, the 2nd column of small points decided about the occupied place of players C and E.

1. A	9	45	0
2. B	6	18	9
3. D	6	9	9
4. E	3	0	15
5. C	3	0	12
6. F	0	0	12

Time limits per round

In order to use the tournament time effectively, the games in each round should be of similar length. It should be avoided that one pair plays the match for an extremely long time while the rest of the players are forced to wait.

To counteract this situation, time constraints have been introduced. Each round lasts a certain amount of time, if after the end of the game the result of the game is still undecided, it is considered a draw. The amount of time you spend per round depends on the type of game.

What to do after time?

If the organizer announces the end of time and the game has not yet been completed, the last 7 turns are played. If the game is still tied after these 7 turns (regardless of the game state), the entire match is considered a draw.

Intentional prolonging/long thinking may result in warnings and even disqualification from the tournament.

Top-4 / Top-8

In example 2, BD players did not play each other and have the same big score. There is a high probability that player D could be a better player than B after all. What's more, there are usually a large number of prizes dedicated to such high places, so this problem matters (especially with more players).

In order for the final classification to be really fair, sometimes the so-called top-4, and with more players (>=16) top-8. These are some extra matches in the ladder system for the first 4/8 players. The ladder system is the one in which the semi-finals and finals in football are played. The results of these matches determine the final classification.