Swiss system

The Swiss system is a system for holding sports tournaments . It is especially common in intellectual games, such as chess , checkers , shogi , go , renju and the like. It was first applied at a chess tournament in Zurich ( Switzerland ) in 1895 , from where it got its name. The tournament is held without elimination, in each round, starting from the second, pairs of opponents are selected so that the participants who score the same number of points meet each other. At this expense, parties are excluded from the tournament between opponents that are obviously incomparable in strength, which allows us to make a small number of rounds with a large number of participants in order to determine the winners.

Content

1 Terms of use
2 Tournament procedure
3 advantages
4 disadvantages
5 Use
6 Example
7 See also
8 References
9 notes

Terms of use

Traditionally, to obtain the most objective result, tournaments were held according to a circular system in which each participant plays at least one game with each and the winner is determined by the sum of the points scored. But in a circular system with an increase in the number of participants, the required number of meetings is growing rapidly, so its application with the number of participants over two or three dozen becomes unrealistic. In tournaments held according to the Swiss system, sometimes more than a hundred players take part - if in a round-robin system 100 players would need 4950 meetings in 99 rounds, then in Switzerland enough 450 games in 9 rounds (a win eleven times).

The Swiss system allows you to reduce time costs due to the fact that it plays a certain number of rounds predetermined by the regulations on the tournament, and the pair selection system for each round is organized in such a way as to ensure a confident distribution of seats according to the points accumulated. It is believed that to identify the winner, as many rounds are needed as there are steps necessary to identify the winner in the knockout system with the same number of participants. According to some estimates ^[1] , with N participants ${\sqrt {N+2k}}$ ${\ displaystyle {\ sqrt {N + 2k}}}$ rounds rightly placed by k + 1 first players, in practice apply the formula $\log _{2}N+\log _{2}k$ ${\ displaystyle \ log _ {2} N + \ log _ {2} k}$ , rounding off during calculations the values of both logarithms to the nearest integer. The total number of meetings is determined by the formula M * N / 2, where N is the number of players (even) and M is the number of rounds (when all players play in all rounds).

The minimum number of rounds required for a fair determination of the prize troika, depending on the number of participants:

the participants	tours
7-8	5
9-16	6
17–32	7
33–64	8
65-128	9
129—256	10

Tournament Procedure

In the first round, all players are ordered (by random draw, or by rating ). Pairs are made according to the principle: the first of the upper half of the table with the first of the lower half, the second with the second, and so on. If, for example, the tournament has 40 participants, the first one plays from the 21st, the second from the 22nd, etc. With an odd number of players, the player with the last number gets a point without a game.
In the following rounds, all players are divided into groups with the same number of points scored. So, after the first round of groups there will be three: winners, losers and tied. If the group has an odd number of players, then one player is transferred to the next point group.
The pairs of players for the next round are made up of one point group according to the same principle as in the first round, the rating principle (the best player from the upper half of the group whenever possible meets the best player from the lower half of this group). At the same time, however, it is not allowed for the same couple to play more than one game in the tournament. When playing chess or checkers, in addition, the rule of color alternation applies: it is desirable that each participant alternates the color of the pieces from round to round (so that the player has an equal number of games in white and black), in any case, three games in a row are not allowed (in checkers - four) in one color, except for the last round. With an odd number of players, the player with the last number in the last point group (from those who have not yet received a point for a pass) receives a point without a game.
Seats in the tournament are distributed according to the number of points scored.
Participants with an equal number of points are usually allocated according to the Buchholz coefficient , which is defined as the sum of points scored by all rivals of a given player in a tournament or by the Solkoff coefficient , which is defined as the sum of points scored by all rivals of a given player in a tournament, excluding the best and the best worst results. In addition to them (or together with them), an average rating of opponents can be applied (those who have higher average ratings are awarded a higher final place) or the so-called “progress coefficient” - a higher position is given to a player who lasts longer during the tournament was in a higher place than the opponent who scored an equal number of points).

Advantages

The Swiss system is the only alternative to the elimination game when a large number of players participate in the competition. The number of rounds in it slightly exceeds the number of rounds of the knockout system, remaining within an acceptable framework even for the largest tournaments.

During the tournament according to the Swiss system, in each round (except for the first one or two), players of approximately equal strength meet, and a victory in such a meeting provides a significant improvement in the position in the tournament, and defeat sensitively lowers the player down. This feature of the Swiss system involves a tense and interesting struggle.

The draw, if applicable, plays a smaller role than in systems with a knockout ( knockout system or Double Elimination ) - the player, even if he is not lucky to meet the strongest in the first rounds and lose, plays the entire tournament and can score his points. This is especially important in tournaments with the participation of players of various levels, in which the weakest obviously do not reach the first places, but gain experience and the opportunity to compete with participants of their level. On the other hand, the selection rules exclude games that are knowingly weak with knowingly strong, which are of no interest.

Weaknesses

In the Swiss system, winners and outsiders are more or less fairly determined, but in the middle of the tournament table places are often allocated insufficiently accurately. Due to the small total number of games, it sometimes happens that two winners with the same number of points do not meet each other during the tournament. The winner has to be determined by additional factors, which, of course, is not as interesting as the final match of applicants in other systems.

If there is a fairly marked difference in strength between the participants of the tournament, a significant part of the parties, especially in the first rounds, turns out to be predictable - despite the allocation of groups by ratings, initially players of too different classes often appear in the same group. This problem is solved in the McMahon system , where the top rated players automatically receive a certain amount of “starting” points, but this system has its drawbacks.

One of the main drawbacks of the Swiss system in relation to chess and checkers is that the principle of alternating colors and the number of games white and black cannot always be maintained. In general, the rules for the distribution of pairs are quite complex, currently pairs are compiled by computer programs. If you strictly adhere to all the rules of distribution by pairs, then all pairs are added up unambiguously, that is, there is no freedom of choice.

Another technical problem is how to deal with retired participants (with a paper grid option). If during the tournament one of the players drops out, then in the next round the participant who gets to play with the dropped out just gets a point, as if for a victory. This is unfair, but there is no other way - in the Swiss system it is impossible to act as a round robin, where the result of a retired player is canceled if he played less than half of the stipulated rounds, otherwise, a point is awarded to those with whom he has not played. In the Swiss system, it is impossible to cancel the results of previous rounds, as in this case some players will lose one game. It is also impossible to award points for unplayed games. A similar problem arises with an odd number of tournament participants: you have to award one technical victory in each round (though having the least number of points).

With the computer version, there is a “bad weather problem”: with a large number of participants who have dropped out (voluntarily) at one time, you have to manually pair , which requires more experience (repeated games between two players who have already played with each other cannot be played).

In games with a significant draw (chess, drafts, xiangqi) in tournaments according to the Swiss system, artificial (contractual) draws are possible and, in some cases, desirable for players. The ground is created for them when there are players of approximately the same level, each of whom has a suitable position in the standings. In this case, the players are not profitable to play for a win, because in an acute game there is a higher probability of losing, and therefore, significantly losing points. This situation provokes the rivals to an explicit or “tacit” agreement: to start the game, play easily and without aggravation, and agree to a draw on the second or third dozen moves, regardless of the situation. As a result, both players will receive half a point, retaining their position without unnecessary risk, usually hoping to get points in games with weaker opponents. Naturally, contractual draws are undesirable: they badly affect the quality component of the game, reduce interest in the tournament and, accordingly, the attractiveness of tournaments for sponsors. Various measures have been proposed to eradicate contractual draws, such as the prohibition of a draw by agreement of the parties or a change in the procedure for scoring points, but their effectiveness remains in question.

In games in which a draw is disappearingly small or absent (shogi, go), there are no such problems.

Usage

The Swiss system has become widespread in Western Europe . There are many so-called "open" or "open" ( English open ) chess tournaments. Grandmasters and masters, as well as a large number of less qualified chess players and amateurs at the same time take part in such tournaments.

Example

As an example, here is a hypothetical table of the tournament according to the Swiss system in chess held between 8 participants (player-1 - player-8). The tournament was held in three rounds.

1st round	Score	2nd round	Score	3rd round	Score	Members	Glasses
player-1 - player-8	1-0	player 1 - player 2	1-0	player 1 - player 3	1-0	player 1	3
						player 3	2
player 2 - player 7	1-0	player 3 - player 5	1-0	player 5 - player 2	0: 1	player 2	2
						player 8	1½
player 3 - player 6	1-0	player-8 - player-7	1-0	player 4 - player 8	½: ½	player 4	1½
						player 5	one
player 4 - player 5	0: 1	player 6 - player 4	0: 1	player 6 - player 7	1-0	player 6	one
						player 7	0

The number of points after three rounds is maximum for player player 1 . He gets 1 place. Next come pairs of players with an equal number of points. If the tournament rules require the use of the Buchholz coefficient , then player-2 has a coefficient of 4, and player-3 has a coefficient of 5, so player-3 takes second place, and player-2 takes third. Then go player 8 and player 4 (1.5 points each, Buchholz odds 4.5 and 3.5), then player 5 and player 6 (odds 5.5 and 3.5), closes player-7 table having 0 points.

Links

Tournament Rules for the Swiss FIDE System

Notes

↑ Charles Weatherly “Programming Etudes”, Ch. 5 Winners are judged.

[1] Charles Weatherly “Programming Etudes”, Ch. 5 Winners are judged.