McMahon system tournament

The Mac Mahon system - the spelling in German is uneven and includes variants such as McMahonsystem and more - is a tournament format for two-person games. It is used in particular in the Go.

Basic principle

A fully transmitted in this mode tournament consists of a predetermined number of rounds. The participants generally take part in all rounds. For each participant, a score is performed, which is determined by the specified strength of the participant at the start of the tournament. In each round, the various matches are so drawn that as participants meet the same score. The score of the winner will increase by one point.

The overall result of the tournament is given by the number of points after the last round.

To win the tournament can be played fairly among the promising players, the scores on the start of the tournament, limited by a value ( " Mac -Mahon- bar "), which ensures that a certain number of participants at the top starts with the same score.

Formally, this system represents a generalization of the Swiss system is, as a Tournament Swiss system can be understood as a limiting case of a tournament after MacMahon system, in which all participants start on the Mac -Mahon bar.

Subtleties

Case of a tie various secondary criteria are used, similar to the fine ratings for chess tournaments. This is in each case left to the discretion of the tournament hosts, as MacMahon system does not denote a completely defined algorithm, but only the principle.

This also applies to the method by which the pairings are determined. In addition to the above mentioned point criterion and the requirement that during a tournament may not take place for a second time the encounter between two specific players, there are several possible target requirements, such as a highly balanced ratio of games as black and as white in the individual players, avoiding encounters of players from the same city ( at about regional tournament ), criteria for the walk-through with an odd number of participants, and the like, through which the role of the random draw is limited.

The exposure in a round ( if permitted ) and a draw ( Jigo, the Go is the exception) is usually calculated with a half MacMahon point.

Pairings are unavoidable ( for example in particularly disparate skill level distribution in the field of participants ) in which the score of the opponent to two or more points different from each other when the constellation of scores, even games can be recognized at default. The default is then usually lower than would correspond to the difference in points ( by 1 or 2 reduced default) to not completely abolish the advantage of a better player.

Conditions and benefits in terms of Go

The sensible use of this system requires that the participants be different and reasonably estimable in advance levels. Also, only those participants should come to lie below the MacMahon bar, which anyway had no realistic chance to win the tournament understandable.

In amateur Goturnieren outside of East Asia (ie in countries where the proportion of Go players in the population is relatively small ) these conditions are often met. There are the Kyu or Dan grades a recognized measure of the skill level, and many tournaments a wide range from beginners which represented up to Dan, so that experience has shown that the odds of the weaker player in many games would be very low in purely random pairing.

Under these conditions, the Mac -Mahon- method offers the advantage that it avoids encounters whose outcome as good as it is clear from the outset. To this end, there are at Go even the opportunity to play with setting stones. However, this change the strategic character of the game. By Mac Mahon tournaments are for good opportunity to compete in balanced games with equal opponents.

The success of such a Goturnier is measured for most players after the share won games. This can be compared with the expected value, after which wins and losses should hold the balance. Compared to purely random draw of opponents both the frustration of inexperienced players, barely being able to win a game, and the excessive influence of Losglücks to win the tournament omitted.

For Mac -Mahon- Goturnieren the start point numbers are usually assigned so that a difference between adjacent Kyu or Dan - degrees corresponds to a difference of one point. Here, in the direction of the stronger player more points are awarded.

Therefore, it is difficult to win in all or even nearly all rounds, as it is drawn against opponents often after initial victories that one - are clearly superior - at least on paper. Such success can be seen as a sign that the strength of a player has reached a higher level than the one with which he has registered for the tournament. The same applies to defeats. With this success, the feedback MacMahon system supports the practice of self-assessment in Go, as is customary in Germany.

Criticism

The combination of self-assessment and MacMahon system but is regarded by critics as problematic. The classification could about from -assertion better than the objective skill level are elected, or worse, in order to win against weaker opponents more wins. In both cases, the meaning of MacMahon mode would be undermined. Therefore, the initial classification is occasionally for Mac -Mahon Tournaments propagated according to the rank list as described for the Elo rating.

Also, a certain complexity is criticized, which could manifest itself in a lack of transparency and in additional expense for the organizers. The results of a round must generally be fully determined before the next round can be drawn, which makes the scheduling susceptible to interference.

History

The system is named after the computer scientist Lee E. McMahon and goes back to an internal rating system in the New York Go Club. In competitions it has been used since 1971 in London. (Source: Sensei 's Library, see Related links )

Since then it has become widespread and pushed back another tournament forms such as group tournaments and the pure Swiss system. In Germany, the typical open weekend tournaments are now (mostly with five rounds) held predominantly by MacMahon system. After the German Federal Go- Cup order, it is a prerequisite for the inclusion of a tournament in Germany Cup competition.