From: Ben Nagy <ben@...>
Date: 2006-08-31T15:02:52+09:00
Subject: Re: Pairs tournament algorithm

> -----Original Message-----
> From: list-bounce@example.com 
> [mailto:list-bounce@example.com] On Behalf Of Christer Nilsson
> Sent: Wednesday, August 30, 2006 11:19 PM
> To: ruby-talk ML
> Subject: Re: Pairs tournament algorithm
> 
> This is a system, mainly used by chess players, called Monrad.
> 
> Example: 100 players, 10 rounds.
> 
> The players are sorted according to their score, after every round.
> Players are paired from the top.
> Two players can only meet once.

They use this kind of this in Bridge tournaments as well, but call it a
"Swiss". Swiss systems work well for a very rough sort, but there are two
main issues. 

1. If there are too many rounds, the movement will 'over swiss' since most
people are already in more or less the correct order, so the rounds would
need to be carefully balanced. Over swissing means that weaker players get
"sucked up" into the top of the draw, since the top players have already
played each other - at that point it shifts to a game of which top players
are best at beating up weaker teams / players.

2. The other issue is that Swiss tournaments are pretty bad at picking the
exact best player / team because some good teams might play a harder set of
players during the rounds etc.

Most of the time in Bridge the tournaments are run through a Swiss with a
knockout series following for the top (eg) 8 or 16 teams / players, and
using longer / more matches. Swiss works well when the field is too large
for a round robin, but it works best if you can seed the top 10% or so of
players and match them against non-seeds for the first round - but it should
only be considered as a compromise.

Single or double round robin is the best if you can afford n(n-1) rounds,
another option is pure knockout (Wimbledon), or knockout with a repecharge
(also used a lot in sports).

Ruby content of this mail: 0

Cheers,

ben