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To: britdisc@csv.warwick.ac.uk
Subject: how to seed tournaments
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From: "David J.C. MacKay" <mackay@mrao.cam.ac.uk>
Date: Mon, 19 Jun 2000 07:46:59 +0100
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Dear Britdisc,
a note for anyone planning to hold a tournament. (I put
these notes on the web in 1995, and it still seems relevant...)
Planning a tournament schedule
"We'll see you in the final!" you say to your opponents after a game
in the pool play of a tournament. But sometimes it turns out that you
meet them just a couple of games later during the knockout! This is
likely to happen if, after the pool play, the teams are numbered thus:
Pool A B C D
Rank in pool
1st 1 2 3 4
2nd 5 6 7 8
and then have a standard knockout (1v8, 2v7, 3v6, 4v5, etc.). If, for
example, 5 beats 4 and 1 beats 8 (not implausible), then the teams
that started out as 1 and 5 play each other in the second round of the
knockout -- and 1 and 5 already met in the pool play; and the same
goes for 4 and 8, who already met in pool D. This situation can arise
in the other pools too if 7 beats 2 or if 6 beats 3, so it must be
quite a common occurrence in tournaments that are scheduled in this
way. Similar problems can also arise after cross-over games too. For
example, at the 1995 Nationals, Strange Blue played in a pool with
PhatEds and then lost a crossover game with the Bears; our next game
was then with PhatEds. I think Bliss and Skunks had a similar
experience. Wouldn't it be preferable to have a tournament schedule
in which this couldn't happen - so that each team meets as many other
teams as possible? (Not that we didn't have fun playing PhatEds
twice!)
As the Druids have demonstrated for years at their fine tournaments,
it is actually quite easy to set up a schedule such that teams who've
played each other in a pool are guaranteed not to meet in the first
two rounds of an eight-team knockout. All that is required is to
number the teams in the four pools thus:
1 2 3 4
7 8 5 6
and proceed with a normal knockout.
I hope that this note may help tournie organisers plan even better
tournaments.
David MacKay, Strange Blue
mackay@mrao.cam.ac.uk
------------
More ideas for sixteen-team tournaments, added June 2000:
If the conventional format "pools of 4 then 1-8 knockout and 9-16 knockout"
is used, then the following seedings seem good:
1 2 3 4
7 8 5 6
10 9 12 11
16 15 14 13
--------------
It is also possible to add the following "peer games" after the pool games
in the above format:
1v3, 2v4, 5v7, 6v8, 9v11, 10v12, 13v15, 14v16
--------------
If an extra crossover game between 5-8 and 9-12 is to be included to allow
3rd rank teams a chance to get into the top 8, then the following seeding
is good:
1 2 3 4
7 8 5 6
12 11 10 9
14 13 16 15
The top 4 and bottom 4 could play peer games (1v3, 2v4, 13v15, 14v16) while the
crossover games (5v12, 6v11, 7v10, 8v9) are happening.
---------------
Finally, here is a seeding for a tournament with pool games followed
by peer games at all levels, then a 5-12 crossover, then 1-8 and 9-16
playoffs.
1 2 3 4
7 8 5 6
11 12 9 10
13 14 15 16