Round Robin Tournament Scheduling

round robin for 12 people

denisegw · 5 · 8166

denisegw

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on: March 04, 2009, 09:13:23 AM
I want to run a round robin for 12 people where everybody has a different partner on every round and where they dont play each other twice.  If they occasionally have to have the same partner or play each other twice it can't be helped.  I spend hours at home writing out schedules and I always find that the same people have been playing with each other too many times.  They play 5 rounds.

I am also running another tournament for 40 people along the same lines in the summer and would appreciate your help.  They will play 5 rounds.


Ian Wakeling

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Reply #1 on: March 05, 2009, 05:12:52 AM
It is not clear to me what sport and format you are playing, my guess is that each round consists of 3 doubles matches, but would you please confirm this.

If I am right, then with 5 rounds of play and 12 players then there will be at least six pairs of players who never meet either as partners or as opponents.  In other words it's not possible with these constraints to have a full social mixing of the 12 players.

Ian.


denisegw

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Reply #2 on: March 05, 2009, 05:48:17 AM
Its a tennis doubles tournament.  I know the same people will be on the same court some of the time but every time I try and work something out I end up with the same people playing with each other a few times.

e.g.

1 & 2
v 3 & 4

5 & 6
v 7 & 8

9 & 10
v
11 & 12

1 & 3
v
7 & 12

4 & 6
v
8 & 10

2 & 7
v
11 & 5

and so on :

I can end up with 3 people being in the same four again.

With 5 rounds I would like to get as much of a mix as possible.


Ian Wakeling

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Reply #3 on: March 05, 2009, 08:03:31 AM
Thank you for sending the extra information.

I think the following is about the best you can do with 12 players:

   (4  9 v 12  2)  ( 8 10 v 1  5)  (3 11 v  7  6)
   (5 10 v 12  3)  ( 9  6 v 2  1)  (4 11 v  8  7)
   (1  6 v 12  4)  (10  7 v 3  2)  (5 11 v  9  8)
   (2  7 v 12  5)  ( 6  8 v 4  3)  (1 11 v 10  9)
   (3  8 v 12  1)  ( 7  9 v 5  4)  (2 11 v  6 10)


No player partners another player more than once.  No two players play on the same court together more than twice.  There are six pairs of player who never meet on the same court.  Players 11 & 12 are always on the same court, however you could randomise the assignment of matches to courts in each round to lessen this problem.

Although it might seem otherwise, the forty player problem is actually much easier to solve.  Just use any 5 rounds of this schedule.  No two players ever occur twice in the same foursome, so no matter how you divide a foursome into two sets of partners, you will always get a schedule where a player's 5 partners and 10 opponents are all distinct.


denisegw

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Reply #4 on: March 06, 2009, 09:58:19 AM
Thank  you very much for your help.

Denise