Double round robin with 9 teams at 3 sites each week

[dbronco23]

Trying to put together a schedule that would have 3 sets of 3 teams playing each other (3 games at each site) in which everyone plays each other twice over an 8-week period.  The problem I'm having is making sure that the team hosting the other two teams doesn't host the same team twice during the 8 weeks.  Each team would get to host either 2 (3 teams) or 3 (6 teams) times, but can't host a team more than once.  Also need to balance out the schedule so that there are 2-4 weeks between a team hosting its games.  Any suggestions?  Much appreciated.

[Ian Wakeling]

I think I can see a way to get most, or perhaps all of what you want.  If you made the following assignments of groups of 3 teams in the 1st 4 weeks:

(4 1 7)
(8 5 2)
(6 3 9)

(1 2 3)
(5 6 4)
(7 8 9)

(9 1 5)
(2 7 6)
(3 4 8)

(8 6 1)
(4 9 2)
(5 3 7)

with the requirement that the teams in the first column are the ones that host (so 4,8 & 6 host in week 1, and 1,5 & 7 host in week 2, etc.).  Now for weeks 5 to 8 use exactly the same groups of 3 teams, however the teams that host are the ones in column 3.  So for example consider team 7 who

host 8 & 9 in week 2
host 1 & 4 in week 5
host 3 & 5 in week 8

There should be a break of at least one week between two hosting occasions.  I don't think it is possible to have a schedule where the minimum break is two weeks (but that's just a gut feeling).

Hope that helps.

[Ian Wakeling]

Just noticed in the schedule above that team 9 hosts in both weeks 5 and 6, and I can't see a way to fix it.  Would you consider using it as it is?

[dbronco23]

This looks great!  If I just swap weeks 6 and 7, it takes care of the back-to-back hosts for team 9.  Thanks for your help!