Round Robin Tournament Scheduling

Euchre / Bridge round-robin scorecard help?

AEuchreDude · 2 · 2819

AEuchreDude

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on: August 28, 2023, 02:00:26 PM
I want to create Euchre tournament charts where I have anywhere from 8-48 (or even higher) number of players. I want to setup at least 7 rounds of play, but could vary to be lower or higher. I want to set up the groupings so that no two players appear together at a table more than once, regardless of whether they are teammates or not. At a minimum, no two players should be partners more than once. In a given round, each player is one of a foursome at a table. If there are extras that don't fit at a table, these would be sitouts for that round, I would want no one to sitout more than once if possible.

Is there a reasonably simple search algorithm that will set up these rounds for me? I am not a mathematician but a programmer and would love an Excel VBScript algorithm or similar; charts? I already have an algorithm that generates unique pairs, is this a good start or not really for this solution?



Ian Wakeling

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Reply #1 on: August 30, 2023, 02:24:56 AM
It can be relatively simple if the final schedule has the "no pair at a table more than once" property that you discuss above.  Then you can 1st decide who has the bye in each round, next assign the remaining players randomly to each table, now consider an algorithm that swaps pairs of players between two tables in the same round that improves a criterion measuring how frequently all pairs of players occur together at a table (minimize the sum of squares of the symmetric pairwise frequency table). So for each iteration make a swap that gives the best reduction in the criterion.  When the frequency table contains entries that are all zero or one, then you have found an optimal schedule.

If there are n players, b of whom have a bye in each of r rounds. Then a necessary condition for the no pair more than once property to be met is:

3r <= n(n-1)/(n-b)

The closer the parameters n, b & r are to equality, the worse the algorithm above will perform and you would be well advised to have a library of schedules to cover these sorts of condions.  You should be able to find quite a few of these on this forum.

When you are the other side of the inequality, some pairs of players sit together at a table more than once, which complicates matters as the number of times pairs of players appear as partners and as opponents has to be considered.

Hope that helps.
« Last Edit: August 30, 2023, 02:31:31 AM by Ian Wakeling »