How do Tournaments Work?

I’ve never participated in a tournament on this site before, so I’m not familiar with how these work. I was looking at the tournament info page, but some things left me confused.

Can someone help explain how the various tournament structures work?

Are there also non-simultaneous round robin tournaments that just last P-1 rounds (where P is the number of players)?
What does “qualified places” for Swiss tournaments mean?
What are the player “pairing methods” (the link on page seems to be broken)?
Why are “upper and lower bars” used in McMahon tournaments to seemingly put lower ranked players at a disadvantage?

1 Like

Both Swiss and McMahon are pairing systems; they’re used to decide who plays against whom. Basically, players who are close in points are matched up against each other.

In Swiss pairing, it’s possible for the strongest players to beat on the weakest players resulting in multiple people getting perfect records, resulting in tie breaks determining who wins. McMahon was designed to avoid that situation.

The idea with McMahon is to help expedite the process of actually finding a winner. Basically, the higher ranked players are expected to win, so they’re given extra points and start off playing against each other earlier on in the tournament (because players who are close in points are paired with each other).

I don’t think non-simultaneous round robin tournaments are possible on OGS.

1 Like

Swiss and McMahon are not strictly pairing systems they both have pairing components but that’s only a part of it.

Our basic Swiss and McMahon tournaments all pair the same way which utilizes the McMahon strength and points based pairing with some other logic (preventing the same players from being paired in further rounds… favoring alternating black and white if possible… etc). We have more pairing options coming in the near future.

For tournament structure:

  • In our Swiss tournaments all players start with the same number of points: 0
  • In McMahon tournaments we allow the touranment director to set upper and lower bars that determine the number of initial points that are assigned to players at the beginning of the tournament.

With McMahon tournaments we allow the TD to set the number of rounds but for swiss tournaments we compute the number of rounds for a certain number of qualified places. Right now the number of qualified places is fixed at one (determining the overall winner) but we’ll be increasing that and/or making it tunable in the future. This is the algorithm:

R = (P + 7 x Q) /5

Where P is the number of players and Q is the number of qualified places.

As @Jamada said… McMahon tournaments are designed to make sure that players are matched and group based on their skill to eliminate or reduce really lop sided games.


What is the “number of qualified places” ? I want to calculate the number of rounds in our tournament ( At present we have 19 participants. Hoy many rounds do we have to play?
Thanks in advance.

Did you read the previous post?

Yes, but I didn’t understand how to get the “number of qualified places”.

Ah OK :slight_smile:

Apologies, if I seemed dismissive.

The post is quite old but according to what it says with one qualified place you get 5 rounds, with two qualified places you would get 6 and with 3 you would have 8. That is with 19 players.

I have no idea if that’s how it actually works now, hopefully someone else can answer your question too.

Yes, Q=1 in sep 2014, maybe it has changed. Also I think they round it to the “ceiling”, i.e. (19 + 7 x 1) / 5 = 5.2 means 6 rounds. Let’s see if one OGS developer clarifies it.

Oh yes, I wasn’t sure how the rounding would work, perhaps rounding to the ceiling makes more sense actually, seeing as the purpose seems to be to find a unique first place (of course that’s never guaranteed anyway).

Hopefully a dev will chime in :slight_smile: