McMahon for Dummies?

[Eugene]

Could someone explain how McMahon tournaments work, particularly at OGS.

I’ve read http://senseis.xmp.net/?McMahon and am none-the-wiser.

Thanks!

GaJ

[Kosh]

I don’t know but maybe matburt does:

How do Tournaments Work?

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 p…

[smurph]

Sorry, not for dummies… also more useful for German speakers (because the thesis is available for download) but here’s a pairing program and a summary: http://www.cgerlach.de/go/macmahon.html

[trohde]

Does this help, perhaps?

McMahon system tournament

It’s a lot shorter than the SL page though, but maybe that’s good in this case? I for one have read neither of them

[trohde]

@Jamada’s comment right before @matburt’s also seems informative:

How do Tournaments Work?

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,…

[Eugene]

Thanks - the wikipedia one in particular gives me the basic idea.

One thing missing: in OGS, how many games do you get simultaneously in this system?

[Kosh]

Depends on the Minimum Group Size. If the minimum group size is ‘m’ then:

• The minimum number of games you will get in one round will be m-1.
• The maximum number of games you will get in one round will be 2(m-1).

For example: If the minimum group size is 5 then you have to get at least 4 games in each round by definition. However if there are 9 entrants then you would end up with 8 games/round as the group would be too small to split.

[Kosh]

Looking at this: https://online-go.com/tournament/31532

It seems I was wrong about the maximum number of games which makes your question even better. Now I’m just guessing that the maximum is 2m-1 but who knows.

Literally: Who knows? because I would like to.

[trohde]

I know NOTHING of these things (and I’m slightly dyscalculic also, so that’s my excuse ), but maybe @anoek and/or @matburt can/will explain a bit more.

[Eugene]

Well, that didn’t work out as I might have hoped and expected…

For Lovers of Fast Correspondence

m=3. GaJ in a group of 9 players, well at the bottom!

… and all other DDKs in the other, smaller group!