McMahon for Dummies?

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

I’ve read and am none-the-wiser.



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I don’t know but maybe matburt does:

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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:


Does this help, perhaps?

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 :wink:

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

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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?

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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.


Looking at this:

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

Literally: Who knows? because I would like to.


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

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

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

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