From: David J Bush CSTONE NET>
Date: 14 may 2003
Subject: Re: MacMahon & SOS [was: Shogi Tournament in Pullach  Munich]
 >  <....
 > 
 >  This is not enirely correct:
 >  With 6 players,
 >  In McMahon, you get N vs N+1, N+2 vs N+3 and N+4 vs N+5
 >  In Swiss you get N vs N+3, N+1 vs N+4, N+2 vs N+5
 >
 > Are you referring to the pairing of opponents for the first round?
 > In a Swiss system, the players are initially ordered from highest rating
 > to lowest followed by unrated players, and then for the first round
 > player 1 plays player (N/2)+1 (halfway down the list), player 2 plays
 > (N/2)+2, ... , player N/2 plays player N.
Of course, N is assumed to be even here.

 I thought, that the way of doing the pairing inside of a group with the
 same number of points is not a defining feature of the system  that how
 to do that is just a matter of what you (or the writer of your pairing
 program) thinks to be best.
In later rounds there are other considerations which may have higher
priority, such as trying to give each player the black pieces as often as
the white pieces (a greater concern for chess than shogi), but within each
point group, the initial "base" pairing pits the top half against the
bottom half, or so I have been taught. This is especially important in the
first round. You don't want the top players to play each other right away.
For example, suppose the top rated player played the 3rd rated player in
round 1, on board 1. Meanwhile, on the bottom board, the lowest rated player
played the 3rd lowest rated player. Whoever wins on board 1 arguably had to
work a lot harder than whoever wins on the bottom board, but from the
standpoint of a Swiss system, these two winners both have the same score so
far, one point. It's better for the top half to play the bottom half; that
way there is greater correlation between the expected tournament result for
any given player and the actual result. The top players should tend to have
the best score in the final rounds, and will usually play each other then.
David