From: jmh@athena.mit.edu (J Michael Hammond)
Newsgroups: rec.games.chess
Subject: Re: Tournament design
Date: 19 Aug 92 12:07:25 GMT
Article-I.D.: athena.1992Aug19.120725.17952
Distribution: na
Organization: Massachusetts Institute of Technology

In article <1992Aug19.051411.22593@pasteur.Berkeley.EDU> stevena@cory.Berkeley.EDU (Steven Alexander) writes:
>I am interested in any scholarly, including empirical, articles on
>the design of fair tournaments.  (Standard methods of searching
>through mathematical and computer science journals came up with
>nothing.  Perhaps chess periodicals have something?)  Has any work
>been done on which of the common methods of pairing people in
>tournaments give the 'best' results, by some measurement?

I don't know of any literature, but can briefly explain an alternative
pairing system, designed by Bruce Diesen, that was used in 1983 at the
Aquatennial Open in Minnesota.  (Bert Wilson:  I think you played in
that tournament too, and can probably corroborate my story here if you
still have your really really old MCJs in a drawer somewhere.)

Diesen designed this pairing system for the "standard American weekend
Swiss tournament", meaning

(1) A wide range of playing strengths
(2) A large number of players relative to the time available; e.g. at
the 1983 Aqua there were on the *rough* order of 80-90 players for 4
rounds)
(3) The tournament organizers would like to produce a clear winner, or
failing that, a very small number of ties for top places
(4) The organizers want to have one section to give some of the weaker
players a shot at the local masters

So here's the way the pairing system works.  For the first round,
pair the strongest player against the second-strongest, the
third-strongest against the fourth-strongest, etc etc.  (I forget whom
the bye is given to if there are an odd number of players; it's either
the middle player or the lowest player.) 

After round 1, the description gets a little tough: You break the
players up into groups based on their score so far in the tournament.
As much as possible, you pair players in one score group to those who
have scored either half a point or a full point less, but whose
ratings are at least N points higher.  (The 1983 Aqua nominally used a
200-point factor but as I'll show you that factor gets a little weird
in early rounds.)  You sort of figure out the actual rating
differential by the seat of your pants.  OK, so after pairing as many
people by this method, you'll have some people who have won all their
games and are rated too high to pair down; pair them in the 1-vs-2,
3-vs-4 style.  Same goes for those remainders who have lost all their
games and are rated too low to pair up.

It's surprising how quickly the majority of the players get even or
near-even scores with this pairing system.  The 1983 Aqua Open was,
like I said above, about 80-90 players for four rounds.  I was rated
1473.  In the first round was White and beat my 1474-rated neighbor.
I was rewarded for that victory by being given Black against an
annoyed 1900-rated first round loser.  (He CRUSHED me.)  That left me
in the lower-rated half of the pool sitting at 1-1, so it ended up
that I was given White against a 1670-rated player who only had half a
point so far.  I beat him, and had Black against an 1800-or-so rated
player in the last round and went down fighting; ending the tournament
tied for dead middle with a *bunch* of other people at 2-2.

Here's the weird thing: 80-90 people, four rounds, and *nobody* ended
with a 4-0 score.  There were four guys tied at 3.5.  Whoops.  Just
guessing a little about the number of draws to expect, I'd say that
you could expect to get two or three 4-0 scores in a standard
Harkness-paired 80-player Swiss System section and one (or no!)
perfect score in a Diesen-paired section.

-----

Diesen was there at the beginning of the tournament (although he
didn't play) to explain the system a little.  He claimed that the
"Swiss Gambit" (playing safely for a draw in the first round if you
had Black) seemed to be more effective if you were trying to maximize
your score and didn't care about losing a shot at first overall.
(e.g. if you were going for a class prize.)  I also note that there
were four masters at the tournament, and the two who lost their
first-round game both dropped out.  I *think* that the Minnesota State
Chess Association tried to get around that problem by offering an
entry fee refund to masters -- provided they played all their games.
Dunno whether it worked, or whether they're still using Diesen
pairings there.  (Bert?)

-------------------------------------------------------------------------
--J. Michael Hammond                                   0 o
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  The MathWorks, Inc.                                   U  
  jmike@mathworks.com -or- jmh@athena.mit.edu        Ackpth!