From: jmh@athena.mit.edu (J Michael Hammond)
Newsgroups: rec.games.chess
Subject: Re: Tournament design
Date: 20 Aug 92 12:16:47 GMT
Distribution: na
Organization: Massachusetts Institute of Technology

In article <1992Aug19.160021.13744@cco.caltech.edu> direwolf@seismo.gps.caltech.edu (Kathy Watts) writes:
>I read with great interest the old article in the Minnesota Chess Journal (or
>whatever it was called) about Diesen's pairing system, and was quite impressed.
>
>But the previous post only described one of its two intended functions, which
>was reducing the chance of multiple perfect scores in a large field with very
>few rounds (the report I saw was on a 100-player 4-round event, and there were
>0 or 1 perfect scores!).
>
>Most interesting to me was the idea that players with middling scores would be
>paired against players with similar ratings (within 100 or 200 points, and this
>WAS numerically defined - no seat-of-the-pants guesswork needed by the TD - in
>the article).  Players who were performing above expectation (low-rated players
>with high scores) would be paired with high-rated players who were performing
>below expectation (i.e., had lower scores).
>
>The most interesting thing to me was the level of satisfaction of the
>participants, as measured in a survey accompanying the report.  Despite the
>event being a held in a single section, an incredibly high percentage of the
>games were played between players rated near each other, thus giving both
>players a chance to win, and to improve their ratings.
>
>The report was reprinted in the BINFOs circulated to the USCF policy board at
>that time.  Maybe someone can find it?
>
>-Hal Bogner
> International Arbiter
>

Last night I dug up the original source (see below).

Here are the actual statistics of the tournament.   87 people
participated; nine of whom withdrew and one who was dragged off the
street to play in the last round.  There were actually seven masters
present, two of whom withdrew after losing their first round game.
There were four players tied for first with 3.5-0.5 and only eight
people at 3-1!  (on the other end, there was only one player who
played all four rounds to score 0-4, four with 0.5 including the one
off the street, and seven players who played all four rounds scoring
1-3.)

I missed the boat a little bit in the original description of the
pairing system.  It isn't just the top and bottom score groups that
will have a number of players playing 1 vs. 2, 3 vs 4, etc -- rather,
there will usually be *some* people doing this in each score group in
each round.

The actual pairing system description might take two or three
screensful but I'm typing it in here now given that there's at least
one International Arbiter who's interested in it!  ;-)

The article below hints at the main difficulty in actually carrying
out these pairings -- determining the number of people that you're
supposed to "feed to the sharks" in the lower score group.  If you are
paying attention to everyone's complete rating, you have to look at
*every* player in the score group, determine how many players are 200+
points above him, take the maximum of these differences, and that's
the number of people to pair 1-2 3-4 etc. in the score group.  If I
remember correctly the rounds in the 1983 Aqua were generally a little
late (for many reasons not just pairings.)  On the other hand,
ignoring 100-pt categories might be a little much.  I suggest the
compromise of breaking the players up into 50-pt categories instead.
(You could mark the cards 18-, 18+, 19-, etc.)

Anyway, here's the article, verbatim (with the exception of my
{}-delimited comments.)

--JMike


-------------------
{originally published in the Minnesota Chess Journal, Vol. 20 No. 1 &
2, Jan. - Oct. 1983, pp 1268-1269.}

Proposal for a new pairings system  by  Bruce Diesen    July 8, 1983

Purpose: This system should eliminate the possibility of two or more
perfect scores, even for a tournament with 200 players and only four
rounds.  It gives high rated players and players who do well tougher
poponents than in a Swiss tournament.  Likewise, the bottom half of a
tournament will face easier competition than with Swiss pairings.

Use: This system should work well in all tournaments with a wide
disparity in playing strength where at least two-thirds of the players
have reliable ratings.  The tournament should have at least four
rounds.

Pairing numbers
Use pairing cards and arrange the players by rating, starting with the
highest-rated player at the top.  Space the unrated players at even
intervals throughout the bottom half, e.g. if there are 60 players,
including 6 unrateds, have the unrateds be numbers 35, 40, 45, 50, 55
and 60.

Basic rules

1) No two players may play twice.
2) Each player should play the person closest to him/her on the
pairing cards (and the wallchart) who has the same score, with the
exception of rule 3.
3) As many players as possible should be given opponents with a half
or one point less in score, but who are rated at least 200 points
higher.
4) Colors are generally assigned as in Swiss pairings.

Round one

Player no. 1 plays player no. 2, no. 3 plays no. 4, etc., all the way
down.  Alternate colors between the odd- and even-numbered players.

Round two

As many players in the 1-0 score group as possible play players who
have 1/2 or 0 points, but who are 200 or more rating points higher. 
Unrated players use the average of the rating of the player
immediately above and below them in start number for their ratings
throughout the tournament - unless, of course, a tmt. director wants
to calculate performance ratings after each round.  Unrated players
may never face an opponent with a higher score!
Those players who aren't paired down against opponents with lower
scores play among themselves in consecutive order, e.g. no. 1 plays
no. 2, no. 3 plays no. 4, etc.
Important - all players with the same score who play among themselves
should be higher rated than those who are paired down.
Pairings are made in the same way for the 1/2-point group, and then
the remaining 0 point players play among themselves in consecutive
order.

Round three and subsequent rounds

Pair as in round two, starting with the top point group, and working
downward.  You will probably find that as many as 1/2 the games will
be between players with unequal scores.  Since in all these games, the
players with the lower scores are 200 or more points higher rated,
they will tend to score 75-80% or more, and the result will be
significantly less high and low scores than in Swiss {I think he
means "Harkness"} pairings.

Variations

The rating difference of 200 is merely my suggestion. If a lower
difference is used, say 100 pts., there will be more games between
players with unequal scores (but those games will be more even); using
a higher difference, say 250 pts., will increase the number of games
between players who have the same score.

If large cash prizes are at stake, last round pairings may be modified
to allow as many players as possible who are vying for class or top
prizes to play opponents vying for the same prizes.

In Swiss tmts., you seldom play someone with the same rating as
yourself.  With this system, you will generally not meet players rated
from 100-199 pts. above or below you.  A variation is to ignore the
last two digits of all ratings, e.g. all ratings from 1900-1999 become
'19', 1800-1899 become '18', etc.  This can be done in arranging the
pairing cards, e.g. all 19s are arranged by lot; in making pairings,
e.g. 1801 playing 1699 or 1899 playing 1601 are considered 200-pt
differences; or it can be done in both.  In tournaments with more than
150-200 players, this will allow the TD to determine how many players
in each score group play among themselves (the remainder are paired
down by Rule 3) much more quickly.  For example, the TD need only
compare the number of 1-0 players over 2000, over 1900, over 1800,
etc., with the no. of 1/2-1/2 and 0-1 players over 2200, 2100, 2000,
etc., the largest difference found is the number of 1-0 players who
play among themselves, the remainder are paired down.  If the largest
difference found was 11, between 49 1-0 players rated 1900+ and 38
1/2-1/2 and 0-1 players rated 2100+, then the 12 highest-rated 1-0
players play among themselves in consecutive order, the remaining 1-0
players are paired down.

Some final notes

Since players who do well face tougher opponents than in Swiss
tournaments, and since lower scores will suffice for a high finish,
the Swiss Gambit (losing or drawing in Rd. 1) will work better under
this system.  Players should probably be told this - contenders
playing black in Rd. 1 might want to play for draws.

Allowing players to choose a 1/2-point bye in, say, rounds 1 or 2,
will pose no problems in this system.

If a player a 1/2-point behind and a player a full point behind could
equally well be paired up against the same opponent, the player who is
a 1/2-point behind is given priority.

Comments appreciated, write B. Diesen, Blindernv. 58-A, Oslo 3,
NORWAY  {note that this address is 9 years old now but what the heck
there it is anyway}

-----------------
{this table is from the same issue}

There was a post-tournament survey asking many question ("How did you
like the tournament hall", etc.)  Seventy players returned the survey.

                                   Exp+  A  B  C  D/E  Overall
                                   ---- -- -- --  ---  -------
Better than Harkness pairings       21% 36 45 14   19     28%
As good as Harkness pairings        18  18 27 25   13     20
worse than Harkness pairings         7  14  0 39   13     15
no opinion                           0   5 18 14   25      9
It's too early to tell...           54  23  9  7   32     27
(this question left blank)           0   5  0  0    0      1
----------------------------------------------------------------
Number of players in each group     14  22 11 14    8     70


{paraphrasing Diesen's analysis:}

Note particularly that the experts and masters seemed to like the
system, whereas the C players didn't (!).  Note also the increased
willingness of the lower-rated players to express an opinion ;-)
Newsgroups: rec.games.chess