Re: Essentials of Round Robins pt. 2

Case 3 differs considerably from cases 1 and 2.
It remains the same that each team plays n-1 games.
Each team furthermore cannot play on its own packet,
as in 
case 1. However, in addition to the above
constraints, there is a 3rd: one team cannot play on its own
packet, and teams must play matches in pairs; therefore,
in 
most rounds there will be two bye teams.
Because each team receives one bye on its own packet and
another bye not on its own packet, it is clear that in
the round 
robin each team will receive two byes.
Because each team must play n-1 games and receive two bye
rounds, in a submission tournament where n is even, a

round robin requires n+1 rounds. Because only n rounds
will be submitted, the n+1st round needs to be
obtained by the hosting organization and be blind to all

teams. However, only on this round will all teams play
at once, and therefore only on this round will n/2
rooms be in operation. At all other points during the
round 
robin, only (n/2)-1 rooms are
required.

Case 4 varies the most greatly from those outlined
above. Every team still plays n-1 games. However, teams
are blind to all packets, and with an even number of

teams, all teams can play in pairs. Therefore, in a
blind tournament where n is even, a round robin
requires n-1 rounds.

Assumptions and
requirements

For a fair round robin, certain requirements must be
met. The first, as discussed above, is that all teams
must be blind to every round on which they
play.

An assumption of the round robin is that the results
of each test be comparable to the results of each
other test, i.e. that each match be comparable to each
other 
match. At the outset of the round robin,
furthermore, each match (all else being equal) is of equal
importance. This implies that two conditions should be
met:

1. All rounds should be of equal distribution and
difficulty. Although in a submission tournament some
variation is inevitable, the editors of a tournament should
do 
their best to make sure that the rounds are
of nearly equal difficulty and distribution
throughout. In central-source tournaments, this is somewhat
easier.

2. All teams approach each game under essentially
equal conditions. This condition is impossible to
thoroughly ensure; as the round robin progresses, individual

matches will take on unpredictably variable importance.
However, another factor in teams preparedness for games
is fatigue. This factor can be contained by

keeping the time spent playing the round robin below a
certain figure, generally taken to be eight hours of
play. In the event that a tournaments overall field is
large, 
multiple divisions or, in exceptionally large
cases, Swiss pairs or other formats may be considered in
favor of round robins.
--
That's the end of the
first half. Feel free to send comments along to
ers_at_...

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