The double round robin: playing everyone twice

Everything doubles. Which sounds obvious until you count the evenings it takes.

The formula is 2 × (N − 1) rounds and N × (N − 1) games. With an odd field it is 2N rounds, since somebody sits out in each cycle - the single round robin.

The practical ceiling for an amateur event is six players: ten rounds is two or three club evenings, which people will actually attend. Eight players at fourteen rounds is already a month of Tuesdays.

• Colours are exactly equal. The single round robin always leaves somebody with an extra White; the double one cannot. Nobody can attribute their result to the draw.
• One bad game matters less. Twice the games means twice the sample, and the final table reflects strength rather than a single evening's mood.
• Ties are rarer. More games spread the scores out, so the coefficients are called on less often.
• A rematch is interesting. Playing the same opponent again, having seen how they play, is a different exercise - and players notice.
• It is enough for a title norm. Six players double is ten games, above the nine-game minimum, which is exactly why closed norm events use this shape - norms and titles.

That last point explains most of the format's existence at professional level: it is the smallest field that produces a valid norm event.

The second cycle is the first one repeated with colours reversed. There is nothing to generate twice - the standard tables cover it.

• Cycle two mirrors cycle one. Round eight of a six-player event repeats round one with the colours swapped - the Berger tables.
• Do not shuffle the second cycle. Re-ordering the rounds to «freshen it up» breaks the colour sequence and produces three of one colour in a row.
• Watch the join between cycles. The last round of one cycle and the first of the next can hand a player the same colour twice; the standard tables shift the order to prevent it.
• Publish it all at once. The full schedule is known before the start - one of the format's genuine conveniences.

Spread over several weeks, the natural division is one cycle per block: a first half and a second half, with the standings published in between - schedule arithmetic.

Which is most of the time. The alternatives, in the order worth considering them:

The choice is really about field size: which system to use.

• Tie-break is Sonneborn-Berger, as in any round robin. Buchholz is meaningless here - everybody has the same opponents - how it is computed.
• Direct encounter is now two games. Which makes it a better tie-break than in a single cycle: the mini-match result is more meaningful than one game.
• Withdrawals are the real risk. Over two cycles somebody will disappear, and half a table of unplayed games distorts every coefficient. Decide the rule in advance and write it down - what to put in the regulations.
• Confirm availability before you start. A player who cannot make the second half should not be in the field at all.
• Publish the crosstable after every round. Over a month-long event, the table is what keeps people involved between sessions.

For a club with six to eight regulars and a free evening each week, the double round robin makes an excellent championship: everybody plays everybody twice, the standings stay live for weeks, and nobody can argue with the result - keeping people coming back.