Starting numbers: how they are assigned and what they decide

It does three jobs.

• It sets the first-round pairings. In a Swiss the list is halved: number one plays the first player of the second half, number two the second, and so on.
• It resolves ties inside the pairing. Where several pairings are equally valid under the rules, the numbers decide.
• It decides who gets the bye and the colour. All else being equal, the lower number takes precedence.

Hence the rule: the number is issued before round one and does not change. Even if a player turns out to be far stronger than expected, you do not renumber a tournament in progress.

The standard order is by descending rating: number one is the strongest. Equal ratings are separated alphabetically.

The point is to make round one pair the strong against the weak: by round two players are already in groups matching their level and the field separates faster. Hand the numbers out at random and round one can pair two leaders, knocking one of them out of the running immediately.

Where there are no ratings at all - the norm at amateur events - people use:

• Self-assessment at entry. «Beginner, casual, club player» - crude, but better than randomness.
• Any national category some of the field may hold.
• Past results. A club or app internal rating.
• Alphabetical order. Transparent and raises no questions.
• A draw. Fair, but it turns round one into a lottery.

Whichever you choose, say so out loud. «Why am I number twenty» always gets asked, and «alphabetically» closes it instantly.

With 16 players the list splits into two halves, 1 to 8 and 9 to 16. Round one looks like this:

Colours in round one are handed out so that the top half gets an even split: odd numbers take White and even ones Black, or the reverse - decided by a draw before the event.

From round two the numbers recede: pairings follow the scores. But where everything else is equal the algorithm still falls back on the number - how the engine handles it.

In other systems the number works differently, but matters no less.

• A round robin. The number sets the entire schedule: the Berger tables state who plays whom, and with which colour, in every round. Which is why the numbers are drawn by lot - the only fair method - the round-robin system.
• A knockout. The number is the seeding: first plays last, second plays second-last, so the favourites do not meet in round one - knockout events.
• A team event. The number within a team is the board: number one plays board one and cannot be moved mid-event - team scoring.

• Arrives before round one is paired. Added to the list and numbered under the usual rules - the list is recalculated.
• Arrives after round one. Takes the next free number at the end of the list. The missed round scores zero or half a point, as announced - late arrivals.
• Withdraws mid-event. The number stays with them, but they are excluded from subsequent pairings - withdrawals.
• A wrong rating. If it turns out a rating was entered incorrectly, the number still does not change: the event has started.

In the app the numbers are assigned automatically when the tournament starts, from the players actually present - there is nothing to arrange by hand.