tournament-pairings

Node.js package containing functions to generate tournament pairings.

If you want a full-fledged package for organizing tournaments, consider tournament-organizer.

Algorithms

Double elimination: avoids rematches in the loser's bracket by alternating how matches are routed.

Round-robin: players are paired via Berger tables.

Swiss: generated using a weighted blossom algorithm with maximum cardinality.

Swiss Pairings

Players are preferred to play against other players with equal point totals
If there are an odd number of players, players with the lowest point total who have not previously received a bye are preferred to receive the bye
If the tournament is rated, players are preferred to play other players with similar ratings
If the seating in a tournament is relevant, such as white and black in chess, players are preferred to play the opposite seat than last played and strongly preferred to not play the same seat more than two times consecutively

Requirements

This is an ESM module. You will need to use import instead of require and add type: "module" to your package.json. See this for more information.

Installation

npm i tournament-pairings

Documentation

Imports

There are 5 named exports you can import into your project.

import {
    SingleElimination,
    DoubleElimination,
    RoundRobin,
    Stepladder,
    Swiss
} from 'tournament-pairings';

You can also import them all.

import * as Pairings from 'tournament-pairings';

Additionally, a couple interfaces are available for TypeScript users.

import {
    Match,
    Player
} from 'tournament-pairings/interfaces';

Parameters

SingleElimination() has four parameters:

players: either a number of players or an array of unique strings or numbers representing players
startingRound (optional): an integer indicating the starting round (default: 1)
consolation (optional): a boolean to determine if a third place match should be created (default: false)
ordered (optional): a boolean to indicate if the array provided for players is ordered (default: false)

DoubleElimination() and RoundRobin() have three parameters:

players: either a number of players or an array of unique strings or numbers representing players
startingRound (optional): an integer indicating the starting round (default: 1)
ordered (optional): a boolean to indicate if the array provided for players is ordered (default: false)

Stepladder() has three parameters:

players: either a number of players or an array of unique strings or numbers representing players
startingRound (optional): an integer indicating the starting round (default: 1)
ordered (optional): a boolean to indicate if the array provided for players is ordered (default: true)

Swiss() has four parameters:

players: an array of objects with the following structure

{
  id: String | Number, // unique identifier
  score: Number, // current score
  pairedUpDown?: Boolean, // if the player has been paired up/down prior (optional)
  receivedBye? : Boolean, // if the player has received a bye prior (optional)
  avoid?: Array<String | Number>, // array of IDs the player can not be paired with (optional)
  seating?: Array<1 | -1>, // array of seats player has been assigned (often used for chess) (optional)
  rating?: Number | null // rating of the player (optional)
}

round: the round number
rated (optional): a boolean to indicate if the players have a rating that should be considered when pairing (default: false)
seating (optional): a boolean to indicate if the seating of the players needs to be considered (default: false)

Returns

Each function returns an array of matches. Matches are objects with the following structure:

{
    round: Number,
    match: Number,
    player1: String | Number | null,
    player2: String | Number | null,
    // the following objects are only present in elimination pairings
    win?: {
        round: Number,
        match: Number
    },
    loss?: {
        round: Number,
        match: Number
    }
}

For Swiss pairings, if seating = true, then player1 would be seat 1 and player2 would be seat 2.

The Swiss function returns matches for one round, while single/double elimination and round-robin functions return all matches for the tournament.

Examples

Creating a generic single elimination bracket for 8 players with a third place match:

import { SingleElimination } from 'tournament-pairings';

const elimBracket = SingleElimination(8, 1, true);

console.log(elimBracket);
/*
Expected output:
[
  {
    round: 1,
    match: 1,
    player1: 1,
    player2: 8,
    win: { round: 2, match: 1 }
  },
  {
    round: 1,
    match: 2,
    player1: 4,
    player2: 5,
    win: { round: 2, match: 1 }
  },
  {
    round: 1,
    match: 3,
    player1: 2,
    player2: 7,
    win: { round: 2, match: 2 }
  },
  {
    round: 1,
    match: 4,
    player1: 3,
    player2: 6,
    win: { round: 2, match: 2 }
  },
  {
    round: 2,
    match: 1,
    player1: null,
    player2: null,
    win: { round: 3, match: 1 },
    loss: { round: 3, match: 2 }
  },
  {
    round: 2,
    match: 2,
    player1: null,
    player2: null,
    win: { round: 3, match: 1 },
    loss: { round: 3, match: 2 }
  },
  { round: 3, match: 1, player1: null, player2: null },
  { round: 3, match: 2, player1: null, player2: null }
]
*/

Creating round-robin pairings for the Teenage Mutant Ninja Turtles:

import { RoundRobin } from 'tournament-pairings';

const pairings = RoundRobin([
    'Leonardo',
    'Raphael',
    'Donatello',
    'Michelangelo'
]);
console.log(pairings);
/*
Expected output:
[
  { round: 1, match: 1, player1: 'Donatello', player2: 'Michelangelo' },
  { round: 1, match: 2, player1: 'Leonardo', player2: 'Raphael' },
  { round: 2, match: 1, player1: 'Michelangelo', player2: 'Raphael' },
  { round: 2, match: 2, player1: 'Donatello', player2: 'Leonardo' },
  { round: 3, match: 1, player1: 'Leonardo', player2: 'Michelangelo' },
  { round: 3, match: 2, player1: 'Raphael', player2: 'Donatello' }
]
*/

Discussion

You can discuss this repository more in my Discord.

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