Progressive

Progressive is a TypeScript library implementing the Progressive Score tiebreak for chess tournaments, following the FIDE Tiebreak Regulations (section 7.5). Zero runtime dependencies.

Installation

npm install @echecs/progressive

Quick Start

import { progressive } from '@echecs/progressive';
import type { Game, GameKind } from '@echecs/progressive';

// games[n] = round n+1; Game has no `round` field
const games: Game[][] = [
  [{ black: 'B', result: 1, white: 'A' }], // round 1 → running: 1
  [{ black: 'C', result: 0.5, white: 'A' }], // round 2 → running: 1.5
  [{ black: 'A', result: 0, white: 'D' }], // round 3 → running: 1.5
  // Unplayed rounds use kind to classify the bye type
  [{ black: '', kind: 'half-bye', result: 0.5, white: 'A' }], // round 4 → running: 2
];

const score = progressive('A', games);
// 1 + 1.5 + 1.5 + 2 = 6

API

All functions accept (player: string, games: Game[][]) and return number. Round is determined by array position: games[0] = round 1, games[1] = round 2, etc. The Game type has no round field. The optional kind?: GameKind field on Game identifies unplayed rounds (byes score their awarded points for the running total).

progressive(player, games)

FIDE section 7.5 — Progressive score. Accumulates the player's running score after each round, then sums all those running totals. Rounds are processed in array order (games[0] = round 1). A player who scores 1, 0.5, 1 across three rounds produces a progressive score of 1 + 1.5 + 2.5 = 5.

Also exported as tiebreak from @echecs/progressive.

progressiveCut1(player, games)

FIDE section 7.5 + modifier 14.1 Cut-1 (PS-C1) — Progressive score excluding the first round. Round 1 (games[0]) is dropped entirely: the running total resets to 0 at round 2 and accumulates from there. The cumulative totals from rounds 2, 3, … are then summed.

For example, a player who scores 1, 0.5, 1 across three rounds:

• progressive running totals: 1, 1.5, 2.5 → sum = 5
• progressiveCut1 running totals (round 1 dropped): 0.5, 1.5 → sum = 2

Returns 0 when fewer than two rounds have been played.

Import from the /cut1 subpath:

import { progressiveCut1, tiebreak } from '@echecs/progressive/cut1';

Also exported as tiebreak from @echecs/progressive/cut1.

Exports

@echecs/progressive

Export	Kind	Description
progressive	function	Progressive score (FIDE 7.5)
tiebreak	function	Alias for progressive
Game	type	A single chess game with result and players
GameKind	type	Unplayed-round classifier ('half-bye', etc.)
Player	type	Player shape ({ id: string })
Result	type	Score value (0 | 0.5 | 1)

@echecs/progressive/cut1

Export	Kind	Description
progressiveCut1	function	Progressive score excluding round 1 (PS-C1)
tiebreak	function	Alias for progressiveCut1
Game	type	A single chess game with result and players
GameKind	type	Unplayed-round classifier ('half-bye', etc.)
Player	type	Player shape ({ id: string })
Result	type	Score value (0 | 0.5 | 1)

Contributing

Contributions are welcome. Please open an issue at github.com/echecsjs/progressive/issues.