doubleswiss

Documentation

Overview

Package doubleswiss implements the FIDE Double-Swiss pairing system (C.04.5).

The Double-Swiss system (approved Oct 2025, effective Feb 2026) treats each round as a 2-game match. Scores are cumulative game points (win=2, draw=1, loss=0 per match). The system uses lexicographic bracket pairing (Art. 3.6) from the shared pairing/lexswiss package.

Key characteristics:

• Each round is a 2-game match (colours alternate within the match)
• PAB awards 1.5 points (Art. 3.4)
• Lexicographic enumeration of pairings (no Blossom matching)
• Simplified criteria: C1 (absolute) + C8 (colour, relaxable in last round)
• Colour allocation with 5-step priority (Art. 4)

Index

• func AllocateColor(a, b *lexswiss.ParticipantState, roundNumber, boardNumber int, ...) (string, string)
• type Options
  • func ParseOptions(m map[string]any) Options
  • func (o Options) WithDefaults() Options
• type Pairer
  • func New(opts Options) *Pairer
  • func NewFromMap(m map[string]any) *Pairer
  • func (p *Pairer) Pair(_ context.Context, state *chesspairing.TournamentState) (*chesspairing.PairingResult, error)

Functions

func AllocateColor

func AllocateColor(a, b *lexswiss.ParticipantState, roundNumber, boardNumber int, topSeedColor *string) (string, string)

AllocateColor decides which participant gets White in Game 1 of the match and which gets Black, implementing Art. 4 of the Double-Swiss system.

In Double-Swiss, "colour" means who gets White in Game 1 of the 2-game match. The other participant gets White in Game 2 (colours alternate within the match).

Priority:

1. Hard constraint: no participant plays Game 1 as the same colour 3 times in a row
2. Equalise: participant with more white Game-1s gets Black in Game 1
3. Alternate: participant who had White in Game 1 last round gets Black
4. Rank tiebreak: higher ranked (lower TPN) gets White in Game 1
5. Round 1: board alternation (odd board → higher ranked White, even board → Black)

Parameters:

• a, b: the two participants in the pairing
• roundNumber: 1-based round number
• boardNumber: 1-based board number (for round 1 alternation)
• topSeedColor: override for round 1 top seed colour (nil or "auto" = default)

Returns (whiteID, blackID) indicating who plays White in Game 1.

Types

type Options

type Options struct {
	// TopSeedColor forces the top seed's colour in round 1.
	// Values: "auto" (default), "white", "black".
	TopSeedColor *string `json:"topSeedColor,omitempty"`

	// ForbiddenPairs lists participant ID pairs that must not be paired together.
	ForbiddenPairs [][]string `json:"forbiddenPairs,omitempty"`

	// TotalRounds is the total number of rounds in the tournament.
	// Used to determine "last round" for criteria relaxation (C8).
	TotalRounds *int `json:"totalRounds,omitempty"`
}

Options holds Double-Swiss-specific pairing configuration. All pointer fields use nil = use default.

func ParseOptions

func ParseOptions(m map[string]any) Options

ParseOptions converts a generic map[string]any into typed Options.

func (Options) WithDefaults

func (o Options) WithDefaults() Options

WithDefaults returns a copy of options with defaults applied for nil fields.

type Pairer

type Pairer struct {
	// contains filtered or unexported fields
}

Pairer implements the chesspairing.Pairer interface for the Double-Swiss system.

func New

func New(opts Options) *Pairer

New creates a new Double-Swiss pairer with the given options.

func NewFromMap

func NewFromMap(m map[string]any) *Pairer

NewFromMap creates a new Double-Swiss pairer from a generic options map.

func (*Pairer) Pair

func (p *Pairer) Pair(_ context.Context, state *chesspairing.TournamentState) (*chesspairing.PairingResult, error)

Pair implements chesspairing.Pairer for the Double-Swiss system.