trueskill-tt/CLAUDE.md

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Commands

cargo build                          # Build the library
cargo test --lib                     # Run all library tests
cargo test --lib <test_name>         # Run a single test by name
cargo test --lib -- --nocapture      # Run tests with stdout output
cargo clippy                         # Lint
cargo bench                          # Run benchmarks (criterion)

The approx feature enables approx::AbsDiffEq for Gaussian:

cargo test --features approx

Architecture

This is a Rust port of TrueSkillThroughTime.py — a Bayesian skill rating system that tracks skill evolution over time using Gaussian message passing.

Data flow

History  →  Batch[]  →  Game[]  →  teams/players

• History (history.rs) — top-level container. Organizes games by time into Batches, runs forward/backward message passing across batches, and exposes learning_curves() and log_evidence().
• Batch (batch.rs) — all games at a single time step. Runs iteration() to update skill estimates via Game::posteriors(), collecting Skill distributions per player.
• Game (game.rs) — a single match. Given teams (slices of Gaussian), computes posterior skill distributions using Gaussian factor graphs and message.rs helpers.
• Agent (agent.rs) — wraps a Player with temporal state (last_time, message). receive() applies time-decay (gamma) when the player reappears after a gap.
• Player (player.rs) — static configuration: prior Gaussian, beta (performance noise), gamma (skill drift per time unit).
• Gaussian (gaussian.rs) — core probability type. Stored as natural parameters (pi = 1/sigma², tau = mu/sigma²). Arithmetic ops implement message multiplication/division in the factor graph.
• message.rs — TeamMessage and DiffMessage: intermediate factor graph messages used inside Game.
• lib.rs — exports the public API (Game, Gaussian, History, Player) and standalone functions (quality(), pdf(), cdf(), erfc()). Also defines global defaults: MU=0.0, SIGMA=6.0, BETA=1.0, GAMMA=0.03, P_DRAW=0.0, EPSILON=1e-6, ITERATIONS=30.

Key design points

• History uses IndexMap<K> (defined in lib.rs) to map arbitrary player keys to Agent state.
• Convergence is measured by the maximum delta() across all skill distributions; iteration stops when below EPSILON or after ITERATIONS rounds.
• The approx feature gates AbsDiffEq on Gaussian for use in tests — the feature is optional and only needed for approximate equality assertions.
• time in History/Batch is currently an f64; the README notes it needs to become an enum to support richer temporal states.