Crate ai_connect4

Expand description

§ai-connect4

A Connect Four rules and search library built on two bitboards.

Play against it compiled to Wasm here: https://thegustafson.com/games/connect-four

§Self-play

The selfplay binary runs deterministic paired-color matches. Each opening is played twice with the engines swapping Red and Yellow.

cargo run --release --bin selfplay -- \
  --a maximum --b expert --games 12 --opening-plies 4 --seed 1

The six built-in profiles are beginner, easy, medium, hard, expert, and maximum. Use --a-depth, --a-nodes, and the corresponding --b-* options to override their limits. Library users can read the same settings with search_preset or SEARCH_PRESETS.

§Use it

Add the crate to your project:

[dependencies]
ai-connect4 = "0.1"

use ai_connect4::{Algorithm, Move, Position, SearchLimits, search};

let mut position = Position::default();
position
    .make_move("4".parse::<Move>().expect("valid column"))
    .expect("legal move");

let result = search(
    position,
    Algorithm::TranspositionTable,
    SearchLimits::depth(7),
);

assert!(result.best_move.is_some());

The crate includes reversible moves, perft, alpha-beta search, move ordering, and an optional transposition table.

cargo test
cargo run

Licensed under the MIT License.

Modules§

verification: Slow reference code and fixed oracle cases used to verify the engine.

Structs§

Cell: A physical board cell. Rank zero is the bottom row.
Column: One of Connect Four’s seven columns, indexed left to right.
Engine: One line-oriented engine session shared by tests and the native binary.
IterationSummary
IterativeSearchReport: Result of iterative deepening under one cumulative budget.
Move: A move drops one disc into a column.
MoveList: At most seven moves exist, so search never needs a heap-backed move list.
Position: Two 42-bit player boards inside Connect Four’s 7×7 sentinel layout.
RootBranch
Score: A raw search score with terminal results deliberately outside the heuristic band. The type prevents an evaluation estimate from masquerading as a proven win or loss.
SearchLimits
SearchPreset: A named depth and cumulative node budget for interactive play.
SearchReport: Complete result of one fixed-depth search attempt.
SearchStats
Undo

Enums§

Algorithm: Controlled configurations used by search regression tests.
GameResult
MoveError
ScoreKind
Side

Constants§

HEIGHT
SEARCH_PRESETS: The built-in strength ladder, ordered from least to most search work.
WIDTH

Functions§

iterative_search: Iteratively deepen while preserving the table and the last completed root move. A cumulative node budget is split exactly across iterations. If an iteration is interrupted, callers receive the prior complete result.
perft: Count legal move sequences to exactly depth plies with the bitboard core.
search: Search one fixed depth. All algorithms use the same terminal scores and frontier evaluator, so changing algorithm isolates search efficiency.
search_preset: Finds a built-in strength preset by its lowercase name.