Stockshark

A small, dependency-free Ruby wrapper for talking to a UCI-speaking chess engine (Stockfish, or anything else that implements the protocol) over stdin/stdout/stderr pipes: start it, hand it a FEN, get back a structured evaluation (centipawns or mate score, best move, principal variation, depth reached). No chess rules engine, no board representation, no opinions about perspective or move classification — just the UCI protocol, cleanly wrapped.

bundle add stockshark

Or add it to your Gemfile directly:

gem "stockshark"

engine = Stockshark::Engine.new
result = engine.analyze(fen: "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1", depth: 18)

result.best_move        # => "e2e4"
result.depth            # => 18
result.lines.first.pv   # => ["e2e4", "e7e5"]
engine.quit

Pass movetime_ms: instead of depth: for a time-bounded search, and multipv: to get more than one ranked line back (result.lines is sorted by rank, so lines.first is always the primary line).

configuration = Stockshark::Configuration.new(threads: 4, hash_mb: 128)
engine = Stockshark::Engine.new(configuration)

Every option also has an environment variable default (see lib/stockshark/configuration.rb) — deliberately named STOCKFISH_*, not STOCKSHARK_*, since they configure the actual engine binary being launched rather than this library:

• STOCKFISH_PATH (default stockfish) — path to the engine binary, resolved via $PATH if not absolute.
• STOCKFISH_THREADS (default 1) — UCI Threads.
• STOCKFISH_HASH (default 16) — UCI Hash, transposition table size in MB.
• STOCKFISH_MAX_ANALYZE_MS (default 30000) — how long the engine is given to respond before Stockshark::TimeoutError is raised.

All raised errors descend from Stockshark::Error:

• Stockshark::EngineNotFoundError — the configured binary doesn't exist, isn't executable, or couldn't be spawned.
• Stockshark::TimeoutError — the engine didn't respond within the configured deadline.
• Stockshark::CrashedError — the engine process exited mid-conversation.

After checking out the repo, run bin/setup to install dependencies. Then:

bundle exec rspec                 # fake-engine suite, no binary required
bundle exec rspec --tag stockfish  # also runs the real-engine integration spec

The --tag stockfish run needs an actual Stockfish binary on $PATH (or pointed to via STOCKFISH_PATH) — it's skipped automatically otherwise (see spec/support/stockfish_availability.rb). Install one with:

brew install stockfish        # macOS
apt install stockfish         # Debian/Ubuntu

or download a build from stockfishchess.org/download.

Lint with:

bundle exec rubocop

CI (.github/workflows/ci.yml) runs both the test suite and RuboCop on every push and pull request.

Run bin/console for an interactive prompt with the gem already loaded.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, bump the version in lib/stockshark/version.rb, then run bundle exec rake release, which tags the version, pushes the commit and tag, and pushes the .gem file to rubygems.org.

MIT — see LICENSE.txt.

Built by TrueFlux.