Teaching a Kotlin Chess Engine to Debug Itself
Automated debugging and repair with independent verification systems
1The Problem: Silent Failures
Modern mobile apps may look correct on screen but have silent errors in the underlying logic. For example, a chess app may smoothly move a piece while mishandling a special move. Such errors often go unnoticed and threaten the app's integrity.
2The Solution: Perft Rig
The perft rig is a test system designed to ensure the accuracy of a chess engine. It uses two independent verification sources (perft counts and Stockfish engine) to detect and automatically fix errors. This system runs on every PR and nightly, enhancing code reliability.
3Independent Verification Sources
The perft rig uses two independent verification sources: published perft counts and the Stockfish engine. These sources independently check the code's accuracy and detect errors. Thus, even if one source has an error, the other reveals it.
4Bug Localization
The perft rig uses a method called 'divide' to pinpoint the exact location of errors. This method calculates separate numerical values for each move and isolates the faulty move. This allows the exact location of the error to be determined, speeding up the repair process.
5Pure Functions
At the heart of the perft rig is a pure function called 'applyMove()'. This function takes the current game state and returns a new game state. Pure functions, free from side effects, simplify debugging and testing processes.
6Module Boundary
The perft rig uses the module boundary to maintain code purity. Helper functions within the module are marked 'internal' and inaccessible from outside. This ensures the code remains free from side effects and makes debugging more effective.
7Automatic Repair
The perft rig uses an AI coding agent to automatically fix errors. This agent runs tests, reads failures, and repairs the engine without human intervention. This process speeds up software development and reduces error rates.
8General Applicability
The model used by the perft rig can be applied beyond chess. Any deterministic logic module can set up a similar system using independent verification sources and a bug localizer. This is an effective method to enhance code reliability.
9Next Steps
The success of the perft rig indicates that automated debugging and repair systems will become more common in the future. Such systems can make software development processes more efficient and reliable.
10Conclusion
The perft rig offers an effective solution to ensure the integrity of a Kotlin Multiplatform chess engine. Independent verification sources and an automatic repair system enhance code reliability and accelerate the software development process.