Fourthreaded

Fourthreaded is a term for a software design pattern that structures a program around four concurrent threads intended to run simultaneously, with clear separation of responsibilities and minimal shared state.

Typical fourthreaded architecture assigns roles to four threads: a controller or input thread, a worker or processing thread, an I/O or communication thread, and a monitor or watchdog thread. The idea is to reduce contention by isolating concerns and using message passing or queues to communicate.

Inter-thread communication is typically done with thread-safe queues and synchronized data structures; shared state is minimized; patterns such as producer-consumer and fan-out/fan-in may be used; care is taken to avoid deadlock and ensure timely progress; some implementations use lock-free structures.

Advantages include improved responsiveness, simpler reasoning about each thread, easier testing of isolated components, and potential performance on multi-core CPUs; drawbacks include added complexity in design, increased context switching, and potential bottlenecks at communication points.

Use cases include real-time data processing pipelines, streaming services, GUI applications with background tasks, or embedded systems where four distinct threads map well to input, compute, output, and health monitoring.

The term is informal and not standardized; used mainly in informal discussions and niche tutorials. It is not a formal programming paradigm.