Turnfor

Turnfor is a coordination primitive discussed in the context of concurrent programming and task orchestration. It describes a mechanism in which control is handed from the currently running task to the next ready task in a predefined order, with the system “turning” execution forward after each defined interval. The concept emphasizes predictable advancement of tasks and aims to prevent starvation by ensuring every eligible task receives a turn.

Etymology and concept. The name turnfor is a portmanteau of “turn” and “forwarding.” In turnfor-based designs, a central scheduler or executor maintains a circular queue of ready tasks and enforces a fixed or variable time quantum for each turn. After a task completes its allotted turn, the scheduler forwards control to the next task in the queue, even if the preceding task has not completed, depending on system policy. This approach blends elements of cooperative and preemptive scheduling, seeking a balance between low overhead and bounded latency.

Usage and variants. Turnfor can be implemented in asynchronous runtimes, coroutines, or microservice orchestration layers. Variants differ in whether turns are time-sliced (fixed quantum), event-driven (based on readiness signals), or prioritization-based (weights influence turn order). Turnfor is often discussed as a teaching abstraction or design pattern to illustrate fair advancement and deterministic task switching, rather than as a universally adopted standard.

Relation to related concepts. Turnfor is related to round-robin scheduling, yield-based cooperative multitasking, and preemptive multitasking. It is commonly contrasted with strict preemption to highlight trade-offs in overhead, responsiveness, and simplicity.

See also. Concurrency, Scheduling, Cooperative multitasking, Round-robin, Task orchestration.