Termination of Multiple Task Queue

When multiple task queues are used in the same program, their dependence can be either of the following:

• Acyclic. The task queues forms a hierarchy, where adjacent levels of task queues act as producers and consumers of tasks. Termination detection can proceed top-down, since tasks the producers of tasks for a task queue are at the same or higher levels. To chain together the termination detection protocols, the programmer asserts that a processor is clear of task for task queue only after all task queues higher than have terminated. The program terminates when all task queues have terminated.

• Cyclic. The dependency graph for the task queues are no longer acyclic. The task queue runtime system must consider these task queues as a whole when performing termination detection; the local partitions of different task queues are grouped into one conceptual partition, and the termination detection protocol must combine the enqueue and dequeue counts of all task queues. The current implementation does not support such grouping.