Event synchronization analysis for debugging parallel programs

One of the major difficulties of explicit parallel programming for a shared memory machine model is detecting the potential for nondeterminacy and identifying its causes. There will often by shared variables in a parallel program, and the tasks constituting the program may need to be synchronized when accessing these variables. This problem is discussed, and a method for automatically detecting nondeterminacy in parallel programs that utilize event-style synchronization instructions, using the Post, Wait, and Clear primitives, is presented. With event-style synchronization, especially when there are many references to the same event, the difficulty lies in computing the execution order that is guaranteed given the synchronization instructions and the sequential components of the program. The main result is an algorithm that computes such an execution order and yields a task graph to which a nondeterminacy detection algorithm can be applied.