Consistency And

tion function is essential for a shared-memory system, it is only occasionally that the memory is used in this way. For example, all references during the computation of f() are probably not even shared. Even if they are, it is unlikely that a program would want to use the values while Process 1 is computing f(). 1 So what really matters, in general, is that at a certain point in the execution of a program, a new value (or set of values) has been computed and after that point other processors will access the new values. Such a point is usually synchronized through explicit synchronization mechanisms, such as a semaphore or a barrier[Jord78]. It is generally regarded as good programming technique to synchronize explicitly, rather than depending on the memory system to provide implicit synchronization. While there are well-known methods for implementing semaphores from a memory in which all reads and writes