Concurrent Programming
Concurrent Programming
P || Q || R states that the executions of P, Q and R may overlap, however, although the instructions of these processes may consequently be interleaved, the instructions from any single process since it executes on a logical processor must be strictly ordered i.e.
forall e, i < j: pi ® pj
Because of the temporal variability of logical processors, different executions of a concurrent program will produce different instruction orderings although the above must hold true. If two operations are concurrent with one another:
the operations are permitted to overlap in time;
the textual order does not define the order of execution.
The operations are partially ordered. Concurrent programs can behave non-deterministically, in the sense that they can deliver different results when repeatedly run with the same input data.