order, nonblocking, order
Nonblocking communication operations are ordered according to the execution
order of the posting calls. The non-overtaking
requirement of Section 
is extended to
nonblocking communication.
The order requirement specifies how post-send calls are matched to
post-receive calls.
There are no restrictions
on the order in which operations complete. Consider the code in Example
.
Since the completion of a receive can take an arbitrary amount of time, there is no way to infer that the receive operation completed, short of executing a complete-receive call. On the other hand, the completion of a send operation can be inferred indirectly from the completion of a matching receive.
