blocking vs nonblocking

從UVM user guide抽出的文句整理

blocking—
1. the tasks block execution until they complete;
2. they are not allowed to fail.
3. There is no mechanism for any blocking call to terminate abnormally or
otherwise alter the flow of control.
4, They simply wait until the request is satisfied.
5. In a timed system, this means that time may pass between the time the call was initiated and the time it returns.

nonblocking
1. call returns immediately.
2. call guarantee that the call returns in the same delta cycle in which it was issued, that is, without consuming any time, not even a single delta cycle.
3. In UVM, nonblocking calls are modeled as functions.