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[Issue] event call notify at the same time


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Hello @all


I have 2 input port sc_in<Data> input[2];

2 method "HandleInput(int port_index)" (using sc_spawn) with sensitive is input port

1 method "MainProcess"

"HandleInput" method will trigger "MainProcess" with main_process_event.notify(SC_ZERO_TIME)

Symptom :

"HandleInput" is called 2 times ( port_index = 0 and 1) at the same time (It is called before "MainProcess" is called )

"MainProcess" is called 2 times -> This is not desirable, My expected is "MainProcess" is called 1 time

I tried to reproduce it with the simple code ( as my attached), but I can't

As my check:

1. "HandleInput" with port index = 0 is called -> main_process_event.notify(SC_ZERO_TIME) is called -> m_notify_type = DELTA -> sc_event::trigger() is called

2. "HandleInput" with port index = 1 is called -> main_process_event.notify(SC_ZERO_TIME) is called ....

Because at (1) sc_event::trigger() is called => m_notify_type = NONE => So, at (2), when  main_process_event.notify(SC_ZERO_TIME) is called, kernel add new delta event => MainProcess triggered 2 times   

But I don't know why at(1) sc_event::trigger() is called ?, I think (1) and (2)  are same phase (Evaluate), I don't know this is a systemc bug or not?
Could you please to support?

DUT.cpp main.cpp

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  • DS1701 changed the title to [Issue] event call notify at the same time

Your understanding is correct: if a process (MainProcess in your case) is waiting on an event (main_process_event) that is notified twice in two different processes that are part of the same eval phase (using delta notification), then the process will be triggered only once - in the next evaluation phase.

In general, an event will have only one pending notification. The details are in "5.10.8 Multiple event notifications".

So, you have to debug your original code - to find out why MainProcess is getting triggered twice. In addition to sc_time_stamp(), you can also print sc_delta_count() - to check which delta cycle the event notification is being done (and which delta cycle the process is getting triggered).

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