What’s the difference between wait() and next_trigger()

DIFFERENCE:

• wait() sử dụng cho 1 thread, next_trigger() sử dụng cho 1 method
• Không giống wait(), việc dùng next_trigger() không suspend 1 process

EXAMPLE:

#include <systemc.h>

SC_MODULE(next_trigger_and_wait) {
	sc_in<bool> clock;

	sc_event  e1, e2;
	int cnt,cnt0;

    void do_wait_thread() {
        while (1) {
            cout << "[        THREAD] "<<sc_time_stamp().to_string()<<endl;
            switch (cnt0) {
            case 0: cout << "                @" << sc_time_stamp() << " Default trigger clk triggered" << endl;
                wait(e1);
                break;
            case 1: cout << "                @" << sc_time_stamp() << " Event e1 triggered" << endl;
                wait(10, SC_NS);
                break;
            case 2: cout << "                @" << sc_time_stamp() << " Event e1 occured or time 10ns passed" << endl;
                wait(e1 | e2);
                break;
            case 3: cout << "                @" << sc_time_stamp() << " Event e1 or e2 triggered" << endl;
                break;
            default:cout << "                @" << sc_time_stamp() << " Default trigger clk triggered" << endl;
                cnt0 = 0;
                break;
            }
            cnt0++; cout << " THREAD : count ++" << sc_time_stamp().to_string()<<endl;
        }
    }

	void do_next_trigger_method() {
        cout << "[        METHOD] " << sc_time_stamp().to_string()<<endl;
		switch (cnt) {
		case 0: cout << "                @" << sc_time_stamp() << " Default trigger clk triggered" << endl;
            next_trigger(e1);
			break;
		case 1: cout << "                @" << sc_time_stamp() << " Event e1 triggered" << endl;
			next_trigger(10, SC_NS);
			break;
		case 2: cout << "                @" << sc_time_stamp() << " Event e1 occured or time 10ns passed" << endl;
			next_trigger(e1 | e2);
			break;
		case 3: cout << "                @" << sc_time_stamp() << " Event e1 or e2 triggered" << endl;
			break;
		default:cout << "                @" << sc_time_stamp() << " Default trigger clk triggered" << endl;
            cnt = 0;
			break;
		}
		cnt++; cout << " METHOD : count ++" << sc_time_stamp().to_string()<<endl;
	}

	void event_thread() {
		while (true) {
			wait(2);
			// Trigger event e1
			cout << "@" << sc_time_stamp() << " Triggering e1" << endl;
			e1.notify();
			wait(20);
			cout << "@" << sc_time_stamp() << " Triggering e2" << endl;
			e2.notify();
			// Wait for  2 posedge of clocks
			wait(2);
			cout << "@" << sc_time_stamp() << " Terminating simulation" << endl;
			sc_stop(); // sc_stop triggers end of simulation
		}
	}

    void clock_thread() {
        cout << "clock positive at : " << sc_time_stamp().to_string()<<endl;
    }
	SC_CTOR(next_trigger_and_wait) {
        cnt = 0; cnt0 = 0;
        SC_THREAD(do_wait_thread);
        
        SC_METHOD(clock_thread);
        sensitive << clock.pos();

		SC_METHOD(do_next_trigger_method);
		
		SC_CTHREAD(event_thread, clock.pos());
	}
};

int sc_main(int argc, char* argv[]) {
	sc_clock clock("my_clock", 1, 0.5);

	next_trigger_and_wait  object("wait");
	object.clock(clock);

	sc_start();  // Run the simulation till sc_stop is encountered
	return 0;// Terminate simulation
}

OUTPUT:

        SystemC 2.3.2-Accellera --- Nov 27 2018 17:08:10
        Copyright (c) 1996-2017 by all Contributors,
        ALL RIGHTS RESERVED

Info: (I804) /IEEE_Std_1666/deprecated:
    sc_clock(const char*, double, double, double, bool)
    is deprecated use a form that includes sc_time or
    sc_time_unit
clock positive at : 0 s
[        METHOD] 0 s
                @0 s Default trigger clk triggered
 METHOD : count ++0 s
[        THREAD] 0 s
                @0 s Default trigger clk triggered
clock positive at : 0 s
clock positive at : 1 ns
clock positive at : 2 ns
@2 ns Triggering e1
[        METHOD] 2 ns
                @2 ns Event e1 triggered
 METHOD : count ++2 ns
 THREAD : count ++2 ns
[        THREAD] 2 ns
                @2 ns Event e1 triggered
clock positive at : 3 ns
clock positive at : 4 ns
clock positive at : 5 ns
clock positive at : 6 ns
clock positive at : 7 ns
clock positive at : 8 ns
clock positive at : 9 ns
clock positive at : 10 ns
clock positive at : 11 ns
[        METHOD] 12 ns
                @12 ns Event e1 occured or time 10ns passed
 METHOD : count ++12 ns
 THREAD : count ++12 ns
[        THREAD] 12 ns
                @12 ns Event e1 occured or time 10ns passed
clock positive at : 12 ns
clock positive at : 13 ns
clock positive at : 14 ns
clock positive at : 15 ns
clock positive at : 16 ns
clock positive at : 17 ns
clock positive at : 18 ns
clock positive at : 19 ns
clock positive at : 20 ns
clock positive at : 21 ns
clock positive at : 22 ns
@22 ns Triggering e2
[        METHOD] 22 ns
                @22 ns Event e1 or e2 triggered
 METHOD : count ++22 ns
 THREAD : count ++22 ns
[        THREAD] 22 ns
                @22 ns Event e1 or e2 triggered
 THREAD : count ++22 ns
[        THREAD] 22 ns
                @22 ns Default trigger clk triggered
 THREAD : count ++22 ns
[        THREAD] 22 ns
                @22 ns Event e1 triggered
clock positive at : 23 ns
clock positive at : 24 ns
@24 ns Terminating simulation

Analytics output log:

Khi 1 process gặp next_trigger(args)/wait(args) function, method/thread đó sẽ bị lock bởi điều kiện trong args. NHƯNG,
[+] Khi do_wait_thread() được gọi, cnt0 = 0 nên “Default trigger clk triggered” in ra màn hình, và sau đó, nó gặp wait(e1) và nó sẽ suspend ở đây.
[+] Không giống như wait(), khi do_next_trigger_method() được gọi, cnt = 0 nên “Default trigger clk triggered” in ra màn hình, và sau đó, nó gặp next_trigger(e1) nhưng nó sẽ KHÔNG suspend ở đây. Nó sẽ chạy đến hết do_next_trigger_method() function. “METHOD : count ++0 s “ in ra màn hình.

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