what the initialize phase do really?

[red_dandelion]

Codes  as follows:

#include <systemc>
using namespace sc_core;

SC_MODULE(DELTA) {
    sc_in<bool> clk;
    int y = 1; 
    SC_CTOR(DELTA) {

        SC_THREAD(add_y); 
        sensitive << clk.pos();

        SC_THREAD(multiply_y); 
        sensitive << clk.pos();

        //dont_initialize();

    }

    void add_y() { // y += 2 happens after a delta cycle
        while (true)
        {
            std::cout << "add_y0 stamp: " << sc_time_stamp() << std::endl;
            wait(SC_ZERO_TIME);
            std::cout << "add_y: " << y << " + 2" << " = ";
            y += 2;
            std::cout << y << std::endl;
            std::cout << "add_y stamp: " << sc_time_stamp() << std::endl;
            wait();
        }
    }
    void multiply_y() { 
        while (true)
        {
            std::cout << "multiply_y: " << y << " * 3" << " = ";
            y *= 3;
            std::cout << y << std::endl;
            std::cout << "multiply_y stamp: " << sc_time_stamp() << std::endl;
            wait();
        }
    }

};

int sc_main(int, char* []) {
    sc_clock clk("clock", 5, SC_SEC);
    DELTA delta("delta");
    delta.clk(clk);
    sc_start(30, SC_SEC);
    return 0;
}

output:

add_y0 stamp: 0 s
multiply_y: 1 * 3 = 3
multiply_y stamp: 0 s
multiply_y: 3 * 3 = 9
multiply_y stamp: 0 s
add_y: 9 + 2 = 11
add_y stamp: 0 s
multiply_y: 11 * 3 = 33
multiply_y stamp: 5 s
add_y0 stamp: 5 s
add_y: 33 + 2 = 35
add_y stamp: 5 s
multiply_y: 35 * 3 = 105
multiply_y stamp: 10 s
add_y0 stamp: 10 s
add_y: 105 + 2 = 107
add_y stamp: 10 s

I am confused for function multiply_y execute twice,  If I make the "dont_initialize();" valid, the function only execute once! 

Appreciate Any one who can explain why.

 

[maehne]

During initialization, all processes are executed once except those, which have been marked with dont_initialize(). See IEEE 1666-2011, clause "4.2.1.1 Initialization phase" for details.