Fork join_none inside for loop

SystemVerilog
9

In reply to ssubramaniam1990@gmail.com:

In reply to dave_59:

In reply to ssubramaniam1990@gmail.com:
The change you show should not work, and introduces a race condition. You are now spawning two independent threads inside the fork/join_none. The two statements

j = I;
thread(j);

execute in parallel, so there is no guarantee that thread(j) gets the updated value of j. Also, the value of i at the point when j = i gets executed should be 5, for all iterations.

Adding code tags:
Hi Dave,

You are right. I should have shown my code previously.
Here is my code:

program automatic fork_join;

  initial begin
    for(int i = 0; i < 16; I++)
      begin
        fork 
         // begin
	      int index =I  ;
	      send(index);
         // end 
    	join_none 
      end
      wait fork;
  end
   
   task send(int j);
     temp();       
     $display("driving port %0d %t" , j, $realtime);
   endtask // send

endprogram

I am trying 3 different cases:

  1. Executing the above program, I can see the prints “Driving port 0-16”.
  2. In the fork block doing something like this:
        fork 
         // begin
	        int index ;
            index = I  ;
	        send(index);
         // end 
	    join_none

With this change Driving port 16 printed 16 times.

  1. Adding begin-end around fork - join_none:
        fork 
          begin
	        int index ;
            index = I  ;
	        send(index);
          end 
	    join_none

Again I see driving port16 being printed 16 times.

Can you please explain what is the difference between the 3 cases.

Thanks
Subramaniam