Different threads don't work together while doing different tasks

Question

I'm creating two different threads which will solve same problem with different ways and I will calculate their solving time. I've created a structure like that;

MainController.java

public static void main(String[] args) throws Exception {
        MainController mc= new MainController();
        mc.setProblem();
        Thread1 thread1 = new Thread1("thread1",problem,approach1);
        Thread2 thread2 = new Thread2("thread2",problem,approach2);
        thread1.start();
        thread2.start();
    }

Thread1.java

class Thread1 implements Runnable{

       public void run() {
          System.out.println("Running " +  threadName );
          try {
             solve(approach);
          } catch (Exception e) {
             System.out.println("Thread " +  threadName + " interrupted.");
          }
          //showTable();
          System.out.println("Thread " +  threadName + " exiting.");
       }

       public void start () {
          System.out.println("Starting " +  threadName );
          if (t == null) {
             t = new Thread (this, threadName);
             t.start ();
          }
       }

       public void solve(approach) throws Exception {

            // Throw an exception to stop the process if the puzzle is solved
            if (didIsolve())  {//true if yes
                    System.out.println("----" + threadName +"----");
                    showResult();
                    System.out.println("--------------------------");
                    throw new Exception("ex");
            }
        }
    }

Thread2.java is the same as above code block.

And output like

    Creating thread1
    Creating thread2
    Starting thread1
    Starting thread2
    Running thread2
    Running thread1
    Thread thread1 exiting.
    ----thread2----
   RESULT METHOD OUTPUT
    --------------------------
    Thread thread2 interrupted.
    Thread thread2 exiting.

As you see above, thread1 did not solve problem, at least did not show result.

Also I've checked this topics so far

multiple threads performing different tasks

Java threads to do different tasks?

Edit:

Well, I think I found the problem. I changed MainController class;

public static void main(String[] args) throws Exception {
        MainController mc= new MainController();
        mc.setProblem();
        MainController mc2 = new MainContoller();
        mc1.setProblem();
        Thread1 thread1 = new Thread1("thread1",mc.problem,approach1);
        Thread2 thread2 = new Thread2("thread2",mc1.problem,approach2);
        thread1.start();
        thread2.start();
    }

And it worked, but I don't know why. I will not accept my answer as correct answer for few days, may someone explain this situation?

score 0 · Answer 1 · answered Nov 17 '17 at 01:19

0

If your goal is to measure the solving time of each approach, doing it in a multithreaded way is not going to give you consistent and reliable results. It would be better to run each approach in a serial fashion, and probably many times, to get an average completion time of each approach. Take care to avoid taxing the CPU with other processes during the test.

answered Nov 17 '17 at 01:19

Zach

11
2

Not just measuring solving time, also I need to see solving progress, and it must be at same time. But thanks for advice. – nerdicsapo Nov 17 '17 at 01:21
Try calling thread.join() on each thread after starting both. – Zach Nov 17 '17 at 01:28
They are working in order now. Thread2 is starting after thread1's die. – nerdicsapo Nov 17 '17 at 01:33

score 0 · Accepted Answer · answered Nov 17 '17 at 01:44

Well, I think I found the problem. I changed MainController class;

public static void main(String[] args) throws Exception {
        MainController mc= new MainController();
        mc.setProblem();
        MainController mc2 = new MainContoller();
        mc1.setProblem();
        Thread1 thread1 = new Thread1("thread1",mc.problem,approach1);
        Thread2 thread2 = new Thread2("thread2",mc1.problem,approach2);
        thread1.start();
        thread2.start();
    }

And it worked, but I don't know why. I will not accept my answer as correct answer for few days, may someone explain this situation?

If this solved your problem, then you haven't posted enough information in your question about your code and your issue by far - it's impossible to reach this solution based on the information in your question. — Erwin Bolwidt, Nov 17 '17 at 02:14

Different threads don't work together while doing different tasks

2 Answers2