how to temporary disable parallel working threads

[Thorsten]

Hi,

I have a lot of threads working parallel at my program. For time
measurements of some passages of the threads I take same timestamps on
an easy way like:

long t1 = System.currentTimeMillis();
System.out.println("something to do");
long t2 = System.currentTimeMillis();
System.out.println(t2-t1);

But there is a fault: assume I have 100 threads. One thread has just
printed "something to do" and the java vm "decides" to let all other
99 threads run, which takes 10 sec. Now t2 is calculated and has a
value which is 10 sec to high.

Is there a way to say for a thread that some code has to be executed
non-parallel? I think of something like:

atomic {
long t1 = System.currentTimeMillis();
System.out.println("something to do");
long t2 = System.currentTimeMillis();
System.out.println(t2-t1);
}

Does anyone have a hint ?

Regrads
Thorsten

 

[Gordon Beaton]

Is there a way to say for a thread that some code has to be executed
non-parallel? I think of something like:

atomic {
long t1 = System.currentTimeMillis();
System.out.println("something to do");
long t2 = System.currentTimeMillis();
System.out.println(t2-t1);
}

Does anyone have a hint ?

Synchronize the critical section on a common object:

synchronized (foo) {
long t1 = System.currentTimeMillis();
System.out.println("something to do");
long t2 = System.currentTimeMillis();
System.out.println(t2-t1);
}

foo in the example can be any valid object reference, but it must
refer to the *same* object in each of the threads that should be
synchronized. The operation will be mutually atomic among only the
threads sharing the same synchronization object.

/gordon

 

[Thorsten]

Hi Gordon,

thanks a lot, this is a very good hint and it almost works if I get
you right. But the synchronized (foo) {} sections are still
interrupted by other threads if theses other threads are outside their
own synchronized (foo) {} section.

Regards
Thorsten