Re: Parallel processing using Executor?
On Aug 14, 12:15 pm, howa <howac...@gmail.com> wrote:
Hello,
I have a method, e.g. foo(int i), which take an integer i and do some
heavy processing
now, i want to find the summation of foo() of i = 1..10000, I want to
take the advantage of speedup by multithreads, then I use executors to
create the threads...,e.g.
public class Foobar implements Runnable {
public Foobar() {}
public void run() {
System.out.println("thread is running...");
}
public int foo(int i) {
//...
}
}
Executor tp = Executors.newFixedThreadPool(10);
for (int i =1; i <=10000; i++) {
tp.execute(new Foobar() );
}
but how can i get back the information return from the execute method,
i.e. from the foo(int i)?
Thanks...
You'd need a synchronized method that can keep the sum, and then pass
that as a callback to the thread.
Also, you'd need to wait till all threads are done executing - which
is why I do not think threading is a good solution for this case.
For example:
class Calculator{
private int total;
public synchronized void add(int result){
total+=result;
}
public void spawnThreads(){
for(int i=0;i<10000;i++){
//spawn the threads, passing in this Calculator as a
reference
//have the thread's run() call add(result) once it has
calculated the value
//join() on the thread <--- this is why threading will not
help here!
}
}
In other words, since the sum is dependent on complete execution of
all the theads taking part in the computation, evaluating the sum is
in a way a blocking call (and hence the join() is needed).
-cheers,
Manish