Re: thread::join() usage

From: bill_kempf (williamkempf_at_[hidden])
Date: 2002-06-10 15:55:50

--- In Boost-Users_at_y..., "rgalek2002" <rfox_at_s...> wrote:
> Hi,
> 
> I have an application which starts a number of threads, and I want 
> the application to wait for the threads to finish before exiting. 
> Standard stuff, I know, but never having used threads before I am 
> wondering what the stadard way is to accomplish this.
> 
> I have (psuedo code)
> 
>     for (each record in database) {
>         thread thrd(func(), data);
>         }
> 
> I could imagine storing all my thread objects in a list, and then 
> calling join() on each one. For example something like
> 
>     list <thread> threads;
>     for (each rec in db) {
>        thread thrd(func(), data);
>        threads.insert(threads.begin(),thrd);
>        }
>     list<thread>::iterator i;
>     for (i=threads.begin(); i!=threads.end(); i++) {
>        thread t = *i;
>        t.join();
>        }
> 
> Does this seem reasonable? Is there a better/standard way?

This is precisely what boost::thread_group was designed for, and it 
works very similar to your pseudo code.

> One thing 
> I don't like here is that each join will block, when what I would 
> like to do is something more like join_all();

There's no "end result" difference between calling join() for each 
individual thread and calling some "join_all()" method.  On platforms 
like Win32 there might be some subtle performance differences, but 
probably not enough to be worth considering.

Bill Kempf