Re: [boost] Re: Boost.Threads - thread_desc concept

From: Peter Dimov (pdimov_at_[hidden])
Date: 2001-07-02 10:59:49

From: <williamkempf_at_[hidden]>

> > You don't look convinced that a handle/body based design is easier
> to use,
> > though.
>
> I'm not.  The only example given by either of us that indicates more
> ease of use is the example you just gave with a vector.

If you expand the examples that had a thread_manager or a thread_group in
them, giving the full implementation, you'll see that they, too, demonstrate
the same point.

> However, we
> deal with this all the time in C++ using a smart pointer, and the
> ease of use with a smart pointer is nearly identical even if the
> overhead becomes a wash again.  In fact, the thread ref concept is
> just a variation on a smart pointer!

Of course it is! Call it whatever you like, a smart pointer, a handle, or a
thread reference.

So, your unspoken question is probably "why provide a thread::ref when we
already have shared_ptr?"

Here's an example of creating a thread:

shared_ptr<thread> p(new thread(f));

This requires an explicit 'new', which several people have objected to. An
easy way to eliminate the 'new' is:

shared_ptr<thread> p = thread::create(f);

This is better, but a custom thread-safe reference counted smart pointer
may, under some conditions, outperform shared_ptr. (Plus, its operator==
isn't exactly what you want.) So we get to:

thread::ref p = thread::create(f);

Now the only question left is whether we need the underlying 'thread' object
or not. I've not been terribly successful in convincing people that it's, in
fact, not needed - and sometimes harmful - so it will probably survive, much
to my dissatisfaction. Such is life.

--
Peter Dimov
Multi Media Ltd.