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

From: Peter Dimov (pdimov_at_[hidden])
Date: 2001-07-02 13:20:38

From: <williamkempf_at_[hidden]>
> --- In boost_at_y..., "Peter Dimov" <pdimov_at_m...> wrote:

> > class thread_group
> > {
> > public:
> >
> >     // all implicit members are fine and useful
> >
> >     template<class F> void create(F f)
> >     {
> >         v_.push_back(thread::create(f));
> >     }
> >
> >     void join_all()
> >     {
> >         thread::join(v_.begin(), v_.end());
> >     }
> >
> > private:
> >
> >     std::vector<thread::ref> v_;
> > };
> >
> > As you can see, it's very similar to my vector example.
>
> There are two problems here.  First, as I pointed out the details are
> hidden in the other concept, so the ease of use is not impacted.

Ease of use - provided you have a working thread_group - if of course not
impacted. Implementing a thread_group does, however, demonstrate the ease of
use of the base design.

> Second, you chose to use a ref-count design internally, when such a
> design is not needed.
>
> class thread_group
> {
> public:
>     // all implicit members are fine and useful
>
>     template<class F> void create(F f)
>     {
>         v_.push_back(new thread(f));
>     }
>
>     void join_all()
>     {
>         std::vector<thread*>::iterator it = v_.begin();
>         while (it != v_.end())
>         {
>            (*it)->join();
>            it = v_.erase(it);
>         }
>     }
>
> private:
>     std::vector<thread*> v_;
> };
>
> You should note that like you I didn't include proper
> synchronization, so this implementation isn't valid, but it
> illustrates the point.

You didn't say anything about sharing a thread_group between threads, so a
non-synchronized thread_group still matches the ad-hoc specification given
in your 'void foo()' example.

> My implementation required no reference
> management, only explicit lifetime management.

And explicit management is error prone, as you have demonstrated.

--
Peter Dimov
Multi Media Ltd.