Re: [boost] [thread] new thread_pool and dispatcher classes

From: Atry (pop.atry_at_[hidden])
Date: 2007-05-06 19:52:03

Yuval Ronen 写道:
> Here are a few classes which I think are very useful:
>
> 1. A thread_pool class. I think there's not much I can tell you that 
> you don't know about it. It's something that has threads, and can 
> accept tasks to be pushed into a queue, and executed in turn when a 
> thread is available. It can also be suspended (stop handling tasks, 
> but keep the threads alive) and resumed.
>
> 2. Two 'dispatcher' classes, one for plain threads, and one for 
> thread_pools. They accept a single task, or several tasks, to be 
> executed, either by dedicated threads (the thread_dispatcher class), 
> or by a thread_pool (the thread_pool_dispatcher class). These classes 
> provide a wait() method that block until all tasks are done.
>
> IMO, these classes fill a hole in the Boost.Thread library, and can be 
> a basic for the future<> template (I have to admit I didn't follow the 
> future<> discussion, so I hope there's nothing here to contradict any 
> consensus reached in that discussion, if any).
>
> A few notes:
>
> 1. The semahpore class is there because it was needed for the 
> thread_pool_dispather, but I think it will be a good general purpose 
> addition to Boost.Thread. If I'm the only one thinking so, it can be 
> moved as implementation detail of thread_pool_dispather.
>
> 2. The thread_task typedef should really be removed. Instead, a 'task' 
> typedef should be added to boost::thread. So all occurances of 
> 'thread_task' should be replaced with 'thread::task'.
>
> 3. I'm not sure about the name 'dispatcher', but couldn't find 
> anything I'm happy with. Something that catches the essence of the 
> classes. Any suggestions are welcome.
>
> 4. The thread_pool class can benefit from two additional features:
>
> 4.A. add_threads(size_t) and remove_threads(size_t). I think I can add 
> those if found useful.
>
> 4.B. pre_loop and post_loop hooks to be executed by each of the worker 
> threads in the thread_pool, immediately after creation, and before 
> termination. I actually have a use case for those, but I don't want to 
> distract the discussion from the main things.
>
> 5. The asserts in thread_pool::~thread_pool, thread_pool::suspend, 
> thread_pool::resume, thread_dispatcher::~thread_dispatcher, 
> thread_pool_dispatcher::~thread_pool_dispatcher are supposed to catch 
> user errors. These asserts are questionable. I'm not sure whether 
> those use cases are indeed errors, and if so, should assert be the 
> right way to deal with them. I chose to be a hard-liner for now, with 
> an option to soften.
>
> 6. The other asserts are there to catch errors in my code.
>
> 7. Some or maybe all of the asserts should be replaced by 
> BOOST_ASSERT. I'm not sure of the Boost convention here.
>
> I hope it will be found useful!
> ------------------------------------------------------------------------
>
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We already have thread pool and dispatcher in Boost.Asio, although it is 
a very simple one.