Re: [boost] [GSoC] Scheduled Executors beta 1 release

Subject: Re: [boost] [GSoC] Scheduled Executors beta 1 release
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2014-07-27 02:58:43

Le 26/07/14 20:29, Ian Forbes a écrit :
>> The approach I have in mind for this library respect to scheduled work
>> of the N3785 proposal is quite different. Instead of adding the
>> scheduled operations to a specific scheduled_executor polymorphic
>> interface, I opted by adding two member template functions to a class
>> scheduled_executor that wraps an existing executor. This
>> scheduled_executor will probably have a thread to take of the time
>> scheduled operations, but this is not necessary. The semantic of the
>> time scheduled operations is a little bit different. The task will be
>> submitted to the associated executor at/after the given time_point/duration.
> This describes the scheduling_adaptor class.
> Since there are no virtual methods the addition of template functions is possible.
Right.
>
>> Note that your base class scheduled_executor is not an executor at all.
> Perhaps I should move this into detail then.
> I could also change the name to scheduled_executor_base and perhaps then change scheduling_adaptor to scheduled_executor.
>
> This however would rule out any possible use of the scheduled_executor class a polymorphic base class since it would be hidden in detail.
It seems that there is consensus on replacing the polymorphic approach 
by a type-erased approach. See 
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4032.html.

Anyway if you want to provide a dynamic polymorphic class and an 
adaptor, you could use scheduled_executor, scheduled_executor_adaptor 
for the dynamic polymorphic classes. If you take in account my design, 
the class could be named scheduled_executor_wrapper.

>
>> This has several advantages:
>> * The time scheduled operations are available for all the executors.
> This is provided via the scheduling_adaptor class.
This is not correct, as your schedulling_adaptor needs an executor that 
has a timed queue.
With my design, only the scheduled_executor would need a timed_queue.
>
>> * The template functions could accept any chrono::steady_clock::time_point or any chrono::duration.
> I can add template functions to do this. Others have requested this.
>
>> * The non-time scheduled task don't pay for the additional cost to manage with a priority queue.
> I can override (non-virtually) the submit(work) function in scheduling_adaptor to do this.
See above. This doesn't change anything, as the queue is a timed queue 
and so you will pay for the non-timed operations.
>
>
Vicente