Re: [boost] Boost MSM parallel behavior with delayed self-transitions?

Subject: Re: [boost] Boost MSM parallel behavior with delayed self-transitions?
From: Danylo Malyuta (danylo.malyuta_at_[hidden])
Date: 2017-03-23 20:29:11

Hi Christophe,

Thank you for the input. As you suggest, I've put on pause trying to
achieve parallelism with pthreads/std::thread and will have a serious look
into Asynchronous. To be sure: you are saying that Asynchronous+MSM is able
to fulfill my objective of having a state machine with states that execute
tasks in parallel (in the multi-thread sense) and that can be exited (i.e.
threads closed) in response to MSM events (process_event)? If so, then it
makes sense for me to read all of the documentation.

Please feel free to use the example in the Asynchronous doc, it would be my
honor!

Best,

Danylo.

On Thu, Mar 23, 2017 at 1:11 PM, Christophe Henry <
christophe.j.henry_at_[hidden]> wrote:

> >Christophe,
> >
> >Thanks for the knowledge. It would be nice if you could give your opinion
> on this question of mine regarding calling process_event from inside a
> thread:
> >
> > http://stackoverflow.com/questions/42941228/boost-msm-call-
> process-event-from-a-custom-function-not-an-action-inside-
> a-sta/42949021?noredirect=1#comment72995089_42949021
> <http://stackoverflow.com/questions/42941228/boost-msm-call-process-event-from-a-custom-function-not-an-action-inside-a-sta/42949021?noredirect=1#comment72995089_42949021>
> >
> >I'd like to know if what Takatoshi Kondo answered is really the only way
> to achieve the result, or if maybe there is a cleaner and more straight
> forward approach.
> >
> >Best,
> >
> >Danylo.
>
> Hi Danylo,
>
> I think he's mostly right, the self-join is the problem. Your timer thread
> should not call anything which will join itself. I'm also afraid your
> options are limited, exception or resource leak, none of them appeals to me.
> I'll also add that the code is still wrong. stop_threads_ should not be
> bool but atomic<bool> or mutexed. As it is now, it might work by luck on
> some compilers and will fail on others because of optimizations.
>
> Frankly, this is the point where you might want to pause, step back and
> realize that no, it is not that easy and when your code grows, you'll be
> debugging for ever.
> This kind of code is simply hard if not impossible to maintain. With your
> permission, I'd even want to add it to the doc of Asynchronous to show why
> the library is needed. I would never manage to come up with such a good
> example myself.
>
> I suggest you again to have a look at Asynchronous. For example:
> https://github.com/henry-ch/asynchronous/blob/master/libs/
> asynchronous/doc/examples/example_asio_deadline_timer.cpp
>
> Now imagine that your Servant would be a state machine, all you'd need
> would be to call async_wait and enjoy having saved yourself quite some
> debugging time.
>
> Regards,
> Christophe
>