Re: Periodic tasks in Simpy?

The PEM usually contains the process’ event loop (comparable to an event loop in a server or in a Qt
application). Usually, you ``activate`` your processes and when you call ``simulate`` (or peek and
step), SimPy calculates all events for the process. If you also call the process' PEM from within another
process, your simulation may break. However, you can generate events for a process from within another
process, e.g., via SimEvent or if you interrupt or reactivate another process.

Cheers,
Stefan

Am 2012-04-22 um 10:07 schrieb Forrest Iandola:

> One quick follow-up question:
> 
> In a recent email thread, Stefan advised "Don’t call a process’ PEM from within another process."
> 
> In the pseudo-code below, I do call a PEM from within an other process. It works properly based on some unit
testing and visualization. Why is it a bad idea to call a PEM from within another process?
> 
> Thanks,
> Forrest
> 
> On Thu, Apr 19, 2012 at 2:27 PM, Forrest Iandola <iandola1 <at> illinois.edu> wrote:
> Stefan, Tony,
> 
> Thanks! This is exactly what I was looking for. 
> 
> In the case where the period is smaller than the deadline, it's possible for multiple invocations of a task
to run simultaneously. The following pseudo-code outlines how I handled this:
> 
> Invocation(Process):
>     def run(self, ...):
>         # implement the behavior of the task here
> 
> Task(Process):
>     def run(self):
>         while 1:
>             myInvocation = new Invocation(sim=self, ...)
>             myInvocation.activate(myInvocation, myInvocation.run(...))
>             yield hold, self, period   # e.g. period could be 10
> 
> Sorry for the slow reply--I just got around to redesigning my code to handle periodic tasks. :)
> 
> Forrest
> 
> 
> On Sat, Apr 7, 2012 at 3:33 AM, Stefan Scherfke <stefan <at> sofa-rockers.org> wrote:
> of course 
> 
> 
> Am 2012-04-06 um 21:33 schrieb Tony Vignaux:
> 
> > if that "yield hold, self, 10" is in a loop.
> >
> > ====
> >
> > Tony  Vignaux
> >
> >
> >
> >
> >
> > On Fri, Apr 6, 2012 at 8:57 PM, Stefan Scherfke <stefan <at> sofa-rockers.org> wrote:
> > Hi Forrest,
> >
> > an example would be useful. If your process’ PEM does e.g., a "yield hold, self, 10", than it’s imho
like a periodic task that is activated every 10 time steps.
> >
> > Cheers,
> > Stefan
> >
> >
> >
> > Am 2012-04-06 um 01:03 schrieb Forrest Iandola:
> >
> > > Hi,
> > >
> > > I'm using SimPy to simulate distributed control systems that have periodic tasks. Some tasks may have a
periods smaller than their deadlines, so there may be multiple instances of a task in the system.
> > >
> > > I've read a fair amount of the SimPy documentation, and I searched simpy.sourceforge.net for the word
"periodic." So far, I haven't found any information on built-in support for periodic tasks in SimPy. Can
anyone suggest some such functionality in SimPy?
> > >
> > > Alternatively, I think it would be straightforward to periodically feed a particular task into my
simulation. I'm just trying to keep my code as clean as possible, so I want to use built-in functionality
where possible.
> > >
> > > Let me know if this question makes sense. If it sounds too abstract, I can give a concrete example.
> > >
> > > Thanks,
> > > Forrest
> > >
> > >
> > > --
> > > Forrest Iandola
> > > Department of Computer Science
> > > University of Illinois at Urbana-Champaign
> > > http://www.forrestiandola.com
> > > ------------------------------------------------------------------------------
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> >
> >
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> 
> 
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> Boundary is the first to Know...and Tell You.
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> 
> 
> 
> -- 
> Forrest Iandola
> Department of Computer Science
> University of Illinois at Urbana-Champaign
> http://www.forrestiandola.com
> 
> 
> 
> -- 
> Forrest Iandola
> Department of Computer Science
> University of Illinois at Urbana-Champaign
> http://www.forrestiandola.com

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