Subject:
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Re: Tasks in RCX
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 22 Dec 1999 02:24:24 GMT
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Viewed:
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834 times
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Not sure about the newer VM's, but the early Java systems got bogged down pretty
quickly when you started to fire up lots of concurrent threads, particularly if
you were doing 'real-time' type tasks such as animation or network access. This
sort of thing can slow down the CPU scheduler with too many context switches.
If I remember correctly, this is an even bigger problem in embedded real-time
controllers. I would assume this would apply to the RCX (more-or-less), hence
the desire to limit the number of tasks to ten.
- Greg
Tilman Sporkert wrote:
>
> > In lugnet.robotics, Ram Meenakshisundaram writes:
> > > Hi,
> > >
> > > I read somewhere that the RCX is limited to only 10 concurrent tasks.
> > > Is this limitation in the firmware? If so, can I use a replacement
> > > firmware like legOS to overcome this. I basically want to have an
> > > unlimited number of tasks so that I can port OCCAM-2 to the RCX. Thanks
> >
> > <chuckle> 10 seems like a small number (yes its limited by the firmware)
> > until you try to use them all. In my experience only email and webserver type
> > applications kick off more than 4 or 5 threads at once.
>
> That highly depends on the programming environment, and the skills and
> preferences of the programmer. Thread creation and management is very easy in
> Java, and therefore, Java programmers tend to use threads more liberally for
> example. Dozens of threads are common in applications I'm working with.
>
> The RCX environment leads you towards liberal use of concurrent tasks, too. You
> don't want to stop monitoring your sensors while performing some motor
> operations for example. The big red "Emergency shut down" button has to work at
> any time. Other real-time operation systems use interrupt handlers to accomplish
> the same goals.
>
> The RCX has a limited number of inputs (3 sensors, IR, timer, counter) and
> outputs (3 motors, speaker). That limits the number of useful tasks that you can
> have. Not many people using the Lego Mindstorms programming environment will be
> seriously inconvenienced by a limit of 10 concurrent tasks.
>
> Tilman
--
G. Crisp - gcrisp@mindspring.com
"Indian, indian, what did you die for? Indian says 'Nothing at all.'"
-- Jim Morrison
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Message is in Reply To:
 | | RE: Tasks in RCX
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| (...) That highly depends on the programming environment, and the skills and preferences of the programmer. Thread creation and management is very easy in Java, and therefore, Java programmers tend to use threads more liberally for example. Dozens (...) (25 years ago, 21-Dec-99, to lugnet.robotics)
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