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RE: Objects, processes, and encapsulation
Gerald and all,
Your camera application sounds very interesting, as does your
real-time scheduler. I take it that means the "one real-time
thread" can really be more than one process?
My notion (run long ago in DOS) would be a simple loader
that could run multiple threads as independent programs,
communicating through channel-equivalents. It would
probably be even easier than DOS, since there really
aren't any system calls except pipes. If I had time
and funding I'd tinker with multiple, ALTing stimuli...
And add some "low priority" math stuff.
Larry
>From g.h.hilderink@xxxxxxx Tue Oct 9 12:23:17 2001
Reply-To: <g.h.hilderink@xxxxxxx>
From: "Gerald Hilderink" <g.h.hilderink@xxxxxxx>
To: "'Lawrence Dickson'" <tjoccam@xxxxxxxxxxxxx>, <IanPage99@xxxxxxx>,
<P.H.Welch@xxxxxxxxx>
Cc: <java-threads@xxxxxxxxx>, <ldickson@xxxxxxxxxx>, <occam-com@xxxxxxxxx>
Subject: RE: Objects, processes, and encapsulation
Date: Tue, 9 Oct 2001 21:21:15 +0200
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Currently, we are experimenting with RTLinux for building control
applications. We use RTLinux purely for its operating system resources
(network, windows, filesystem etc.). Our real-time control application
is build with our "CSP for C++" (CTC++) and runs on one real-time thread
(whatever that is?). CTC++ contains a real-time (nestable) scheduler and
runs on top of RTLinux. Other Linux threads are used for the Linux (soft
or non real-time) tasks that are related to the operating system. "CSP
for C++" (CTC++) is much easier to use than the multithreading (POSIX)
stuff for our control engineer students. The learning cycle for CTC++ is
much lower than learning and mastering POSIX. Special channels
communicate with the OS resources and the Linux tasks. These channels
use the rt-fifo's.
We use OO to model the software, but OO and C++ alone would easily
result in a sequential control application. Such sequential application
inherits all the disadvantages of a single thread of control. Control
applications are concurrent in many aspects. Multithreading breaks down
the clean OO principles, simply because POSIX is not OO (sorry Oyvind
for repeating this :)). CSP does match naturally with OO and CSP
encapsulates the (hard to get right) POSIX stuff.
Our experimental setup is a 2-degree camera setup that is controlled by
the RTLinux system whereby the images are seen over the internet.
Gerald.
> -----Original Message-----
> From: Lawrence Dickson [mailto:tjoccam@xxxxxxxxxxxxx]
> Sent: dinsdag 9 oktober 2001 17:53
> To: IanPage99@xxxxxxx; P.H.Welch@xxxxxxxxx
> Cc: java-threads@xxxxxxxxx; ldickson@xxxxxxxxxx; occam-com@xxxxxxxxx
> Subject: Re: Objects, processes, and encapsulation
>
>
> Don't be so gloomy Ian... If we can just get a WORKING
> MODEL over something like RTLinux we can show the world
> how easy it is to do things that are incredibly
> difficult in OO. Like sensors and robotics.
>
> I love the RTLinux model because it has the single
> bloated thread where you can do everything the
> gooey standard way... with our stuff underneath
> it, behaving rationally.
>
> Larry
>
> From owner-occam-com-out@xxxxxxxxx Tue Oct 9 04:28:08 2001
> From: IanPage99@xxxxxxx
> Date: Tue, 9 Oct 2001 07:27:31 EDT
> Subject: Re: Objects, processes, and encapsulation
> To: P.H.Welch@xxxxxxxxx
> CC: java-threads@xxxxxxxxx, occam-com@xxxxxxxxx
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>
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> In a message dated 08/10/2001 13:41:59 GMT Daylight Time,
> P.H.Welch@xxxxxxxxx
> writes:
>
>
> > It's strange what the Object Orientists have achieved ... they have
> > managed to make serial programming as dangerous as unconstrained
> > concurrent programming. .....
>
> Well said Peter. As usual of course, saying it is unlikely
> to make much difference to the progress of events (especially,
> as you say, this group is mostly about preaching to the already
> converted), but not saying it certainly won't!
>
> Cheers,
> Ian
>
>
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> Content-Type: text/html; charset="US-ASCII"
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>
> <HTML><FONT FACE=arial,helvetica><FONT SIZE=2>In a message
> dated 08/10/2001 13:41:59 GMT Daylight Time,
> P.H.Welch@xxxxxxxxx writes: <BR> <BR> <BR><BLOCKQUOTE
> TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT:
> 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">It's strange what
> the Object Orientists have achieved ... they have managed
> <BR>to make serial programming as dangerous as unconstrained
> concurrent <BR>programming. .....</FONT><FONT
> COLOR="#000000" SIZE=3 FAMILY="SANSSERIF" FACE="Arial"
> LANG="0"></BLOCKQUOTE> <BR></FONT><FONT COLOR="#000000"
> SIZE=2 FAMILY="SANSSERIF" FACE="Arial" LANG="0"> <BR>Well
> said Peter. As usual of course, saying it is unlikely <BR>to
> make much difference to the progress of events (especially,
> <BR>as you say, this group is mostly about preaching to the already
> <BR>converted), but not saying it certainly won't!
> <BR>
> <BR>Cheers,
> <BR>Ian
> <BR></FONT></HTML>
>
> --part1_158.22e1e50.28f43923_boundary--
>
>