realtime design

Will Stuyvesant hwlgw at hotmail.com
Thu Oct 17 09:08:24 CEST 2002


> [Greg Ewing]
> ...a certain amount of *simulated* time, not actual 
> time...your simulator needs to have a notion of how much
> simulated time each operation takes, and keep track
> of it.
> 
> So, before going any further, the question which must
> be answered is: how accurately does the behaviour of
> the simulated system in simulated time have to reflect
> the behaviour of the real system in real time?

Yes indeed there are several approaches to simulation realtime.  What
I am working on is an academic project (with industrial partners
though) and I am not tied to existing methodology but free to 'invent'
something new.

Sorry I cannot show you much more since they have this disclosure
thing.  Also am busy today and I am also preparing a response to Tim
Daneliuk on this thread since it looks like he is on target too with
ideas.

Maybe you do know the CSP realtime book by Steve Schneider?  That also
covers realtime issues and our research is going in that direction.

One of my ideas was to drop the variables and logic for simulating
time and using *real time*.  It would not matter how much slower that
would be.  And it also would not matter if the 'rcall' function
described earlier in this thread would return timeouts more often than
in a real realtime system with a realtime OS.
But it looks like we found the limit of that approach already (also
see the posts by mr. Bieber on this thread).


'''
Simulations are like miniskirts, they show a lot and hide the
essentials.
                -- Hubert Kirrman
'''



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