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Date: 15 Oct 92 14:41:35 GMT
From: cis.ohio-state.edu!news.sei.cmu.edu!jbg@ucbvax.Berkeley.EDU  (John Gooden
ough)
Subject: Re: Ada and real-time
Message-ID: <1992Oct15.144135.24045@sei.cmu.edu>
List-Id: <comp.lang.ada>

In article <1992Oct14.143733.842@saifr00.cfsat.honeywell.com>,
walls@saifr00.cfsat.honeywell.com (Gerald Walls) writes: 

|> determinism is very important.  we've ditched Ada's nondeterministic
|> task and have instead implemented our own, deterministic tasking.
|> 
|> Ada's tasking is not suitable for embedded real-time systems.

By "non-deterministic tasking" do you mean the fact that it can be difficult
or impossible to write down a timeline for a set of Ada tasks, given
variations in execution times and the effect of preemption?  If so, this is
not, in itself, sufficient reason to conclude that Ada tasking is unsuitable
for embedded real-time systems.  

These issues are discussed in the paper "Real-time Scheduling and Ada" in the
April 1990 issue of COMPUTER magazine.  In essence, the paper shows how rate
monotonic theory allows you to ignore the "non-determinism" of Ada tasking by
showing whether each task will get enough compute time to meet its deadline.
The theory has been used on delivered embedded systems, so it is actually
applicable to real systems, and it is being used on real-time systems that are
using Ada tasking in its "non-deterministic" sense.

John B. Goodenough					Goodenough@sei.cmu.edu
Software Engineering Institute				412-268-6391