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From: dewar@cs.nyu.edu (Robert Dewar)
Subject: Re: Concurrency in Gnat 3.05?
Date: 1996/07/18
Message-ID: <dewar.837740961@schonberg>#1/1
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references: <4sjqte$3mu@masala.cc.uh.edu>
 <19960718.082642.172@satcom.whit.org> <4smktd$phu@masala.cc.uh.edu>
organization: Courant Institute of Mathematical Sciences
newsgroups: comp.lang.ada
Date: 1996-07-18T00:00:00+00:00
List-Id: <comp.lang.ada>


Spasmo says

"Well others did manage to do it, so I had assumed that GNAT
was the same.  Still it's a shame not having tasks that
time slice, I mean it doesn't really seem all that big a
deal to have tasking when they don't appear to run
concurrently.  Entries into them and all are allright,
but still without time slicing..."


That's quite wrong. Serious use of tasking for real-time programs
generally prefers to completely avoid time slicing. That is why the
requirement in the real time annex of Ada is that time slicing must
NOT occur using the default scheduling policy (FIFO_Within_Priorities).

Generally time slicing can be made available on many operating systems,
but it is a bit tricky in DOS, because of limitations in the operating
system. It certainly would be possible, but since it is not required (in
fact it is only permitted as an option), it is not a high priority item.

If what you want is effective concurrency between multiple threads, there
are many ways to achieve this in correctly programmed Ada. An Ada program
that depends on time slicing is non-portable.