Re: Distributed Computing in Ada

[Robert A Duff <bobduff@shell01.TheWorld.com>]

"Jeffrey R. Carter" <spam.jrcarter.not@spam.acm.org> writes:

> Robert A Duff wrote:
>> Well, not exactly the "original" design -- Annex E was not present in
>> Ada 83, and was added in Ada 95.
>
> Ada 83 had support for distribution. Tasks may run on separate
> processors; these processors need not all be part of the same
> computer.

Well, sort of, but not in a practical way.  Ada tasks share memory, and
there's no way to tell which variables are shared.  "Distributed" means
no shared memory.

I actually implemented such a system for Ada 83, where tasks could run
on different computers.  But there were some severe restrictions on
shared variables.  Terminate alternatives are "interesting" in that
context.

>...There was no language-defined way to specify which tasks run
> on which processors, but that's true with Annex E, too.

Yes.  But with Annex E there is a requirement that the implementation
provide some such mechanism.

- Bob