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From: ted@grebyn.com (Ted Holden)
Newsgroups: comp.lang.ada
Subject: Ada tasking
Message-ID: <20075@grebyn.com>
Date: 25 May 90 04:18:36 GMT
Organization: Grebyn Timesharing, Vienna, VA
List-Id: <comp.lang.ada>


 
 
I must have been really tired the other night to have written the little
formula for saving Ada and not mentioned tasking;  sorry.
 
From: Jeffrey M. Schweiger, Naval Postgraduate School, Monterey CA
 
>In his book, Hoare does not seem to be very upset with Ada, either, just viewing
>it as unnecessarily complicated for his purposes.  Closing out a three page
>section on Ada, he writes (page 234):
>
>"Apart from the complexities listed in the preceding paragraph, tasking in Ada
>seems to be quite well designed for implementation and use on a multiprocessor
>with shared storage."
 
>Jeff Schweiger
 
Probably the DOD got to him somehow or other;  maybe put a horses head
in bed with him like in Godfather I ...  who knows;  made him promise to
say SOMETHING nice about Ada and the statement about semetrically
parallel machines (like the Sequent) was probably all he could think of.
Ada DOES run reasonably well on the Sequent, but I should mention the
following:
 
   1.  Neither I nor any of my friends OWNS a Sequent (they cost upwards
   of $50,000 and the top-end models go for around $800,000).
 
   2.  The problems mentioned by Ms. Edwards and others concerrning
   priorities of tasks are not solved by parallelism.
 
   3.  The Sequent is a bit on the HEAVY side of it for an embedded
   system, which is the original mandate of Ada;  kind of hard to fit
   one on an F16.
 
There are numerous other reasons why the notion of Ada tasking on
multiprocessors probably won't help YOU today or tommorrow.
 
 
From: Markku Sakkinen, University of Jyvaskyla, Finland
 
>Why _should_ Hoare have mentioned a baroque language that is not
>the least bit concerned about parallelism?
 
Why should any language BE concerned with parallelism?
 
Tasking is naturally an operating system feature;  the idea of tasking
as a part of a language is one of the dumber ideas since communism.
There's no right way to do it, as a careful reading of the 750 little
"problems" should make obvious to anybody.  In all truth, I can't really
believe that any of the serious people in this group who have read
through any of that would argue this point with me.  Probably what you
want to do is to define a standard set of features to be provided by
operating systems/real-time kernals for uses which involve tasking, a
standard set of function calls, and have libraries to provide these
functions to applications which need them.
 
 
Ted Holden
HTE