Re: Ada and Unix--Blocked Tasks

[telesoft!rlk@uunet.uu.net (Bob Kitzberger @midnight)]

Many excellent points have been made on this thread in support of
the de facto practice of mapping multiple Ada tasks onto a single
Unix process -- increased efficiency, necessity due to the shared-
memory model of Ada task hierarchies, etc.  Of course, any serious
software system must make numerous tradeoffs, and I believe that we've
made the right ones.  The majority of developers would scream bloody
murder if a rendezvous took as long as a Unix context switch, which
is only one of the implications of a one-to-one mapping of Ada tasks
to Unix processes.

When Unix supports threads/lightweight processes (ref. current POSIX 
work), rest assured that you'll see Ada implementations taking full 
advantage of them.  Ada has just beaten Unix to the punch by five or 
ten years ;-)

As further data points, TeleSoft's MVS development system supports
the ability to map M tasks to N MVS processes.  Our Sun 3 and Sun 4 
development systems map all of the Ada tasks (within a single Ada 
program) onto a single Unix process.  Non-blocking I/O is provided for 
Text_IO.  Other than Text_IO, I recommend using an earlier poster's
fcntl() and SIGIO/Interrupt entry solution.

Thanks for the feedback indicating how strongly people desire a
stronger cooperation between Unix and Ada tasking.  if you have
specific requirements, I suggest that you contact your vendor's
marketing department... we honestly want to develop the tools
that engineers want, rather than take the moral high ground and
put forth edicts about how people must develop systems.

	.Bob.
	Software Engineer, Ada tasking
-- 
Bob Kitzberger               Internet : rlk@telesoft.com
TeleSoft                     uucp     : ...!ucsd.ucsd.edu!telesoft!rlk
5959 Cornerstone Court West, San Diego, CA  92121-9891  (619) 457-2700 x163
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