Re: Ada and real-time

[cis.ohio-state.edu!zaphod.mps.ohio-state.edu!darwin.sura.net!cs.ucf.edu!c rigler@ucbvax.Berkeley.EDU (James Crigler)]

The summary says it all.  No one has mapped Ada tasking constructs
to _general_purpose_ hardware.  As I recall (don't have my LRM handy),
the language is required to execute tasks AS IF THEY WERE EXECUTING ON
SEPARATE CPU's.  This does not map directly on to any general purpose
hardware that I know of.  I've often wondered why.  Any compiler gurus
care to enlighten the universe (or are we back to the days of DP-priests
in white coats? :-).

The Ada compilers with which I've worked closely (Alsys 80286, Tartan
C30) have a large run-time penalty imposed by using the language's
tasking.  In the 2 Alsys-80286 jobs, the overhead was within
acceptable limits (the requirement was for soft real time (I bet
that raises some heckles :-)); the Tartan C30 (TI 320C30) compiler
was unable to mix interrupt handling with tasking under our timing
constraints, so we wrote procedural code called from the interrupt
handler (the requirement was for hard real time).

Jim Crigler
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