Re: Ichbiah 2022 compiler mode

On 2024-09-12 7:46, Randy Brukardt wrote:

"Niklas Holsti" <niklas.holsti@tidorum.invalid> wrote in message
news:lk3fsvF7aaaU1@mid.individual.net...
...

I disagree with Randy's view that tasks and "parallel" are much
overlapping. Tasks are able to communicate with each other, but AIUI
parallel tasklets are not meant to do that, and may not be able to do
that. Tasks can have different priorities; tasklets cannot.

 I was (of course) presuming that "tasklets" would get those capabilities if
they were to replace tasks. That's what I meant about "suspension", which is
not currently allowed for threads in Ada (parallel code is not allowed to
call potentially blocking operations). If that was changed, then all forms
of existing task communication would be allowed.

Ok, I understand. In that case, what "parallel" adds to the current tasking feature is an easy way to create a largish and perhaps dynamically defined number of concurrent threads from a "parallel" loop, where the threads are automatically created when the loop is started and automatically "joined" and destroyed when the loop completes.
I don't mind at all if a future Ada evolution merges tasks and "parallel", although it might defeat the easier access to multi-core true parallelism that is the goal of the "parallel" extension, AIUI.

I'm less certain about the value of priorities, most of the time, they don't
help writing correct Ada code. (You still need all of the protections
against race conditions and the like.) I do realize that they are a natural
way to express constraints on a program. So I admit I don't know in this
area, in particular if there are things that priorities are truly required
for.

Priorities (or the equivalent, such as deadlines) are absolutely required for real-time systems where there are fewer cores than concurrent/parallel activities so that the system has to schedule more than one such activity on one core.
If Ada did not have tasks with priorities, most of the Ada applications I have worked on in my life would have had to avoid Ada tasking and retreat to using some other real-time kernel, with ad-hoc mapping of the kernels's threads to Ada procedures.
Despite the transition to multi-core processors, I think that there will continue to be systems where scheduling is required, because the number of concurrent/parallel activities will increase too.