Re: Ichbiah 2022 compiler mode

["J-P. Rosen" <rosen@adalog.fr>]

Le 12/09/2024 à 06:46, Randy Brukardt a écrit :
> 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.
Well, tasks are not only for speeding up code. They can be a very useful 
design tool (active objects, independant activities). I think the Ada 
model is clean and simple, I would hate to see it disappear.

> 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.
If you had as many cores as tasks, you would not need priorities. 
Priorities are just optimization on how to manage cores when there are 
not enough of them.
I know that people use priorities to guarantee mutual exclusion, and 
other properties. All these algorithms were designed at the time of 
mono-CPU machines, but they fail on multi-cores. Nowadays, relying on 
priorities for anything else than optimization is bad -and dangerous- 
design.
-- 
J-P. Rosen
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