Re: GNAT and Tasklets

[vincent.diemunsch@gmail.com]

Le mercredi 17 décembre 2014 22:08:33 UTC+1, Brad Moore a écrit :

>> I could understand that a Library level task (i.e. a task declared immediately 
>> in a package that is at lirary level) be mapped to an OS thread, but a 
>> simple local task should definetly not. 
>
> Why not? 

Because a thread is, in my understanding of an OS, an abstraction of a CPU. And
technicaly a kernel thread is a scarce ressource, because it needs to store data
inside the kernel, with a strong overhead because creating it, destroying it and
even using it is done through expensive kernel - process transitions.

A local task is a simple way to express parallelism in a part of an alogrithm inside a subrogram. It must be lightweight otherwise it is useless. And it is exactly the problem we encountered, for current compiler creates heavy kernel threads even for little tasks. Remember it was also my motivation at the beginning
of this post : to have a Library to do parallelism.

So I have a good response now, for I think you have very well solved the problem with your Library, that I will try to use !

But it remains the question of the Ada language : it is not acceptable that Ada
degenerates slowly into a low level langage, where we need to replace a task abstraction by 
- a procedure
- an access to that procedure
- the instanciation of a spawning mecanism, taking the access to subprogramm.
This is exactly the job of a compiler !

So the next step is to integrate the good job you made in your Library in a compiler...

Kind regards,

Vincent

 
and given good solutions for