Re: deallocation tasks

[Robert A Duff <bobduff@world.std.com>]

Alfred Hilscher <Alfred.Hilscher@icn.siemens.de> writes:

> What I want do is this: I have a loop that reads input and processes it.
> If the input is something that would require long runtime, I want create
> a new task so that it can run in background. But if the task terminates
> I think I should free the (heap) memory.
> 
> My code would look someting like this:
> 
> task type t is ...
> 
> type a_t  is access t;
>  
> n_t : a_t;
> ...
> 
> loop
>  -- get input
> 
>   if  -- input requires less time
>   then
>     -- consume it
>   else -- input requires much time, start background task
>     n_t := new a_t(input);  -- memory allocated here should be
> deallocated after task termination
>   end if;
> end loop;
> 
> 
> Any suggestions how to 'DEALLOCATE' the memory ? There can be more than
> one task at a time. Any other ideas ?

Read the RM rules about Unchecked_Deallocation.  If the task has no
discriminants, then it's safe to call Unchecked_Deallocation before
the task is terminated.  (Which seems strange to me.)  If it has
discriminants, then don't do that.

You can find out whether a task is terminated using 'Terminated, but
that generally requires some sort of busy waiting.

You could also consider having a single task, or a pool of several
tasks, that gets reused for each input-processing.  You probably don't
want to create 1_000_000 tasks if the input has 1_000_000 lines.

- Bob