Re: Child vs nested package : efficiency matter

[Adam Beneschan <adam@irvine.com>]

On May 29, 5:56 am, Yannick Duchêne (Hibou57)
<yannick_duch...@yahoo.fr> wrote:
> Hillo,
>
> For some reasons, I've turned some nested package -- packages nested in  
> the body of package -- into a set of child packages instead.
>
> I've noticed the application's execution time is now an average of 125% of  
> that of the old implementation.
>
> The implementation did not changed otherwise and is still the same.
>
> What can make invokation of subprograms slower when the subprograms are in  
> a child package rather than in a nested package ?
>
> Note: this is with optimization enabled -- with -O -- and both old and new  
> implementation was compiled with the same options.
>
> I can't explain that and can't imagine a reason why. That's a mystery to  
> me.

I can't say anything about any particular compiler.  One possibility:
if procedure A calls procedure B, and A and B are in the same source,
a compiler may be able to put the code of B inline in procedure A's
code---i.e. the code for A will include B's code, rather than
including a "call" instruction.  If it does this, then in the process,
it may also to be able to eliminate instructions in B's code that have
no effect on A.  It's a lot harder to do this if A and B are in
different sources, which I'm assuming is happening if you are pulling
code out of a nested package and putting it in a child package.

Again, this is just a wild guess; without knowing anything about your
source, and with my limited knowledge of GNAT, I can't say anything
for certain.

                                       -- Adam