Re: compiler settings in AdaGIDE

[Ada novice <posts@gmx.us>]

On Jul 26, 12:57 am, jonathan <johns...@googlemail.com> wrote:
> On Jul 25, 2:29 pm, Ada novice <po...@gmx.us> wrote:
>
> > Many thanks for all these precious information. The settings
>
> > -gnatnp -O2 -march=native -ffast-math -funroll-loops
>
> > was only 1 s faster (1537 s) as compared to using
>
> > -gnatVa -O3 -gnatn -funroll-loops -gnatf -gnato
>
> Interesting result. I repeated the 100 calls to
> COMPLEX_EIGENVALUES.Eigen ( P, W, V, FAIL) test on a
> 121 x 121 sized matrix.
> I still get the same big decrease in running time from the
> -ffast-math switch.

Maybe what I have in my code is not affected by the -ffast-math
switch.


> On a high percentage of ordinary problems (usually data
> analysis) I would not care at all about the increased
> running time, and I would not remove the checks. There
> is another class of program I write and these run for days
> or weeks. These I never stop optimizing and testing, and
> all checks are removed!

I would prefer to keep the -gnatn.

> > 2. In the specification -march="machine architecture here", you use
> > native for the machine architecture. Does this apply to Intel
> > processors as well?
>
> I just checked the gcc man pages and found nothing at all about
> -march=native.  It helps a little on all the machines I've
> used and occasionally in the past it has helped enormously.  Just
> now I removed -march=native from the Generic_Complex_Eigenvalues
> test and running time went from 3.61 sec to 3.58 sec. When
> I remove it from the Jacobi benchmark, the program slows down
> slightly. So the switch seems to do something on my intel machine,
> but all I can say now is that the difference is very small and
> unpredictable.


Thanks for this information.

YC