Re: GNAT & GCC performace (bad news)

[Geoff Bull <gbull@acenet.com.au>]

Harald Schmidt wrote:
 What I was expecting,
> because gnat isn't a compiler env. but a to-C(++) translator,
> the performance decrease about ten to twenty percent but
> not 50 percent.

Gnat is a true compiler. It does not translate to-C(++).

My experience is that, for equivalent code, Gnat produces code
that is as fast or slightly faster than C. This is not
surprising when one considers that Gnat and the Gnu C compiler
share the *same* backend code generator.
OTOH, my first Gnat program was about 100 times slower than the C
I had translated. Once I understood why (the C was buffering its IO,
the Ada was not) and made a few changes, the Ada version was a few
percentage points faster.

I suggest you look at your benchmarks to make sure they
are really equivalent.
Also, did you compile both with the same levels of optimisation
and turn off Ada's run time checks (in my experience, the latter
doesn't usually make an enormous difference, but it is worth a try)?

__
Geoff