Re: C/Ada performance comparison

["Marin David Condic" <marin.condic.auntie.spam@pacemicro.com>]

In general, I'd agree. However, there might be cases where this is not true.
If, for example, I'm doing a lot of computations in a tight loop over a
really large number of iterations, the constraint checking of numeric values
might add a considerable overhead. Imagine you write X := X + 1 ; That ought
to degenerate to a single add instruction with descent optimization, but if
you have to do the computation then check that you have not exceeded the
range of X's subtype and possibly do something to raise Constraint_Error,
that single instruction can expand to quite a few. Do that in a tight loop a
million times or so and you'll see some significant changes in performance.

Just for the record, turning off the checks should result in code just as
tight as what you'd get from a C compiler for a similar operation.

MDC
--
Marin David Condic
Senior Software Engineer
Pace Micro Technology Americas    www.pacemicro.com
Enabling the digital revolution
e-Mail:    marin.condic@pacemicro.com
Web:      http://www.mcondic.com/


"Jeffrey Carter" <jeffrey.carter@boeing.com> wrote in message
news:3B424298.9A7849CF@boeing.com...
> Tomas Hlavaty wrote:
>
> Although one of the factors for programs to be equivalent is run-time
> checks, I would not expect them to give a factor of 7 difference.
> Suppressing Ada run-time checks usually does not reduce run times by
> more than about 10%.
>