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From: Robert Dewar <robert_dewar@my-deja.com>
Subject: Re: Apex vs GNAT on solaris
Date: 1999/12/08
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In article <82hokf$b9l$1@nnrp1.deja.com>,
  reason67@my-deja.com wrote:
> This is true. I was actually personally concerned with the
> defaults that both compilers used.

It is completely meaningless to measure GNAT at -O0. The basic
code generation technique used is designed to generate extremely
inefficient code at this level, in a manner which is often hard
to duplicate with a hand written code generator :-)

>From time to time we have discussed making the default -O2
-gnatn, *precisely* so that naive benchmarks run with default
options look better :-)

Seriously, you have to decide what you are doing here. If
you are measuring performance, then you need to make sure
you are selecting comparable levels of optimization.

If all you want to do is to find out the default options used
for optimization, then it is more efficient to simply read the
manuals to find this out, than to run meaningless comparisons
of times.

> > You also need to specify all other parameters. For instance,
> > if you are running tasking, make sure you are comparing
> > comparable underlying threads implementations, otherwise you
> > again have apples and oranges (e.g. which of the two threads
> > libraries did you use for GNAT).


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