From: rracine@myremarq.com (Roger Racine)
Subject: Re: Apex vs GNAT on solaris
Date: 1999/12/07
Date: 1999-12-07T12:38:38+00:00 [thread overview]
Message-ID: <384cfdb3.691883075@newsnew.draper.com> (raw)
In-Reply-To: 82hnll$ahu$1@nnrp1.deja.com
On Tue, 07 Dec 1999 01:25:13 GMT, Robert Dewar <dewar@gnat.com> wrote:
>In article <82hiuj$74o$1@nnrp1.deja.com>,
> reason67@my-deja.com wrote:
>
>
>You need to say what options you are using for both compilers.
>We have sometimes found people making the *amazing* mistake
>of compiling GNAT with -O0. Generally the appropriate options
>for benchmarking are -O2 -gnatn.
>
>The options are critical, because otherwise you may simply
>be measuring differences in choices of default options. For
>example if one compiler inlines by default, the other one
>does not, then the comparison may be meaningless.
>
>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).
>
Is it a mistake to use the default options for a compiler? Many
people will assume that the default options are the most reliable
options. Others will assume that the default options are the best
options. The default options generally turn out to be the most
reliable because most people use them, and bugs will be discovered and
corrected sooner than those to be found using the non-default options.
The same can be said for tasking.
I have been hit many times by optimizer bugs, and generally assume
that the compiler vendors knows what they are doing when the defaults
are created. They are giving what they think should be the most
common values for the options.
Roger Racine
next prev parent reply other threads:[~1999-12-07 0:00 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-12-07 0:00 Apex vs GNAT on solaris reason67
1999-12-07 0:00 ` reason67
1999-12-07 0:00 ` Robert Dewar
1999-12-07 0:00 ` reason67
1999-12-08 0:00 ` Robert Dewar
1999-12-08 0:00 ` reason67
1999-12-07 0:00 ` Vladimir Olensky
1999-12-07 0:00 ` Vladimir Olensky
1999-12-09 0:00 ` Geoff Bull
1999-12-09 0:00 ` Vladimir Olensky
1999-12-09 0:00 ` Vladimir Olensky
1999-12-10 0:00 ` Vladimir Olensky
1999-12-07 0:00 ` reason67
1999-12-07 0:00 ` reason67
1999-12-07 0:00 ` Robert Dewar
1999-12-07 0:00 ` reason67
1999-12-07 0:00 ` reason67
1999-12-07 0:00 ` reason67
1999-12-07 0:00 ` reason67
1999-12-07 0:00 ` Robert Dewar
1999-12-07 0:00 ` reason67
1999-12-08 0:00 ` Robert Dewar
1999-12-08 0:00 ` reason67
1999-12-08 0:00 ` Robert A Duff
1999-12-08 0:00 ` Robert Dewar
1999-12-08 0:00 ` Larry Kilgallen
1999-12-07 0:00 ` Roger Racine [this message]
1999-12-07 0:00 ` Larry Kilgallen
1999-12-07 0:00 ` Samuel T. Harris
1999-12-07 0:00 ` David Starner
1999-12-08 0:00 ` Robert Dewar
1999-12-07 0:00 ` Jean-Pierre Rosen
1999-12-08 0:00 ` Ted Dennison
1999-12-08 0:00 ` Robert Dewar
1999-12-08 0:00 ` Robert A Duff
1999-12-08 0:00 ` Roger Racine
1999-12-08 0:00 ` Larry Kilgallen
1999-12-08 0:00 ` Roger Racine
1999-12-08 0:00 ` Larry Kilgallen
1999-12-08 0:00 ` tmoran
1999-12-09 0:00 ` Robert Dewar
1999-12-09 0:00 ` Roger Racine
1999-12-09 0:00 ` Larry Kilgallen
1999-12-10 0:00 ` Robert Dewar
1999-12-09 0:00 ` Mike Silva
1999-12-10 0:00 ` Robert Dewar
1999-12-16 0:00 ` Stefan Skoglund
1999-12-07 0:00 ` reason67
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