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Mail Archives: cygwin/1996/11/25/20:58:46

From: khan AT xraylith DOT wisc DOT edu (Mumit Khan)
Subject: Re: Maths ruined when optimizing in gcc
25 Nov 1996 20:58:46 -0800 :
Sender: daemon AT cygnus DOT com
Approved: cygnus DOT gnu-win32 AT cygnus DOT com
Distribution: cygnus
Message-ID: <9611260416.AA08499.cygnus.gnu-win32@modi.xraylith.wisc.edu>
Original-To: setzer AT rsdws3 DOT herl DOT epa DOT gov
Original-Cc: "Pedro A. Aranda =?iso-8859-1?Q?Guti=E9rrez?=" <paag AT tid DOT es>,
gnu-win32 AT cygnus DOT com
In-Reply-To: Your message of "Mon, 18 Nov 1996 10:09:27 EST."
<Pine DOT GSO DOT 3 DOT 95 DOT 961118100251 DOT 13871A-100000 AT rsdws3>
Original-Sender: owner-gnu-win32 AT cygnus DOT com

Woodrow Setzer <setzer AT rsdws3 DOT herl DOT epa DOT gov> writes:
> On Fri, 15 Nov 1996, Pedro A. Aranda [iso-8859-1] Guti=E9rrez wrote:
> 
> > ...
> > When I compile WITHOUT optimization, floating point
> > ops are ok. If I dare do any optimization, I always
> > get all sorts of errors.
> >=20
> > Has anyone experieced a similar thing?
> 
> This may be related.  I am working with an f2c-converted version of
> dmngb.f, one of the routines for optimization from the ATT PORT library.=20
> It compiles and works OK using gcc 2.7.2.1 under Solaris 2.3 on a Sun
> Sparc 20 using the option -O.  Under cyg-win32 and the same option, the
> code compiles and runs without compile-time or run-time errors, but I get
> the wrong answer.  If I omit the -O flag on the compiler invocation under
> cyg-win32, I get essentially the same answer as I do on the Sun.=20
> 
> --

Another data point here. I'm in the process of testing g77 port to 
cygwin32 (it was quite simple once I figured out the right flags to
libfI77) and the big gotcha is the every time I use -O, some of the
programs produce NaNs all over the place! Haven't been able to pin
point where it happens yet, but hopefully soon.

Anybody have a short program that screws up the numerics with -O? If
so, please email it me (if fortran, then either original or f2c'd will
do fine).

regards,
Mumit -- khan AT xraylith DOT wisc DOT edu
http://www.xraylith.wisc.edu/~khan/

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