Question about gcc optimisation ...

Article View: gnu.gcc.help

Article #50734

#50734

From: Sam Waugh
Date: Tue, 17 Aug 1993 07:02

22 lines
1619 bytes

Hi.

Sorry if this is a common question.  I've been running some code using the
2.4.5 version of gcc (AIX RS/6000).  The code is a specialised neural network
which uses arrays, floating point arith. and the random number generator.  My
problem is that I get different results with the optimised code to those from
the unoptimised code.  I'd like to know whether this is a problem with my
coding (quite possible :-) or just a difference between the compiling
options which may be altering the results slightly but correctly.

I have set the -ffloat-store flag when checking the optimised compilation,
and I was wondering if there are any other features that may tweak the
code a bit to get that extra performance, that may be affecting the results.

Thanks for any help.

Sam.
--
Sam Waugh
Department of Computer Science
University of Tasmania
email: waugh@cs.utas.edu.au

Technical Details

Message-ID: <waugh.745570979@probitas>

Path:

arc1-ca.pugleaf.net!gmd.de!xlink.net!howland.reston.ans.net!europa.eng.gtefsd.com!uunet!munnari.oz.au!newsroom.utas.edu.au!probitas!waugh

Show Full Headers

Complete Article Headers

X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 11318c,354d9b089738a8b6,start
X-Google-Attributes: gid11318c,public
X-Google-ArrivalTime: 1993-08-17 01:05:58 PST
Newsgroups: gnu.gcc.help
Path: arc1-ca.pugleaf.net!gmd.de!xlink.net!howland.reston.ans.net!europa.eng.gtefsd.com!uunet!munnari.oz.au!newsroom.utas.edu.au!probitas!waugh
From: waugh@probitas.cs.utas.edu.au (Sam Waugh)
Subject: Question about gcc optimisation ...
Message-ID: <waugh.745570979@probitas>
Summary: Differences in results from gcc optimised and unoptimised -- worry?
Keywords: gcc, optimisation, differences in results
Sender: news@newsroom.utas.edu.au
Organization: University of Tasmania, Australia.
Date: Tue, 17 Aug 1993 07:02:59 GMT
Lines: 22