Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!snorkelwacker!spdcc!esegue!compilers-sender
From: ok@goanna.cs.rmit.OZ.AU (Richard A. O'Keefe)
Newsgroups: comp.compilers
Subject: Re: Intermediate Representation
Keywords: optimize, C, Fortran
Message-ID: <3582@goanna.cs.rmit.oz.au>
Date: 20 Aug 90 02:00:02 GMT
References: <1990Aug07.153407.8877@esegue.segue.boston.ma.us> <250@cadlab.sublink.ORG>
Sender: compilers-sender@esegue.segue.boston.ma.us
Reply-To: ok@goanna.cs.rmit.OZ.AU (Richard A. O'Keefe)
Organization: Comp Sci, RMIT, Melbourne, Australia
Lines: 25
Approved: compilers@esegue.segue.boston.ma.us

In article <250@cadlab.sublink.ORG>, staff@cadlab.sublink.org (Alex Martelli) writes:
> marti@antares.inf.ethz.ch writes:
> ...and don't forget Fortran... (see my msg of today in comp.lang.fortran-
> f2c + Sun's cc produce code which runs almost twice as fast as Sun's
> f77, for a strictly numerical code -2d complex fft- on a Sparcstation 1!).

On reading this I immediately went and converted a small numerical code
from Fortran to C and ran it on an Encore MultiMax (NS 32532 processors)
running UMAX V 2.2M.  The f77 and cc compilers on that machine do not appear
to be ATT or Berkeley derived; the f77 compiler in particular is described
as "an advanced, optimizing compiler".  The code didn't exploit any of the
micro-tasking or parallel features of Encore Fortran or Encore C, and no
special declarations ('register' or the like) were used.  Both used double
precision.  Result:  the C code ran twice as fast (4 seconds / 8 seconds).

The Fortran code used 2D arrays.  The C code used 1D with strength reduction
(a standard optimising technique) done by hand, and indexing replaced by
pointer increments (also a standard technique, and the NS32532 doesn't use
auto-??crement addressing) by hand.  f2c starts to sound interesting...

So it wasn't just Sun.  (I say "wasn't" because as the original poster
pointed out, Sun have some new compilers.)
-- 
Send compilers articles to compilers@esegue.segue.boston.ma.us
{ima | spdcc | world}!esegue.  Meta-mail to compilers-request@esegue.