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From: gwyn@brl-vgr.ARPA (Doug Gwyn )
Newsgroups: net.physics
Subject: Re: VMS vs. Unix (timings)
Message-ID: <345@brl-vgr.ARPA>
Date: Tue, 26-Jun-84 20:45:32 EDT
Article-I.D.: brl-vgr.345
Posted: Tue Jun 26 20:45:32 1984
Date-Received: Sun, 1-Jul-84 02:55:27 EDT
References: <359@noao.UUCP>
Organization: Ballistics Research Lab
Lines: 24

I do not understand these (Fortran & C on UNIX & VMS) benchmark results.
I took the posted C source code and got execution time not much worse
than the reported VMS Fortran (single-precision) time.  More interestingly,
the C source code was written the way a Fortran programmer would write it;
doing the obvious things that an experienced C programmer would have done
in the first place doubled the speed of execution, placing the UNIX C
version well ahead of even the reported VMS Fortran times:

	Using BRL UNIX System V emulation on 4.2BSD, VAX-11/780
	with FPA:

	C code as posted	38.1 sec user time, 1.4 sec system time

	proper C code		18.9 sec user time, 0.9 sec system time

I think the moral is:  "Do not believe benchmarks unless you control them."
A secondary moral is that professionally-written C code can be as fast as
the machine will allow (give or take a few percent improvement possible by
tweaking assembly language), so that the language performance argument made
in favor of Fortran is bogus.  I would love to see a Fortran programmer
take some of my favorite C code using linked data structures and make it
work at all using Fortran, let alone work well.  (I used to do this sort
of thing before C became available, and it is really hard to do right in
portable Fortran.)