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From: tmb@bambleweenie57.ai.mit.edu (Thomas M. Breuel)
Newsgroups: comp.lang.fortran
Subject: Re: Missing the whole point (the Fortran vs. C debate)
Message-ID: <TMB.90Dec2200247@bambleweenie57.ai.mit.edu>
Date: 3 Dec 90 01:02:47 GMT
References: <28548@usc> <7552@lanl.gov>
Sender: news@ai.mit.edu
Organization: MIT Artificial Intelligence Lab
Lines: 45
In-reply-to: jlg@lanl.gov's message of 1 Dec 90 21:47:11 GMT

In article <7552@lanl.gov> jlg@lanl.gov (Jim Giles) writes:
   But the economics of computing still values speed over programmer time
   for most of the interesting problem domains.

This is the economics of computing for some people. If you pay
for your Cray time and if your programs take days to run even
on a Cray, then you may be concerned with speeding them up
by a factor of 2 or 3.

In our environment, we use workstations (and the Connection Machine).
Computer time is essentially free. For many applications, it makes
little difference to me whether my program finishes in 1 hour or 1
day, and if I have really serious number crunching to do, I can often
split up the work among a number of workstations. I think many
scientists are in similar situations.

It does make a significant difference, however, how long it takes me
to write the program in the first place, how long it takes me to debug
it, and how confident I can be that it is correct. If I really care
about efficiency, I can identify the short section of code that does
the real work with a profiler and help the compiler in generating
better code (using pragmas, etc.).

   In any case, I am in complete agreement that language designers
   should try to include features that promote more efficient coding
   and maintenance.  But so far, no language is widely available
   which does so AND is as efficient as Fortran-like languages.

The major opportunities for optimization that exist in FORTRAN and
that are absent in many other programming languages are ones that
result from assumptions about the lack of aliasing. These lead
to significant speedups only on machines with some kind of
parallelism.

You can easily add this as a pragma to a language like Modula or Ada.
In many languages, a compiler can also generate separate versions for
the aliased and unaliased case and use runtime dispatching. From a
purely technical point of view, opportunity for optimization is no
reason to stick with FORTRAN, since the difference to other languages
is slight.

From a practical point of view, it is, of course, true that in
most numerically oriented computing environments, FORTRAN compilers
generate the best code. But if you are using workstations, the
situation is often reversed.


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