From chemistry-request@ccl.net Wed Dec 11 14:18:15 1991
Date: Wed, 11 Dec 91 14:10:14 EST
From: G. Ravishanker <ravishan@swan.wesleyan.edu>
To: chemistry@ccl.net
Subject: F90 -> C
Status: R


Hi

I have seen a sudden increase in activity in this group related to Fortran
vs C. It is indeed interesting and I thought I will voice my opinion on
this too. I have been programming in both Fortran '77 and C for the past
several years. I try to keep all my scientific code in Fortran and others,
such as networking, input/output, parsing using lex and yacc in C. I
personally feel that this kind of separation builds on the strengths of
each language. 

Given that what we are trying to accomplish is a readable and modular
code, it is hard to justify writing a piece of well readable scientific
code in C. Since several of the users of that code are likely to be
Fortran programmers, what is readable in C may not be well readable for a
Fortran programmer. Regarding portability, I have found that several of
the well written C programs are indeed system dependent, however small the
system dependency may be. Same can be argued for Fortran too. One can
always write Fortran programs with minimal system dependency. Fortran '77
gives enough flexibility to organize your program to look like a
"structured program", if you wish to do that. You can write top-down
programs, go-to less programs and all that. Someone needs to explain this
to me clearly that structured programs are easier written in C than in
Fortran '77. The only major disadvantage is you cannot have recursive
subroutines in Fortran (some Unix machines even allow that), but how many
have we all written in our lifetime! (factorial, Tower of Hanoi and Eight
Queen problem....)

What has gotten us much more than anything else in Fortran code (other
than old spaghetti code) is the lack of bounds checking for arrays. Some
of the old Fortran programs used this to their advantage in manipulating
some scratch commons differently in different subroutines. But it stinks.
You run an MD simulation and burn 5 hrs of Cray time only to see that your
temperature in the common block got overwritten by the next to last member
of the previous array in the common block. C of course would not allow you
to do it (sometimes you can, in case of strings...)


Though I do not have many things in support of C in the above paragraphs,
I do a fair amount of code development in C, but I feel that it is more
appropriate for doing things other than developing scientific code. Once
you have put in all the strengths of C to develop a very good piece of
code, you have lost a fair amount of your scientific users. Thanks for
your attention.

Ravi