Subject: Re: CCL:Good Fortran Compiler for computational science on PC?

From: "Walter E. Reiher III" <[email-masked]>
Date: Thu, 04 Jan 1996 22:05:08 -0800

Related issues have been raised here before, so I'm responding to the list:

At 09:18 PM 1/4/96 -0500, Taisung Lee <[email-masked]> wrote:
>     We are developing some quantum calculation codes.  According to our 
>test, the performance of Intel Pentium-100 is around 1/2-1/5 of an 
>IBM/RS6000 3CT (the same CPU as 590).  And, surely, Pentium is much much 
>cheaper.  According the last issue of Byte magzine, the PentiumPro-200 
>(P6), with SPECint92=~360, SPECFp92=~260), is as fast as IBM/RS6000 3CT.  
>But the problem comes, we don't any good Fortran90 compiler.  We just 
>tried Microsoft Fortran PowerStation 4.0.  It has very nice developer 
>interface and is quite easy to use.  However, it only compiles small test 
>programs; for big 'real' programs, we just got a lot of ridiculous errors.  
>Afer two weeks work, we returned it.
>
>    So, we want to know is there any computation chemist using PC as a 
>calculational power and can anyone suggest a good Fortran 90 compiler?
>
>    If there is any good Fortran90 compiler, it seems to us that PC can 
>be a much cheaper choice for scientists.

I've spent an inordinate amount of time over the past year and a half or so
fiddling around with PC FORTRAN compilers, and the bottom line, IHMO, is
that you'd better not count on them being like what you're accustomed to
under UNIX.  In general, PCs seem like a false economy to me.

There are two issues here:  the compiler and the operating system.

You don't mention which OS you're using, but MS FPS only runs under NT or
Win95.  If you're running Win95, or DOS/Win, that's the first thing to get
rid of.  Windows NT is a reasonable OS; many say OS/2 is also.  There are
also UNIXes available for Intel CPUs.  Just don't waste your time with a 16
bit OS like DOS or a hybrid 16/32 system like 95.
     Many 'big program' problems are related to trying to run in 16 bits or
tricking a 16 bit OS into looking like a 32 bit one.  How long has it been
since we're tried doing this with UNIX?  Years!  Who needs to go back to _that_?

On compilers, I've worked with three--Watcom, MS FORTRAN PowerStation 32
(predecessor to 4.0), and Absoft--and all of them have some problems for my
applications, which involve mixed FORTRAN and C programming and
interoperability with a MS Visual C++ graphics DLL.  Watcom had loads of
incompatibility problems and really poor tech support, but produces fast
code when you can make it work.  MS FPS also produces fast code and has a
nice development environment, but has surprisingly poor interoperability
with C.  I'm continuing to use Absoft, who has excellent tech support and C
interoperability but produces slow code on a Pentium and has some other quirks.
     Other compiler vendors I have not tried include Salford (a British
company; expensive compiler but it must be a 'real' one since all of Chem-X
builds under it), Microway NDP, and Lahey.
     BTW, I've only used these as FORTRAN 77's, not 90's.

If you don't need to worry about working with C and calling DLLs, life will
probably be easier for you.  It seems to me that FORTRAN really isn't taken
seriously by the compiler vendors--the emphasis is on C/C++.
     I was disappointed to learn this week that the FORTRAN on my
'reference' platform, the SGI, also isn't what it used to be.  Some switches
that I found valuable for finding bugs in old code on my old IRIX 5.2 system
are missing on my new IRIX 6.1 system (e.g., -trapuv and -u).

See the "SciTech Software for Science" catalog for a comprehensive list of
FORTRAN compilers and other technical software tools.  800-622-3345,
http://www.scitechint.com/scitech/.  I'm not affiliated with them.

Hope this helps...good luck.  I'd be interested in hearing the experiences
of others.

Wally
========================================================================
Walter E. Reiher III, Ph.D.                           [email-masked]
CompChem Innovations
P.O. Box 61056                                        voice 408-720-0240
Sunnyvale, CA 94088                                     fax 408-720-0378

---

From: Craig Taverner <[email-masked]>
Date: Fri, 5 Jan 1996 08:28:45 +0200 (GMT+0200)

> be a much cheaper choice for scientists.

We use PC's as computational tools extensively in crystallography, but we 
run them all (the computational ones that is) under LINUX for which f77 
is freely available (g77 and f2c), and we also have the NAG f90 compiler, 
which so far seems to compile fine with true fortran 90 programs, but has 
proved to be somewhat tricky with fortran 77 programs.  Unfortunately I 
have not used it nearly enough to give you any performance spec.'s or say 
whether it can cope with very large programs, but I should certainly 
expect it to be able to.

So far our experience with using Linux instead of Dos/windows has 
definitely demonstrated it to be more appropriate for computational 
work.

Contact NAG at:
           NAG Ltd                 NAG Inc
tel        +44 (0)1865 311744      +1 708 971 2345
fax        +44 (0)1865 311755      +1 708 971 2346
post       NAG Response Centre     NAG Response Center
           NAG Ltd                 NAG Inc
           Wilkinson House         1400 Opus Place
           Jordan Hill Road        Suite 200
           OXFORD                  Downers Grove
           United Kingdom          IL 60515-5702
           OX2 8DR                 USA
email      [email-masked]      [email-masked]
www        http://www.nag.co.uk
gopher     NAME=NAG Gopher Server, Type=1, Port=70, Path=1/,
           Host=www.nag.co.uk

This is straight from their magazine, verbatum.  I hope it's not 
overboard.

Cheers, Craig

"If God had meant us to be naked, we would have been born that way."

Craig Taverner
Structural Chemistry, University of the Witwatersrand, South Africa