Subject: Must g98 be compiled with pgf77

From: Elmar Gerwalin <[email-masked]>
Date: Wed, 05 Jul 2000 16:32:19 +0200

Here's a (short) summary of the about 20 answers I got:
(I edited them a bit)

The original questions were:

? Do I have to use the pgf77 compiler to install gaussian98 on a LINUX PC ?
? What happens after the trial period ?
( I don't want to buy a Fortran compiler, as there are free ones available
  and Gaussian itself was expensive enough ;-)   )
? What has to be done to use the g77 compiler (from my SuSE LINUX distribution) ?

---------- the answers: --------

Why pgf77?

*(Gaussian themselves:)  
  The only supported compiler on Linux for G98 is the PGF77 compiler.  We made 
  this choice because it gives good performance improvements over the public 
  domain compiler at a moderate price.  In terms of manpower and support we 
  need to choose one and this compromise seems the best.

*(Gaussian themselves again:) When we decided to switch to the PGI compilers, 
  it was not a decision we made lightly.  We found that performance was 
  typically a factor of two or more better than gcc/g77.  We weighed that 
  performance gain against the need to buy a compiler, and decided that the 
  benefits outweighed the costs. 

* (Gaussian ...:) You also have the option of getting a precompiled distribution. 
  This is a viable option for many sites where they primarily wish to run the code 
  as distributed and are not doing development.

* It's far the best compiler for LINUX (much faster than g77 or f2c)

What happens after the evaluation period ?
(members of the Portland group(pg): please ignore this part ;-)

Old versions of the pgf77:

* Dont worry. Install the PGI compilers and G98 will run OK even after the
  license expires

Actual evaluation version:( Version 3.1 of pgf77 )

* different from earlier trial versions executables compiled
  with it cease to work after the trial period, unfortunately.

* The compiled binaries will fail after the trial period!

* executables are deleted  after the trial period

So why not using another f77 compiler ?

* Problems are the files mdutil.F and mdutil.c.  
  There are a few changes .., depending on the revision of gaussian.

*  hand-edit the Makefile. I remember I once compiled g98 with g77, and
   for some reason I started from the Sun Makefile instead of the i386 Makefile.
   Then, you have to modify byteorder-specific things etc. You can get a flavour
   what has to be done if you compare the individual Makefiles coming along with
   g98....
  --> So in summary, if you are a decent hacker, no problem.

* No. It will compile quite happily with g77, with a few minor changes.

* I did it and it worked for redhat 6.1 (changes in bsd/i386.make)

What did I do ?

I didn't test another compiler yet(!),although the executables were 
deleted after 14 days...
I won't buy pgf77 therefore, I guess

-------end of summary ---------

Elmar