Subject: Building g98A11.3 with 64-bit integers

From: Bryan Putnam <[email-masked]>
Date: Tue, 29 Oct 2002 12:30:49 -0500 (EST)

Has anyone had success in building g98A11.3 with large-file support, using
64-bit integers, on a Red Hat Linux (7.3) Pentium machine?  I understand
that only the 32-bit version of g98 is supported by Gaussian, Inc. on the
Pentium, which has a 32-bit architecture.

I have been successful in using large files (>2GB) in a small Fortran
program, compiled with pgf77 (ver. 4.0), and specifying
"-L/usr/pgi/linux86/liblf" on the link.  Therefore, I suppose getting g98
to handle files larger than 2GB on our system (actually larger than 16GB
since you can break up the RWF file into 8 pieces of 2GB) is simply a
matter of "tweaking" the g98 code and adjusting build options.

However, I'm beginning to think it might be a bit more complicated then
simply playing around with options such as

I8CPP = -DI64
I8FLAG = -i8 -r8
LIBS = -L/usr/pgi/linux86/liblf

since the resulting g98 Links immediately fail when run, although the
build does complete without errors.

Thanks for any advice or experience with this,
Bryan
--
Bryan Putnam, IT Research Computing Services
   Mathematical Sciences Building            Email: [email-masked]
   150 North University Street               Phone: 765.496.8225
   West Lafayette, IN 47907-2068               Fax: 765.494.0566
   http://www.purdue.edu/ITaP   http://www-rcd.cc.purdue.edu/~bfp/

---

From: Aaron Deskins <[email-masked]>
Date: Tue, 29 Oct 2002 14:56:57 -0500

Hello CCL'ers,
  I need some help damped molecular dynamics that I use in two programs. 
  The programs allow for specification of a friction coefficient and
time step. My questions are: 

1) What is a good strategy to reach the relaxed structure? My runs
either do one of two things. They either will eventually 'die' to zero
kinetic energy with little change in atom positions, or will slow down,
then oscillate and explode as the kinetic energy takes off. Ideally the
kinetic energy should die down as the relaxed structure is reached,
right? This isn't always the case. 

2) What are good strategies to decide the friction coefficient and time
step? I noticed that if the time step is too large, the kinetic
instabilities are common. 

thanks for any help.

Aaron Deskins
Purdue University