Re: My machine is 64 bit, but does it think it is 32 bit?

On Mon, Oct 22, 2007 at 02:56:53AM -0500, Stephen Ware wrote:
> Hi Aurora group!

Hello!

> I've just recently downloaded Aurora and installed it on some old Sun
> Ultra 10's at my school in the hopes of making them into a cluster.
> The program I want to compile and run is called GAMESS, which is a
> quantum chemistry program that can run in parallel.  Because there is
> no pre-compiled version for SPARC, I am building it from source.  In
> the configuration process, I have to choose several options based on
> the operating system of the computer.  My first instinct was to choose
> "64 bit linux" since the Ultra 10 is a 64 bit machine, but as I was
> reading around online about other SPARC linux ports, I realized that
> perhaps some applications are running in 32 mode.  GAMESS is mostly
> fortran with a tiny bit of C, and I am compiling it from the command
> line.  Should I choose the 64 bit options, or the 32 bit option?

32bit code, unlike on x86, runs much faster than 64bit on SPARC. So
if you don't need to access large heaps of memory or if you don't need
64bit precision, then go for the 32bit option. It'll be faster.

Regards,
R.

-- 
Dominik 'Rathann' Mierzejewski <rathann*at*icm.edu.pl>
Interdisciplinary Centre for Mathematical and Computational Modelling
Warsaw University  |  http://www.icm.edu.pl  |  tel. +48 (22) 5540810
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