[Beowulf] Athlon64 / Opteron test

[Greg Lindahl]

On Fri, May 14, 2004 at 11:49:34AM -0400, Robert G. Brown wrote:

> rgb at s02|B:1003>./Ospin
> -bash: ./Ospin: /lib/ld-linux.so.2: bad ELF interpreter: No such file or directory
> rgb at s02|B:1004>

Pilot error. You have to install a couple of additional rpms to run
32-bit stuff on an Opteron. The annoying thing about it is that they
have the same names as x86_64 packages, grrrr. In this case you need
glibc-*.i686.rpm.

> ...it also refers to anecdotal accounts that numerical performance
> significantly degrades if one runs i386 code compared to recompiled
> x86_64 code.

The hard thing about anecdotes is that they're hard to disprove.
However, if you look at SPECfp scores for Opteron using the Intel
compiler (32-bit mode) and the PathScale compiler (64-bit mode), I
don't think that you'd come to that conclusion. It is an apples to
oranges comparison: our compiler has a better optimization framework.
But the benefit from 64-bit mode is clearly moderate. I talk about it
in a recent ClusterWorld article.

-- greg