y use fma if you have a PowerPC-based system with
<code>gcc</code> (or IBM <code>xlc</code>).  This includes all GNU/Linux systems for PowerPC and the older PowerPC-based MacOS systems.  Also
use it on PA-RISC and Itanium with the HP/UX compiler. 

<p>
Definitely do not use the fma version if you have an ia-32 processor
(Intel, AMD, MacOS on Intel, etcetera). 

<p>
For other architectures/compilers, the situation is not so clear.  For
example, ia-64 has the fma instruction, but
<code>gcc-3.2</code> appears 