In article <3f94a116$1@news.povray.org> , "Jenna Olson" 
<wan### [at] comcastnet> wrote:

> POV Ray compiled with IBM's xlC V6.0 BETA compiler
> (switches -qarch=ppc970 -qtune=ppc970 -qalign=natural -O3)

Note that -O3 is _not_ the maximum optimisation setting for IBMs compiler.
The maximum is -O5.  Also note that the default architecture/tuning will be
automatically selected to be correct for the architecture you are running
on, so if you compile on the G5, no need to tell the compiler to optimise
for it.  Also, you shouldn't be forcing unsuitable structure alignment on
the compiler, leaving it at the default for the core code files will be
best.

In any case, make sure you specify -qaltivec, -qnostrict, qfloat=nonans,
-qignerrno .  ALso, you may want to try profile guided optimisations on
texture.c .

> POV Ray compiled with gcc3.3 as part of fink distribution (no
> optimizations):

I think there is something wrong with these results if the compiler is
indeed gcc.  Most likely the cause is that the ppc970 option (instead of the
ppcv option) for xlc just like the mpowerpc64 option for gcc generates 64
bit code rather than 32 bit code.  Hence, with a heavily memory dependent
program like POV-Ray, you will always see a significant loss of performance
when generating 64 bit code, especially with the plain 3.5 source code (but
that is another story).

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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