On Apr 16, 2009, at 5:57 PM, Kirk, Benjamin (JSC-EG311) wrote:
> So have you learned your lesson and gone to gcc-4.3.3 on OSX?
No way... GCC is horrifically slow on OSX. It takes _3_ times longer
to solve a problem compiled with GCC as opposed to Intel.... and
that's not doing anything fancy with the Intel compiler.
And that doesn't depend on which version of GCC at all. Currently,
I'm using GCC 4.4.0 (pre-release) with auto-vectorization.... it does
the best... but is still 2-3x slower than Intel. Really. I know it's
hard to believe... I didn't believe it for a long time either....
I've talked to Apple about this... and they don't understand either.
We first started investigating because Linux on the same machine was
twice as fast! For a long time we thought OSX was just a dog... but
it turns out to be some interaction between OSX and GCC....
Doesn't matter much though. Buying a few floating licenses of the
Intel compiler suite is chump change next to the Dual-quadcore 2.93GHz
Nehalem Mac Pro I just bought (yes, with hyperthreading it shows up as
having _16_ processors.... and actually acts like it has about 12-14
in it). ;-)