On Mon, 2004-10-11 at 02:49, Robert Snyder wrote:
> I dont see it passing any -O3 commands to the compilier. As I watch it
> go passing by.
> The defualt cflags for Portage when compiling are "-O2 -march=pentium4
> -fomit-frame-pointer" Now I have noticed when using a gui front end like
> porthole that at the bottom they do list additional flags that the
> piticular ports mantainer decided to use extra usually you see thing
> like mmx and sse flags but never seen the -O3
Okay, maybe the package offers SSE support.
That's fine for gaming, but for scientific/engineering, do _not_ use SSE
on a Pentium 3/4! Trust me on this.
> But things are stable and "FEEL" slightly faster. I will emphansize
> "FEEL" because I have no hard proof that it is faster.
If SSE is being liberally used where it shouldn't, which I've seen a few
packages do not, then I don't doubt it.
You should _never_ use SSE for double-precision floating-point on a
Pentium 3/4 when you need accuracy. It's lossy and inaccurate by a
significant number of digits.
The P3/4 SSE pipes were designed to be fast, not accurate.
Most people don't know this until they get major error in a calculation.
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