my crude benchmark results

Wed Jul 14 02:32:00 GMT 2004

I was of the understanding that -ffast-math in the normal C compilation
world was generally a bad idea unless one knows what one was doing:
From gcc's man page:
> -ffast-math
> Sets -fno-math-errno, -funsafe-math-optimizations, -fno-trap-
> ping-math, -ffinite-math-only and -fno-signaling-nans.
>> This option causes the preprocessor macro "__FAST_MATH__" to be
> defined.
>> This option should never be turned on by any -O option since it can
> result in incorrect output for programs which depend on an exact
> implementation of IEEE or ISO rules/specifications for math func-
> tions.

like floating point operations needing to come out with correct
answers ;), ie, it's ok one is doing a problem that is dealing with
positive integers or some carefully designed number theory problem, etc.
But,
On Tue, 2004年07月13日 at 13:45 -0400, Bryce McKinlay wrote:
> But, theres another option you should know about. With --fast-math 
> (which causes the Math.* calls to be inlined directly into FPU 
> instructions), the performance improves dramatically:

From the sounds of it, --fast-math as an option to gcj is something else
entirely. If so, 
a) that's very cool
b) that's very confusing
AfC
Sydney
-- 
Andrew Frederick Cowie
OPERATIONAL DYNAMICS
Operations Consultants and Infrastructure Engineers
http://www.operationaldynamics.com/
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