Re: GCC beaten by ICC in stupid trig test!

[Robert Dewar <dewar at gnat dot com>]

Joe Buck wrote:

> On Tue, Mar 23, 2004 at 10:32:13PM -0500, Robert Dewar wrote:
>
> > Well I don't know exactly what stuff is in -ffast-math, but I suspect it 
> > is a mistake to just think in terms of rounding error vs the mantissa 
> > length. 
>  
> Most of the optimizations have to do with ignoring the need to distinguish
> +0 and -0, or handle NaNs.
>
> > For example, if -ffast-math is so sloppy as to consider
> > that (a+b)+c can be replaced by a+(b+c), then all bets are off.
>
> That's why -ffast-math doesn't do that; such a transformation would be
> massively brain-damaged.

It would be a useful achievement in this thread if everyone understood
the truth of the above sentence. Clearly that is not the case from other
contributions to the thread :-)