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Re: How bad is fast-math?

Jean Francois Martinez <> writes:

> On Wednesday 30 May 2001 01:02, Michael Meissner wrote:
> > On Wed, May 30, 2001 at 12:25:50AM +0200, Jean Francois Martinez wrote:
> > > According to the doc fast-math generates incorrect code.   Has the
> > > situation changed?   In case it has doc should be updated, in case it
> > > hasn't name should be changed and become something derogatory since there
> > > are people who see the fast in fast-math and use it without further
> > > investigation.   It is being used in aLinux distribution and I have seen
> > > it recommended in a Linux magazine
> >
> > In general, it depends on what you consider the correct code to be :-)
> >
> > If your code never encounters infinities and denormals, and never passes an
> > out of range argument to an intrinsic function, then -ffast-math will
> > certainly generate faster code on some machines.  I can't say how well that
> > matches up with the numeric code out there.  I would imagine many codes
> > don't stray into these dark corners (but then again, many do go into that
> > territory).
> Use in glibc would be certainly foolish.   And I think it is being done.

If you think so, then send a bug report to the glibc folks.

But I'm convinced that glibc never uses -ffast-math.


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