Re: [BENCHMARK] AIM Independent Resource Benchmark results for kernel-2.5.44

[Jakob Oestergaard <jakob@unthought.net>]

On Mon, Oct 28, 2002 at 12:28:39PM -0600, Nathan Straz wrote:
> > 
> > The AIM7/AIM9 new_raph is broken code.  The convergence loop termination
> > conditional looks something like:
> >    if (delta == 0) break;
> > for a type "double" delta.  You ought to change that to be something
> > like:
> >    if (delta <= 0.00000001L) break;
> 
> I usually specify the compiler flag -ffloat-store and that fixes the
> issue for me.  

Maybe that will work as a work-around.  But it is nothing but a
work-around. The previous poster was right - the code is broken.

The "==" operator usually doesn't have any reasonable use on floating
point values (yes there are cases where it makes sense, but this is not
one of them).

A result from any computation on double values cannot be assumed to
"equal" anything in particular. Zero included.

The correct way to terminate that loop is, like was already suggested,
doing a comparison to see if the residual is "numerically zero" or
"sufficiently zero-ish for the given purpose". Eg.  "delta < 1E-12" or
eventually "fabs(delta) < 1E-12".

Comparing to zero makes *no* sense.  It's written by someone who has no
understanding of numerics (or perhaps just didn't think clearly at that
moment - /me trying not to insult more people than strictly necessary ;)

-- 
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:   jakob@unthought.net   : And I see the elder races,         :
:.........................: putrid forms of man                :
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