Re: [Groff] Floating point arithmetic in groff

[Miklos Somogyi]

On 07/02/2006, at 11:06 PM, Bruno Haible wrote:

> Werner Lemberg wrote:
> > I then hesitated to add it to groff because it adds code which
> > produces platform-dependent results, .... the
> > situation has become much better, and today most of the IEEE
> > implementations appear to work fine.
>
> Results of elementary and transcendental functions are still far from 
> being
> platform-independent today:
>   - The x86 compatible processors perform many 'double' computations 
> with
>     64 bits of precision, instead of 53 bits as in IEEE. After 
> rounding,
>     this manifests through changes in the last mantissa bit.
>   - The file listing the maximum deviation of the transcendental 
> function
>     results from the exact values in glibc (called
>     glibc/sysdeps/i386/fpu/libm-test-ulps) is updated occasionally,
>     when new processor versions from Intel or AMD are published.
>   - The behaviour of floating-point division by 0 or of floating-point
>     overflow is platform dependent: On Linux/alpha these yield an 
> exception
>     (SIGFPE) by default, whereas on Linux/x86 they yield a NaN and 
> Infinity
>     value, respectively.
>
> > (see http://www.math.utah.edu/pub/hoc/)
>
> The comments in hoc-7.0.6.beta/chkieee.c and the #ifdefs in the rest 
> of this
> package also indicate that there are major portability problems.
>
> TeX had platform-independent output as a design goal; I believe this 
> is still
> as important as it was 25 years ago.
>
> Bruno

Yes, I agree that portability is important and that there are some 
problems.
However, I'd like to add a quote from the father of operator calculus, 
Oliver
Heaviside, an engineer, strongly criticized by mathematicians 'cause of 
his
not too strict adherence to the way of the mathematician:

"Why should I refuse a good dinner simply because I don't understand the
digestive processes involved?"

:-)

Miklos