🚀 go-pugleaf

In article <6@pzbaum.uucp> jimv@pzbaum.UUCP (Jim Valerio) writes:
>
>I believe that IEEE 854's permission to return an infinity or zero in the
>case of massive overflow or underflow, rather than IEEE 754's QNaN, was an
>attempt to correct a perceived mistake in the 754 exception handling.  If
>you need to choose a result here, I recommend returning the infinity or
>zero result, and not the QNaN.

754 machines return denormalized numbers for underflow ... not QNaN.
Massive overflow yeilds +- inf not QNaN. 0/0 yeilds NaN.
>
>I understand that there is a review of IEEE 754 coming up in the next few
>years.  Personally, I'm looking forward to arguing for a number of modest
>changes, including:
>   (1)	Replace subnormal/denormal numbers by a single value (call it epsilon
>	or infinitesimal), and define arithmetic underflow in terms of this
>	limiting value.
>   (2)	Remove bias adjusted results for trapped overflow and underflow, and
>	always return either infinity or epsilon when overflow or underflow
>	occurs.
>-- 

for 32-bit machines the subnormization process is a good thing (if one
cares about getting the right answer). For better or worse, most folks
don't care about getting it right; or if they do they use 64-bit math.

Kahan has been pitching a pre-substitution scheme. Those interested
should contact him for details.





Keith H. Bierman      |*My thoughts are my own. Only my work belongs to Sun*
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