2 Sep
2006
2 Sep
'06
7:58 p.m.
On Saturday 02 September 2006 09:50 pm, Chuck Guzis wrote:
On 9/2/2006 at 7:34 PM Jim Battle wrote:
I'm not at all up on the details of the differences between different
representations of floating point numbers, and I fully realize that there
_are_ differences and that there are tradeoffs -- just like with any other
bit of engineering. And to "standardize" on one particular implementation
without allowing for any choices and without allowing for how other choices
might be better in some situations strikes me as being a really bad idea.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
Why do we need a floating-point arithmetic
standard?
http://www.cs.berkeley.edu/~wkahan/ieee754status/why-ieee.pdf
It includes some tables of the features of FP arithmetic of various
mainframe architectures, plus some handheld calculators, and the hp-85.
Interestingly, it mentions the proposed IEEE standard, as implemented
by the intel 8087 and the motorola 6839.
I started reading this--and then realized that I'd seen this before--20
years ago! I wasn't happy with it then, and my feelings still haven't
changed much. Boiled down to it's basic message "because it's somewhat
better for portability" didn't do much for me back then and does even less
for me now, when the choice of deployment architectures seems to have
boiled down to a precious few.
What the IEEE standard doesn't address--and this is where most numerical
programmers get their shorts in a twist is the differences used in
computation of the transcendental functions. Some implementations are
really good--and some, such as that on S/360 FORTRAN IV is horrible.
AFAIK, Lawrence Livermore didn't use ANY vendor's math function pack, but
wrote their own and deployed it on all of their machines--and it was much
better than anything they could buy.