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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: floating point comparison
Date: 1997/08/06
Message-ID: <dewar.870870067@merv>#1/1
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References: <mheaney-ya023680002907972345420001@news.ni.net>
 <33DF6F43.6EEA4806@digicomp.com> <5rqehs$g1r$1@odin.cc.pdx.edu>
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Organization: New York University
Newsgroups: 
 comp.lang.ada,sci.math.num-analysis,comp.software-eng,comp.theory,sci.math
Date: 1997-08-06T00:00:00+00:00
List-Id: <comp.lang.ada>


Wes says

<<I understand floating point well enough to compute with pencil &
paper the correct bit pattern for Pi (3.14159.....) in a VAX
D_FLOAT, but I have never seen IEEE 754.  Yet I almost always
treat floats "as if" they were "true" real numbers--and I have
NEVER had a bug traced to this "mistake".

I've worked with a lot of decent programmers whose degrees are in
English, History, EE, ME, .... and most of them could say the same.
I KNOW some of my colleagues have no clue how floating point numbers
are represented, yet still manage to produce working code.
>>


But how would you know it was working as expected? If you have not
done the numerical analysis required to ensure that the accuracy of
the results meets the specification, you are basically in the
hack-away-and-don't-worry-about-whether-it-works-if-it-looks-more-
or-less-reasonable-it-must-be-right mode.

Sure people write code in this mode all the time, and some of it works
by accident. But the cases in which people taking this kind of attitude 
to floating-point have created catastrophes are many!