[NetBehaviour] The trouble with rounding floating point numbers.

[Marcus Kirsch]

for sure a problem that, as the social impact of our machines is evident,
should be an issue of global concern.
The issue of where to round a number is equally an interesting one, never
have we been living in a world that is less black and white, yet the
tendency to ignore the greyscales is as much a genetic one as a concerning
one.

I am writing not from a pure programmers point of view, but as designer,
artist,researcher. parseInt(me)?
Or this one for a little story, a few Macromedia Flash versions ago, a bug
caused a movieclicp(graphic) to slowly shrink and eventually dissapear if
you would spin it with the command  grfx._rotation = grfx._rotation + 1
This was caused by rounding errors when rescaling then spinning grfx. It
might just as well have oversized it to infinity, yet it did the opposite.


marCus



> The trouble with rounding floating point numbers.
>
> So, Prudence, computers do make mistakes�
> By Dan Clarke.
>
> We all know of floating point numbers, so much so that we reach for them
> each time we write code that does math. But do we ever stop to think
> what goes on inside that floating point unit and whether we can really
> trust it?
>
> I hate to cast aspersions on its good name but when I hear stories of
> space craft crashing, inconsistent information on bank statements and
> pensioners being short changed (all of which have happened: see, for
> example, Risks Digest entries here and here), I start to realise that
> there is a real danger of misusing floating point numbers. Indeed,
> anyone with a few years of experience under their belt will probably
> have either had the pleasure of dealing with a floating-point related
> bug; or have watched a colleague slowly go crazy over one.
>
> Often, the underlying cause of such problems falls into common
> categories: a division by zero or a narrowing conversion that loses
> information. Other times however, it's not so evident � sometimes
the
> cause is the futile attempt of a software developer to round a
> floating-point number.
>
> That's right, one of the most basic operations in math, a thing that we
> learn to do before we can ride a bike, eludes the combined efforts of
> the finest engineers over the last 30 years. Of course, this is
> something that is intuitively nonsensical - why should it be impossible
> to round a floating-point number reliably?
>
> more...
> http://www.regdeveloper.co.uk/2006/08/12/floating_point_approximation/
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--
Marcus Kirsch
MA (RCA) Interaction Designer and Technoartist
London, UK

+44 (0) 7950 177633
marCus at resonancedesign.co.uk