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Re: bizarre number transformation [message #31664 is a reply to message #31489]

Fri, 26 July 2002 07:39

Paul Van Delst[1]
Messages: 1157
Registered: April 2002

Senior Member

James Kuyper wrote:
>
> Craig Markwardt wrote:
>>
>> James Kuyper <kuyper@gscmail.gsfc.nasa.gov> writes:
> ...
>>> The point is, that it's pretty rare to need that many significant
>>> digits. There aren't many real-world numbers that can be measured to
>>> within one part in a billion. Precision needs like that can come up in
>
> ...
> [some examples where such precision is needed]
>> Admittedly those are pretty specialized applications :-)
>
> Precisely. I also do scientific programming, where such needs are pretty
> common. But the vast bulk of the world's programming involves numbers
> that can be represented with adequate accuracy using single precision
> floating point. For instance, how many million-dollar quantities are
> actually measured with a precision of +/-$1?

I would hope the answer is not any at all. I would think that 10th's of a US dollar/Euro
(or even 100th's) would be used. Exchange rates are usually quoted to 1000th's of a US
Dollar. This is all a hopeful thought on my part since my past and forecast number of
million dollar transactions is, unfortunately, zero.

> And how many people would
> actually care if such quantities were in error by $1 or two?

Depends how many transactions the error occurs in and whether it's a random or systematic
error. These little bits can add up to a lot. Which is sort of what this whole thread is
about in a way - cumulative numeric precision "errors".

paulv

--
Paul van Delst
CIMSS @ NOAA/NCEP/EMC Beer is good.
Ph: (301)763-8000 x7274 My wife.
Fax:(301)763-8545

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[Message index]

		bizarre number transformation By: merlecorp on Thu, 25 July 2002 04:46
		Re: bizarre number transformation By: R.Bauer on Mon, 29 July 2002 02:04
		Re: bizarre number transformation By: David Fanning on Fri, 26 July 2002 10:36
		Re: bizarre number transformation By: David Fanning on Fri, 26 July 2002 10:33
		Re: bizarre number transformation By: mperrin+news on Fri, 26 July 2002 10:14
		Re: bizarre number transformation By: Paul Van Delst[1] on Fri, 26 July 2002 07:39

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