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Re: Inaccuracies [message #5304 is a reply to message #5303]

Tue, 14 November 1995 00:00

lpmix
Messages: 2
Registered: March 1994

Junior Member

In article <30A7BC4D.7018@cdc.noaa.gov>, Andy Loughe <afl@cdc.noaa.gov> wrote:
>
>
> TRIAL #1
> ========
> IDL> a = findgen(15)*.2 - 1.4
> IDL> print, total(a)
> 7.15256e-07
Stuff deleted***********
>
> Maybe I am missing something here, but this kind of behavior
> makes IDL a bit problematical for scientific use. With only 15
> numbers and double precision arithmetic, I can't believe this
> would fail in FORTRAN or C!
>
> --
> Andrew F. Loughe (afl@cdc.noaa.gov)
> University of Colorado, CIRES * Campus Box 449 * Boulder, CO 80309
> phone: (303) 492-0707 fax: (303) 497-7013

Try
IDL> a = findgen(8)*0.2
IDL> a = [-rotate(a(1:*), 2), a]
IDL> print, total(a, /double)
0.0000000
I'm not sure what you want to do, but expecting perfect math with
floats is not generally possible.

Paul
============================================================ ==================
L. Paul Mix
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Computational Electromagnetics and Plasma Physics Department

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[Message index]

		Re: Inaccuracies By: C R Shaw on Thu, 16 November 1995 00:00
		Re: Inaccuracies By: Hermann Mannstein on Thu, 16 November 1995 00:00
		Re: Inaccuracies By: wclodius on Wed, 15 November 1995 00:00
		Re: Inaccuracies By: Andy Loughe on Wed, 15 November 1995 00:00
		Re: Inaccuracies By: thompson on Wed, 15 November 1995 00:00
		Re: Inaccuracies By: hahn on Tue, 14 November 1995 00:00
		Re: Inaccuracies By: lpmix on Tue, 14 November 1995 00:00
		Re: Inaccuracies By: Andy Loughe on Tue, 14 November 1995 00:00
		Re: Inaccuracies By: wclodius on Tue, 14 November 1995 00:00
		Re: Inaccuracies By: thompson on Tue, 14 November 1995 00:00
		Re: Inaccuracies By: Jackel on Tue, 14 November 1995 00:00

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