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Re: fix(4.70*100) is... 469 [message #53574 is a reply to message #53572]

Wed, 18 April 2007 17:14

mmeron
Messages: 44
Registered: October 2003

Member

In article <f06ane$21t$1@news.ucalgary.ca>, "Jean H." <jghasban@DELTHIS.ucalgary.ANDTHIS.ca> writes:
>> Hooboy! Haven't had one of these in awhile. :-)
>>
>> http://www.dfanning.com/math_tips/sky_is_falling.html
>>
>> Cheers,
>>
>> David
>
> It seems a bit weirder though...
>
> IDL> print, 470.0 - (4.70*100)
> 3.05176e-005
>
> which is bigger than the smallest float
>
> IDL> print, (machar()).eps
> 1.19209e-007
>
> .... so how can it be the float accuracy problem if the difference
> between the expected and the real value is 256 times bigger than the
> float error?
>
Careful here. The smallest float provides relative accuracy, meaning
the difference between exact and stored value X doesn't exceed
X*(machar()).eps. This is well satisfied here.

Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"

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[Message index]

		Re: fix(4.70*100) is... 469 By: b_efremova@yahoo.com on Thu, 19 April 2007 11:47
		Re: fix(4.70*100) is... 469 By: mmeron on Thu, 19 April 2007 11:15
		Re: fix(4.70*100) is... 469 By: b_efremova@yahoo.com on Thu, 19 April 2007 11:13
		Re: fix(4.70*100) is... 469 By: David Fanning on Thu, 19 April 2007 12:07
		Re: fix(4.70*100) is... 469 By: David Fanning on Thu, 19 April 2007 11:52
		Re: fix(4.70*100) is... 469 By: b_efremova@yahoo.com on Thu, 19 April 2007 10:44
		Re: fix(4.70*100) is... 469 By: b_efremova@yahoo.com on Thu, 19 April 2007 10:03
		Re: fix(4.70*100) is... 469 By: mmeron on Thu, 19 April 2007 10:00
		Re: fix(4.70*100) is... 469 By: mmeron on Thu, 19 April 2007 09:50
		Re: fix(4.70*100) is... 469 By: David Fanning on Thu, 19 April 2007 09:54
		Re: fix(4.70*100) is... 469 By: Paolo Grigis on Fri, 20 April 2007 01:04
		Re: fix(4.70*100) is... 469 By: Jean H. on Thu, 19 April 2007 08:35
		Re: fix(4.70*100) is... 469 By: David Fanning on Thu, 19 April 2007 09:35
		Re: fix(4.70*100) is... 469 By: Christopher Thom on Thu, 19 April 2007 08:21
		Re: fix(4.70*100) is... 469 By: eddedmondson on Thu, 19 April 2007 08:13
		Re: fix(4.70*100) is... 469 By: Paolo Grigis on Thu, 19 April 2007 08:02
		Re: fix(4.70*100) is... 469 By: b_efremova@yahoo.com on Thu, 19 April 2007 07:41
		Re: fix(4.70*100) is... 469 By: b_efremova@yahoo.com on Thu, 19 April 2007 07:32
		Re: fix(4.70*100) is... 469 By: David Fanning on Thu, 19 April 2007 07:48
		Re: fix(4.70*100) is... 469 By: David Fanning on Thu, 19 April 2007 07:42
		Re: fix(4.70*100) is... 469 By: KRDean on Thu, 19 April 2007 06:41
		Re: fix(4.70*100) is... 469 By: Paolo Grigis on Thu, 19 April 2007 01:13
		Re: fix(4.70*100) is... 469 By: mmeron on Wed, 18 April 2007 22:56
		Re: fix(4.70*100) is... 469 By: Qing on Wed, 18 April 2007 21:38
		Re: fix(4.70*100) is... 469 By: Qing on Wed, 18 April 2007 21:36
		Re: fix(4.70*100) is... 469 By: Qing on Wed, 18 April 2007 21:31
		Re: fix(4.70*100) is... 469 By: Jean H. on Wed, 18 April 2007 17:58
		Re: fix(4.70*100) is... 469 By: mmeron on Wed, 18 April 2007 17:14
		Re: fix(4.70*100) is... 469 By: Jean H. on Wed, 18 April 2007 16:48
		Re: fix(4.70*100) is... 469 By: David Fanning on Wed, 18 April 2007 17:12
		Re: fix(4.70*100) is... 469 By: mmeron on Fri, 20 April 2007 00:33
		Re: fix(4.70*100) is... 469 By: Qing on Thu, 19 April 2007 23:43
		Re: fix(4.70*100) is... 469 By: Paul Van Delst[1] on Thu, 19 April 2007 12:06

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