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[Caml-list] float type with better precision than the default
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Date: -- (:)
From: Remi Vanicat <remi.vanicat@l...>
Subject: Re: [Caml-list] float type with better precision than the default
skaller <skaller@ozemail.com.au> writes:

> On Sat, 2003-12-06 at 14:18, Brian Hurt wrote:
>> 30 decimal digits is enough accuracy to measure the 
>> distance between here and the Andromeda Galaxy in microns.  Why does he 
>> need such a ridiculous amount of precision?
>
> Standard eigen problem sometimes needs ridiculous precision:
> the scalar product of two vectors:
>
> 	sigma (i=1,n) (v1_i * v2_i)
>
> sometimes involves cancellation of large values.
> To see why there is a problem here, consider:
>
> 	1.000001e20 - 1e20 -
> 	(1.000001e-20 - 1e-20) 
>

[...]


This is what is called a numerical unstable algorithm...
-- 
Rémi Vanicat

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