From: Remi Vanicat <remi.vanicat@laposte.net>
To: caml-list@inria.fr
Subject: Re: [Caml-list] float type with better precision than the default
Date: Sat, 06 Dec 2003 12:54:47 +0100 [thread overview]
Message-ID: <87k75axit4.dlv@wanadoo.fr> (raw)
In-Reply-To: <1070682167.6259.31.camel@pelican> (skaller@ozemail.com.au's message of "06 Dec 2003 14:42:50 +1100")
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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next prev parent reply other threads:[~2003-12-06 11:54 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-12-06 0:44 romildo
2003-12-06 3:18 ` Brian Hurt
2003-12-06 3:42 ` skaller
2003-12-06 11:54 ` Remi Vanicat [this message]
2003-12-08 10:11 ` Jean-Christophe Filliatre
2003-12-08 11:29 ` Jean-Christophe Filliatre
2003-12-08 11:57 ` romildo
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