From: Steve Graegert <graegerts@gmail.com>
To: linux-c-programming@vger.kernel.org
Subject: Re: Double values - what precision do I use for fprintf?
Date: Thu, 12 Jan 2006 19:51:08 +0100 [thread overview]
Message-ID: <6a00c8d50601121051n691ee179kef3298829025e973@mail.gmail.com> (raw)
In-Reply-To: <200601121800.19678.samjnaa@gmail.com>
On 1/12/06, Shriramana Sharma <samjnaa@gmail.com> wrote:
> Please observe the following printf output of eighteen double variables:
>
> First I tried using "%20.15f" as the format string:
>
> 268.229220252114942 1.018511211250181
> 66.833038547989787 12.450505533056681
> 20.512170161382819 0.334923179252419
> 259.358845955701327 1.571934717666495
> 201.111247720862963 0.139476171219810
> 270.658029698352152 -0.612280599380678
> 105.175902698424665 -0.076345132989225
> 343.809699615507384 -0.219206370786681
>
> Then I used "%30.25f":
>
> 268.2297152740335377529845573 1.0185111507334088098986058
> 66.8390907719954157073516399 12.4504269834231084956854829
> 20.5123328842112115921736404 0.3349264346316725426966343
> 259.3596100022817267927166540 1.5719383906021777708161835
> 201.1113154335791932680876926 0.1394751696317115263745734
> 270.6577319741974747557833325 -0.6122834912138217511312632
> 105.1758654981413201312534511 -0.0763454696609412730712307
> 343.8095929658045974974811543 -0.2192182978826520134418843
>
> Ignoring the small differences in the two sets of data (longitude and speed of
> eight celestial bodies computer at two different instants) I wonder - if I
> keep increasing the number of decimal places where will it end?
Shriramana,
Double precision numbering format is standardized by IEEE 754 with an
8 byte encoding. 1 bit is used for the sign, 11 bits for the exponent
and the remaining 52 bits are used for the precision, which means
precision "ends" at %.52f.
\Steve
--
Steve Graegert <graegerts@gmail.com>
Software Consultant {C/C++ && Java && .NET}
Office: +49 9131 7123988
Mobile: +49 1520 9289212
next prev parent reply other threads:[~2006-01-12 18:51 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-12 12:30 Double values - what precision do I use for fprintf? Shriramana Sharma
2006-01-12 14:17 ` Patrick Leslie Polzer
2006-01-12 18:51 ` Steve Graegert [this message]
2006-01-12 21:22 ` Nate Jenkins
2006-01-12 22:00 ` Mihai Dontu
2006-01-13 23:47 ` Glynn Clements
2006-01-14 0:35 ` Nate Jenkins
2006-01-17 5:37 ` Glynn Clements
2006-01-12 21:57 ` Scott
2006-01-12 22:06 ` Scott
2006-01-13 5:25 ` Steve Graegert
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