From: Bogdan Cristea <cristeab@gmail.com>
To: Chrysostomos Nanakos <nanakos@wired-net.gr>
Cc: linux-c-programming@vger.kernel.org
Subject: Re: printf and long double
Date: Mon, 4 Oct 2010 15:03:27 +0300 [thread overview]
Message-ID: <201010041503.27721.cristeab@gmail.com> (raw)
In-Reply-To: <4CA9C086.1050401@wired-net.gr>
On Monday 04 October 2010 14:54:46 you wrote:
> I wish I could get 24 decimal digits precision with the current long
> double (80-bit). I can't get more than 15 digits even in a simple division.
> I think that the extended-precision can't give more than 19 decimal
> digits of precision (log(10,2^64)=19.2). The quadruple precision can
> give at most 34 decimal digits (log(10,2^113)=34).
>
> Please consider the example below:
> --------------------------------------------------
> long double a = 1.0L/7.0L;
> printf("%Lf\n",a);
> --------------------------------------------------
>
> Can't get more than 15 digits precision....-:(
> Is this a compiler problem or libc's problem? In x86_64 machines the
> long double values supposed to give at least 106-bit precision even when
> implemented in software. Is gcc compliant with the quadruple notation?
Have you tried to specify manually the number of digits after the decimal
point ?
long double a = 1.0L/7.0L;
printf("%'.100Lf\n",a);
On a 64 bits machine the output is:
0.1428571428571428571409210675491330277964152628555893898010253906250000000000000000000000000000000000
regards
Bogdan
next prev parent reply other threads:[~2010-10-04 12:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-03 22:56 printf and long double Nanakos Chrysostomos
2010-10-04 0:43 ` Gedare Bloom
2010-10-04 1:44 ` Glynn Clements
2010-10-04 1:33 ` Glynn Clements
2010-10-04 11:54 ` Chrysostomos Nanakos
2010-10-04 12:03 ` Bogdan Cristea [this message]
2010-10-04 12:12 ` Chrysostomos Nanakos
2010-10-06 20:18 ` printf and long double [SOLVED] Nanakos Chrysostomos
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=201010041503.27721.cristeab@gmail.com \
--to=cristeab@gmail.com \
--cc=linux-c-programming@vger.kernel.org \
--cc=nanakos@wired-net.gr \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).