From: Takashi Yano <takashi.yano@nifty.ne.jp>
To: cygwin@cygwin.com
Subject: Re: possible snprintf() regression in 3.3.2
Date: Thu, 25 Nov 2021 21:02:01 +0900 [thread overview]
Message-ID: <20211125210201.7627ca1c2cac69e5f1833516@nifty.ne.jp> (raw)
In-Reply-To: <YZ4FrdeJtPb7B04W@calimero.vinschen.de>
On Wed, 24 Nov 2021 10:28:13 +0100
Corinna Vinschen wrote:
> On Nov 24 18:14, Takashi Yano via Cygwin wrote:
> > On Wed, 24 Nov 2021 17:52:04 +0900
> > Takashi Yano wrote:
> > > The printed value is still something wrong...
> > > sqrt(2)*1e70 should be an integer value.
> >
> > I mean...
> >
> > sqrt(2)*1e70 is actually not an integer, however, double has mantissa
> > of only 52 bit. So, (double value)*(5^70*2^70) should be an integer.
>
> The conversion is a bit inexact, I guess, but that's another problem
> of this old ldto, right?
I looked into this problem and found that:
This problem is in principle unavoidable with current algorithms.
This is because the current algorithm uses a value of 10^n for
the conversion. When n>62, the value does not fit into the 144
bits of the mantissa part of the internal representation in ldtoa.
This degrades the precision.
--
Takashi Yano <takashi.yano@nifty.ne.jp>
next prev parent reply other threads:[~2021-11-25 12:02 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-17 0:37 Tony Cook
2021-11-17 9:21 ` Takashi Yano
2021-11-17 12:27 ` Corinna Vinschen
2021-11-18 0:06 ` Tony Cook
2021-11-18 11:35 ` Takashi Yano
2021-11-18 13:19 ` Corinna Vinschen
2021-11-18 14:11 ` Noel Grandin
2021-11-18 14:27 ` Corinna Vinschen
2021-11-18 21:08 ` Sam Edge
2021-11-21 0:16 ` Tony Cook
2021-11-22 10:34 ` Corinna Vinschen
2021-11-22 13:04 ` Corinna Vinschen
2021-11-22 23:23 ` Tony Cook
2021-11-23 8:34 ` Takashi Yano
2021-11-23 9:48 ` Corinna Vinschen
2021-11-24 3:40 ` Takashi Yano
2021-11-24 8:48 ` Corinna Vinschen
2021-11-24 8:52 ` Takashi Yano
2021-11-24 9:14 ` Takashi Yano
2021-11-24 9:28 ` Corinna Vinschen
2021-11-24 12:29 ` Lemke, Michael SF/HZA-ZI2E
2021-11-25 12:02 ` Takashi Yano [this message]
2021-11-25 12:45 ` Corinna Vinschen
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