From: Peter Stephenson <p.stephenson@samsung.com>
To: <zsh-workers@zsh.org>
Subject: Re: Terminal theme tool – a workaround for lack of 24-bit color in Zsh?
Date: Thu, 15 Nov 2018 12:44:37 +0000 [thread overview]
Message-ID: <1542285877.4637.3.camel@samsung.com> (raw)
In-Reply-To: <B2AC3BAB-4105-4C49-BE8C-55DA32F94DE7@kba.biglobe.ne.jp>
On Thu, 2018-11-15 at 20:50 +0900, Jun T wrote:
> In nearcolor.c, function RGBtoLAB(), floating point data are saved in
> float (not double) variables; for example:
>
> >
> > + float R = (float)red / 255.0;
> (snip)
> >
> > + R = 100.0 * (R > 0.04045 ? powf((R + 0.055) / 1.055, 2.4) : R / 12.92);
> Is this to improve performance?
> If so, it would be better to explicitly use float literals, such as 255.0f.
> Otherwise, since 255.0 is double, all the calculations are done in double
> (after promoting all values to double), and the final result is truncated
> back to float.
>
> I believe there is virtually no performance difference (on most CPUs).
The majority of standardish Unixy systems I know about are designed to
assume most floating point calculations are going to be done as double
--- I see Linux supplies float and long double versions of library
functions as a supplement. But I doubt Oliver was thinking that much
about optimisation here --- terminal IO is slow enough I can't see how
it could be a big deal.
pws
next prev parent reply other threads:[~2018-11-15 12:53 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAKc7PVCEmTTMRR0P3kx9ktpLDBYqJ+MRsE77UMLFjonEZAixfA@mail.gmail.com>
2018-10-30 23:41 ` Oliver Kiddle
2018-11-01 18:42 ` dana
2018-11-04 1:42 ` PATCH: true colour support Oliver Kiddle
2018-11-04 22:57 ` Oliver Kiddle
2018-11-05 14:36 ` Sebastian Gniazdowski
[not found] ` <46482-1541429525.040210@53iC.Cv7F.M2xE>
2018-11-05 15:48 ` Sebastian Gniazdowski
2018-11-05 16:22 ` Sebastian Gniazdowski
2018-11-06 12:12 ` Sebastian Gniazdowski
2018-11-06 13:37 ` Oliver Kiddle
2018-11-06 21:46 ` Sebastian Gniazdowski
2018-11-06 12:22 ` Should there be a Zsh release for true-color support to adopt earlier? Sebastian Gniazdowski
2018-11-06 22:35 ` Daniel Shahaf
2018-11-06 23:46 ` Bart Schaefer
2018-11-05 14:03 ` Terminal theme tool – a workaround for lack of 24-bit color in Zsh? Sebastian Gniazdowski
2018-11-15 11:50 ` Jun T
2018-11-15 12:44 ` Peter Stephenson [this message]
2018-11-16 7:54 ` Jun T
2018-11-19 8:29 ` Oliver Kiddle
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