On 2023-12-05 01:00, David C. Rankin wrote:
On 12/4/23 21:56, Darryl Gregorash wrote:
On 2023-12-04 20:52, Carlos E. R. wrote:
On 2023-12-05 03:37, Darryl Gregorash wrote:
On 2023-12-04 18:24, David C. Rankin wrote:
All,
To celebrate the list working again, I'll pass along something that brought a smile to my face a bit ago. I was looking at help for kcalc, and I noticed a entry for long-double precision and clicked it:
https://paste.opensuse.org/pastes/b1300d1770a4
Remember when user-choice and customization was the touchstone of Linux? Back when the help pages told you about defines to tailor the app to your needs and then a simple:
./configure make make install
The good ole days.... :)
Ordinarily I hesitate to ask silly questions, but when was the last time you needed double precision calculation, much less long double? Never mind it's not even a IEEE standard..
Yet the processor has those types,, I assue so someone uses them.
Yeah, if you are working, for example, at places like CERN or LIGO.
Precisely!
/* estimate the solar declination angle (in radians) */ sp.decl = 0.006918 - 0.399912 * cos(sp.fracyr) + 0.070257 * sin(sp.fracyr) - 0.006758 * cos(2 * sp.fracyr) + 0.000907 * sin(2 * sp.fracyr) - 0.002697 * cos(3 * sp.fracyr) + 0.00148 * sin(3 * sp.fracyr);
I rather doubt one needs that much precision for astronomical calculations, especially when working with an object that a) has an angular diameter of approximately 0.5 degrees, and b) is an oblate spheroid whose oblateness isn't really known to very much precision. I used LHC and LIGO as examples, because those are two examples where high precision is really needed. In the case of LIGO, for example, the delay is very, very small between receiving a true wave signal at each detector (gravitational waves travel at the speed of light). With the LHC, the time windows are even more critical, given a) the huge numbers of decay products that happen between the original collision and detection of the final decay products, and b) the relatively small sizes of the detectors. Besides, that equation you give looks to me like a perturbation expansion, unlikely anything close to single precision, and only taken out to 3 terms.