Hi Stephen,
On 2016-12-01 01:08 PM, Stephen Scott wrote:
Hello Brooks, Stephen;
What's all this discussion about precision?
Merely about the math of their smear method.
The smear has tossed the precision of the second SI out the window.
This is totally unacceptable for an application that requires a
precise and stable frequency reference (telecommunications and
broadcast for example).
Yes, of course, but the whole purpose of the smear is to hide the Leap
Second from the downstream 86400-second-day systems, especially
operating systems, that may not be prepared to cope with the Leap
Second. As I understand it, it compromises accuracy for reliability,
buts that the best solution to avoiding potential wide-spread problems.
Further, this is not the only smear algorithm.
A proliferation of smears could be the best reason for getting rid of
the leap second.
As I read it I think Google's intention is to publish their method and
algorithm in the hopes others may follow it. It would be better if
everybody did it the same way, but it will remain to be seen if others
will choose to follow the example.
-Brooks
The time community is not monolithic and there are different
requirements of users.
No single approach is likely to satisfy all.
There is a requirement for a minimal set of standardized approaches.
-Stephen
On 2016-12-01 12:39, Brooks Harris wrote:
Hi Stephen,
On 2016-12-01 02:49 AM, Stephen Colebourne wrote:
More details on the developer site:
https://developers.google.com/time/
Notably this page:
https://developers.google.com/time/smear
which include "Our proposed standard smear" - "We would like to
propose to the community, as the best practice for leap seconds in the
future, a 24-hour linear smear from noon to noon UTC"
Hip hip hooray! De facto standards for the win!
Stephen
Ah, this is good. I'd missed that page yesterday.
I might suggest you good go a little further.
You say "Each second of time marked by Google's servers will be about
13.9 μs longer than an SI second. "
Some developers may probably need to know exactly, or as exactly as
possible, the ratio.
If I've got this right:
20 hours = 20 * 60 * 60 = 72000 seconds
Plus the Leap Second = 72001 second
So the ratio is 72001 / 72000 = 1.000013889 (rounded to 10-9th
precision, nanoseconds)
This a repeating decimal number which may be denoted 1.000013(8).
Applications should be careful to provide adequate precision for the
purpose.
-Brooks
On 30 November 2016 at 21:05, Tom Van Baak <[email protected]> wrote:
I'm surprised no one has posted this news yet:
"Making every (leap) second count with our new public NTP servers"
https://cloudplatform.googleblog.com/2016/11/making-every-leap-second-count-with-our-new-public-NTP-servers.html
/tvb
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