Re: [Scheme-reports] current-posix-second is a disastrous mistake

["Thomas Bushnell, BSG" <tb@x>]

On Fri, Dec 10, 2010 at 2:40 PM, John Cowan <cowan@x> wrote:

Taylor R Campbell scripsit:

> The proposal claims that `there is about a 1 in 10^-8 probability that
> a computation of elapsed time made by calling this procedure twice
> will be off by 1.'  This langauge suggests that there is some random
> chance involved here.  But there isn't: leap seconds aren't drawn
> uniformly at random from time.  Instead, in a network of POSIX agents
> with reasonably accurate and well-synchronized clocks, every agent
> will observe an erratic clock simultaneously, once every few years.

I have removed this paragraph.

The real point of the 10^-8 is that an interval clock cannot keep the
difference between Posix and UTC time unless it is at least that
accurate, which is very improbable.

This is still a great misunderstanding. Many computers have perfectly good accuracy on that level without any trouble, because they use things like NTP to keep themselves in sync.

Thomas

 

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