[Python-Dev] PEP 564: Add new time functions with nanosecond resolution (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Mon Oct 16 11:06:31 EDT 2017

Hi,

On Mon, 16 Oct 2017 12:42:30 +0200 Victor Stinner <victor.stinner at gmail.com> wrote:

time.time() returns seconds elapsed since the UNIX epoch: January 1st, 1970. This function loses precision since May 1970 (47 years ago)::

This is a funny sentence. I doubt computers (Unix or not) had nanosecond clocks in May 1970.

This PEP adds five new functions to the time module:

* time.clockgettimens(clockid) * time.clocksettimens(clockid, time: int) * time.perfcounterns() * time.monotonicns() * time.timens()

Why not time.process_time_ns()?

Hardware clock with a resolution better than 1 nanosecond already exists. For example, the frequency of a CPU TSC clock is the CPU base frequency: the resolution is around 0.3 ns for a CPU running at 3 GHz. Users who have access to such hardware and really need sub-nanosecond resolution can easyly extend Python for their needs.

Typo: easily. But how is easy is it?

Such rare use case don't justify to design the Python standard library to support sub-nanosecond resolution.

I suspect that assertion will be challenged at some point :-) Though I agree with the ease of implementation argument (about int64_t being wide enough for nanoseconds but not picoseconds).

Regards

Antoine.

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