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[Python-Dev] Drop the new time.wallclock() function?

Victor Stinner victor.stinner at gmail.com
Wed Mar 14 00:57:16 CET 2012 
Hi,

I added two functions to the time module in Python 3.3: wallclock()
and monotonic(). I'm unable to explain the difference between these
two functions, even if I wrote them :-) wallclock() is suppose to be
more accurate than time() but has an unspecified starting point.
monotonic() is similar except that it is monotonic: it cannot go
backward. monotonic() may not be available or fail whereas wallclock()
is available/work, but I think that the two functions are redundant.

I prefer to keep only monotonic() because it is not affected by system
clock update and should help to fix issues on NTP update in functions
implementing a timeout.

What do you think?

--

monotonic() has 3 implementations:
* Windows: QueryPerformanceCounter() with QueryPerformanceFrequency()
* Mac OS X: mach_absolute_time() with mach_timebase_info()
* UNIX: clock_gettime(CLOCK_MONOTONIC_RAW) or clock_gettime(CLOCK_MONOTONIC)

wallclock() has 3 implementations:
* Windows: QueryPerformanceCounter() with QueryPerformanceFrequency(),
with a fallback to GetSystemTimeAsFileTime() if
QueryPerformanceFrequency() failed
* UNIX: clock_gettime(CLOCK_MONOTONIC_RAW),
clock_gettime(CLOCK_MONOTONIC) or clock_gettime(CLOCK_REALTIME), with
a fallback to gettimeofday() if clock_gettime(*) failed
* Otherwise: gettimeofday()

(wallclock should also use mach_absolute_time() on Mac OS X)


Victor
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