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

[Victor Stinner]

On 14/03/2012 01:18, Nadeem Vawda wrote:
> So wallclock() falls back to a not-necessarily-monotonic time source
> if necessary,
> while monotonic() raises an exception in that case? ISTM that these
> don't need to
> be separate functions - rather, we can have one function that takes a
> flag (called
> require_monotonic, or something like that) telling it which failure mode to use.
> Does that make sense?

I don't think that time.monotonic() can fail in practice and it is 
available for all modern platforms (Windows, Mac OS X and OS implemented 
clock_gettime()).

On Windows, time.monotonic() fails with an OSError if 
QueryPerformanceFrequency() failed. QueryPerformanceFrequency() can fail 
if "the installed hardware does not support a high-resolution 
performance counter" according to Microsoft documentation. Windows uses 
the CPU RDTSC instruction, or the ACPI power management timer or event 
the old 8245 PIT. I think that you have at least one of this device on 
your computer.

I suppose that you can use a manual fallback to time.time() if 
time.monotonic() failed. If time.monotonic() fails, it fails directly at 
the first call. Example of a fallback working with Python < 3.3:

try:
    time.monotonic()
except (OSError, AttributeError):
    get_time = time.time
else:
    get_time = time.monotonic

Victor