Calculating Elapsed Time

[Grant Edwards]

On 2005-12-07, Fredrik Lundh <fredrik at pythonware.com> wrote:
> Peter Hansen wrote:
>
>> Going by memory, Linux will generally be 1ms resolution (I might be
>> off by 10 there...), while Windows XP has about 64 ticks per second,
>> so .015625 resolution...
>
> here's a silly little script that measures the difference between
> two distinct return values, and reports the maximum frequency
> it has seen this far:
>
>     import time
>
>     def test(func):
>         mm = 0
>         t0 = func()
>         while 1:
>             t1 = func()
>             if t0 != t1:
>                 m = max(1 / (t1 - t0), mm)
>                 if m != mm:
>                     print m
>                     mm = m
>                 t0 = t1
>
>     test(time.time)
>     # test(time.clock)
>
> if I run this on the Windows 2K box I'm sitting at right now, it settles
> at 100 for time.time, and 1789772 for time.clock.  on linux, I get 100
> for time.clock instead, and 262144 for time.time.

At least under Linux, I suspect you're just measuring loop time
rather than the granularity of the time measurement.  I don't
know which library call the time modules uses, but if it's
gettimeofday(), that is limited to 1us resolution.
clock_gettime() provides an API with 1ns resolution.  Not sure
what the actual data resolution is...

-- 
Grant Edwards                   grante             Yow!  Yow! I just went
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