How to measure elapsed time under Windows?

[Gabriel Genellina]

En Tue, 09 Feb 2010 13:10:56 -0300, Grant Edwards  
<invalid at invalid.invalid> escribió:

> What's the correct way to measure small periods of elapsed
> time.  I've always used time.clock() in the past:
>
> However on multi-processor machines that doesn't work.
> Sometimes I get negative values for delta.  According to
> google, this is due to a bug in Windows that causes the value
> of time.clock() to be different depending on which core in a
> multi-core CPU you happen to be on.   [insert appropriate
> MS-bashing here]

I'm not sure you can blame MS of this issue; anyway, this patch should fix  
the problem:
http://support.microsoft.com/?id=896256

> Is there another way to measure small periods of elapsed time
> (say in the 1-10ms range)?

No that I know of. QueryPerformanceCounter (the function used by  
time.clock) seems to be the best timer available.

> Is there a way to lock the python process to a single core so
> that time.clock() works right?

Interactively, from the Task Manager:
http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/taskman_assign_process.mspx

In code, using SetProcessAffinityMask and related functions:
http://msdn.microsoft.com/en-us/library/ms686223(VS.85).aspx

-- 
Gabriel Genellina