OT: recommended way of timing two pieces of code in C

[Ranjan Maitra]

On Fri, 26 Feb 2016 12:44:10 -0500 Tom Horsley <horsley1953 at gmail.com> wrote:

> On Fri, 26 Feb 2016 09:51:24 -0600
> Ranjan Maitra wrote:
> 
> > How does this happen? The number of operations are exactly the same (or should be).
> 
> The number of operations in your program are the same, but
> your program is running on the same machine as the linux
> OS which has deamons running in the background, and may
> even be stopping to page in code your program needs, or grow
> pages as it allocates memory. Vast numbers of things
> affect timing. Even the stupid dynamic library load address
> randomization linux does can result in totally different
> cache hits in memory. The list goes on and on...
> 
> Apart from linux, most motherboards these days have SMI
> interrupts happening behind everyone's back which leave
> missing chunks of time no one can account for.

Thank you! So, is there any way that these other processes can be separated out in the time calculations? I can not come up with definitive statements unless I can do these comparisons in a fair manner.

Best wishes.
Ranjan

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