Fair enough. Personally I like the math that Benchmark::cmpthese() does for me.

More to the point. Even attempting to time operations that take so little time that Benchmark's internal math is subject to rounding errors, is mostly pointless. More so if you only time one (or 10 or 100) occurance(s) of that operation.

With operations that require 84 million iterations to accumulate 1 second of cpu--that's 0.000000012 seconds per!--you're not timing the operation. You're timing the time it takes to get two successive TOD values from the OS!

Your numbers will vary widely depending upon whether a task switch occured inside your timing window. So widely that your results will be meaningless.

The only way to derive any meaning from comparisons of such low cost operations, is to do them 1000s of times and time the entire loop and then divide (hence my expectation of your math). Sure, that means the overhead of the loop is measured also, but if the same (and cheapest) loop mechanism is use for all the tests, then the same overhead will be in all timings.

Whilst this renders the absolute values (end - start) completely useless for comparison purposes, the relative timings--

((end1 - start1)/n1) / ((end2 - start2)/n2)

[download]

is a useful function for comparisons. Not only does this minimise the overhead of the loop, it also minimises the differences between your cpu performance and mine; your OS and mine. Hence the relative performance ratios (percentages) that result are useful, whereas absolute numbers--of wall time; cpu time; or iterations counts in a given period--are completely useless.

And guess what. These are exactly the figures that Benchmark::cmpthese() produces for you! And this is why I use Benchmark (and advocate the use of cmpthese() over timethese).

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re^7: &1 is no faster than %2 when checking for oddness. (Careful what you benchmark) by BrowserUk
in thread &1 is no faster than %2 when checking for oddness. Oh well. by diotalevi

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