Exact time measurement on c++

Question

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I am on a project and i have to compare some sorting algorithms execution times. However, as you know some values are to close, but i can not see difference. I have to know, small difference for example 1 nanosecond or something.

Is that possible to measure very small difference-smaller then microsecond or something.

Posted 1-Jan-14 1:33am

Yiğit Yüksel

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Comments

[no name] 1-Jan-14 8:06am

Surely you are not trying to measure the speed of one iteration. You do not need nanosecond resolution to measure the speed of algorithms. You measure large numbers of iterations so that a small error in time measurement doesn't matter. This is a very fundamental principle of mensuration.

CPallini 5-Jan-14 15:31pm

(virtual) 5.

CPallini 5-Jan-14 15:36pm

As already suggested by pwasser measuring algorithm speed that way doesn't make sense. Moreover usually the interesting feature of an algorithm is its order of growth, see
http://en.wikipedia.org/wiki/Analysis_of_algorithms#Orders_of_growth

5 solutions

Solution 2

See this, hpoe it helps:

http://stackoverflow.com/questions/1825720/c-high-precision-time-measurement-in-windows[^]

Posted 1-Jan-14 1:47am

idle63

Comments

Philippe Mori 1-Jan-14 16:58pm

Link was already provided in Solution 1...

[no name] 2-Jan-14 7:11am

Can happen in a parallel envirnoement, while two persons write the answer about the same time ;)

Solution 3

__time_t is defined as __time64_t or __time32_t, for time holder, and the macro is

/* Clock ticks macro - ANSI version */
#define CLOCKS_PER_SEC 1000

so if you want to redefine it in your code

C++

#ifdef CLOCKS_PER_SEC
#undef CLOCKS_PER_SEC
#define CLOCKS_PER_SEC 10000000000000
#else
#define CLOCKS_PER_SEC 10000000000000
#endif

Posted 1-Jan-14 2:18am

The_Inventor

Solution 4

dear friend
I road somthing about this topic in

www.cs.rpi.edu/~musser/gp/timing.html‏[^]
I hope that it help you

Posted 5-Jan-14 7:57am

m-salahshour

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Espen Harlinn · Accepted Answer · 2014-01-05T11:24:00

Solution 5

I've written a nice high resolution C++ Stopwatch class, located at the bottom of hwindatetime.h[^].

It's easy to use with an interface that should be familiar to many .Net developers.

Best regards
Espen Harlinn

Posted 5-Jan-14 11:24am

Espen Harlinn

Nelek · Accepted Answer · 2014-01-01T01:45:00

Solution 1

Plase have a look:
http://www.informit.com/guides/content.aspx?g=cplusplus&seqNum=272[^]
http://stackoverflow.com/questions/1825720/c-high-precision-time-measurement-in-windows[^]
http://stackoverflow.com/questions/275004/c-timer-function-to-provide-time-in-nano-seconds[^]

Posted 1-Jan-14 1:45am

Nelek