How to get the time elapsed running a function in C++

Question

I tried some codes by googling :

clock_t start, end;
start = clock();
//CODES GOES HERE
end = clock();
std::cout << end - start <<"\n";
std::cout << (double) (end-start)/ CLOCKS_PER_SEC;

but the result elapsed time always was 0, even with

std::cout << (double) (end-start)/ (CLOCKS_PER_SEC/1000.0 );

Don't know why but when I get the similar in Java : getCurrentTimeMillis() it works well. I want it to show the milliseconds as maybe the computer compute so fast.

Any OS / framework restrictions? (C++ doesn't have a standard way of getting high-resolution timings...) — Macke
– Macke, Commented Mar 12, 2011 at 15:29

Fred Foo · Accepted Answer · 2011-03-12 14:24:57Z

1

I don't think it's guaranteed that clock has a high enough resolution to profile your function. If you want to know how fast a function executes, you should run it maybe a few thousands times instead of once, measure the total time it takes and take the average.

answered Mar 12, 2011 at 14:24

Fred Foo

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Daniel Lidström · Accepted Answer · 2011-03-12 16:14:21Z

1

#include <boost/progress.hpp>

int main()
{
    boost::progress_timer timer;
    // code to time goes here
}

This will print out the time it took to run main. You can place your code in scopes to time several parts, i.e. { boost::progress_timer timer; ... }.

answered Mar 12, 2011 at 16:14

Daniel Lidström

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2 Comments

Duc Tran Over a year ago

the compiler couldn't recognize <boost/progress.hpp> .I use Netbeans in Ubuntu

Daniel Lidström Over a year ago

Well, you need Boost. Try sudo apt-get install boost-dev or something similar.

Community · Accepted Answer · 2017-05-23 10:33:09Z

0

This question is somehow similar to yours: Timing a function in a C++ program that runs on Linux

Take a look at this answer!

edited May 23, 2017 at 10:33

CommunityBot

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answered Mar 12, 2011 at 15:21

karlphillip

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