CODEWITHSUNDEEP
c++timeexecution-timeelapsedtime
AvZ
AvZ

Reputation: 1035

Cleanest and simplest way to get elapsed time since execution in C++

What is the simplest and cleanest way to get the time since execution of the program (with milliseconds precision) in C++ ?

I am making a wave interference simulator to produce Lissajous curves in C++. It requires the time since execution of the program (with at least milliseconds precision) to function. I can't seem to find any clean and simple way to do it after a bit of research.
All <chrono> functions seem very confusing to me. Similar questions on here on Stack Overflow seem to be either unrelated, confusing (to me) or inapplicable for my situation. I tried using functions from <time.h>, only to discover that they have precision upto seconds only.
I am running Windows 7 x64. The program need not be platform independent as it's for personal use. Any help is greatly appreciated.
Thank you!

Upvotes: 4

Views: 1417

Answers (1)

Galik
Galik

Reputation: 48665

The new <chrono> functions take a little getting used to but they make things fairly easy when you get to know how they work.

Your problem could be solved like this for example:

#include <chrono>
#include <thread>
#include <iostream>

// for readability
using hr_clock = std::chrono::high_resolution_clock;
using hr_time_point = hr_clock::time_point;
using hr_duration = hr_clock::duration;
using milliseconds = std::chrono::milliseconds;

int main()
{
    // note the program start time
    hr_time_point prog_start = hr_clock::now();

    // do stuff
    std::this_thread::sleep_for(milliseconds(1000));

    // find the duration
    hr_duration d = hr_clock::now() - prog_start;

    // cast the duration to milliseconds
    milliseconds ms = std::chrono::duration_cast<milliseconds>(d);

    // print out the number of milliseconds
    std::cout << "time passed: " << ms.count() << " milliseconds.\n";
}

For convenience you could create a function to return the time since that function was last called:

milliseconds since_last_call()
{
    // retain time between calls (static)
    static hr_time_point previous = hr_clock::now();

    // get current time
    hr_time_point current = hr_clock::now();

    // get the time difference between now and previous call to the function
    milliseconds ms = std::chrono::duration_cast<milliseconds>(current - previous);

    // store current time for next call
    previous = current;

    // return elapsed time in milliseconds
    return ms;
}

int main()
{
    since_last_call(); // initialize functions internal static time_point

    // do stuff
    std::this_thread::sleep_for(milliseconds(1000));

    milliseconds ms = since_last_call();

    // print out the number of milliseconds
    std::cout << "time passed: " << ms.count() << " milliseconds.\n";
}

Upvotes: 7

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