c++-chrono

How to get the difference between two points in time in milliseconds

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std::chrono::duration has two template parameters, the second being exactly the unit of measure. You can invoke std::chrono::duration_cast to cast from one duration type to another. Also, there is a predefined duration type for milliseconds: std::chrono::milliseconds. Composing this together: auto milliseconds = std::chrono::duration_cast<std::chrono::milliseconds>(foo – now); To get the actual number of milliseconds, use duration::count: auto ms … Read more

Resolution of std::chrono::high_resolution_clock doesn’t correspond to measurements

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I’m going to guess you are using Visual Studio 2012. If not, disregard this answer. Visual Studio 2012 typedef‘s high_resolution_clock to system_clock. Sadly, this means it has crappy precision (around 1 ms). I wrote a better high-resolution clock which uses QueryPerformanceCounter for use in Visual Studio 2012… HighResClock.h: struct HighResClock { typedef long long rep; typedef std::nano period; typedef std::chrono::duration<rep, … Read more

When is std::chrono epoch?

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It is a function of both the specific clock the time_point refers to, and the implementation of that clock. The standard specifies three different clocks: system_clock steady_clock high_resolution_clock And the standard does not specify the epoch for any of these clocks. Programmers (you) can also author their own clocks, which may or may not specify … Read more

std::chrono and cout

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As others have noted, you can call the count() member function to get the internal count. I wanted to add that I am attempting to add a new header: <chrono_io> to this library. It is documented here. The main advantage of <chrono_io> over just using count() is that the compile-time units are printed out for … Read more

How to convert std::chrono::time_point to string

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Update for C++20: This can now easily be done in C++20: #include <chrono> #include <format> #include <iostream> #include <string> int main() { using namespace std::chrono_literals; std::chrono::time_point tp = std::chrono::sys_days{2016y/1/16} + 11h + 25min; std::string s = std::format(“{:%Y%m%d%H%M}”, tp); std::cout << s << ‘\n’; } Output: 201601161125 Demo. Original Answer: Howard Hinnant’s free, open source, header-only, … Read more

Chrono – The difference between two points in time in milliseconds?

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std::chrono::duration has two template parameters, the second being exactly the unit of measure. You can invoke std::chrono::duration_cast to cast from one duration type to another. Also, there is a predefined duration type for milliseconds: std::chrono::milliseconds. Composing this together: auto milliseconds = std::chrono::duration_cast<std::chrono::milliseconds>(foo – now); To get the actual number of milliseconds, use duration::count: auto ms … Read more

precise time measurement

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C++11 introduced the chrono API, you can use to get nanoseconds : auto begin = std::chrono::high_resolution_clock::now(); // code to benchmark auto end = std::chrono::high_resolution_clock::now(); std::cout << std::chrono::duration_cast<std::chrono::nanoseconds>(end-begin).count() << “ns” << std::endl; For a more relevant value it is good to run the function several times and compute the average : auto begin = std::chrono::high_resolution_clock::now(); uint32_t … Read more