C++ 高精度时钟获取当前时间 std::chrono::high_resolution

C++ 高精度时钟获取当前时间 std::chrono::high_resolution_clock::now

1. `std::chrono::high_resolution_clock::now`
- 1.1. Parameters
- 1.2. Return value
- 1.3. Example
2. `std::chrono::milliseconds`
3. `std::chrono::microseconds`
- 3.1. Example
References

1. `std::chrono::high_resolution_clock::now`

Get current time
https://cplusplus.com/reference/chrono/high_resolution_clock/now/

// public static member function
static time_point now() noexcept;

Returns the current time_point in the frame of the high_resolution_clock.

1.1. Parameters

none

1.2. Return value

The time_point representing the current time.

time_point is a member type, defined as an alias of time_point<high_resolution_clock>.

1.3. Example

#include <iostream>
#include <ctime>
#include <ratio>
#include <chrono>int main() {using namespace std::chrono;high_resolution_clock::time_point begin = high_resolution_clock::now();std::cout << "Printing out 1000 stars...\n";for (int i = 0; i < 1000; ++i) { std::cout << "*"; }std::cout << std::endl;high_resolution_clock::time_point end = high_resolution_clock::now();duration<double> time_span = duration_cast<duration<double>>(end - begin);std::cout << "It took me " << time_span.count() << " seconds.";std::cout << std::endl;return 0;
}

在这里插入图片描述

Printing out 1000 stars...
****************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************
It took me 0.0411305 seconds.
请按任意键继续. . .

time_point is a member type, defined as an alias of time_point<high_resolution_clock>.

#include <iostream>
#include <ctime>
#include <ratio>
#include <chrono>int main() {using namespace std::chrono;time_point<high_resolution_clock> begin = high_resolution_clock::now();std::cout << "Printing out 1000 stars...\n";for (int i = 0; i < 1000; ++i) { std::cout << "*"; }std::cout << std::endl;time_point<high_resolution_clock> end = high_resolution_clock::now();duration<double> time_span = duration_cast<duration<double>>(end - begin);std::cout << "It took me " << time_span.count() << " seconds.";std::cout << std::endl;return 0;
}

Printing out 1000 stars...
****************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************
It took me 0.033101 seconds.
请按任意键继续. . .

2. `std::chrono::milliseconds`

Duration in milliseconds

// class
typedef duration < /* see rep below */, milli > milliseconds;

Instantiation of duration to represent milliseconds.

A millisecond (from milli- and second; symbol: ms) is a unit of time in the International System of Units equal to one thousandth (0.001 or $10^{-3}$ or 1/1000) of a second or 1000 microseconds.

1 millisecond (1 ms)

3. `std::chrono::microseconds`

Duration in microseconds

// class
typedef duration < /* see rep below */, micro > microseconds;

Instantiation of duration to represent microseconds.

A microsecond is a unit of time in the International System of Units (SI) equal to one millionth (0.000001 or $10^{-6}$ or 1/1,000,000) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available.

1 microsecond (1 μs)

3.1. Example

#include <iostream>
#include <ctime>
#include <ratio>
#include <chrono>int main() {std::chrono::time_point<std::chrono::high_resolution_clock> begin = std::chrono::high_resolution_clock::now();std::cout << "Printing out 1000 stars...\n";for (int i = 0; i < 1000; ++i) { std::cout << "*"; }std::cout << std::endl;std::chrono::time_point<std::chrono::high_resolution_clock> end = std::chrono::high_resolution_clock::now();std::chrono::milliseconds time_span_ms = std::chrono::duration_cast<std::chrono::milliseconds>(end - begin);std::chrono::microseconds time_span_us = std::chrono::duration_cast<std::chrono::microseconds>(end - begin);std::cout << "It took me " << time_span_ms.count() << " milliseconds (ms).\n";std::cout << "It took me " << time_span_us.count() << " microseconds (us).\n";std::cout << std::endl;return 0;
}

在这里插入图片描述

Printing out 1000 stars...
****************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************
It took me 33 milliseconds (ms).
It took me 33908 microseconds (us).请按任意键继续. . .