chrono库功能挺强大的，但是太长了不方便记忆使用，写个简单的计时工具库。
libjc

#pragma once
#ifndef LIBJC_H
#define LIBJC_H
#include <chrono>

namespace libjc
{
    class jctime_duration;
    class jctime_high_resolution_clock
    {
    private:
        std::chrono::high_resolution_clock::time_point start_t;
        std::chrono::high_resolution_clock::time_point stop_t;
        unsigned char state;

    public:
        int start();
        int stop();
        libjc::jctime_duration duration() const;

        libjc::jctime_duration operator-(const libjc::jctime_high_resolution_clock &) const;
        jctime_high_resolution_clock();
        // ~jctime_high_resolution_clock();
    };

    class jctime_duration
    {

        friend libjc::jctime_duration libjc::jctime_high_resolution_clock::operator-(const libjc::jctime_high_resolution_clock &) const;
        friend libjc::jctime_duration libjc::jctime_high_resolution_clock::duration() const;

    private:
        std::chrono::nanoseconds rt;

    public:
        double tohour() const;
        double tominute() const;
        double tosecond() const;
        double toms() const;
        double tous() const;
        long long int tons() const;
    };
} // namespace libjc

#endif

libjc.cpp

#include "libjc"

namespace libjc
{

    libjc::jctime_high_resolution_clock::jctime_high_resolution_clock()
    {
        this->state = 0;
    }

    libjc::jctime_duration jctime_high_resolution_clock::operator-(const jctime_high_resolution_clock &t) const
    {

        jctime_duration a;
        a.rt = this->start_t - t.start_t;
        return a;
    }
    int libjc::jctime_high_resolution_clock::start()
    {
        if (state == 1)
            return 1;
        this->start_t = std::chrono::high_resolution_clock::now();
        state = 1;
        return 0;
    }
    int libjc::jctime_high_resolution_clock::stop()
    {
        this->stop_t = std::chrono::high_resolution_clock::now();
        state = 2;
        return 0;
    }
    libjc::jctime_duration libjc::jctime_high_resolution_clock::duration() const
    {
        libjc::jctime_duration a;
        a.rt = this->stop_t - this->start_t;
        return a;
    }

    double libjc::jctime_duration::tohour() const
    {
        return std::chrono::duration<double, std::ratio<3600LL>>(rt).count();
    }

    double libjc::jctime_duration::tominute() const
    {
        return std::chrono::duration<double, std::ratio<60LL>>(rt).count();
    }

    double libjc::jctime_duration::tosecond() const
    {
        return std::chrono::duration<double>(rt).count();
    }
    double libjc::jctime_duration::toms() const
    {
        return std::chrono::duration<double, std::ratio<1LL, 1000LL>>(rt).count();
    }
    double libjc::jctime_duration::tous() const
    {
        return std::chrono::duration<double, std::ratio<1LL, 1000000LL>>(rt).count();
    }
    long long int libjc::jctime_duration::tons() const
    {
        return rt.count();
    }

} // namespace libjc

使用方法：

#include <stdio.h>
#include "libjc"

int main()
{
    // start the timer
    libjc::jctime_high_resolution_clock tm1;
    tm1.start();

    // do some your own work
    unsigned  int a = ~(0);
    int b = 0;

    for (unsigned int i = 0; i < a; i++)
    {
        b++;
    }

    // stop the timer
    tm1.stop();
    auto da = tm1.duration();

    // print the duration in different units
    printf("time is :\n %lf s\n %lf hour \n %lf minutes \n %lf ms \n %lf us \n %lld ns\n",
            da.tosecond(),
            da.tohour(),
            da.tominute(),
            da.toms(),
            da.tous(),
            da.tons());

    return 0;
}

用chrono库写个方便使用的计时器