//***C++11 Style:***
#include <chrono>

std::chrono::steady_clock::time_point begin = std::chrono::steady_clock::now();
std::chrono::steady_clock::time_point end = std::chrono::steady_clock::now();

std::cout << "Time difference = " << std::chrono::duration_cast<std::chrono::microseconds>(end - begin).count() << "[µs]" << std::endl;
std::cout << "Time difference = " << std::chrono::duration_cast<std::chrono::nanoseconds> (end - begin).count() << "[ns]" << std::endl;

从所看到的内容来看，tv_sec存储所经过的秒数，而tv_usec单独存储所经过的微秒数。它们不是彼此的转换。因此，必须将它们更改为适当的单位，并添加它们以获得所消耗的总时间。

struct timeval startTV, endTV;

gettimeofday(&startTV, NULL); 

doSomething();
doSomethingLong();

gettimeofday(&endTV, NULL); 

printf("**time taken in microseconds = %ld\n",
    (endTV.tv_sec * 1e6 + endTV.tv_usec - (startTV.tv_sec * 1e6 + startTV.tv_usec))
    );

time(NULL)函数将返回从1970年1月1日00:00开始经过的秒数。因为这个函数在程序中不同的时间被调用，所以它总是不同的 c++中的时间

这两个值相同的原因是因为您的长过程不需要那么长时间—不到一秒。你可以试着添加一个长循环(for (int i = 0;I < 100000000;i++);)在函数的末尾确保这是问题所在，然后我们可以从那里…

如果上面的情况是正确的，你将需要找到一个不同的系统函数(我知道你在linux上工作，所以我不能帮助你知道函数名称)来更准确地测量时间。我相信在linux中有一个类似于GetTickCount()的函数，你只需要找到它。

#include <ctime>
#include <cstdio>
#include <iostream>
#include <chrono>
#include <sys/time.h>
using namespace std;
using namespace std::chrono;

void f1()
{
  high_resolution_clock::time_point t1 = high_resolution_clock::now();
  high_resolution_clock::time_point t2 = high_resolution_clock::now();
  double dif = duration_cast<nanoseconds>( t2 - t1 ).count();
  printf ("Elasped time is %lf nanoseconds.\n", dif );
}

void f2()
{
  timespec ts1,ts2;
  clock_gettime(CLOCK_REALTIME, &ts1);
  clock_gettime(CLOCK_REALTIME, &ts2);
  double dif = double( ts2.tv_nsec - ts1.tv_nsec );
  printf ("Elasped time is %lf nanoseconds.\n", dif );
}

void f3()
{
  struct timeval t1,t0;
  gettimeofday(&t0, 0);
  gettimeofday(&t1, 0);
  double dif = double( (t1.tv_usec-t0.tv_usec)*1000);
  printf ("Elasped time is %lf nanoseconds.\n", dif );
}
void f4()
{
  high_resolution_clock::time_point t1 , t2;
  double diff = 0;
  t1 = high_resolution_clock::now() ;
  for(int i = 1; i <= 10 ; i++)
  {
    t2 = high_resolution_clock::now() ;
    diff+= duration_cast<nanoseconds>( t2 - t1 ).count();
    t1 = t2;
  }
  printf ("high_resolution_clock:: Elasped time is %lf nanoseconds.\n", diff/10 );
}

void f5()
{
  timespec ts1,ts2;
  double diff = 0;
  clock_gettime(CLOCK_REALTIME, &ts1);
  for(int i = 1; i <= 10 ; i++)
  {
    clock_gettime(CLOCK_REALTIME, &ts2);
    diff+= double( ts2.tv_nsec - ts1.tv_nsec );
    ts1 = ts2;
  }
  printf ("clock_gettime:: Elasped time is %lf nanoseconds.\n", diff/10 );
}

void f6()
{
  struct timeval t1,t2;
  double diff = 0;
  gettimeofday(&t1, 0);
  for(int i = 1; i <= 10 ; i++)
  {
    gettimeofday(&t2, 0);
    diff+= double( (t2.tv_usec-t1.tv_usec)*1000);
    t1 = t2;
  }
  printf ("gettimeofday:: Elasped time is %lf nanoseconds.\n", diff/10 );
}

int main()
{
  //  f1();
  //  f2();
  //  f3();
  f6();
  f4();
  f5();
  return 0;
}

struct profiler
{
    std::string name;
    std::chrono::high_resolution_clock::time_point p;
    profiler(std::string const &n) :
        name(n), p(std::chrono::high_resolution_clock::now()) { }
    ~profiler()
    {
        using dura = std::chrono::duration<double>;
        auto d = std::chrono::high_resolution_clock::now() - p;
        std::cout << name << ": "
            << std::chrono::duration_cast<dura>(d).count()
            << std::endl;
    }
};

#define PROFILE_BLOCK(pbn) profiler _pfinstance(pbn)

用法如下:

{
    PROFILE_BLOCK("Some time");
    // your code or function
}

这在范围上类似于RAII

注:这不是我的，但我认为这是相关的