我希望在用C ++实现的程序的微秒内获得准确的执行时间。我试图用clock_t获得执行时间，但这不准确。
如果您使用的是c ++ 11或更高版本，则可以使用std::chrono::high_resolution_clock。
一个简单的用例：
auto start = std::chrono::high_resolution_clock::now();
...
auto elapsed = std::chrono::high_resolution_clock::now() - start;
long long microseconds = std::chrono::duration_cast<std::chrono::microseconds>(elapsed).count();
该解决方案具有便携的优点。
如果您正在查看从Unix shell执行程序所消耗的时间，请使用Linux time，如下所示，
time ./a.out
real 0m0.001s
user 0m0.000s
sys 0m0.000s
其次，如果你想在程序代码（C）中执行多少语句，请尝试使用gettimeofday()，如下所示，
#include <sys/time.h>
struct timeval tv1, tv2;
gettimeofday(&tv1, NULL);
/* Program code to execute here */
gettimeofday(&tv2, NULL);
printf("Time taken in execution = %f seconds\n",
(double) (tv2.tv_usec - tv1.tv_usec) / 1000000 +
(double) (tv2.tv_sec - tv1.tv_sec));
如果您使用的是Windows，则可以使用QueryPerformanceCounter
见How to use the QueryPerformanceCounter function to time code in Visual C++
__int64 ctr1 = 0, ctr2 = 0, freq = 0;
int acc = 0, i = 0;
// Start timing the code.
if (QueryPerformanceCounter((LARGE_INTEGER *)&ctr1)!= 0)
{
// Code segment is being timed.
for (i=0; i<100; i++) acc++;
// Finish timing the code.
QueryPerformanceCounter((LARGE_INTEGER *)&ctr2);
Console::WriteLine("Start Value: {0}",ctr1.ToString());
Console::WriteLine("End Value: {0}",ctr2.ToString());
QueryPerformanceFrequency((LARGE_INTEGER *)&freq);
Console::WriteLine(S"QueryPerformanceCounter minimum resolution: 1/{0} Seconds.",freq.ToString());
// In Visual Studio 2005, this line should be changed to: Console::WriteLine("QueryPerformanceCounter minimum resolution: 1/{0} Seconds.",freq.ToString());
Console::WriteLine("100 Increment time: {0} seconds.",((ctr2 - ctr1) * 1.0 / freq).ToString());
}
else
{
DWORD dwError = GetLastError();
Console::WriteLine(S"Error value = {0}",dwError.ToString());// In Visual Studio 2005, this line should be changed to: Console::WriteLine("Error value = {0}",dwError.ToString());
}
// Make the console window wait.
Console::WriteLine();
Console::Write("Press ENTER to finish.");
Console::Read();
return 0;
您可以在整个过程生命周期内调用CreateProcess(...)和WaitForSingleObject(...)，否则围绕代码的主要功能。
新的C ++ 11 std::chrono库是我见过或试图弄清楚如何使用的最复杂的混乱堆之一，但至少它是跨平台的！
所以，如果你想简化它并使它更像“C-like”，包括删除它所做的所有类型安全类的东西，这里有3个简单易用的函数来获取时间戳，以毫秒为单位，微秒和纳秒...只花了我大约12小时写*：
#include <chrono>
// NB: ALL OF THESE 3 FUNCTIONS BELOW USE SIGNED VALUES INTERNALLY AND WILL EVENTUALLY OVERFLOW (AFTER 200+ YEARS OR
// SO), AFTER WHICH POINT THEY WILL HAVE *SIGNED OVERFLOW*, WHICH IS UNDEFINED BEHAVIOR (IE: A BUG) FOR C/C++.
// But...that's ok...this "bug" is designed into the C++11 specification, so whatever. Your machine won't run for 200
// years anyway...
// Get time stamp in milliseconds.
uint64_t millis()
{
uint64_t ms = std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::high_resolution_clock::
now().time_since_epoch()).count();
return ms;
}
// Get time stamp in microseconds.
uint64_t micros()
{
uint64_t us = std::chrono::duration_cast<std::chrono::microseconds>(std::chrono::high_resolution_clock::
now().time_since_epoch()).count();
return us;
}
// Get time stamp in nanoseconds.
uint64_t nanos()
{
uint64_t ns = std::chrono::duration_cast<std::chrono::nanoseconds>(std::chrono::high_resolution_clock::
now().time_since_epoch()).count();
return ns;
}
*（对不起，我更像是一个嵌入式开发人员，而不是标准的计算机程序员，因此所有这些高级的，抽象的静态成员在命名空间内的命名空间内的命名空间让我感到困惑.Don别担心，我会好起来的。）
这里有一些参考：