Getting an accurate execution time in C++ (micro seconds)

Question

I want to get an accurate execution time in micro seconds of my program implemented with C++. I have tried to get the execution time with clock_t but it\'s not accurate.

Answer 1

If you're on Windows, you can use QueryPerformanceCounter

See 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;

You can put it around a call to CreateProcess(...) and WaitForSingleObject(...) for the entire process lifetime, otherwise around the main function for your code.