I am trying to use time() to measure various points of my program.
What I don't understand is why the values in the before and after are the same? I understand this is not the best way to profile my program, I just want to see how long something take.
printf("**MyProgram::before time= %ld\n", time(NULL));
doSomthing();
doSomthingLong();
printf("**MyProgram::after time= %ld\n", time(NULL));
I have tried:
struct timeval diff, startTV, endTV;
gettimeofday(&startTV, NULL);
doSomething();
doSomethingLong();
gettimeofday(&endTV, NULL);
timersub(&endTV, &startTV, &diff);
printf("**time taken = %ld %ld\n", diff.tv_sec, diff.tv_usec);
How do I read a result of **time taken = 0 26339? Does that mean 26,339 nanoseconds = 26.3 msec?
What about **time taken = 4 45025, does that mean 4 seconds and 25 msec?
25 Answers
//***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;
0 - Delta
Use a delta function to compute time differences:
auto start = std::chrono::steady_clock::now();
std::cout << "Elapsed(ms)=" << since(start).count() << std::endl;
since accepts any timepoint and produces any duration (milliseconds is the default). It is defined as:
template <
class result_t = std::chrono::milliseconds,
class clock_t = std::chrono::steady_clock,
class duration_t = std::chrono::milliseconds
>
auto since(std::chrono::time_point<clock_t, duration_t> const& start)
{
return std::chrono::duration_cast<result_t>(clock_t::now() - start);
}
