How to time a function in milliseconds without boost::timer - c++

Question

I am using boost 1.46 which does not include boost::timer, What other way can I time my functions.
I am currently doing this:
time_t now = time(0);
<some stuff>
time_t after = time(0);
cout << after - now << endl;
but it just gives the answer in seconds, so if the function takes < 1s it displays 0.
Thanks

Answer 1

In linux or Windows:
#include <ctime>
#include <iostream>
int
main(int, const char**)
{
std::clock_t start;
start = std::clock();
// your test
std::cout << "Time: " << (std::clock() - start) / (double)(CLOCKS_PER_SEC / 1000) << " ms" << std::endl;
return 0;
}
Good Luck ;)

Answer 2

Using std::chrono:
#include <chrono>
#include <thread>
#include <iostream>
// There are other clocks, but this is usually the one you want.
// It corresponds to CLOCK_MONOTONIC at the syscall level.
using Clock = std::chrono::steady_clock;
using std::chrono::time_point;
using std::chrono::duration_cast;
using std::chrono::milliseconds;
using namespace std::literals::chrono_literals;
using std::this_thread::sleep_for;
int main()
{
time_point<Clock> start = Clock::now();
sleep_for(500ms);
time_point<Clock> end = Clock::now();
milliseconds diff = duration_cast<milliseconds>(end - start);
std::cout << diff.count() << "ms" << std::endl;
}
std::chrono is C++11, std::literals is C++14 (otherwise you need milliseconds(500)).

Answer 3

Turns out there is a version of time in boost 1.46 (just in different location). Thanks to
#jogojapan for pointing it out.
It can be done like this:
#include <boost/timer.hpp>
timer t;
<some stuff>
std::cout << t.elapsed() << std::endl;
Or alternatively using std libs as #Quentin Perez has pointed out (and I will accept as is what was originally asked)

Answer 4

Building on Quentin Perez's solution, you can pass an arbitrary function to time using std::function and a lambda.
#include <ctime>
#include <iostream>
#include <functional>
void timeit(std::function<void()> func) {
std::clock_t start = std::clock();
func();
int ms = (std::clock() - start) / (double) (CLOCKS_PER_SEC / 1000);
std::cout << "Finished in " << ms << "ms" << std::endl;
}
int main() {
timeit([] {
for (int i = 0; i < 10; ++i) {
std::cout << "i = " << i << std::endl;
}
});
return 0;
}

Answer 5

You can use a long to hold the current time value as a start value, and then convert the current time to a double. here is some snippet code to use as an example.
#include <iostream>
#include <stdlib.h>
#include <time.h>
#include <sys/types.h>
#include <sys/timeb.h>
int main()
{
struct _timeb tStruct;
double thisTime;
bool done = false;
long startTime;
struct _timeb
{
int dstflag; // holds a non-zero value if daylight saving time is in effect
long millitm; // time in milliseconds since the last one-second hack
long time; // time in seconds since 00:00:00 1/1/1970
long timezone; // difference in minutes moving west from UTC
};
_ftime(&tStruct); // Get start time
thisTime = tStruct.time + (((double)(tStruct.millitm)) / 1000.0); // Convert to double
startTime = thisTime; // Set the starting time (when the function begins)
while(!done) // Start an eternal loop
{
system("cls"); // Clear the screen
_ftime(&tStruct); // Get the current time
thisTime = tStruct.time + (((double)(tStruct.millitm)) / 1000.0); // Convert to double
// Check for 5 second interval to print status to screen
cout << thisTime-startTime; // Print it.
}
}