Re: elapsed time 0 with std::cin

"Christopher Pisz" <>
Fri, 23 Nov 2007 21:16:06 -0600
"pekka" <pekka@nospam.invalid> wrote in message

I'm trying to measure user input time with my Timer class object. It isn't
as easy as I expected. When using std::cin between timer start and stop, I
get zero elapsed time. For some unknown reason, the clock seems to stop
ticking during execution of std::cin.

Here's my code:

#include <ctime>
#include <iostream>
#include <string>

class Timer
clock_t start_, nticks_;

Timer() : nticks_(0) { start(); }
~Timer() {}

void start() { start_ = clock(); }
void stop() { nticks_ = clock() - start_; }
double elapsed() const { return double(nticks_) / CLOCKS_PER_SEC; }

int main()
std::string answer;
Timer T;
// for (int n=0; n<100000000; ++n);
std::cout << "? ";
std::cin >> answer;
std::cout << "time elapsed: " << T.elapsed() << "\n";

If I use the loop at the commented line, instead of std::cin, the timer
works as expected. I can't figure out what's wrong here.


If you are looking to do a timer, you are better off using a OS specific
timer. The ctime family is really only good for precisions of 1 second.
Things like input can happen more often than 1 second. I am fairly certain
that *nix offers some form of high precision timer and I know that MS does.
You'll have to google around a bit.

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