Why is this output waiting for something after it?

Question

void Wait(double Duration)
{
    clock_t End;
    End = clock() + (Duration*CLOCKS_PER_SEC);

    while (clock() < End)
    {
        // This loop just stalls the program.
    }
}

My function works perfectly half the time, but it occasionally stalls the program before it's even called. For example, take the following snippet:

cout << "This is\n";
Wait(2.5)
cout << "a test!";

You'd expect the first line to appear immediately and the second line to appear after 2.5 seconds, but it sometimes ALL appears after 2.5 seconds. What's the deal?

Answer 1

try

cout.flush();

before your Wait

Answer 2

That might be because of I/O buffering. You should flush the output buffer (either try << endl instead of '\n' or writing cout.flush) manually.

Answer 3

Try cout << "This is" << endl;

It looks like a buffering, not clock issue.

Answer 4

The flush()/std::endl has already been mentioned - but is your intention to really consume 100% of one core while you wait? This is what the while() loop is doing! If you want a nicer approach to "waiting", consider one of the following:

1. boost::thread::sleep() - millisecond granularity
2. alarms (1 second granularity)
3. select()
4. pthread_cond_timedwait()

etc.