title: How to measure function running time in Qt?
body: <p>I am calling <a href="https://en.wikipedia.org/wiki/Argon2" rel="noreferrer">argon2</a> - memory intensive hashing function in Qt and measuring its running time:</p>
  
  <pre><code>...
  QTime start = QTime::currentTime();
  // call hashing function
  QTime finish = QTime::currentTime();
  time = start.msecsTo(finish) / 1000.0;
  ...
  </code></pre>
  
  <p>In argon2 library's test case, time is measured in another way:</p>
  
  <pre><code>...
  clock_t start = clock();
  // call hashing function
  clock_t finish = clock();
  time = ((double)finish - start) / CLOCKS_PER_SEC;
  ...
  </code></pre>
  
  <p>I am calling the function exactly as they call in their test case. But I am getting a twice bigger number (twice slower). Why? How to measure function running time in Qt? What clock() actually measures?</p>
  
  <p><strong>env</strong>:virtualBox, Ubuntu14.04 64bit, Qt5.2.1, Qt Creator 3.0.1.</p>