title: why C clock() returns 0
body: <p>I've got something like this:</p>
  
  <pre><code>clock_t start, end;
  start=clock();
  
  something_else();
  
  end=clock();
  printf("\nClock cycles are: %d - %d\n",start,end);
  </code></pre>
  
  <p>and I always get as an output "Clock cycles are: 0 - 0"</p>
  
  <p>Any idea why this happens?</p>
  
  <p>(Just to give little detail, the something_else() function performs a left-to-right exponentiation using montgomery representation, moreover I don't know for certain that the something_else() function does indeed take some not negligible time.)</p>
  
  <p>This is on Linux. The result of uname -a is:</p>
  
  <p><code>Linux snowy.*****.ac.uk 2.6.32-71.el6.x86_64 #1 SMP Fri May 20 03:51:51 BST 2011 x86_64 x86_64 x86_64 GNU/Linux</code></p>