title: Fastest primality test
body: <p>Could you suggest a fast, deterministic method that is usable in practice, for testing if a large number is prime or not?   </p>
  
  <p>Also, I would like to know how to use non-deterministic primality tests correctly. For example, if I'm using such a method, I can be sure that a number is not prime if the output is "no", but what about the other case, when the output is "probably"? Do I have to test for primality manually in this case?</p>
  
  <p>Thanks in advance. </p>