title: OpenMP #pragma num_threads
body: <p>I am trying to understand OpenMP a bit, but I am confused how I am allowed to enter variables in num_threads() when it is a part of a #pragma which is a place to give information to the compiler. I was expecting it would not allow variables as a parameter to the num_threads but looks like I am allowed to use variables. How is that? How does it work?</p>