A `for` loop with a large number of iterations is a good candidate for parallel execution, and Julia has a special construct to do this: the `@parallel` macro, which can be used for the `for` loops and comprehensions.

Let's calculate an approximation for `Π` using the famous Buffon's needle problem. If we drop a needle onto a floor with equal parallel strips of wood, what is the probability that the needle will cross a line between two strips? Let's take a look at the following screenshot:

Without getting into the mathematical intricacies of this problem (if you are interested, see http://en.wikipedia.org/wiki/Buffon's_needle ...