let description = [{
This op uses two algorithms, depending on rate. If rate >= 10, then
the algorithm by Hormann is used to acquire samples via
transformation-rejection.
See http://www.sciencedirect.com/science/article/pii/0167668793909974.

Otherwise, Knuth's algorithm is used to acquire samples via multiplying uniform
random variables.
See Donald E. Knuth (1969). Seminumerical Algorithms. The Art of Computer