Although more practical than Karnaugh mapping when dealing with more than four variables, the Quine-McCluskey algorithm also has a limited range of use since the algorithmproblem it solves is [[NP-complete]]: the [[runtime]] of the Quine-McCluskey algorithm grows [[expontential growth|exponentially]] with the input size. It can be shown that for a function of ''n'' variables the upper bound on the number of prime implicants is 3<sup>''n''</sup>/''n''. If ''n'' = 32 there may be over 6.1 * 10<sup>14</sup>, or 617 trillion prime implicants. Functions with a large number of variables have to be minimized with potentially non-optimal [[heuristic (computer science)|heuristic]] methods.
