From an engineering point of view it really does not matter. The chance that the probabilistic algorithm fails is so insignificantly small, that cosmic rays hit

From an engineering point of view it really does not matter. The chance that the probabilistic algorithm fails is so insignificantly small, that cosmic rays hitting your CPU registers is probably a bigger problem. From a mathematical/CS point of view, indeed it was a fairly recent, and fairly pleasant discovery that the primality testing algorithm can be derandomized while still retaining its low complexity (it was suspected for a long time, but proving it was awesome).