Except that every sort algorithm in every library on earth falls back to selection sort (or similar) for small problems (e.g. N < 10), because that's more efficient than drilling a merge sort all the way down.
How is that relevant? Is your contention that the code in question will never see performance problems because there's a constant factor that outweighs the runtime? That's not my read at all. It looks to me like sorting 40k items that happen to be packed in a sparse array is going to take on the order of a billion operations. No?
