I'm be surprised if there was that large of a speedup going from a well-written numpy implementation to C/C++ (assuming a non-parallel implementation in both)..

I'm be surprised if there was that large of a speedup going from a well-written numpy implementation to C/C++ (assuming a non-parallel implementation in both)... In my experience, it's usually more like 2x-5x for a straight translation of the algorithm from numpy to C. (Though I have to confess that I often write rather naive C...) Numpy performs quite well if you avoid a few common pitfalls. It certainly can be beat, but it's often faster than people think it is.