Absolutely agreed, especially the part about needing to hide the inner loop in extension module. If you're using numpy to mutiply 2 x 2 matrices together then t

Absolutely agreed, especially the part about needing to hide the inner loop in extension module. If you're using numpy to mutiply 2 x 2 matrices together then the fact it releases the GIL is not that much help. As I said, my experience is that this is not normally a problem in practice. Clearly that's not your experience! I'm not sure whether I've been unusually lucky or you've been unusually unlucky.