Maybe I didn't have appropriate compiler flags. I didn't devote much time to it, as it didn't seem promising from my initial attempts and I found it easier to

Maybe I didn't have appropriate compiler flags. I didn't devote much time to it, as it didn't seem promising from my initial attempts and I found it easier to get faster performance with other methods (see reply to sibling comment). This was integer numerical code filling in a 2D array with lots of individual comparisons and backtracking (no whole-array operations). Terrible for plain Python, but Cython and C ate it up.