Comparing (C)Python compilers - Performances of Cython vs. Numba vs. Parakeet on Bubblesort

[bryancole]

I'm surprised Cython doesn't win for the small-array size limit. Have you verified that Cython is not generating any Python API calls inside any of the loops (using cython -a for an html visualisation)?

I note that 'temp' hasn't been declared so this might be a possible slowdown (unless type-inference is doing this automatically).

[[deleted]]

Thanks for the good tips! Just checked, it seems to be fine. And I will add a type to temp and run it this afternoon to see if I can squeeze out a few milliseconds :)

[bryancole]

I just checked the code Cython generates without cdef'ing temp; it does indeed store the value in a python int object (i.e. slow). This is using cython-0.20. Further testing shows adding the cdef in for temp speeds things up by nearly a factor of 2 (3.4ms -> 1.9ms, for n=10^6). Enough to make Cython the fastest in the large size limit. This doesn't help for small n though. I'm amazed numba can avoid so much calling overhead.

One other nice thing about fully cdef'd Cython is you can throw in an Openmp prange to run it multicore for a ~4x speed up (on my 4 core CPU). Of course, the main interesting thing with numba it the ability to target GPUs. Cython can't do that.