In [4]:

%load_ext cythonmagic

In [8]:

%%cython
cimport numpy as cnp
import numpy as np

ctypedef cnp.float64_t FLOAT_t


cpdef FLOAT_t cython_sum(cnp.ndarray[FLOAT_t, ndim=1] A):
   cdef double [:] x = A
   cdef double sum = 0
   cdef unsigned int N = A.shape[0]
   for i in xrange(N):
     sum += x[i]
   return sum

cpdef FLOAT_t cython_avg(cnp.ndarray[FLOAT_t, ndim=1] A):
   cdef double [:] x = A
   cdef double sum = 0
   cdef unsigned int N = A.shape[0]
   for i in xrange(N):
     sum += x[i]
   return sum/N


cpdef FLOAT_t cython_silly_avg(cnp.ndarray[FLOAT_t, ndim=1] A):
   cdef unsigned int N = A.shape[0]
   return cython_avg(A)*N

In [11]:

A = np.random.random(100000)

In [12]:

%timeit A.mean()

10000 loops, best of 3: 143 µs per loop

In [13]:

%timeit cython_avg(A)

10000 loops, best of 3: 120 µs per loop

In [14]:

%timeit cython_sum(A)

10000 loops, best of 3: 119 µs per loop