import numpy as np
cimport numpy as np

# Fixing datatypes
DTYPE = np.float
ctypedef np.float_t DTYPE_t

def chebyshev_derivative_gc():
    """ Calculate the first derivative of a function
    """
    cdef int m = 6
    cdef int N = 64
    cdef np.ndarray[DTYPE_t, ndim = 2] a = np.random.random( ( m, N ) )
    cdef np.ndarray[DTYPE_t, ndim = 2] b = np.zeros( (m, N), dtype = DTYPE )
    
    cdef int i, j

    for i in xrange(m):
        b[i, N - 2] = 2 * ( N - 1 ) * a[i, N - 1]
        
    for i in xrange(m):
        for j in xrange( N - 2, 0, -1 ):
            # The next line is the offender - try by commenting out.
            b[i, j - 1] = ( 2 * j ) * a[i, j] + b[i, j + 1]