title: Cython: understanding what the html annotation file has to say?
body: <p>After compiling the following Cython code, I get the html file that looks like this:</p>
  
  <pre><code>import numpy as np
  cimport numpy as np
  
  cpdef my_function(np.ndarray[np.double_t, ndim = 1] array_a,
                    np.ndarray[np.double_t, ndim = 1] array_b,
                    int n_rows,
                    int n_columns):
  
      array_a[0:-1:n_columns] = 0
      array_a[n_columns - 1:n_rows * n_columns:n_columns] = 0
      array_a[0:n_columns] = 0
      array_a[n_columns* (n_rows - 1):n_rows * n_columns] = 0
      array_b[array_a == 3] = 0
  
      return array_a, array_b
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/CwT9n.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/CwT9n.jpg" alt="enter image description here"></a></p>
  
  <p>My question is that why those operations of my function are still yellow? Does this mean that the code is still not as fast as it could be using Cython?</p>