title: python np.dot outer product works but inner product returns nan, so weird
body: <p><a href="https://i.stack.imgur.com/CguBb.png" rel="nofollow noreferrer">jupyter notebook partial output, please check it out</a></p>
  
  <p><a href="https://i.stack.imgur.com/CguBb.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/CguBb.png" alt="enter image description here"></a></p>
  
  <p>I try a lot of method to change the datatype but still not working. Is it a bug for numpy?</p>