the different between np.dot and np.multiply

np.dot is the dot product of two matrices.

|A B| . |E F| 　　　|A*E+B*G　 A*F+B*H|

　　　　　　＝

|C D| 　|G H| 　　|C*E+D*G 　C*F+D*H|

Whereas np.multiply does an element-wise multiplication of two matrices.

|A B| ⊙ |E F| 　　 |A*E B*F|

　　　　　　=

|C D| 　  |G H|        |C*G D*H|

When used with np.sum, the result being equal is merely a coincidence.

>>> np.dot([[1,2], [3,4]], [[1,2], [2,3]])array([[ 5,  8],      [11, 18]])

>>> np.multiply([[1,2], [3,4]], [[1,2], [2,3]])array([[ 1,  4],      [ 6, 12]])

>>> np.sum(np.dot([[1,2], [3,4]], [[1,2], [2,3]]))42

>>> np.sum(np.multiply([[1,2], [3,4]], [[1,2], [2,3]]))23

statckoverflow 上的解释