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
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