What does the last two points mean?
Dot product of two arrays. Specifically,
If both a and b are 1-D arrays, it is inner product of vectors (without complex conjugation).
If both a and b are 2-D arrays, it is matrix multiplication, but using
a @ b is preferred.
If either a or b is 0-D (scalar), it is equivalent to
multiply and using
numpy.multiply(a, b) or
a * b is preferred.
If a is an N-D array and b is a 1-D array, it is a sum product over the last axis of a and b.
If a is an N-D array and b is an M-D array (where
M>=2), it is a sum product over the last axis of a and the second-to-last axis of b:
My understanding is that 2-D arrays are a matrix. N-D array is a tensor. The aforementioned example is very clear. Both a and b are 3-D arrays.