Multiplying multidimensional array in python

Question

I have two arrays:

L, M, N = 6, 31, 500
A = np.random.random((L, M, N))
B = np.random.random((L, L))

I am trying to get an array C such that:

C = B * A

C has dimension  [L, M, N]

I tried answer posted at this link but it hasn't given me the desired output.

A for loop version of above code is:

L, M, N = 6, 31, 500
A = np.random.random((L, M, N))
B = np.random.random((L, L))

z1 = []
for j in range(M):
    a = np.squeeze(A[:, j, :])
    z1.append(np.dot(B, a))

z2 = np.stack(z1)

If you make the 2 dimensions of B different, there'll be less ambiguity. I don't think you need the squeeze. A[:,j:] will be 2d. — hpaulj
– hpaulj, Commented Aug 6, 2018 at 22:11
np.einsum('kl,lmn->kmn', B, A) should work; but your iterative solution implies a 'mkn' order. — hpaulj
– hpaulj, Commented Aug 6, 2018 at 22:13

tif · Accepted Answer · 2018-08-06 21:37:33Z

1

I think you are looking for numpy.tensordot() where you can specify along which axes to sum:

np.tensordot(B,A,axes=(1,0))

answered Aug 6, 2018 at 21:37

tif

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