Numpy 二维矩阵 乘以 三维矩阵 (Numpy, 2D matrix multiplies 3D matrix)

Numpy 二维矩阵 乘以 三维矩阵 (Numpy, 2D matrix multiplies 3D matrix)

Learn to apply the broadcast rule in Numpy.

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goal: element-wise matrix multiplication

arguments:

A: 2×3×4

B: 2×4

C = A*B (* means element-wise multiplication in Numpy)

========

code:

import numpy as np

A = np.ones([2, 3, 4])

B = np.ones([2, 4])

C = A*B[:, None, :]

Because the dimension of B[:, None, :] is thus 2×1×4, in which the second axis is 1, so it's ok to apply broadcast rule.

That's all!