How to multiply a tensor row-wise by a vector in PyTorch?

Question

When I have a tensor m of shape [12, 10] and a vector s of scalars with shape [12], how can I multiply each row of m with the corresponding scalar in s?

Answer 1

You need to add a corresponding singleton dimension:

m * s[:, None]

s[:, None] has size of (12, 1) when multiplying a (12, 10) tensor by a (12, 1) tensor pytorch knows to broadcast s along the second singleton dimension and perform the "element-wise" product correctly.