PyTorch: Row-wise Dot Product

Question

Suppose I have two tensors:

a = torch.randn(10, 1000, 1, 4) b = torch.randn(10, 1000, 6, 4)

Where the third index is the index of a vector.

I want to take the dot product between each vector in b with respect to the vector in a.

To illustrate, this is what I mean:

dots = torch.Tensor(10, 1000, 6, 1) for b in range(10): for c in range(1000): for v in range(6): dots[b,c,v] = torch.dot(b[b,c,v], a[b,c,0])

How would I achieve this using torch functions?

Seyed Sajad Ashrafi · Accepted Answer · 2020-05-18 18:15:40Z

a = torch.randn(10, 1000, 1, 4) b = torch.randn(10, 1000, 6, 4) c = torch.sum(a * b, dim=-1) print(c.shape)

torch.Size([10, 1000, 6])

c = c.unsqueeze(-1) print(c.shape)

torch.Size([10, 1000, 6, 1])

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