Pytorch: tensor multiplication

I want to code this matrix multiplication:

B=16, h=32, w=56, b*b=64, n=25
my code:

torch.mul(torch.rand([16, 32, 56, 64]),torch.rand([16, 32, 56, 64,25]))

but I encountered in with this error:

The size of tensor a (64) must match the size of tensor b (25) at non-singleton dimension 4

Would you mind helping me to fix this problem?


I think the simplest is to write it as a matrix matrix multiplication. And so add a temporary dimension of size 1 on the first Tensor:

torch.matmul(torch.rand([16, 32, 56, 1, 64]),torch.rand([16, 32, 56, 64,25])).squeeze(-2)
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Thanks for your reply. The problem solved.
Would you mind explaining it? I do not understand it.

It consider Bxhxw as batch dimensions. And 1x(bb) and (bb)xn for the other dimensions of each other dimensions.
Doing the matrix multiply between the two, will give you a Tensor with 1xn and with the same batch size.
The squeeze removes the dimension of size 1.

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Thanks for your help dear @albanD :slight_smile: