# How can we compute batch matrix-matrix product of matrices (3-D tensors) in MATLAB?

15 views (last 30 days)
BIPIN SAMUEL on 5 Dec 2023
Commented: BIPIN SAMUEL on 7 Dec 2023
I have two 3-D tensors of size b*n*m and b*m*p. I need the product of these two tensors to get the output size as b*n*p. I have used direct matrix multiplication using * operator. Moreover, I have used 'pagetimes'. But it is not working. Is there any function in MATLAB like 'torch.bmm' in python as shown in link: https://pytorch.org/docs/stable/generated/torch.bmm.html to do the matrix multiplication of two 3-D tensors.

Bruno Luong on 5 Dec 2023
b = 2;
n = 3;
m = 4;
p = 5;
A = rand(b,n,m);
B = rand(b, m,p);
AA = permute(A, [2 3 1]);
BB = permute(B, [2 4 1 3]);
AB=pagemtimes(AA, BB);
AB=permute(AB,[3 1 4 2]);
size(AB)
ans = 1×3
2 3 5
AB
AB =
AB(:,:,1) = 1.1069 0.9331 1.2839 0.4248 1.0635 1.2576 AB(:,:,2) = 1.3688 1.5129 1.6656 0.6568 1.2286 1.3592 AB(:,:,3) = 1.0351 1.2450 1.3362 0.4743 1.1831 1.3162 AB(:,:,4) = 1.2485 1.0840 1.4573 0.7987 1.7168 1.7815 AB(:,:,5) = 0.5739 0.7361 0.7294 0.9621 1.9460 2.0458
Bruno Luong on 6 Dec 2023
Sorry I don't know dlarray, and I'm not sure what layer do you refer to.
BIPIN SAMUEL on 7 Dec 2023
I refer to the deep learning layer where input is 3-D tensor in the formatted dlarray and I want to do these operations as a part of forming that layer.