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How to multiply 3D matrices without using for loop

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KostasK
KostasK on 16 Oct 2020
Commented: KostasK on 16 Oct 2020
Hi all,
I would like to know if there is a way to multiply 3D matrices, preferably without using a for loop. The reason I do not want to use a for loop is because there is a lot of 'ugly' code involved. Certainly this is not life or death, as there are ways to perform this with a for loop, however it would be good to know if there is an alternative way.
In specific, I have the following code:
A = rand(5, 3, 10) ;
B = rand(5, 10) ;
C = zeros(3, 1, 10) ;
for i = 1:size(A, 3)
C(:,:,i) = A(:,:,i)'*B(:,i) ;
end
D = sum(C, 3) ;

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Accepted Answer

Bruno Luong
Bruno Luong on 16 Oct 2020
Edited: Bruno Luong on 16 Oct 2020
If you have R2020b
C = pagemtimes(A,'ctranspose',B,'none');
Or using MTIMESX on File-Exchange
I just make a quick comparison and both seem similarly fast.

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