Speed up Matrix multiplication

Question

0 个投票

I want to do the following Matrix Multiplication. Problem - Example:

A = rand(3,3,1000000);
B = rand(3,1000000)

How to calculate C faster than with this For-loop? I tried parfor but its only slightly faster.

Furthermore i'd prefer not to install the Parallel Computing Toolbox or MTIMESX. Is it possible just with reshape/permute/bsxfun?

C = zeros(3,1,size(B,2));
for idx=1:size(B,2)
    C(:,:,idx) = A(:,:,idx) * B(:,idx);
end

Thanks!

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Michael Soskind 2020-4-20

在 MATLAB Online 中打开

I see a marginal performance improvement by simply getting rid of the middle array index:

A = rand(3,3,1e6);
B = rand(3,1e6);
% original code
tic
C = zeros(3,1,size(B,2));
for idx=1:size(B,2)
    C(:,:,idx) = A(:,:,idx) * B(:,idx);
end
toc
% modified code with one fewer array dimension
tic
C = zeros(3,size(B,2));
for idx=1:size(B,2)
    C(:,idx) = A(:,:,idx) * B(:,idx);
end
toc