Can I make this for loop fast?

Hi, I have a for loop that do some matrix multplicaton. Here, max i and j is 2000, U_new is a matrix of size 200 by 20, K111 cell contains 2000 full matrices of size 200 by 200.

p = 0;
for i =1:max(size(K111))
    for j =1:max(size(K111))
        p = p + 1;
        KQQ{p} = U_new'*K111{i}*K111{j}*U_new;
    end
end

[Matt J]

Are the K111 matrices symmetric?

[Mohammod Minhajur Rahman]

Hi Matt, Yes, the K111 matrices are symmetric

Answer 1

[Matt J]

Here I make occasional use of MAT2TILES (Download),

UK=cell2mat( mat2tiles( U_new'*cell2mat(K111(:).')  ,[20,200]).'  );

KQQ= mat2tiles( UK*UK.'  ,[20,20]);
 KQQ=KQQ(:);

[Mohammod Minhajur Rahman]

Much Thanks! It works great