matlab - vectorizing a nested loop where one loop variable depends on the other

Question

I've recently learned how to vectorize a "simple" nested loop in a previous question I've asked. However, now I'm trying also to vectorize the following loop

A=rand(80,80,10,6,8,8);

I=rand(size(A1,3),1);
C=rand(size(A1,4),1);
B=rand(size(A1,5),1);

for i=1:numel(I)
    for v=1:numel(C)
        for j=1:numel(B)
            for k=1:j
                A(:,:,i,v,j,k)= A(:,:,i,v,j,k)*I(i)*C(v)*B(j)*((k-1>0)+1);               
            end
        end
    end
end

So now k depends in j... What have I tried so far: The combination of j and k terms (i.e. B(j)*((k-1>0)+1) gives a triangular matrix that I manage to vectorize independently:

  B2=tril([ones(8,1)*B']');
  B2(2:end,2:end)=2*B2(2:end,2:end);

But that gives me the (j,k) matrix properly and not a way to use it to vectorize the remaining loop. Maybe I'm in the wrong path too... So how can I vectorize that type of loop?

Answer 1

In one of your comments to the accepted solution of the previous question, you mentioned that successive bsxfun(@times,..,permute..) based codes were faster. If that's the case, you can use a similar approach here as well. Here's the code that uses such a pattern alongwith tril -

B1 = tril(bsxfun(@times,B,[1 ones(1,numel(B)-1).*2]));
v1 = bsxfun(@times,B1, permute(C,[3 2 1]));
v2 = bsxfun(@times,v1, permute(I,[4 3 2 1]));
A = bsxfun(@times,A, permute(v2,[5 6 4 3 1 2]));