Matlab: Does calling the same mex function repeatedly from a loop incur too much overhead?

Question

I have some Matlab code which needs to be speeded up. Through profiling, I\'ve identified a particular function as the culprit in slowing down the execution. This function i

Answer 1

Well, this is the fastest I can make it in Matlab:

%#eml
function L = test(s,t)

    m = numel(s);
    n = numel(t);

    % trivial cases
    if m==0 && n==0
        L = 0; return; end
    if n==0
        L = m; return; end
    if m==0
        L = n; return; end

    % non-trivial cases
    M = zeros(m+1,n+1);    
    M(:,1) = 0:m;

    for j = 2:n+1
        for i = 2:m+1
            M(i,j) = min([
                M(i-1,j) + 1
                M(i,j-1) + 1
                M(i-1,j-1) + (s(i-1)~=t(j-1));
                ]);
        end
    end

    L = min(M(end,:));

end

Can you compile this and run some tests? (For some weird reason, compilation fails to work on my installation...) Perhaps change %#eml to %#codegen first, if you think that's easier.

NOTE: for the C version, you should also interchange the for-loops, so that the loop over j is the inner one.

Also, the row1 and row2 approach is a lot more memory efficient. If you're going to compile anyway, I'd use that approach.