function [old_dirs,old_stps,Hdiag] = lbfgsUpdate(y,s,corrections,debug,old_dirs,old_stps,Hdiag)

ys = y'*s;

if ys > 1e-10

    numCorrections = size(old_dirs,2);

    if numCorrections < corrections

        % Full Update

        old_dirs(:,numCorrections+1) = s;

        old_stps(:,numCorrections+1) = y;

    else

        % Limited-Memory Update

        old_dirs = [old_dirs(:,2:corrections) s];

        old_stps = [old_stps(:,2:corrections) y];

    end



    % Update scale of initial Hessian approximation

    Hdiag = ys/(y'*y);

else

    if debug

        fprintf('Skipping Update\n');

    end

end