For non-negative matrix factorization with Frobenius norm:
$$\min\limits_{U\in\mathbb{R}_+^{m\times r}, V\in\mathbb{R}_+^{r\times n}}||A-UV||_F^2, A\in\mathbb{R}_+^{m\times n}$$
$r=1$ is a very special case because the optimal solution is given by SVD and there is no need to perform successive minimization by $V$ with fixed $U$ and vice versa.
Is there anything special for $r=1$ when minimization is performed with respect to some other norm, for example, $l_1$, Kullback-Leibler divergence or any other divergence, or should it just be done by the algorithms for the general case?