Assume that we have a non-convex optimization $\min_{A,B} f(A,B)+\lambda g(A,B)$. Specifically, $f(A,B)+\lambda g(A,B)$ is not joint convex, but it is convex with regard to one variable when fixing another variable.
Now the question is could we use the following equation to prove the monotonic decrease of the objective $f(A,B)+\lambda g(A,B)$ value during the alternating technique based algorithm 1 like optimization process?
$$(A^{(t+1)},B^{(t+1)})=\arg \min_{A,B} f(A^{(t)},B^{(t)})+\lambda g(A^{(t)},B^{(t)}), $$
where $t$ is the iteration counter.
Algorithm-1:
Repeat
1. Updating $A^{(t+1)}$
2. Updating $B^{(t+1)}$
3. t=t+1;
Until convergence
Thank you so much for your reply.