“…However, in fact, the convexity assumption may not be required, because the algorithm may be well defined even if the considered set is nonconvexs (e.g., when the considered set is a closed subset of a finite dimensional space or a compact subset of Hilbert space, etc.) see [1,4,20,25,26,27]. While, it may be from the practical point of view, one may see that the nonconvex problems are more useful and general than convex case, subsequently, now many researchers are convinced and paid attention to many nonconvex cases.…”