  This paper uncovers a simple but rather surprising connection: it shows that
the well-known convex-concave procedure (CCCP) and its generalization to
constrained problems are both special cases of the Frank-Wolfe (FW) method.
This connection not only provides insight of deep (in our opinion) pedagogical
value, but also transfers the recently discovered convergence theory of
nonconvex Frank-Wolfe methods immediately to CCCP, closing a long-standing gap
in its non-asymptotic convergence theory. We hope the viewpoint uncovered by
this paper spurs the transfer of other advances made for FW to both CCCP and
its generalizations.
