Stochastic Online Learning with Feedback Graphs: Finite-Time and Asymptotic Optimality

We revisit the problem of stochastic online learning with feedback graphs, with the goal of devising algorithms that are optimal, up to constants, both asymptotically and in finite time. We show that, surprisingly, the notion of optimal finite-time regret is not a uniquely defined property in this context and that, in general, it is decoupled from the asymptotic rate. We discuss alternative choices and propose a notion of finite-time optimality that we argue is meaningful. For that notion, we give an algorithm that admits quasi-optimal regret both in finite-time and asymptotically.