Reviews: Understanding the Role of Momentum in Stochastic Gradient Methods

INDIVIDUAL COMMENTS / QUESTIONS 1) I really appreciate how the paper ties up loose ends by unifying the analysis of several momentum-based methods in the stochastic setting. I am not very closely familiar with the literature analyzing momentum methods, but there's a lot of work out there (e.g., the line of research studying momentum methods in the continuous time limit). A brief review would be very helpful to position the paper within the existing work. To me this implies that the analysis would go through for more general functions. I don't find it obvious that it would.