Several recently proposed stochastic optimization methods that have been successfully used in training deep networks such as RMSProp, Adam, Adadelta, Nadam, etc are based on using gradient updates scaled by square roots of exponential moving averages of squared past gradients. It has been empirically observed that sometimes these algorithms fail to converge to an optimal solution (or a critical point in nonconvex settings). We show that one cause for such failures is the exponential moving average used in the algorithms. We provide an explicit example of a simple convex optimization setting where Adam does not converge to the optimal solution, and describe the precise problems with the previous analysis of Adam algorithm. Our analysis suggests that the convergence issues may be fixed by endowing such algorithms with "long-term memory" of past gradients, and propose new variants of the Adam algorithm which not only fix the convergence issues but often also lead to improved empirical performance.
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Mon Apr 30 03:30 PM -- 03:45 PM (PDT) @ Exhibition Hall A
On the Convergence of Adam and Beyond
In Mon PM Talks