Algorithms, Vol. 18, Pages 268: Adam Algorithm with Step Adaptation

Algorithms doi: 10.3390/a18050268

Authors:
Vladimir Krutikov
Elena Tovbis
Lev Kazakovtsev

Adam (Adaptive Moment Estimation) is a well-known algorithm for the first-order gradient-based optimization of stochastic objective functions, based on adaptive estimates of lower-order moments. As shown by computational experiments, with an increase in the degree of conditionality of the problem and in the presence of interference, Adam is prone to looping, which is associated with difficulties in step adjusting. In this paper, an algorithm for step adaptation for the Adam method is proposed. The principle of the step adaptation scheme used in the paper is based on reproducing the state in which the descent direction and the new gradient are found during one-dimensional descent. In the case of exact one-dimensional descent, the angle between these directions is right. In case of inexact descent, if the angle between the descent direction and the new gradient is obtuse, then the step is large and should be reduced; if the angle is acute, then the step is small and should be increased. For the experimental analysis of the new algorithm, test functions of a certain degree of conditionality with interference on the gradient and learning problems with mini-batches for calculating the gradient were used. As the computational experiment showed, in stochastic optimization problems, the proposed Adam modification with step adaptation turned out to be significantly more efficient than both the standard Adam algorithm and the other methods with step adaptation that are studied in the work.

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