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Constant Step Size Stochastic Gradient Descent for Probabilistic Modeling
Proceedings of the 34th Conference on Uncertainty in Artificial Intelligence, PMLR R16:218-227, 2018.
Abstract
Stochastic gradient methods enable learning probabilistic models from large amounts of data. While large step-sizes (learning rates) have shown to be best for least-squares (e.g., Gaussian noise) once combined with param- eter averaging, these are not leading to con- vergent algorithms in general. In this pa- per, we consider generalized linear models, that is, conditional models based on exponen- tial families. We propose averaging moment parameters instead of natural parameters for constant-step-size stochastic gradient descent. For finite-dimensional models, we show that this can sometimes (and surprisingly) lead to better predictions than the best linear model. For infinite-dimensional models, we show that it always converges to optimal predictions, while averaging natural parameters never does. We illustrate our findings with simulations on synthetic data and classical benchmarks with many observations.