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Effective sketching methods for value function approximation
Proceedings of the 33rd Conference on Uncertainty in Artificial Intelligence, PMLR R15:301-310, 2017.
Abstract
High-dimensional representations, such as ra- dial basis function networks or tile cod- ing, are common choices for policy evalua- tion in reinforcement learning. Learning with such high-dimensional representations, how- ever, can be expensive, particularly for matrix methods, such as least-squares temporal differ- ence learning or quasi-Newton methods that approximate matrix step-sizes. In this work, we explore the utility of sketching for these two classes of algorithms. We highlight issues with sketching the high-dimensional features directly, which can incur significant bias. As a remedy, we demonstrate how to use sketching more sparingly, with only a left-sided sketch, that can still enable significant computational gains and the use of these matrix-based learn- ing algorithms that are less sensitive to param- eters. We empirically investigate these algo- rithms, in four domains with a variety of repre- sentations. Our aim is to provide insights into effective use of sketching in practice.