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Adversarial Soft Advantage Fitting: Imitation Learning without Policy Optimization
Paul Barde · Julien Roy · Wonseok Jeon · Joelle Pineau · Chris Pal · Derek Nowrouzezahrai

Thu Dec 10 07:30 AM -- 07:40 AM (PST) @ Orals & Spotlights: Reinforcement Learning

Adversarial Imitation Learning alternates between learning a discriminator -- which tells apart expert's demonstrations from generated ones -- and a generator's policy to produce trajectories that can fool this discriminator. This alternated optimization is known to be delicate in practice since it compounds unstable adversarial training with brittle and sample-inefficient reinforcement learning. We propose to remove the burden of the policy optimization steps by leveraging a novel discriminator formulation. Specifically, our discriminator is explicitly conditioned on two policies: the one from the previous generator's iteration and a learnable policy. When optimized, this discriminator directly learns the optimal generator's policy. Consequently, our discriminator's update solves the generator's optimization problem for free: learning a policy that imitates the expert does not require an additional optimization loop. This formulation effectively cuts by half the implementation and computational burden of Adversarial Imitation Learning algorithms by removing the Reinforcement Learning phase altogether. We show on a variety of tasks that our simpler approach is competitive to prevalent Imitation Learning methods.

Author Information

Paul Barde (Quebec AI institute - Mila, McGill)
Julien Roy (Mila)
Wonseok Jeon (Mila - Quebec AI Institute, McGill University)

I’m a postdoctoral researcher at Mila/McGill University. My research interests include: - reinforcement learning - imitation learning - inverse reinforcement learning - multi-agent learning - and applying probabilistic tools to the above methods

Joelle Pineau (McGill University)

Joelle Pineau is an Associate Professor and William Dawson Scholar at McGill University where she co-directs the Reasoning and Learning Lab. She also leads the Facebook AI Research lab in Montreal, Canada. She holds a BASc in Engineering from the University of Waterloo, and an MSc and PhD in Robotics from Carnegie Mellon University. Dr. Pineau's research focuses on developing new models and algorithms for planning and learning in complex partially-observable domains. She also works on applying these algorithms to complex problems in robotics, health care, games and conversational agents. She serves on the editorial board of the Journal of Artificial Intelligence Research and the Journal of Machine Learning Research and is currently President of the International Machine Learning Society. She is a recipient of NSERC's E.W.R. Steacie Memorial Fellowship (2018), a Fellow of the Association for the Advancement of Artificial Intelligence (AAAI), a Senior Fellow of the Canadian Institute for Advanced Research (CIFAR) and in 2016 was named a member of the College of New Scholars, Artists and Scientists by the Royal Society of Canada.

Chris Pal (MILA, Polytechnique Montréal, Element AI)
Derek Nowrouzezahrai (McGill University)

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