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About this paper

Jose A. Arjona-Medina, Michael Gillhofer, Michael Widrich, Thomas Unterthiner, Johannes Brandstetter, Sepp Hochreiter

This paper presents RUDDER, a method that addresses the long-term credit assignment problem in reinforcement learning by transforming delayed rewards. It redistributes rewards to make expected future rewards zero, reformulating the task into a regression problem, and achieves exponential speed-ups on artificial delayed reward tasks and improves performance on Atari games.

Key insights

  • Transforming an MDP into a "return-equivalent" Sequence-Markov Decision Process (SDP) allows for a reward redistribution where expected future rewards become zero, simplifying Q-value estimation to immediate rewards.
  • Optimal reward redistribution can be achieved by decomposing the total return of a sequence and assigning contributions to individual state-action pairs, effectively turning the credit assignment problem into a regression task.
  • Long Short-Term Memory (LSTM) networks are effective for learning to predict sequence-wide returns and then attributing these predictions back to specific actions, leveraging their ability to capture long-term dependencies.

Summary by alphaXiv.

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