Target Entropy Annealing for Discrete Soft Actor-Critic

Yaosheng Xu, Dailin Hu, Litian Liang, Stephen Marcus McAleer, Pieter Abbeel, Roy Fox

Keywords: Discrete Soft Actor-Critic, Temperature annealing, Target entropy scheduling

TL;DR: We analyze the drawbacks of using constant target entropy to anneal the temperature, and propose Target Entropy Scheduled SAC (TES-SAC) for discrete action space.

Abstract: Soft Actor-Critic (SAC) is considered the state-of-the-art algorithm in continuous action space settings. It uses the maximum entropy framework for efficiency and stability, and applies a heuristic temperature Lagrange term to tune the temperature $\alpha$, which determines how "soft" the policy should be. It is counter-intuitive that empirical evidence shows SAC does not perform well in discrete domains. In this paper we investigate the possible explanations for this phenomenon and propose Target Entropy Scheduled SAC (TES-SAC), an annealing method for the target entropy parameter applied on SAC. Target entropy is a constant in the temperature Lagrange term and represents the target policy entropy in discrete SAC. We compare our method on Atari 2600 games with different constant target entropy SAC, and analyze on how our scheduling affects SAC.