Efficient Diffusion Policies for Offline Reinforcement Learning
Authors: name: Bingyi Kang, name: Xiao Ma, name: Chao Du, name: Tianyu Pang, name: Shuicheng Yan

Offline reinforcement learning (RL) aims to learn optimal policies from
offline datasets, where the parameterization of policies is crucial but often
overlooked. Recently, Diffsuion-QL significantly boosts the performance of
offline RL by representing a policy with a diffusion model, whose success
relies on a parametrized Markov Chain with hundreds of steps for sampling.
However, Diffusion-QL suffers from two critical limitations. 1) It is
computationally inefficient to forward and backward through the whole Markov
chain during training. 2) It is incompatible with maximum likelihood-based RL
algorithms (e.g., policy gradient methods) as the likelihood of diffusion
models is intractable. Therefore, we propose efficient diffusion policy (EDP)
to overcome these two challenges. EDP approximately constructs actions from
corrupted ones at training to avoid running the sampling chain. We conduct
extensive experiments on the D4RL benchmark. The results show that EDP can
reduce the diffusion policy training time from 5 days to 5 hours on
gym-locomotion tasks. Moreover, we show that EDP is compatible with various
offline RL algorithms (TD3, CRR, and IQL) and achieves new state-of-the-art on
D4RL by large margins over previous methods. Our code is available at
https://github.com/sail-sg/edp.