Masked Trajectory Models for Prediction, Representation, and Control
Authors: name: Philipp Wu, name: Arjun Majumdar, name: Kevin Stone, name: Yixin Lin, name: Igor Mordatch, name: Pieter Abbeel, name: Aravind Rajeswaran

We introduce Masked Trajectory Models (MTM) as a generic abstraction for
sequential decision making. MTM takes a trajectory, such as a state-action
sequence, and aims to reconstruct the trajectory conditioned on random subsets
of the same trajectory. By training with a highly randomized masking pattern,
MTM learns versatile networks that can take on different roles or capabilities,
by simply choosing appropriate masks at inference time. For example, the same
MTM network can be used as a forward dynamics model, inverse dynamics model, or
even an offline RL agent. Through extensive experiments in several continuous
control tasks, we show that the same MTM network -- i.e. same weights -- can
match or outperform specialized networks trained for the aforementioned
capabilities. Additionally, we find that state representations learned by MTM
can significantly accelerate the learning speed of traditional RL algorithms.
Finally, in offline RL benchmarks, we find that MTM is competitive with
specialized offline RL algorithms, despite MTM being a generic self-supervised
learning method without any explicit RL components. Code is available at
https://github.com/facebookresearch/mtm