RoboBoom
GRASP Lab· April 18, 2022· 1:03:35

Spring 2022 GRASP SFI - Jason Ma, University of Pennsylvania

Jason Ma, researcher at the University of Pennsylvania, presents research on safer and reward-free offline reinforcement learning at a GRASP Lab seminar.

In this talk

  1. 0:00

    Why offline learning needs risk sensitivity

    Ma explains that offline reinforcement learning trains a policy from a fixed dataset, without new interaction with the environment. This can suit settings such as healthcare and autonomous driving, where collecting live data is costly or dangerous. He argues that average return can hide risk: three slot-machine options may each average zero while having very different downside, so a risk-averse decision maker would favor the least volatile.

  2. 4:29

    CODAC penalizes unsupported actions

    Ma asks whether a safer policy can be learned from data collected without regard to risk. His CODAC method applies conservative penalties to return quantiles, with stronger penalties for actions less represented in the dataset, helping limit errors from distribution shift. In a navigation experiment with a hazardous region, CODAC’s CVaR variant learned to avoid that region from risk-neutral data and performed better on the risk-sensitive measure than the compared methods.

  3. 22:43

    Imitation without reward labels or matching embodiments

    Ma turns to tasks where writing a reward function is difficult, and proposes using demonstrations or examples of successful outcomes instead. His approach matches distributions over task-relevant states, so expert observations need not include actions or come from the same type of agent. This also lets the method use cheaper, suboptimal data alongside a smaller expert dataset.

  4. 34:10

    SMODICE makes offline state matching practical

    Ma introduces SMODICE, which converts state-distribution matching into three separate supervised learning steps using offline data. The method estimates weights for dataset samples and uses weighted behavior cloning to train a policy, avoiding the need to sample from the learner’s environment during optimization. Across reported D4RL and manipulation tasks, it was competitive with leading methods, declined less under embodiment mismatch, and could learn tasks from examples of success.

Briefs summarise talks and interviews; timestamps open the video at that moment. Claims in a talk are the speaker's own.

More talks