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Q* Approximation for Batch Reinforcement Learning: A Theoretical Comparison (arxiv.org)
21 points by ericzawo on Nov 23, 2023 | hide | past | pdf | 3 comments on HN

In plain words: Two algorithms learn the best action values from past experience by checking how consistent the current guesses are, instead of repeatedly refitting like the usual approach. Their mistakes grow only with how long the task runs, not with its square.

Abstract · Q* Approximation Schemes for Batch Reinforcement Learning: A Theoretical Comparison

We prove performance guarantees of two algorithms for approximating $Q^\star$ in batch reinforcement learning. Compared to classical iterative methods such as Fitted Q-Iteration---whose performance loss incurs quadratic dependence on horizon---these methods estimate (some forms of) the Bellman error and enjoy linear-in-horizon error propagation, a property established for the first time for algorithms that rely solely on batch data and output stationary policies. One of the algorithms uses a novel and explicit importance-weighting correction to overcome the infamous "double sampling" difficulty in Bellman error estimation, and does not use any squared losses. Our analyses reveal its distinct characteristics and potential advantages compared to classical algorithms.

Tengyang Xie, Nan Jiang
arXiv:2003.03924 · cs.LG, cs.AI, stat.ML · submitted Mar 9, 2020 · updated Aug 24, 2020
abstract · pdf · html · Published in UAI 2020

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Related from two days ago: https://www.reuters.com/technology/sam-altmans-ouster-openai...

"Some at OpenAI believe Q* (pronounced Q-Star) could be a breakthrough in the startup's search for what's known as artificial general intelligence" and "wrote a letter to the board of directors warning [it] could threaten humanity"

It seems like people are really stretching here. Q-learning has been a thing for a while now. And in optimization of X, Q, etc. the star is just used to mean the optimal value.
I agree. People are digging up papers with “Q*” in the title without understanding what they’re talking about. I think it’s silly to read into the OpenAI statement but their “Q*” algorithm probably means something pretty specific to them that would be very hard for us to guess from the name “Q*”