arXiv Machine Learning

Lag: A Mean-Field Optimal Policy for Online Assignment with Reusable Resources

The paper introduces Lag, a mean‑field optimal index policy for online assignment problems with reusable resources, such as peer review, call routing, ridesharing, emergency dispatch, and crowdsourcing. By modeling the problem as a contextual restless multi‑armed bandit and deriving an occupancy‑measure linear program, the authors obtain Lag from the dual and prove it is asymptotically optimal in a scaling regime where server copies and arrivals grow together. Experiments on peer‑review and call‑center data show Lag achieves 83–99% of the LP upper bound and outperforms greedy assignment by up to 36% in synthetic settings.

arXiv Machine Learning
Oct 9

Amortized Off-Policy Evaluation for LLMs

The paper introduces PFN‑OPE, a prior‑data fitted network that performs amortized off‑policy evaluation (OPE) for large language models (LLMs). Unlike traditional OPE methods that must be retrained for each new logged dataset or reward definition, PFN‑OPE is pretrained once on a diverse set of contextual‑bandit tasks and can estimate value for any new logged dataset and target response in a single forward pass. Experiments on HelpSteer2 and UltraFeedback with Qwen, Llama, and Gemma policies show that PFN‑OPE reduces error by 2.0 to 9.3 times compared to the best baselines in reward‑shifted settings.

By Younwoo Choi, Leo Feng, Vincent Liu, Haanvid Lee
Hugging Face Trending Papers
Jul 15

Optimal and Efficient Contextual Combinatorial Semi-bandits with General Function Approximation

We study the contextual combinatorial semi-bandit (CCSB) problem with general reward function approximation. At each round, the learner observes a context, selects a combinatorial action consisting of a subset of basic arms, and receives the reward of each selected arm; the goal is to maximize the cumulative reward over time.

arXiv Machine Learning
Aug 18

Sequential Batch Learning in Finite-Action Linear Contextual Bandits

arXiv:2004. 06321v2 Announce Type: replace Abstract: We study the sequential batch learning problem in linear contextual bandits with finite action sets, where the decision maker is constrained to split incoming individuals into (at most) a fixed number of batches and can only observe outcomes for the individuals within a batch at the batch's end.

By Yanjun Han, Zhengqing Zhou, Zihao Hu, Jose Blanchet, Peter W. Glynn, Yinyu Ye, Zhengyuan Zhou
Hugging Face Trending Papers
Jul 15

From Novice to Expert: Cost-Aware Bandits for Evolving Worker Performance in Crowdsensing

Mobile crowdsensing (MC) recruits mobile users to perform sensing tasks using their smartphones, enabling large-scale applications such as traffic monitoring and environmental sensing. A fundamental challenge is online worker recruitment under uncertainty, where the platform must learn workers' sensing performance while operating with a limited budget.