arXiv Machine Learning

Reinforcement learning to choose optimizers

The paper introduces a reinforcement learning framework that selects among a portfolio of gradient‑based and derivative‑free optimizers during a run. At each decision point a recurrent policy reads the current run state and chooses both the next optimizer and its usage duration, passing the best solution and step size forward. The method is trained with a decoupled actor‑critic using the same runtime distribution metric as evaluation, and on unseen problems it outperforms all individual portfolio optimizers except at the smallest budgets, remaining robust to distribution shift.

arXiv AI
Jun 6

Retry Policy Gradients in Continuous Action Spaces

arXiv:2606. 05888v1 Announce Type: new Abstract: Retry-based objectives such as pass@K and max@K optimize the best return obtained from multiple sampled trajectories, and recent work has shown that they can promote exploration without explicit exploration bonuses.

By Soichiro Nishimori, Paavo Parmas
arXiv AI
Aug 19

Task Specialization Fine-Tuning for Contextual Reinforcement Learning

The paper introduces Task Specialization Fine-Tuning (TSFT), an online framework that allocates a limited fine‑tuning budget across multiple task regions in Contextual Reinforcement Learning. TSFT predicts fine‑tuning performance with a simple parametric model and solves the budget allocation problem exactly using integer linear programming. Experiments on combinatorial optimization, continuous control, and LLM fine‑tuning show that TSFT outperforms baselines in task coverage and approaches oracle performance.

By Jianan Zhou, Jung-Hoon Cho, Tianyue Zhou, Han Zheng, Jie Zhang, Roy Dong, Yining Ma, Cathy Wu
arXiv AI
Oct 9

Constrained Command-Conditioned Reinforcement Learning with Bandit Strategy Selection in Real-Time Strategy Games

The paper presents a constrained command‑conditioned Proximal Policy Optimization (PPO) executor for the MicroRTS real‑time strategy environment, enabling a single execution policy to follow diverse strategic commands. A Thompson‑sampling bandit strategist selects command tuples based on in‑game observations of the opponent’s strategy, rather than relying on opponent identity. In controlled experiments, the strategist‑executor system outperforms a flat PPO baseline against three of the four strongest opponents on a training map, including two held‑out opponents, while showing no significant difference against the remaining opponents.

By Nick Leenders, Roy Lindelauf, Joost van Oijen, Boris Cule
arXiv Machine Learning
Oct 3

Reusing Past Samples in Proximal Policy Optimization: When and How Does It Help?

The paper investigates how reusing past samples can improve the sample efficiency of Proximal Policy Optimization (PPO). Two variants, wPPO-U and wPPO-BH, are introduced within a multiple importance weighting framework, each reusing data from recent iterations while preserving core PPO mechanics. The authors derive theoretical policy improvement bounds for both variants and empirically evaluate their impact on continuous control tasks.

By Alessandro Montenegro, Riccardo Venturelli, Marco Mussi, Matteo Papini, Alberto Maria Metelli
arXiv AI
Jun 2

Emergence of Exploration in Policy Gradient Reinforcement Learning via Retrying

arXiv:2606. 00151v1 Announce Type: cross Abstract: In reinforcement learning (RL), agents benefit from exploration only because they repeatedly encounter similar states: trying different actions can improve performance or reduce uncertainty; without such retries, a greedy policy is optimal.

By Soichiro Nishimori, Paavo Parmas, Sotetsu Koyamada, Tadashi Kozuno, Toshinori Kitamura, Shin Ishii, Yutaka Matsuo
arXiv AI
Oct 5

When a Correct Reward Is Not Enough: Diagnosing and Guiding PPO in an Analytically Solved Broker-Trader Game

The paper investigates whether a proximal policy optimisation (PPO) agent can learn to act as a broker in a continuous‑time broker‑trader game that has an analytically solved optimal strategy. By discretising the continuous‑time reward and validating the implementation, the authors show that a PPO agent with a feed‑forward neural network can approximate the reference action when there is no uninformed order flow, but struggles under stochastic uninformed flow, with critics failing to rank actions reliably. The study further demonstrates that a causal certainty‑equivalent controller based on observable history outperforms PPO under partial information, and that freezing the analytical policy and fine‑tuning PPO after a change in execution cost yields a measurable improvement. whyItMatters:"The analytical solution serves both as a diagnostic benchmark for RL performance and as a practical starting policy that can be adapted to changing market conditions, illustrating how theoretical finance models can guide and improve reinforcement learning in complex financial control tasks."

By Siu Tung Wong (Institute of Finance and Technology, University College London), Carlo Campajola (Institute of Finance and Technology, University College London, UZH Blockchain Center)
arXiv AI
Sep 10

HyCO: A Hybrid Neural Solver for Combinatorial Optimization

HyCO is a hybrid neural solver that combines a sequential reinforcement learning (RL) solver with a global diffusion model (DM) to tackle combinatorial optimization problems. The RL component builds an initial solution prefix, after which HyCO switches to a conditional DM to finish the remaining decisions. The authors provide a theoretical framework showing that this hybrid approach yields lower expected regret than either method alone, identify an optimal trigger step for the switch, and implement a lightweight adaptive trigger based on policy entropy and RL‑DM disagreement, achieving consistent performance gains across benchmarks.

By Yuheng Li, Di Yang, Haipeng Chen, Yanhai Xiong