Deep Multi-Agent Reinforcement Learning (MARL) excels in co-operative tasks but often struggles with local optima in high - dimensional joint action spaces. In contrast, Evolutionary Algorithms (EAs) offer robust global exploration capabilities. Although hybrid approaches seek to combine the strengths of both paradigms, they typically face a critical bottleneck: the prohibitive sample cost of evaluating large populations via environment rollouts. To address this challenge, we propose Surrogate-assisted Evolutionary Multi-Agent Reinforcement Learning (SEMARL), a unified framework that synergizes gradient-based refinement with surrogate-assisted evolutionary search. SEMARL employs a cooperative co-evolutionary architecture to maintain diverse agent policies and injects gradient-refined parameters into the population to accelerate convergence. Crucially, we leverage the centralized critic from the gradient learner as a computationally efficient surrogate for fitness estimation. To prevent misleading guidance from an inaccurate critic, we introduce an adaptive reliability control mechanism based on temporal difference (TD) error, which dynamically regulates the surrogate's influence. Experiments on the Multi-Agent MuJoCo benchmark demonstrate that SEMARL significantly outperforms other algorithms, achieving superior asymptotic performance with substantially higher sample efficiency.

Reinforcement learning (RL) has garnered increasing attention in text-to-image (T2I) generation. However, most existing RL approaches are tailored to either diffusion models or autoregressive models, overlooking an important alternative: masked generative models. In this work, we propose Mask-GRPO, the first method to incorporate Group Relative Policy Optimization (GRPO)-based RL into this overlooked paradigm. Our core insight is to redefine the transition probability, which is different from current approaches, and formulate the unmasking process as a multi-step decision-making problem. To further enhance our method, we explore several useful strategies, including removing the Kullback–Leibler constraint, applying the reduction strategy, and filtering out low-quality samples. Using Mask-GRPO, we improve a base model, Show-o, with substantial improvements on standard T2I benchmarks and preference alignment, outperforming existing state-of-the-art approaches.

A key challenge of continual reinforcement learning (CRL) in dynamic environments is to promptly adapt the reinforcement learning (RL) agent's behavior as the environment changes over its lifetime while minimizing the catastrophic forgetting of the learned information. To address this challenge, in this article, we propose DaCoRL, that is, dynamics-adaptive continual RL. DaCoRL learns a context-conditioned policy using progressive contextualization, which incrementally clusters a stream of stationary tasks in the dynamic environment into a series of contexts and opts for an expandable multihead neural network to approximate the policy. Specifically, we define a set of tasks with similar dynamics as an environmental context and formalize context inference as a procedure of online Bayesian infinite Gaussian mixture clustering on environment features, resorting to online Bayesian inference to infer the posterior distribution over contexts. Under the assumption of a Chinese restaurant process (CRP) prior, this technique can accurately classify the current task as a previously seen context or instantiate a new context as needed without relying on any external indicator to signal environmental changes in advance. Furthermore, we employ an expandable multihead neural network whose output layer is synchronously expanded with the newly instantiated context and a knowledge distillation regularization term for retaining the performance on learned tasks. As a general framework that can be coupled with various deep RL algorithms, DaCoRL features consistent superiority over existing methods in terms of stability, overall performance, and generalization ability, as verified by extensive experiments on several robot navigation and MuJoCo locomotion tasks.

The powerful learning ability of deep neural networks enables reinforcement learning (RL) agents to learn competent control policies directly from continuous environments. In theory, to achieve stable performance, neural networks assume identically and independently distributed (i.i.d.) inputs, which unfortunately does not hold in the general RL paradigm where the training data are temporally correlated and nonstationary. This issue may lead to the phenomenon of "catastrophic interference" and the collapse in performance. In this article, we present interference-aware deep Q-learning (IQ) to mitigate catastrophic interference in single-task deep RL. Specifically, we resort to online clustering to achieve on-the-fly context division, together with a multihead network and a knowledge distillation regularization term for preserving the policy of learned contexts. Built upon deep Q networks (DQNs), IQ consistently boosts the stability and performance when compared to existing methods, verified with extensive experiments on classic control and Atari tasks. The code is publicly available at https://github.com/ Sweety-dm/Interference-aware-Deep-Q-learning.