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 Reinforcement Learning


Graph-attention-based Casual Discovery with Trust Region-navigated Clipping Policy Optimization

arXiv.org Artificial Intelligence

In many domains of empirical sciences, discovering the causal structure within variables remains an indispensable task. Recently, to tackle with unoriented edges or latent assumptions violation suffered by conventional methods, researchers formulated a reinforcement learning (RL) procedure for causal discovery, and equipped REINFORCE algorithm to search for the best-rewarded directed acyclic graph. The two keys to the overall performance of the procedure are the robustness of RL methods and the efficient encoding of variables. However, on the one hand, REINFORCE is prone to local convergence and unstable performance during training. Neither trust region policy optimization, being computationally-expensive, nor proximal policy optimization (PPO), suffering from aggregate constraint deviation, is decent alternative for combinatory optimization problems with considerable individual subactions. We propose a trust region-navigated clipping policy optimization method for causal discovery that guarantees both better search efficiency and steadiness in policy optimization, in comparison with REINFORCE, PPO and our prioritized sampling-guided REINFORCE implementation. On the other hand, to boost the efficient encoding of variables, we propose a refined graph attention encoder called SDGAT that can grasp more feature information without priori neighbourhood information. With these improvements, the proposed method outperforms former RL method in both synthetic and benchmark datasets in terms of output results and optimization robustness.


Learning Human-Aware Robot Policies for Adaptive Assistance

arXiv.org Artificial Intelligence

Learning Human-A ware Robot Policies for Adaptive Assistance Jason Qin 1, Shikun Ban 2, Wentao Zhu 2, Yizhou Wang 2, and Dimitris Samaras 1 Abstract -- Developing robots that can assist humans efficiently, safely, and adaptively is crucial for real-world applications such as healthcare. While previous work often assumes a centralized system for co-optimizing human-robot interactions, we argue that real-world scenarios are much more complicated, as humans have individual preferences regarding how tasks are performed. However, to provide effective assistance, robots must still be able to recognize and adapt to the individual needs and preferences of different users. T o address these challenges, we propose a novel framework in which robots infer human intentions and reason about human utilities through interaction. Our approach features two critical modules: the anticipation module is a motion predictor that captures the spatial-temporal relationship between the robot agent and user agent, which contributes to predicting human behavior; the utility module infers the underlying human utility functions through progressive task demonstration sampling. Extensive experiments across various robot types and assistive tasks demonstrate that the proposed framework not only enhances task success and efficiency but also significantly improves user satisfaction, paving the way for more personalized and adaptive assistive robotic systems. Code and demos are available at https: //asonin.github.io/Human-Aware-Assistance/ . I. I NTRODUCTION Developing robots that understand and assist humans is a critical long-term goal in Artificial Intelligence (AI) research.


Efficient and Scalable Deep Reinforcement Learning for Mean Field Control Games

arXiv.org Artificial Intelligence

Mean Field Control Games (MFCGs) provide a powerful theoretical framework for analyzing systems of infinitely many interacting agents, blending elements from Mean Field Games (MFGs) and Mean Field Control (MFC). However, solving the coupled Hamilton-Jacobi-Bellman and Fokker-Planck equations that characterize MFCG equilibria remains a significant computational challenge, particularly in high-dimensional or complex environments. This paper presents a scalable deep Reinforcement Learning (RL) approach to approximate equilibrium solutions of MFCGs. Building on previous works, We reformulate the infinite-agent stochastic control problem as a Markov Decision Process, where each representative agent interacts with the evolving mean field distribution. We use the actor-critic based algorithm from a previous paper (Angiuli et.al., 2024) as the baseline and propose several versions of more scalable and efficient algorithms, utilizing techniques including parallel sample collection (batching); mini-batching; target network; proximal policy optimization (PPO); generalized advantage estimation (GAE); and entropy regularization. By leveraging these techniques, we effectively improved the efficiency, scalability, and training stability of the baseline algorithm. We evaluate our method on a linear-quadratic benchmark problem, where an analytical solution to the MFCG equilibrium is available. Our results show that some versions of our proposed approach achieve faster convergence and closely approximate the theoretical optimum, outperforming the baseline algorithm by an order of magnitude in sample efficiency. Our work lays the foundation for adapting deep RL to solve more complicated MFCGs closely related to real life, such as large-scale autonomous transportation systems, multi-firm economic competition, and inter-bank borrowing problems.


Minimax-Optimal Multi-Agent Robust Reinforcement Learning

arXiv.org Artificial Intelligence

The rapidly evolving field of multi-agent reinforcement learning (MARL), also referred to as Markov games (MGs) (Littman, 1994; Shapley, 1953), explores how a group of agents interacts in a shared, dynamic environment to maximize their individual expected cumulative rewards (Zhang et al., 2020a; Lanctot et al., 2019; Silver et al., 2017; Vinyals et al., 2019). This area has found wide applications in fields such as ecosystem management (Fang et al., 2015), strategic decision-making in board games (Silver et al., 2017), management science (Saloner, 1991), and autonomous driving (Zhou et al., 2020). However, in real-world applications, environmental uncertainties--stemming from factors such as system noise, model misalignment, and the sim-to-real gap--can significantly alter both the qualitative outcomes of the game and the cumulatiev rewards that agents receive (Slumbers et al., 2023). It has been demonstrated that when solutions learned in a simulated environment are applied, even a small deviation in the deployed environment from the expected model can result in catastrophic performance drops for one or more agents (Shi et al., 2024c; Balaji et al., 2019; Yeh et al., 2021; Zeng et al., 2022; Zhang et al., 2020b). These challenges motivate the study of robust Markov games (RMGs), which assume that each agent aims to maximize its worst-case cumulative reward in an environment where the transition model is constrained by an uncertainty set centered around an unknown nominal model. Given the competitive nature of the game, the objective of RMGs is to reach an equilibrium where no agent has an incentive to unilaterally change its policy to increase its own payoff. A classical type of equilibrium is the robust Nash equilibrium (NE) (Nash Jr, 1950), where each agent's policy is independent, and no agent can improve its worst-case performance by deviating from its current strategy. Due to the high computational cost of solving robust NEs, especially in games with more than two agents, this concept is often relaxed to the robust coarse correlated equilibrium (CCE), where agents' policies may be correlated (Moulin & Vial, 1978). In the context of RMGs, achieving equilibrium with minimal samples is of particular interest, as data is often limited in practical applications.


Adaptive Context-Aware Multi-Path Transmission Control for VR/AR Content: A Deep Reinforcement Learning Approach

arXiv.org Artificial Intelligence

These authors present a few critical features for ACMPTC to enhance applications require high bandwidth, ultra-low latency, and its performance--mainly choosing paths with low latency and consistent quality of service (QoS) to deliver seamless, immersive packet loss. It brings a DRL-based agent that can adapt its experiences [2]. Traditional network protocols like the decision to real-time network states and compute dynamic, Transmission Control Protocol (TCP) often struggle to meet optimal choices. This feedback loop, on the other hand, these stringent demands, especially in highly dynamic and allows for real-time path selection and resource allocation that diverse network environments due to single path transmission, enables continuous optimization to provide a smooth AR/VR inadequate for high-bandwidth, low-latency requirement, high experience even with varying network conditions. It confirms latency sensitivity, etc. [3]. These limitations make TCP less that the system operates correctly and provides a way to update effective for dynamic, heterogeneous network environments such a network when there is variation in traffic levels by and the demanding performance needs of modern applications adjusting it effectively.


Active Reinforcement Learning Strategies for Offline Policy Improvement

arXiv.org Artificial Intelligence

Learning agents that excel at sequential decision-making tasks must continuously resolve the problem of exploration and exploitation for optimal learning. However, such interactions with the environment online might be prohibitively expensive and may involve some constraints, such as a limited budget for agent-environment interactions and restricted exploration in certain regions of the state space. Examples include selecting candidates for medical trials and training agents in complex navigation environments. This problem necessitates the study of active reinforcement learning strategies that collect minimal additional experience trajectories by reusing existing offline data previously collected by some unknown behavior policy. In this work, we propose an active reinforcement learning method capable of collecting trajectories that can augment existing offline data. With extensive experimentation, we demonstrate that our proposed method reduces additional online interaction with the environment by up to 75% over competitive baselines across various continuous control environments such as Gym-MuJoCo locomotion environments as well as Maze2d, AntMaze, CARLA and IsaacSimGo1. To the best of our knowledge, this is the first work that addresses the active learning problem in the context of sequential decision-making and reinforcement learning.


xSRL: Safety-Aware Explainable Reinforcement Learning -- Safety as a Product of Explainability

arXiv.org Artificial Intelligence

Reinforcement learning (RL) has shown great promise in simulated environments, such as games, where failures have minimal consequences. However, the deployment of RL agents in real-world systems such as autonomous vehicles, robotics, UAVs, and medical devices demands a higher level of safety and transparency, particularly when facing adversarial threats. Safe RL algorithms have been developed to address these concerns by optimizing both task performance and safety constraints. However, errors are inevitable, and when they occur, it is essential that the RL agents can also explain their actions to human operators. This makes trust in the safety mechanisms of RL systems crucial for effective deployment. Explainability plays a key role in building this trust by providing clear, actionable insights into the agent's decision-making process, ensuring that safety-critical decisions are well understood. While machine learning (ML) has seen significant advances in interpretability and visualization, explainability methods for RL remain limited. Current tools fail to address the dynamic, sequential nature of RL and its needs to balance task performance with safety constraints over time. The re-purposing of traditional ML methods, such as saliency maps, is inadequate for safety-critical RL applications where mistakes can result in severe consequences. To bridge this gap, we propose xSRL, a framework that integrates both local and global explanations to provide a comprehensive understanding of RL agents' behavior. xSRL also enables developers to identify policy vulnerabilities through adversarial attacks, offering tools to debug and patch agents without retraining. Our experiments and user studies demonstrate xSRL's effectiveness in increasing safety in RL systems, making them more reliable and trustworthy for real-world deployment. Code is available at https://github.com/risal-shefin/xSRL.


A Reinforcement Learning-Based Task Mapping Method to Improve the Reliability of Clustered Manycores

arXiv.org Artificial Intelligence

The increasing scale of manycore systems poses significant challenges in managing reliability while meeting performance demands. Simultaneously, these systems become more susceptible to different aging mechanisms such as negative-bias temperature instability (NBTI), hot carrier injection (HCI), and thermal cycling (TC), as well as the electromigration (EM) phenomenon. In this paper, we propose a reinforcement learning (RL)-based task mapping method to improve the reliability of manycore systems considering the aforementioned aging mechanisms, which consists of three steps including bin packing, task-to-bin mapping, and task-to-core mapping. In the initial step, a density-based spatial application with noise (DBSCAN) clustering method is employed to compose some clusters (bins) based on the cores temperature. Then, the Q-learning algorithm is used for the two latter steps, to map the arrived task on a core such that the minimum thermal variation is occurred among all the bins. Compared to the state-of-the-art works, the proposed method is performed during runtime without requiring any parameter to be calculated offline. The effectiveness of the proposed technique is evaluated on 16, 32, and 64 cores systems using SPLASH2 and PARSEC benchmark suite applications. The results demonstrate up to 27% increase in the mean time to failure (MTTF) compared to the state-of-the-art task mapping techniques.


Optimizing Fantasy Sports Team Selection with Deep Reinforcement Learning

arXiv.org Artificial Intelligence

Fantasy sports, particularly fantasy cricket, have garnered immense popularity in India in recent years, offering enthusiasts the opportunity to engage in strategic team-building and compete based on the real-world performance of professional athletes. In this paper, we address the challenge of optimizing fantasy cricket team selection using reinforcement learning (RL) techniques. By framing the team creation process as a sequential decision-making problem, we aim to develop a model that can adaptively select players to maximize the team's potential performance. Our approach leverages historical player data to train RL algorithms, which then predict future performance and optimize team composition. This not only represents a huge business opportunity by enabling more accurate predictions of high-performing teams but also enhances the overall user experience. Through empirical evaluation and comparison with traditional fantasy team drafting methods, we demonstrate the effectiveness of RL in constructing competitive fantasy teams. Our results show that RL-based strategies provide valuable insights into player selection in fantasy sports.


Provably Efficient Exploration in Reward Machines with Low Regret

arXiv.org Artificial Intelligence

We study reinforcement learning (RL) for decision processes with non-Markovian reward, in which high-level knowledge of the task in the form of reward machines is available to the learner. We consider probabilistic reward machines with initially unknown dynamics, and investigate RL under the average-reward criterion, where the learning performance is assessed through the notion of regret. Our main algorithmic contribution is a model-based RL algorithm for decision processes involving probabilistic reward machines that is capable of exploiting the structure induced by such machines. We further derive high-probability and non-asymptotic bounds on its regret and demonstrate the gain in terms of regret over existing algorithms that could be applied, but obliviously to the structure. We also present a regret lower bound for the studied setting. To the best of our knowledge, the proposed algorithm constitutes the first attempt to tailor and analyze regret specifically for RL with probabilistic reward machines.