Millimeter-wave (mmWave) communication systems are highly sensitive to user mobility and environmental changes, often suffering from rapid beam direction shifts and frequent link blockages. These dynamics pose significant challenges to maintaining reliable beam tracking. To enable accurate and robust beam tracking in dynamic environments, we propose a Self-Attention Proximal Policy Optimization (SAPPO) algorithm. The beam tracking task is modeled as a Partially Observable Markov Decision Process (POMDP), where the agent aims to maximize Received Signal Strength (RSS) using only current and previous signal observations, without relying on channel models or complex signal processing. By integrating a multi-head self-attention (MHSA) mechanism with a Gated Recurrent Unit (GRU), the policy network effectively captures temporal dependencies, enhancing the agent’s perception of user motion and channel state variations. To validate the approach, we construct three test scenarios with varying mobility and blockage complexity using the DeepMIMO dataset. Experimental results demonstrate that SAPPO consistently outperforms baseline methods such as DQN and PPO in terms of tracking accuracy, stability, and robustness. Notably, in challenging environments with frequent Line-Of-Sight (LOS)/Non-Line-Of-Sight (NLOS) transitions, SAPPO achieves a beam tracking success rate exceeding 95%, highlighting its strong adaptability and reliable performance under dynamic conditions.

Efficient exploration in high-dimensional observation spaces remains a critical challenge in deep reinforcement learning, particularly in scenarios with sparse extrinsic rewards. A promising approach is to encourage exploration by estimating intrinsic rewards based on the novelty of observations. However, there is a gap between the observed novelty and the actual effectiveness of exploration, as both environmental stochasticity and the agent’s actions may influence observations. To accurately evaluate the novelty contributed by agent exploration in intrinsic rewards, we propose the AIRES (Attention-driven Intrinsic Reward for Exploration Strategy) framework. AIRES leverages the attention mechanisms to analyze the relationship within trajectory sequences generated by agent-environment interactions, employing attention weights to quantify the relevance of observations to actions. By applying attention weights to intrinsic rewards, the novelty brought by agent exploration is enhanced and the impact of environmental stochasticity is reduced. Extensive experiments demonstrate that AIRES significantly enhances the performance of prominent intrinsic reward methods, establishing it as a robust and scalable solution for efficient exploration.

Most prior motion prediction endeavors in autonomous driving have inadequately encoded future scenarios, leading to predictions that may fail to accurately capture the diverse movements of agents (e.g., vehicles or pedestrians). To address this, we propose FutureNet, which explicitly integrates initially predicted trajectories into the future scenario and further encodes these future contexts to enhance subsequent forecasting. Additionally, most previous motion forecasting works have focused on predicting independent futures for each agent. However, safe and smooth autonomous driving requires accurately predicting the diverse future behaviors of numerous surrounding agents jointly in complex dynamic environments. Given that all agents occupy certain potential travel spaces and possess lane driving priority, we propose Lane Occupancy Field (LOF), a new representation with lane semantics for motion forecasting in autonomous driving. LOF can simultaneously capture the joint probability distribution of all road participants' future spatial-temporal positions. Due to the high compatibility between lane occupancy field prediction and trajectory prediction, we propose a novel network for joint prediction of these two tasks. Our approach ranks 1st on two large-scale motion forecasting benchmarks: Argoverse 1 and Argoverse 2, while it is also the champion method of the CVPR 2024 Argoverse 2 motion forecasting challenge.

Causal reasoning capability is critical in advancing large language models (LLMs) towards artificial general intelligence (AGI). While versatile LLMs appear to have demonstrated capabilities in understanding contextual causality and providing responses that obey the laws of causality, it remains unclear whether they perform genuine causal reasoning akin to humans. However, current evidence indicates the contrary. Specifically, LLMs are only capable of performing shallow (level-1) causal reasoning, primarily attributed to the causal knowledge embedded in their parameters, but they lack the capacity for genuine human-like (level-2) causal reasoning. To support this hypothesis, methodologically, we delve into the autoregression mechanism of transformer-based LLMs, revealing that it is not inherently causal. Empirically, we introduce a new causal Q&A benchmark named CausalProbe 2024, whose corpus is fresh and nearly unseen for the studied LLMs. Empirical results show a significant performance drop on CausalProbe 2024 compared to earlier benchmarks, indicating that LLMs primarily engage in level-1 causal reasoning.To bridge the gap towards level-2 causal reasoning, we draw inspiration from the fact that human reasoning is usually facilitated by general knowledge and intended goals. Inspired by this, we propose G$^2$-Reasoner, a LLM causal reasoning method that incorporates general knowledge and goal-oriented prompts into LLMs' causal reasoning processes. Experiments demonstrate that G$^2$-Reasoner significantly enhances LLMs' causal reasoning capability, particularly in fresh and fictitious contexts. This work sheds light on a new path for LLMs to advance towards genuine causal reasoning, going beyond level-1 and making strides towards level-2.

Wavefront sensor-less adaptive optics (WFS-less AO) systems have garnered considerable interest in recent years due to their compact architecture and extensive applicability. However, most algorithms developed for adaptive optics systems predominately rely on conventional control methodologies, which often take an unexpectedly prolonged period to converge and severely hinder the feasibility of practical applications, especially in scenarios where rapid environmental fluctuations necessitate real-time control capabilities. Therefore, we propose an efficient closed-loop wavefront reconstruction method based on a novel forward prediction paradigm. The method leverages information from the current control objective, the wavefront phase, and the previous control signals (typically the voltages applied to deformable mirrors) to predict wavefront distortions and implement anticipatory control actions accordingly. Experimental results demonstrate that, compared to most conventional techniques, our method can reduce the post-control RMS wavefront aberration by nearly one-third while exhibiting robustness to different types of turbulence and showing promising potential for complex multi-layer turbulence scenarios.

Predicting the future motion of road participants is crucial for autonomous driving but is extremely challenging due to staggering motion uncertainty. Recently, most motion forecasting methods resort to the goal-based strategy, i.e., predicting endpoints of motion trajectories as conditions to regress the entire trajectories, so that the search space of solution can be reduced. However, accurate goal coordinates are hard to predict and evaluate. In addition, the point representation of the destination limits the utilization of a rich road context, leading to inaccurate prediction results in many cases. Goal area, i.e., the possible destination area, rather than goal coordinate, could provide a more soft constraint for searching potential trajectories by involving more tolerance and guidance. In view of this, we propose a new goal area-based framework, named Goal Area Network (GANet), for motion forecasting, which models goal areas as preconditions for trajectory prediction, performing more robustly and accurately. Specifically, we propose a GoICrop (Goal Area of Interest) operator to effectively aggregate semantic lane features in goal areas and model actors' future interactions as feedback, which benefits a lot for future trajectory estimations. GANet ranks the 1st on the leaderboard of Argoverse Challenge among all public literature (till the paper submission). Code will be available at https://github.com/kingwmk/GANet.

Visual–inertial odometry (VIO) is widely studied and used in autonomous robots. This article proposes a novel tightly coupled monocular VIO system based on point-line constraints (PLC-VIO). In the front end, PLC-VIO presents a line segment extraction and merging algorithm based on the EDLines method and achieves real-time feature tracking based on the geometric constraints between feature points and lines. In the back end, PLC-VIO reconstructs new 3-D landmarks of feature lines through points on the line and optimizes the states by minimizing a cost function that combines the preintegrated inertial measurement unit (IMU) error term together with the point and line reprojection error terms in a sliding window optimization framework. A loop closure module is also integrated, which enables relocalization and drift elimination. The corresponding experimental evaluations are conducted using public datasets to validate the effectiveness and robustness of the proposed system, and the results show that PLC-VIO can achieve good performance when compared with other state-of-the-art systems and, at the same time, with no compromise to real-time performance.Note to Practitioners—Visual–inertial odometry (VIO) can estimate the states of the rigid body (including position, attitude, and velocity) that is widely used in robotic navigation, autonomous driving, virtual reality (VR), and augmented reality (AR). Aiming at the problem of estimating the states of autonomous robots in the GPS-denied environment, this article proposes a novel VIO system based on the point-line constraints (PLC-VIO). PLC-VIO can not only achieve accurate pose estimation for robots due to the introduction of the line features but also make no concession to real-time performance. Furthermore, PLC-VIO can also enrich the texture features of the environment during the 3-D mapping construction. The corresponding experiments are implemented in public datasets to evaluate the effectiveness, efficiency, and robustness of the proposed system. We believe that PLC-VIO can be widely used in robotic navigation and AR/VR fields to provide accurate position and environment information in real time.

The method of Brownian configuration fields (BCF) is a promising multi-scale approach for the simulationof viscoelastic fluids, however, it is a computationally expensive method, which restricts its application in complex scenarios. Therefore, it is of great importance to optimize the parallel implementation in order to improve computational efficiency. In this paper we propose a hybrid decomposition parallel algorithm named: MCDPar, whichenables the simulation problem to bedecomposed simultaneously over mesh cells andthe Brownian configuration fields. Compution processes are split into multiple groups and Brownian configuration fields are equally associated with these groups. Meanwhile, within each group the processes are concurrently executed based on the traditional mesh decomposition approach. Finally we implemented the MCDPar algorithm in a micro-macro numerical solver based on OpenFOAM. Experimental results show that the micro-macro simulation time of viscoelastic fluids issignificantly reduced with improved scalability and parallel efficiency. In the test case with Nf= 2000 and Ncell= 262144, the speedup of the MCDParis up to 9.23x with a 7.5x increase in number of cores compared to the original parallel algorithm.

For parallel dam break simulations in OpenFOAM (Open Source Field Operation and Manipulation), the core procedure is solving linear systems using iterative methods and the iterative convergence rate is significant to the overall efficiency. A dynamic mesh repartitioning scheme DMRPar (Dynamic Mesh Re-Partitioning) considering the iterative convergence feature is implemented in OpenFOAM. Given that the numerical characteristics of linear systems change a lot along with the complex flow field, DMRPar takes linear system information from the previous timestep into account for the repartitioning at the current timestep. The implementation reuses current mesh topology in OpenFOAM and calculates distributed adjacency graph structure for the mesh. The repartitioning heuristic is based on a general multi-level parallel graph partitioning package called ParMetis. Numerical results on two typical dam break simulations show that DMRPar outperforms the traditional static partitioning method significantly in the total simulation time.

Existing scratchpad memory (SPM) allocation algorithms for arrays, whether they rely on well-crafted heuristics or resort to integer linear programming (ILP) techniques, typically assume that every array is small enough to fit directly into the SPM. As a result, some arrays have to be spilled entirely to the off-chip memory in order to make room for other arrays to stay in the SPM, resulting in sometimes poor SPM utilization.

As a fast on-chip SRAM managed by software (the application and/or compiler), Scratchpad Memory (SPM) is widely used in many fields. This paper presents a Simple Scalar-based multi-level SPM memory hierarchy architecture simulator Sim-spm. We simulate the hardware of the multi-level SPM memory hierarchy successfully by extending Sim-outorder, which is an out-of-order simulator from Simple Scalar. Through the simulating memory method, the simulation framework of the multi-level SPM memory hierarchy has been built under the existing ISA (Instruction Set Architecture), which largely reduces the requirement to modify the existing compiler. The experimental results show that Sim-spm can accurately simulate the running state of the processor with a multi-level SPM memory hierarchy architecture, and it has a good prospect for the research of multi-level SPM memory hierarchy architecture.

As the system scales up continuously, the problem of power consumption for high performance computing (HPC) system becomes more severe. Heterogeneous system integrating two or more kinds of processors, could be better adapted to heterogeneity in applications and provide much higher energy efficiency in theory. Many studies have shown heterogeneous system is preferable on energy consumption to homogeneous system in a multi-programmed computing environment. However, how to exploit energy efficiency (Flops/Watt) of heterogeneous system for a single application or even for a single phase in an application has not been well studied. This paper proposes a power-efficient work distribution method for single application on a CPU-GPU heterogeneous system. The proposed method could coordinate inter-processor work distribution and per-processor's frequency scaling to minimize energy consumption under a given scheduling length constraint. We conduct our experiment on a real system, which equips with a multi-core CPU and a multi-threaded GPU. Experimental results show that, with reasonably distributing work over CPU and GPU, the method achieves 14% reduction in energy consumption than static mappings for several typical benchmarks. We also demonstrate that our method could adapt to changes in scheduling length constraint and hardware configurations.

Graphic Processing Unit (GPU), with many light-weight data-parallel cores, can provide substantial parallel computing power to accelerate several general purpose applications. Both the AMD and NVIDIA corps provide their specific high performance GPUs and software platforms. As the floating-point computing capacity increases continually, the problem of ``memory-wall'' becomes more serious, especially for array-intensive applications. In this paper, we optimize and implement two SPEC2k benchmarks mgrid and swim on multithreaded GPU using CUDA and Brook+. In order to reduce the pressure on off-chip memory, we make use of data locality in multi-level memory hierarchies and hide long memory access latency via double-buffers. To balance inter-thread parallelism and intra-thread locality, we further tune thread granularity for each kernel and empirically study the best equilibrium point for this problem. Flow control instruction can significantly impact the effective instruction throughput. Oriented to this problem, we introduce a diverge elimination technology to convert condition expression into computing operation. Through all the optimizations, we gain the speedup of 10×-34× to the CPU implementation on the GPUs of AMD and NVIDIA respectively. Finally, we summarize and compares the GPUs from AMD and NVIDIA in hardware and software.