Artificial Intelligence (AI) and, in particular, Machine Learning (ML), have emerged to be utilized in various applications due to their capability to learn how to solve complex problems. Over the past decade, rapid advances in ML have presented Deep Neural Networks (DNNs) consisting of a large number of neurons and layers. DNN Hardware Accelerators (DHAs) are leveraged to deploy DNNs in the target applications. Safety-critical applications, where hardware faults/errors would result in catastrophic consequences, also benefit from DHAs. Therefore, the reliability of DNNs is an essential subject of research. In recent years, several studies have been published accordingly to assess the reliability of DNNs. In this regard, various reliability assessment methods have been proposed on a variety of platforms and applications. Hence, there is a need to summarize the state-of-the-art to identify the gaps in the study of the reliability of DNNs. In this work, we conduct a Systematic Literature Review (SLR) on the reliability assessment methods of DNNs to collect relevant research works as much as possible, present a categorization of them, and address the open challenges. Through this SLR, three kinds of methods for reliability assessment of DNNs are identified, including Fault Injection (FI), Analytical, and Hybrid methods. Since the majority of works assess the DNN reliability by FI, we characterize different approaches and platforms of the FI method comprehensively. Moreover, Analytical and Hybrid methods are propounded. Thus, different reliability assessment methods for DNNs have been elaborated on their conducted DNN platforms and reliability evaluation metrics. Finally, we highlight the advantages and disadvantages of the identified methods and address the open challenges in the research area. We have concluded that Analytical and Hybrid methods are light-weight yet sufficiently accurate and have the potential to be extended in future research and to be utilized in establishing novel DNN reliability assessment frameworks.
27 April 2020 in IEEE Computer Architecture Letters
Data copy is a widely-used memory operation in many programs and operating system services. In conventional computers, data copy is often carried out by two separate read and write transactions that pass data back and forth between the memory hierarchy and processor registers. Some prior mechanisms propose to avoid this unnecessary data movement by using the shared internal bus in DRAM chip to directly copy data between two DRAM banks. While these methods exhibit superior performance, compared to conventional techniques, this technique does not allow data copy over different DRAM channels. Hence, this technique has limited benefit for the emerging 3D stacked memories (such as HMC and HBM) that contains tens of banks across multiple memory controllers. In this paper, we present Network-on-Memory (NoM), a lightweight inter-bank communication scheme that enables direct data copy within memory. NoM adopts a TDM-based circuit-switching design, where circuit setup is done by the memory controller. Compared to previous state-of-the-art approaches, NoM enables both data copy over multiple DRAM channels and concurrent copy operation. Our evaluation shows that NoM improves the performance of data-intensive workloads by 3.8X on average compare to the state-of-the-art techniques, respectively.
Traditional methods in 3D NoCs simply use a deterministic routing algorithm to deliver packets from a source to a destination node. However, deterministic methods are unable to distribute the traffic load over the network, which results in degrading the performance. In this paper, we present a fully adaptive routing algorithm for 3D NoCs, named DyXYZ. In DyXYZ, the congestion information at the input buffer of the neighboring routers is used as congestion metric to select among the output channels. This algorithm is proven to be deadlock free by using 4, 4, and 2 virtual channels along the X, Y, and Z dimensions, respectively.
9 November 2021 in IEEE Transactions on Systems, Man, and Cybernetics: Systems
Convolutional neural networks (CNNs) provide the best accuracy for disparity estimation. However, CNNs are computationally expensive, making them unfavorable for resource-limited devices with real-time constraints. Recent advances in neural architectures search (NAS) promise opportunities in automated optimization for disparity estimation. However, the main challenge of the NAS methods is the significant amount of computing time to explore a vast search space [e.g., $1.6\times 10^{29}$ ] and costly training candidates. To reduce the NAS computational demand, many proxy-based NAS methods have been proposed. Despite their success, most of them are designed for comparatively small-scale learning tasks. In this article, we propose a fast NAS method, called FastStereoNet, to enable resource-aware NAS within an intractably large search space. FastStereoNet automatically searches for hardware-friendly CNN architectures based on late acceptance hill climbing (LAHC), followed by simulated annealing (SA). FastStereoNet also employs a fine-tuning with a transferred weights mechanism to improve the convergence of the search process. The collection of these ideas provides competitive results in terms of search time and strikes a balance between accuracy and efficiency. Compared to the state of the art, FastStereoNet provides $5.25\times $ reduction in search time and $44.4\times $ reduction in model size. These benefits are attained while yielding a comparable accuracy that enables seamless deployment of disparity estimation on resource-limited devices. Finally, FastStereoNet significantly improves the perception quality of disparity estimation deployed on field-programmable gate array and Intel Neural Compute Stick 2 accelerator in a significantly less onerous manner.
Interest is growing in the use of autonomous swarms of drones in various mission-physical applications such as surveillance, intelligent monitoring, and rescue operations. Swarm systems should fulfill safety and efficiency constraints in order to guarantee dependable operations. To maximize motion safety, we should design the swarm system in such a way that drones do not collide with each other and/or other objects in the operating environment. On other hand, to ensure that the drones have sufficient resources to complete the required task reliably, we should also achieve efficiency while implementing the mission, by minimizing the travelling distance of the drones. In this paper, we propose a novel integrated approach that maximizes motion safety and efficiency while planning and controlling the operation of the swarm of drones. To achieve this goal, we propose a novel parallel evolutionary-based swarm mission planning algorithm. The evolutionary computing allows us to plan and optimize the routes of the drones at the run-time to maximize safety while minimizing travelling distance as the efficiency objective. In order to fulfill the defined constraints efficiently, our solution promotes a holistic approach that considers the whole design process from the definition of formal requirements through the software development. The results of benchmarking demonstrate that our approach improves the route efficiency by up to 10% route efficiency without any crashes in controlling swarms compared to state-of-the-art solutions.
Three-Dimensional (3D) integration is a solution to the interconnect bottleneck in Two-Dimensional (2D) MultiProcessor System on Chip (MPSoC). 3D IC design improves performance and decreases power consumption by replacing long horizontal interconnects with shorter vertical ones. As the multicast communication is utilized commonly in various parallel applications, the performance can be significantly improved by supporting of multicast operations at the hardware level. In this paper, we propose a set of partitioning approaches each with a different level of efficiency. In addition, we present an advantageous method named Recursive Partitioning (RP) in which the network is recursively partitioned until all partitions contain comparable number of nodes. By this approach, the multicast traffic is distributed among several subsets and the network latency is considerably decreased. We also present Minimal Adaptive Routing (MAR) algorithm for the unicast and multicast traffic in 3D-mesh Networks-on-Chip (NoCs). The idea behind the MAR algorithm is utilizing the Hamiltonian path to provide a set of alternative paths.