Graph neural networks (GNNs) are used for predictive analytics on graph-structured data, and they have become very popular in diverse real-world applications. Resistive random-access memory (ReRAM)-based PIM architectures can accelerate GNN training. However, GNN training on ReRAM-based architectures is both compute- and data intensive in nature. In this work, we propose a framework calledSlimGNNthat synergistically combines both graph and model pruning to accelerate GNN training on ReRAM-based architectures. The proposed framework reduces the amount of redundant information in both the GNN model and input graph(s) to streamline the overall training process. This enables fast and energy-efficient GNN training on ReRAM-based architectures. Experimental results demonstrate that using this framework, we can accelerate GNN training by up to$ {4}. {5} {\times }$while using$ {6}. {6} {\times }$less energy compared to the unpruned counterparts.

Resistive random-access memory has become one of the most popular choices of hardware implementation for machine learning application workloads. However, these devices exhibit non-ideal behavior, which presents a challenge towards widespread adoption. Training/inferencing on these faulty devices can lead to poor prediction accuracy. However, existing fault tolerant methods are associated with high implementation overheads. In this paper, we present some new directions for solving reliability issues using software solutions. These software-based methods are inherent in deep learning training/inferencing, and they can also be used to address hardware reliability issues as well. These methods prevent accuracy drop during training/inferencing due to unreliable ReRAMs and are associated with lower area and power overheads.

Resistive random-access memory (ReRAM)-based manycore architectures enable acceleration of graph neural network (GNN) inference and training. GNNs exhibit characteristics of both DNNs and graph analytics. Hence, GNN training/inferencing on ReRAM-based manycore architectures give rise to both computation and on-chip communication challenges. In this work, we leverage model pruning and efficient graph storage to reduce the computation and communication bottlenecks associated with GNN training on ReRAM-based manycore accelerators. However, traditional pruning techniques are either targeted for inferencing only, or they are not crossbar-aware. In this work, we propose a GNN pruning technique called DietGNN. DietGNN is a crossbar-aware pruning technique that achieves high accuracy training and enables energy, area, and storage efficient computing on ReRAM-based manycore platforms. The DietGNN pruned model can be trained from scratch without any noticeable accuracy loss. Our experimental results show that when mapped on to a ReRAM-based manycore architecture, DietGNN can reduce the number of crossbars by over 90% and accelerate GNN training by${\sim }{2}.{7}{\times }$compared to its unpruned counterpart. In addition, DietGNN reduces energy consumption by more than${\sim }{3}.{5}{\times }$compared to the unpruned counterpart.

Graph Neural Network (GNN) is a variant of Deep Neural Networks (DNNs) operating on graphs. However, GNNs are more complex compared to traditional DNNs as they simultaneously exhibit features of both DNN and graph applications. As a result, architectures specifically optimized for either DNNs or graph applications are not suited for GNN training. In this work, we propose a 3D heterogeneous manycore architecture for on-chip GNN training to address this problem. The proposed architecture, ReGraphX, involves heterogeneous ReRAM crossbars to fulfill the disparate requirements of both DNN and graph computations simultaneously. The ReRAM-based architecture is complemented with a multicast-enabled 3D NoC to improve the overall achievable performance. We demonstrate that ReGraphX outperforms conventional GPUs by up to 3.5X (on an average 3X) in terms of execution time, while reducing energy consumption by as much as 11X.

Three-dimensional (3D) integration has frequently been described as a means to overcome scaling bottlenecks, and advance both “More Moore” and “More Than Moore” through the use of vertical interconnects and die/wafer stacking. Recent industry trends show the viability of 3D integration in real products. Flash memory producers have also demonstrated multiple layers of memory on top of each other. However, conventional TSV-based 3D designs cannot achieve the full-potential of vertical integration and perform suboptimally. Monolithic 3D (M3D) is an emerging vertical integration technology that promises significant power-performance-area benefits compared to TSVs. Hence, it is important to understand the necessary design trade-offs and challenges associated with this new paradigm. In this paper, we present both the advantages and the various design challenges in M3D-enabled system design considering Processing-in-Memory (PIM) and manycore systems as suitable case-studies.

Graph Neural Networks (GNNs) are a variant of Deep Neural Networks (DNNs) operating on graphs. GNNs have attributes of both DNNs and graph computation. However, training GNNs on manycore architectures is a challenging task because it involves heavy communication that bottlenecks performance. DropEdge and Dropout, which we collectively refer to as DropLayer, are regularization techniques that can improve the predictive accuracy of GNNs. Moreover, when implemented on a manycore architecture, DropEdge and Dropout are capable of reducing the on-chip traffic. In this paper, we present a ReRAM-based 3D manycore architecture called DARe, tailored for accelerating on-chip training of GNNs. The key component of the DARe architecture is a Network-on-Chip (NoC) that reduces the amount of communication using DropLayer. The reduced traffic prevents communication hotspots and leads to better performance. We demonstrate that DARe outperforms conventional GPUs by up to 6.7X (5.6X on average) in terms of execution time, while being up to 30X (23X on average) more energy efficient for GNN training.

Resistive random-access memory (ReRAM)-based processing-in-memory (PIM) architectures have recently become a popular architectural choice for deep-learning applications. ReRAM-based architectures can accelerate inferencing and training of deep learning algorithms and are more energy efficient compared to traditional GPUs. However, these architectures have various limitations that affect the model accuracy and performance. Moreover, the choice of the deep-learning application also imposes new design challenges that must be addressed to achieve high performance. In this paper, we present the advantages and challenges associated with ReRAM-based PIM architectures by considering Convolutional Neural Networks (CNNs) and Graph Neural Networks (GNNs) as important application domains. We also outline methods that can be used to address these challenges.

Heterogeneous manycore architectures are the key to efficiently execute compute- and data-intensive applications. Through-silicon-via (TSV)-based 3D manycore system is a promising solution in this direction as it enables the integration of disparate computing cores on a single system. Recent industry trends show the viability of 3D integration in real products (e.g., Intel Lakefield SoC Architecture, the AMD Radeon R9 Fury X graphics card, and Xilinx Virtex-7 2000T/H580T, etc.). However, the achievable performance of conventional TSV-based 3D systems is ultimately bottlenecked by the horizontal wires (wires in each planar die). Moreover, current TSV 3D architectures suffer from thermal limitations. Hence, TSV-based architectures do not realize the full potential of 3D integration. Monolithic 3D (M3D) integration, a breakthrough technology to achieve “More Moore and More Than Moore,” opens up the possibility of designing cores and associated network routers using multiple layers by utilizing monolithic inter-tier vias (MIVs) and hence, reducing the effective wire length. Compared to TSV-based 3D integrated circuits (ICs), M3D offers the “true” benefits of vertical dimension for system integration: the size of an MIV used in M3D is over 100 × smaller than a TSV. This dramatic reduction in via size and the resulting increase in density opens up numerous opportunities for design optimizations in 3D manycore systems: designers can use up to millions of MIVs for ultra-fine-grained 3D optimization, where individual cores and routers can be spread across multiple tiers for extreme power and performance optimization. In this work, we demonstrate how M3D-enabled vertical core and uncore elements offer significant performance and thermal improvements in manycore heterogeneous architectures compared to its TSV-based counterpart. To overcome the difficult optimization challenges due to the large design space and complex interactions among the heterogeneous components (CPU, GPU, Last Level Cache, etc.) in a M3D-based manycore chip, we leverage novel design-space exploration algorithms to trade off different objectives. The proposed M3D-enabled heterogeneous architecture, called HeM3D , outperforms its state-of-the-art TSV-equivalent counterpart by up to 18.3% in execution time while being up to 19°C cooler.

Graph neural network (GNN) is a variant of deep neural networks (DNNs) operating on graphs. However, GNNs are more complex compared with DNNs as they simultaneously exhibit attributes of both DNN and graph computations. In this work, we propose a ReRAM-based 3-D manycore processing-in-memory architecture called ReMaGN, tailored for on-chip training of GNNs. ReMaGN implements GNN training using reduced-precision representation to make the computation faster and reduce the load on the communication backbone. However, reduced precision can potentially compromise the accuracy of training. Hence, we undertake a study of performance and accuracy tradeoffs in such architectures. We demonstrate that ReMaGN outperforms conventional GPUs by up to$9.5\times $(on average$7.1\times $) in terms of execution time, while being up to$42\times $(on average$33.5\times $) more energy efficient without sacrificing accuracy.

3D Network-on-Chip (3D NoC) enables design of high-performance and energy-efficient manycore computing platforms. Two of the commonly used vertical interconnection technologies are: through silicon via (TSV) and near-field inductive coupling (NFIC). Both TSV- and NFIC-based links introduce additional area overhead. One of the possible ways to reduce the area overhead is to design partially connected 3D NoC with minimal effect on overall performance. The achievable performance of the partially connected 3D NoCs depends on the area, energy, and bandwidth of the vertical links. Moreover, the electromigration-induced failure of TSV is more severe than the misalignment-induced error in NFIC. By considering all these pertinent factors, we demonstrate that it is indeed possible to design a partially connected NFIC-based 3D NoC that performs as good as a fully connected TSV-based counterpart when the data rate is below a certain limit. For higher data rates, the partially connected TSV-based 3D NoC is a viable solution. However, NFIC-based 3D NoC is always more robust than the TSV-based counterpart.