VLDB 2026 Research / reviewers in the wild / expert
Abhishek Moitra
dblp:232/8411
· DBLP profile ↗
26ranked-venue papers
5as first author
26since 2021 · last 2026
0000-0002-0534-5206ORCID · corroborated
Domains — the database's venue-derived domains; a paper can count in several
Systems, architecture and hardware · 23 · 5 first-author · 23 since 2021Software engineering, systems software and programming languages · 7 · 7 since 2021Graphics, computer vision, multimedia, augmented reality and games · 2 · 2 since 2021Applied, interdisciplinary, general and emerging computing · 2 · 2 since 2021Artificial intelligence and machine learning · 1 · 1 since 2021
| Year | Publication | Venue | Position |
|---|---|---|---|
| 2026 | MD-SNN: Membrane Potential-aware Distillation on Quantized Spiking Neural NetworkabstractSpiking Neural Networks (SNNs) offer a promising and energy-efficient alternative to conventional neural networks, thanks to their sparse binary activation. However, they face challenges regarding memory and computation overhead due to complex spatio-temporal dynamics and the necessity for multiple backpropagation computations across timesteps during training. To mitigate this overhead, compression techniques such as quantization are applied to SNNs. Yet, naively applying quantization to SNNs introduces a mismatch in membrane potential, a crucial factor for the firing of spikes, resulting in accuracy degradation. In this paper, we introduce Membrane-aware Distillation on quantized Spiking Neural Network (MD-SNN), which leverages membrane potential to mitigate discrepancies after weight, membrane potential, and batch normalization quantization. To our knowledge, this study represents the first application of membrane potential knowledge distillation in SNNs. We validate our approach on various datasets, including CIFAR10, CIFAR100, N-Caltech101, and TinyImageNet, demonstrating its effectiveness for both static and dynamic data scenarios. Furthermore, for hardware efficiency, we evaluate the MD-SNN with SpikeSim platform, finding that MD-SNNs achieve 14.85× lower energy-delay-area product (EDAP), 2.64× higher TOPS/W, and 6.19× higher TOPS/mm2compared to floating point SNNs at iso-accuracy on N-Caltech101 dataset. Code is available at Github. Donghyun Lee 0002, Abhishek Moitra, Youngeun Kim, Ruokai Yin, Priyadarshini Panda |
DATE | 2 |
| 2025 | Rhychee-FL: Robust and Efficient Hyperdimensional Federated Learning with Homomorphic Encryption
Yujin Nam, Abhishek Moitra, Yeshwanth Venkatesha, Xiaofan Yu 0001, Gabrielle De Micheli, Xuan Wang 0040, Minxuan Zhou, Augusto Vega, Priyadarshini Panda, Tajana Rosing |
DATE | 2 |
| 2025 | SITRA: Exploiting Temporal Silence in Spiking Transformers for Fast & Energy-efficient InferenceabstractSpiking Neural Network (SNN) transformers are emerging as a compelling alternative to conventional Artificial Neural Network (ANN) transformers, offering enhanced energy-efficiency through binary spike-based computations and high temporal sparsity. However, a key limitation of SNN transformers is their reliance on sequential processing across multiple timesteps, resulting in a latency drawback. This work introduces SITRA, a hardware evaluation engine tailored for SNN transformers, which employs timestep-parallelization to eliminate the latency bottleneck. Furthermore, SITRA dynamically exploits the inherent sparsity of silent inputs and preemptively detects silent outputs during SNN transformer inference. This enables skipping unnecessary costly memory accesses and operations, thereby achieving significant energy-efficiency and latency improvements over ANN transformers. Using SITRA, we find upto 6.4× higher energy-efficiency and 3.4× lower inference latency when benchmarking a SpikingBERT language transformer against its ANN baseline. Abhiroop Bhattacharjee, Abhishek Moitra, Ruokai Yin, Priyadarshini Panda |
ISLPED | 2 |
| 2025 | ClipFormer: Key-Value Clipping of Transformers on Memristive Crossbars for Write Noise MitigationabstractTransformers have revolutionized various real-world applications from natural language processing to computer vision. However, traditional von-Neumann computing paradigm faces memory and bandwidth limitations in accelerating transformers owing to their massive model sizes. To this end, in-memory computing (IMC) crossbars based on nonvolatile memories (NVMs), due to their ability to perform highly parallelized matrix-vector multiplications (MVMs) with high energy efficiencies, have emerged as a promising solution for accelerating transformers. However, analog MVM operations in crossbars introduce nonidealities, such as stochastic read and write noise, which affect the inference accuracy of the deployed transformers. Specifically, we find pretrained vision transformers (ViTs) to be vulnerable on crossbars due to the impact of write noise on the dynamically generated key$(K)$and value$(V)$matrices in the attention layers, an effect not accounted for in prior studies. We, thus, propose ClipFormer, a transformation on the K and V matrices during inference, to boost the nonideal accuracies of pretrained ViT models. ClipFormer requires no additional hardware and training overhead and is amenable to transformers deployed on any memristive crossbar platform impacted by write nonidealities. Our experiments on Imagenet-1k dataset using pretrained DeiT-S transformers, subjected to standard training and variation-aware training, show >10%–40% higher nonideal accuracies at the high write noise regime by applying ClipFormer. Abhiroop Bhattacharjee, Abhishek Moitra, Priyadarshini Panda |
IEEE Trans. Comput. Aided Des. Integr. Circuits Syst. | 2 |
| 2024 | MINT: Multiplier-less INTeger Quantization for Energy Efficient Spiking Neural NetworksabstractWe propose Multiplier-less INTeger (MINT) quantization, a uniform quantization scheme that efficiently compresses weights and membrane potentials in spiking neural networks (SNNs). Unlike previous SNN quantization methods, MINT quantizes memory-intensive membrane potentials to an extremely low precision (2-bit), significantly reducing the memory footprint. MINT also shares the quantization scaling factor between weights and membrane potentials, eliminating the need for multipliers required in conventional uniform quantization. Experimental results show that our method matches the accuracy of full-precision models and other state-of-the-art SNN quantization techniques while surpassing them in memory footprint reduction and hardware cost efficiency at deployment. For example, 2-bit MINT VGG-16 achieves 90.6% accuracy on CIFAR-10, with roughly 93.8% reduction in memory footprint from the full-precision model and 90% reduction in computation energy compared to vanilla uniform quantization at deployment.11Code is available at https://github.com/Intelligent-Computing-Lab-Yale/MINT-Quantization Ruokai Yin, Yuhang Li 0001, Abhishek Moitra, Priyadarshini Panda |
ASPDAC | 3 |
| 2024 | PIVOT- Input-aware Path Selection for Energy-efficient ViT InferenceabstractThe attention module in vision transformers(ViTs) performs intricate spatial correlations, contributing significantly to accuracy and delay. It is thereby important to modulate the number of attentions according to the input feature complexity for optimal delay-accuracy tradeoffs. To this end, we propose PIVOT - a co-optimization framework which selectively performs attention skipping based on the input difficulty. For this,PIVOT employs a hardware-in-loop co-search to obtain optimal attention skip configurations. Evaluations on the ZCU102 MPSoC FPGA show that PIVOT achieves 2.7× lower EDP at 0.2% accuracy reduction compared to LVViT-S ViT. PIVOT also achieves 1.3% and 1.8× higher accuracy and throughput than prior works on traditional CPUs and GPUs. The PIVOT project can be found at this Github link. Abhishek Moitra, Abhiroop Bhattacharjee, Priyadarshini Panda |
DAC | 1 |
| 2024 | TT-SNN: Tensor Train Decomposition for Efficient Spiking Neural Network TrainingabstractSpiking Neural Networks (SNNs) have gained significant attention as a potentially energy-efficient alternative for standard neural networks with their sparse binary activation. However, SNNs suffer from memory and computation overhead due to spatio-temporal dynamics and multiple backpropagation computations across timesteps during training. To address this issue, we introduce Tensor Train Decomposition for Spiking Neural Networks (TT-SNN), a method that reduces model size through trainable weight decomposition, resulting in reduced storage, FLOPs, and latency. In addition, we propose a parallel computation pipeline as an alternative to the typical sequential tensor computation, which can be flexibly integrated into various existing SNN architectures. To the best of our knowledge, this is the first of its kind application of tensor decomposition in SNNs. We validate our method using both static and dynamic datasets, CIFAR1I0/100 and N-Caltechl0l, respectively. We also propose a TT-SNN-tailored training accelerator to fully harness the parallelism in TT-SNN. Our results demonstrate substantial reductions in parameter size$(7.98\times)$, FLOPs$(9.25\times)$, training time (17.7 %), and training energy (28.3 %) during training for the N-Caltechl0l dataset, with negligible accuracy degradation. Donghyun Lee 0002, Ruokai Yin, Youngeun Kim, Abhishek Moitra, Yuhang Li 0001, Priyadarshini Panda |
DATE | 4 |
| 2024 | HaLo-FL: Hardware-Aware Low-Precision Federated LearningabstractApplications of federated learning involve devices with extremely limited computational resources and often with considerable heterogeneity in terms of energy efficiency, latency tolerance, and hardware area. Although low-precision training methods have demonstrated effectiveness in accommodating the device constraints in a centralized setting, their applicability in distributed learning scenarios featuring heterogeneous client capabilities has not been well explored. In this work, we design a hardware-aware low-precision federated training framework (HaLo- FL) tailored to heterogeneous resource-constrained de-vices. In particular, we optimize the precision for weights, activations, and errors for each client's hardware constraint using a precision selector (named HaLo-PS). To validate our approach, we propose HaLoSim, a hardware evaluation platform that enables precision reconfigurability and evaluates hardware metrics like energy, latency, and area utilization on a crossbar-based In-memory Computing (IMC) platform. Yeshwanth Venkatesha, Abhiroop Bhattacharjee, Abhishek Moitra, Priyadarshini Panda |
DATE | 3 |
| 2024 | Are SNNs Truly Energy-efficient? - A Hardware PerspectiveabstractSpiking Neural Networks (SNNs) have gained attention for their energy-efficient machine learning capabilities, utilizing bio-inspired activation functions and sparse binary spike-data representations. While recent SNN algorithmic advances achieve high accuracy on large-scale computer vision tasks, their energy-efficiency claims rely on certain impractical estimation metrics. This work studies two hardware benchmarking platforms for large-scale SNN inference, namely SATA and SpikeSim. SATA is a sparsity-aware systolic-array accelerator, while SpikeSim evaluates SNNs implemented on In-Memory Computing (IMC) based analog crossbars. Using these tools, we find that the actual energy-efficiency improvements of recent SNN algorithmic works differ significantly from their estimated values due to various hardware bottlenecks. We identify and addresses key roadblocks to efficient SNN deployment on hardware, including repeated computations & data movements over timesteps, neuronal module overhead and vulnerability of SNNs towards crossbar non-idealities. Abhiroop Bhattacharjee, Ruokai Yin, Abhishek Moitra, Priyadarshini Panda |
ICASSP | 3 |
| 2024 | Do we really need a large number of visual prompts?
Youngeun Kim, Yuhang Li 0001, Abhishek Moitra, Ruokai Yin, Priyadarshini Panda |
Neural Networks | 3 |
| 2024 | MCAIMem: A Mixed SRAM and eDRAM Cell for Area and Energy-Efficient On-Chip AI MemoryabstractAI chips commonly employ SRAM memory as buffers for their reliability and speed, which contribute to high performance. However, SRAM is expensive and demands significant area and energy consumption. Previous studies have explored replacing SRAM with emerging technologies, such as nonvolatile memory, which offers fast read memory access and a small cell area. Despite these advantages, nonvolatile memory’s slow write memory access and high write energy consumption prevent it from surpassing SRAM performance in AI applications with extensive memory access requirements. Some research has also investigated embedded dynamic random access memory (eDRAM) as an area-efficient on-chip memory with similar access times as SRAM. Still, refresh power remains a concern, leaving the trade-off among performance, area, and power consumption unresolved. To address this issue, this article presents a novel mixed CMOS cell memory design that balances performance, area, and energy efficiency for AI memory by combining SRAM and eDRAM cells. We consider the proportion ratio of one SRAM and seven eDRAM cells in the memory to achieve area reduction using mixed CMOS cell memory. In addition, we capitalize on the characteristics of deep neural network (DNN) data representation and integrate asymmetric eDRAM cells to lower energy consumption. To validate our proposed MCAIMem solution, we conduct extensive simulations and benchmarking against traditional SRAM. Our results demonstrate that the MCAIMem significantly outperforms these alternatives in terms of area and energy efficiency. Specifically, our MCAIMem can reduce the area by 48% and energy consumption by$3.4\times $compared with SRAM designs, without incurring any accuracy loss. Duy-Thanh Nguyen, Abhiroop Bhattacharjee, Abhishek Moitra, Priyadarshini Panda |
IEEE Trans. Very Large Scale Integr. Syst. | 3 |
| 2023 | Input-Aware Dynamic Timestep Spiking Neural Networks for Efficient In-Memory ComputingabstractSpiking Neural Networks (SNNs) have recently attracted widespread research interest as an efficient alternative to traditional Artificial Neural Networks (ANNs) because of their capability to process sparse and binary spike information and avoid expensive multiplication operations. Although the efficiency of SNNs can be realized on the In-Memory Computing (IMC) architecture, we show that the energy cost and latency of SNNs scale linearly with the number of timesteps used on IMC hardware. Therefore, in order to maximize the efficiency of SNNs, we propose input-aware Dynamic Timestep SNN (DT-SNN), a novel algorithmic solution to dynamically determine the number of timesteps during inference on an input-dependent basis. By calculating the entropy of the accumulated output after each timestep, we can compare it to a predefined threshold and decide if the information processed at the current timestep is sufficient for a confident prediction. We deploy DT-SNN on an IMC architecture and show that it incurs negligible computational overhead. We demonstrate that our method only uses 1.46 average timesteps to achieve the accuracy of a 4-timestep static SNN while reducing the energy-delay-product by 80%. Yuhang Li 0001, Abhishek Moitra, Tamar Geller, Priyadarshini Panda |
DAC | 2 |
| 2023 | XPert: Peripheral Circuit & Neural Architecture Co-search for Area and Energy-efficient Xbar-based ComputingabstractThe hardware-efficiency and accuracy of Deep Neural Networks (DNNs) implemented on In-memory Computing (IMC) architectures primarily depend on the DNN architecture and the peripheral circuit parameters. It is therefore essential to holistically co-search the network and peripheral parameters to achieve optimal performance. To this end, we propose XPert, which co-searches network architecture in tandem with peripheral parameters such as the type and precision of analog-to-digital converters, crossbar column sharing and the layer-specific input precision using an optimization-based design space exploration. Compared to VGG16 baselines, XPert achieves 10.24× (4.7×) lower EDAP, 1.72× (1.62×) higher TOPS/W, 1.93× (3×) higher TOPS/mm2at 92.46% (56.7%) accuracy for CIFAR10 (TinyImagenet) datasets. The code for this paper is available at the following Github link Abhishek Moitra, Abhiroop Bhattacharjee, Youngeun Kim, Priyadarshini Panda |
DAC | 1 |
| 2023 | DeepCAM: A Fully CAM-based Inference Accelerator with Variable Hash Lengths for Energy-efficient Deep Neural NetworksabstractWith ever increasing depth and width in deep neural networks to achieve state-of-the-art performance, deep learning computation has significantly grown, and dot-products remain dominant in overall computation time. Most prior works are built on conventional dot-product where weighted input summation is used to represent the neuron operation. However, another implementation of dot-product based on the notion of angles and magnitudes in the Euclidean space has attracted limited attention. This paper proposes DeepCAM, an inference accelerator built on two critical innovations to alleviate the computation time bottleneck of convolutional neural networks. The first innovation is an approximate dot-product built on computations in the Euclidean space that can replace addition and multiplication with simple bit-wise operations. The second innovation is a dynamic size content addressable memory-based (CAM-based) accelerator to perform bit-wise operations and accelerate the CNNs with a lower computation time. Our experiments on benchmark image recognition datasets demonstrate that DeepCAM is up to$523\times$and$3498\times$faster than Eyeriss and traditional CPUs like Intel Skylake, respectively. Furthermore, the energy consumed by our DeepCAM approach is$2.16\times$to$109\times$less compared to Eyeriss. Duy-Thanh Nguyen, Abhiroop Bhattacharjee, Abhishek Moitra, Priyadarshini Panda |
DATE | 3 |
| 2023 | Examining the Role and Limits of Batchnorm Optimization to Mitigate Diverse Hardware-noise in In-memory ComputingabstractIn-Memory Computing (IMC) platforms such as analog crossbars are gaining focus as they facilitate the acceleration of low-precision Deep Neural Networks (DNNs) with high area- & compute-efficiencies. However, the intrinsic non-idealities in crossbars, which are often non-deterministic and non-linear, degrade the performance of the deployed DNNs. In addition to quantization errors, most frequently encountered non-idealities during inference include crossbar circuit-level parasitic resistances and device-level non-idealities such as stochastic read noise and temporal drift. In this work, our goal is to closely examine the distortions caused by these non-idealities on the dot-product operations in analog crossbars and explore the feasibility of a nearly training-less solution via crossbar-aware fine-tuning of batchnorm parameters in real-time to mitigate the impact of the non-idealities. This enables reduction in hardware costs in terms of memory and training energy for IMC noise-aware retraining of the DNN weights on crossbars. Abhiroop Bhattacharjee, Abhishek Moitra, Youngeun Kim, Yeshwanth Venkatesha, Priyadarshini Panda |
ACM Great Lakes Symposium on VLSI | 2 |
| 2023 | Hardware Accelerators for Spiking Neural Networks for Energy-Efficient Edge ComputingabstractNo abstract available. Abhishek Moitra, Ruokai Yin, Priyadarshini Panda |
ACM Great Lakes Symposium on VLSI | 1 |
| 2023 | SpikeSim: An End-to-End Compute-in-Memory Hardware Evaluation Tool for Benchmarking Spiking Neural NetworksabstractSpiking neural networks (SNNs) are an active research domain toward energy-efficient machine intelligence. Compared to conventional artificial neural networks (ANNs), SNNs use temporal spike data and bio-plausible neuronal activation functions such as leaky-integrate fire/integrate fire (LIF/IF) for data processing. However, SNNs incur significant dot-product operations causing high memory and computation overhead in standard von-Neumann computing platforms. To this end, in-memory computing (IMC) architectures have been proposed to alleviate the “memory-wall bottleneck” prevalent in von-Neumann architectures. Although recent works have proposed IMC-based SNN hardware accelerators, the following key implementation aspects have been overlooked: 1) the adverse effects of crossbar nonideality on SNN performance due to repeated analog dot-product operations over multiple time-steps and 2) hardware overheads of essential SNN-specific components, such as the LIF/IF and data communication modules. To this end, we propose SpikeSim, a tool that can perform realistic performance, energy, latency and area evaluation of IMC-mapped SNNs. SpikeSim consists of a practical monolithic IMC architecture called SpikeFlow for mapping SNNs. Additionally, the nonideality computation engine (NICE) and energy–latency–area (ELA) engine performs hardware-realistic evaluation of SpikeFlow-mapped SNNs. Based on 65nm CMOS implementation and experiments on CIFAR10, CIFAR100 and TinyImagenet datasets, we find that the LIF/IF neuronal module has significant area contribution$(>11\%$of the total hardware area). To this end, we propose SNN topological modifications that leads to$1.24\times $and$10\times $reduction in the neuronal module’s area and the overall energy-delay-product value, respectively. Furthermore, in this work, we perform a holistic comparison between IMC implemented ANN and SNNs and conclude that lower number of time-steps are the key to achieve higher throughput and energy-efficiency for SNNs compared to 4-bit ANNs. The code repository for the SpikeSim tool is available at Github link. Abhishek Moitra, Abhiroop Bhattacharjee, Runcong Kuang, Yu Cao 0001, Priyadarshini Panda |
IEEE Trans. Comput. Aided Des. Integr. Circuits Syst. | 1 |
| 2023 | SATA: Sparsity-Aware Training Accelerator for Spiking Neural NetworksabstractSpiking neural networks (SNNs) have gained huge attention as a potential energy-efficient alternative to conventional artificial neural networks (ANNs) due to their inherent high-sparsity activation. Recently, SNNs with backpropagation through time (BPTT) have achieved a higher accuracy result on image recognition tasks than other SNN training algorithms. Despite the success from the algorithm perspective, prior works neglect the evaluation of the hardware energy overheads of BPTT, due to the lack of a hardware evaluation platform for this SNN training algorithm. Moreover, although SNNs have long been seen as an energy-efficient counterpart of ANNs, a quantitative comparison between the training cost of SNNs and ANNs is missing. To address the aforementioned issues, in this work, we introduce a sparsity-aware training accelerator (SATA), a BPTT-based training accelerator for SNNs. The proposed SATA provides a simple and reconfigurable systolic-based accelerator architecture, which makes it easy to analyze the training energy for BPTT-based SNN training algorithms. By utilizing the sparsity, SATA increases its computation energy efficiency by$5.58\times $compared to the one without using sparsity. Based on SATA, we show quantitative analyses of the energy efficiency of SNN training and make a comparison between the training cost of SNNs and ANNs. The results show that, on Eyeriss-like systolic-based architecture, SNNs consume$1.27\times $more total energy with considering sparsity (spikes, gradient of firing function, and gradient of membrane potential) when compared to ANNs. We find that such high training energy cost is from time-repetitive convolution operations and data movements during backpropagation. Moreover, to propel the future SNN training algorithm design, we provide several observations on energy efficiency for different SNN-specific training parameters and propose an energy estimation framework for SNN training. Ruokai Yin, Abhishek Moitra, Abhiroop Bhattacharjee, Youngeun Kim, Priyadarshini Panda |
IEEE Trans. Comput. Aided Des. Integr. Circuits Syst. | 2 |
| 2023 | XploreNAS: Explore Adversarially Robust and Hardware-efficient Neural Architectures for Non-ideal XbarsabstractCompute In-Memory platforms such as memristive crossbars are gaining focus as they facilitate acceleration of Deep Neural Networks (DNNs) with high area and compute efficiencies. However, the intrinsic non-idealities associated with the analog nature of computing in crossbars limits the performance of the deployed DNNs. Furthermore, DNNs are shown to be vulnerable to adversarial attacks leading to severe security threats in their large-scale deployment. Thus, finding adversarially robust DNN architectures for non-ideal crossbars is critical to the safe and secure deployment of DNNs on the edge. This work proposes a two-phase algorithm-hardware co-optimization approach called XploreNAS that searches for hardware efficient and adversarially robust neural architectures for non-ideal crossbar platforms. We use the one-shot Neural Architecture Search approach to train a large Supernet with crossbar-awareness and sample adversarially robust Subnets therefrom, maintaining competitive hardware efficiency. Our experiments on crossbars with benchmark datasets (SVHN, CIFAR10, CIFAR100) show up to ~8–16% improvement in the adversarial robustness of the searched Subnets against a baseline ResNet-18 model subjected to crossbar-aware adversarial training. We benchmark our robust Subnets for Energy-Delay-Area-Products (EDAPs) using the Neurosim tool and find that with additional hardware efficiency–driven optimizations, the Subnets attain ~1.5–1.6× lower EDAPs than ResNet-18 baseline. Abhiroop Bhattacharjee, Abhishek Moitra, Priyadarshini Panda |
ACM Trans. Embed. Comput. Syst. | 2 |
| 2022 | MIME: adapting a single neural network for multi-task inference with memory-efficient dynamic pruningabstractRecent years have seen a paradigm shift towards multi-task learning. This calls for memory and energy-efficient solutions for inference in a multi-task scenario. We propose an algorithm-hardware co-design approach called MIME. MIME reuses the weight parameters of a trained parent task and learns task-specific threshold parameters for inference on multiple child tasks. We find that MIME results in highly memory-efficient DRAM storage of neural-network parameters for multiple tasks compared to conventional multi-task inference. In addition, MIME results in input-dependent dynamic neuronal pruning, thereby enabling energy-efficient inference with higher throughput on a systolic-array hardware. Our experiments with benchmark datasets (child tasks)- CIFAR10, CIFAR100, and Fashion-MNIST, show that MIME achieves ~ 3.48x memory-efficiency and ~ 2.4 - 3.1x energy-savings compared to conventional multi-task inference in Pipelined task mode. Abhiroop Bhattacharjee, Yeshwanth Venkatesha, Abhishek Moitra, Priyadarshini Panda |
DAC | 3 |
| 2022 | Rate Coding Or Direct Coding: Which One Is Better For Accurate, Robust, And Energy-Efficient Spiking Neural Networks?abstractRecent Spiking Neural Networks (SNNs) works focus on an image classification task, therefore various coding techniques have been proposed to convert an image into temporal binary spikes. Among them, rate coding and direct coding are regarded as prospective candidates for building a practical SNN system as they show state-of-the-art performance on large-scale datasets. Despite their usage, there is little attention to comparing these two coding schemes in a fair manner. In this paper, we conduct a comprehensive analysis of the two codings from three perspectives: accuracy, adversarial robustness, and energy-efficiency. First, we compare the performance of two coding techniques with various architectures and datasets. Then, we measure the robustness of the coding techniques on two adversarial attack methods. Finally, we compare the energy-efficiency of two coding schemes on a digital hardware platform. Our results show that direct coding can achieve better accuracy especially for a small number of timesteps. In contrast, rate coding shows better robustness to adversarial attacks owing to the non-differentiable spike generation process. Rate coding also yields higher energy-efficiency than direct coding which requires multi-bit precision for the first layer. Our study explores the characteristics of two codings, which is an important design consideration for building SNNs1. Youngeun Kim, Hyoungseob Park, Abhishek Moitra, Abhiroop Bhattacharjee, Yeshwanth Venkatesha, Priyadarshini Panda |
ICASSP | 3 |
| 2022 | Examining the Robustness of Spiking Neural Networks on Non-ideal Memristive CrossbarsabstractSpiking Neural Networks (SNNs) have recently emerged as the low-power alternative to Artificial Neural Networks (ANNs) owing to their asynchronous, sparse, and binary information processing. To improve the energy-efficiency and throughput, SNNs can be implemented on memristive crossbars where Multiply-and-Accumulate (MAC) operations are realized in the analog domain using emerging Non-Volatile-Memory (NVM) devices. Despite the compatibility of SNNs with memristive crossbars, there is little attention to study on the effect of intrinsic crossbar non-idealities and stochasticity on the performance of SNNs. In this paper, we conduct a comprehensive analysis of the robustness of SNNs on non-ideal crossbars. We examine SNNs trained via learning algorithms such as, surrogate gradient and ANN-SNN conversion. Our results show that repetitive crossbar computations across multiple time-steps induce error accumulation, resulting in a huge performance drop during SNN inference. We further show that SNNs trained with a smaller number of time-steps achieve better accuracy when deployed on memristive crossbars. Abhiroop Bhattacharjee, Youngeun Kim, Abhishek Moitra, Priyadarshini Panda |
ISLPED | 3 |
| 2022 | Noise Sensitivity-Based Energy Efficient and Robust Adversary Detection in Neural NetworksabstractNeural have achieved remarkable performance in computer vision, however, they are vulnerable to adversarial examples. Adversarial examples are inputs that have been carefully perturbed to fool classifier networks, while appearing unchanged to humans. Based on prior works on detecting adversaries, we propose a structured methodology of augmenting a deep neural network (DNN) with a detector subnetwork. We use adversarial noise sensitivity (ANS), a novel metric for measuring the adversarial gradient contribution of different intermediate layers of a network. Based on the ANS value, we append a detector to the most sensitive layer. In prior works, more complex detectors were added to a DNN, increasing the inference computational cost of the model. In contrast, our structured and strategic addition of a detector to a DNN reduces the complexity of the model while making the overall network adversarially resilient. Through comprehensive white-box and black-box experiments on MNIST, CIFAR-10, and CIFAR-100, we show that our method improves state-of-the-art detector robustness against adversarial examples. Furthermore, we validate the energy efficiency of our proposed adversarial detection methodology through an extensive energy analysis on various hardware scalable CMOS accelerator platforms. We also demonstrate the effects of quantization on our detector-appended networks. Rachel Sterneck, Abhishek Moitra, Priyadarshini Panda |
IEEE Trans. Comput. Aided Des. Integr. Circuits Syst. | 2 |
| 2021 | Efficiency-driven Hardware Optimization for Adversarially Robust Neural NetworksabstractWith a growing need to enable intelligence in embedded devices in the Internet of Things (IoT) era, secure hardware implementation of Deep Neural Networks (DNNs) has become imperative. We will focus on how to address adversarial robustness for DNNs through efficiency-driven hardware optimizations. Since memory (specifically, dot-product operations) is a key energy-spending component for DNNs, hardware approaches in the past have focused on optimizing the memory. One such approach is approximate digital CMOS memories with hybrid 6T-8T SRAM cells that enable supply voltage (Vdd) scaling yielding low-power operation, without significantly affecting the performance due to read/write failures incurred in the 6T cells. In this paper, we show how the bit-errors in the 6T cells of hybrid 6T-8T memories minimize the adversarial perturbations in a DNN. Essentially, we find that for different configurations of 8T-6T ratios and scaledVdd operation, noise incurred in the hybrid memory architectures is bound within specific limits. This hardware noise can potentially interfere in the creation of adversarial attacks in DNNs yielding robustness. Another memory optimization approach involves using analog memristive crossbars that perform Matrix-Vector-Multiplications (MVMs) efficiently with low energy and area requirements. However, crossbars generally suffer from intrinsic non-idealities that cause errors in performing MVMs, leading to degradation in the accuracy of the DNNs. We will show how the intrinsic hardware variations manifested through crossbar non-idealities yield adversarial robustness to the mapped DNNs without any additional optimization. Abhiroop Bhattacharjee, Abhishek Moitra, Priyadarshini Panda |
DATE | 2 |
| 2021 | Activation Density based Mixed-Precision Quantization for Energy Efficient Neural NetworksabstractAs neural networks gain widespread adoption in embedded devices, there is a growing need for model compression techniques to facilitate seamless deployment in resource-constrained environments. Quantization is one of the go-to methods yielding state-of-the-art model compression. Most quantization approaches take a fully trained model, then apply different heuristics to determine the optimal bit-precision for different layers of the network, and finally retrain the network to regain any drop in accuracy. Based on Activation Density-the proportion of non-zero activations in a layer-we propose a novel in-training quantization method. Our method calculates optimal bit-width/precision for each layer during training yielding an energy-efficient mixed precision model with competitive accuracy. Since we train lower precision models progressively during training, our approach yields the final quantized model at lower training complexity and also eliminates the need for re-training. We run experiments on benchmark datasets like CIFAR-10, CIFAR-100, TinyImagenet on VGG19/ResNet18 architectures and report the accuracy and energy estimates for the same. We achieve up to 4.5× benefit in terms of estimated multiply-and-accumulate (MAC) reduction while reducing the training complexity by 50% in our experiments. To further evaluate the energy benefits of our proposed method, we develop a mixed-precision scalable Process In Memory (PIM) hardware accelerator platform. The hardware platform incorporates shift-add functionality for handling multibit precision neural network models. Evaluating the quantized models obtained with our proposed method on the PIM platform yields about 5× energy reduction compared to baseline 16-bit models. Additionally, we find that integrating activation density based quantization with activation density based pruning (both conducted during training) yields up to ~ 198× and ~44× energy reductions for VGG19 and ResNet18 architectures respectively on PIM platform compared to baseline 16-bit precision, unpruned models. Karina Vasquez, Yeshwanth Venkatesha, Abhiroop Bhattacharjee, Abhishek Moitra, Priyadarshini Panda |
DATE | 4 |
| 2021 | DetectX - Adversarial Input Detection Using Current Signatures in Memristive XBar ArraysabstractAdversarial input detection has emerged as a prominent technique to harden Deep Neural Networks(DNNs) against adversarial attacks. Most prior works use neural network-based detectors or complex statistical analysis for adversarial detection. These approaches are computationally intensive and vulnerable to adversarial attacks. To this end, we propose DetectX - a hardware friendly adversarial detection mechanism using hardware signatures like Sum of column Currents (SoI) in memristive crossbars (XBar). We show that adversarial inputs have higher SoI compared to clean inputs. However, the difference is too small for reliable adversarial detection. Hence, we propose a dual-phase training methodology: Phase1 training is geared towards increasing the separation between clean and adversarial SoIs; Phase2 training improves the overall robustness against different strengths of adversarial attacks. For hardware-based adversarial detection, we implement the DetectX module using 32nm CMOS circuits and integrate it with a Neurosim-like analog crossbar architecture. We perform hardware evaluation of the Neurosim+DetectX system on the Neurosim platform using datasets-CIFAR10(VGG8), CIFAR100(VGG16) and TinyImagenet(ResNet18). Our experiments show that DetectX is 10x-25x more energy efficient and immune to dynamic adversarial attacks compared to previous state-of-the-art works. Moreover, we achieve high detection performance (ROC-AUC > 0.95) for strong white-box and black-box attacks. The code has been released at https://github.com/Intelligent-Computing-Lab-Yale/DetectX Abhishek Moitra, Priyadarshini Panda |
IEEE Trans. Circuits Syst. I Regul. Pap. | 1 |