Ritik Raj

dblp:315/7662 · DBLP profile ↗
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11ranked-venue papers
1as first author
11since 2021 · last 2026
—ORCID · conflict

Domains — the database's venue-derived domains; a paper can count in several

Systems, architecture and hardware · 7 · 7 since 2021Software engineering, systems software and programming languages · 5 · 1 first-author · 5 since 2021Artificial intelligence and machine learning · 1 · 1 since 2021Databases, data management, data science and information retrieval · 1 · 1 since 2021
YearPublicationVenuePosition
2026 Compositional AI Beyond LLMs: System Implications of Neuro-Symbolic-Probabilistic Architectures
abstract
Large Language Models (LLMs) have driven remarkable progress in artificial intelligence (AI), but their rapid growth faces challenges of unsustainable computation, limited robustness, and poor explainability. Compositional AI, which integrates LLMs with symbolic reasoning and probabilistic inference, has emerged as a promising paradigm to enable interpretability, robustness, trustworthiness, and data-efficient learning. Recent neuro-symbolic-probabilistic systems demonstrate strong potential in agentic applications, advancing reasoning and cognitive capabilities toward human-like intelligence.
Zishen Wan, Hanchen Yang 0001, Jiayi Qian, Ritik Raj, Joongun Park, Arijit Raychowdhury, Tushar Krishna
ASPLOS (1)4
2025 NSFlow: An End-to-End FPGA Framework with Scalable Dataflow Architecture for Neuro-Symbolic AI
abstract
Neuro-Symbolic AI (NSAI) is an emerging paradigm that integrates neural networks with symbolic reasoning to enhance the transparency, reasoning capabilities, and data efficiency of AI systems. Recent NSAI systems have gained traction due to their exceptional performance in reasoning tasks and human-AI collaborative scenarios. Despite these algorithmic advancements, executing NSAI tasks on existing hardware (e.g., CPUs, GPUs, TPUs) remains challenging, due to their heterogeneous computing kernels, high memory intensity, and unique memory access patterns. Moreover, current NSAI algorithms exhibit significant variation in operation types and scales, making them incompatible with existing ML accelerators. These challenges highlight the need for a versatile and flexible acceleration framework tailored to NSAI workloads. In this paper, we propose NSFlow, an FPGA-based acceleration framework designed to achieve high efficiency, scalability, and versatility across NSAI systems. NSFlow features a design architecture generator that identifies workload data dependencies and creates optimized dataflow architectures, as well as a reconfigurable array with flexible compute units, re-organizable memory, and mixed-precision capabilities. Evaluating across NSAI workloads, NSFlow achieves $31 \times$ speedup over Jetson TX2, more than $2 \times$ over GPU, $8 \times$ speedup over TPU-like systolic array, and more than $3 \times$ over Xilinx DPU. NSFlow also demonstrates enhanced scalability, with only $4 \times$ runtime increase when symbolic workloads scale by $150 \times$. To the best of our knowledge, NSFlow is the first framework to enable real-time generalizable NSAI algorithms acceleration, demonstrating a promising solution for next-generation cognitive systems.
Hanchen Yang 0001, Zishen Wan, Ritik Raj, Joongun Park, Ananda Samajdar, Arijit Raychowdhury, Tushar Krishna
DAC3
2025 Axon: A Novel Systolic Array Architecture for Improved Run Time and Energy Efficient GeMM and Conv Operation with On-Chip im2col
abstract
General matrix multiplication ($GeMM$) is a core operation in virtually all AI applications. Systolic array (SA) based architectures have shown great promise as$GeMM$hardware accelerators thanks to their speed and energy efficiency. Unfortunately, SAs incur a linear delay in filling the operands, due to unidirectional propogation via pipeline latches. In this work, we propose a novel in-array data orchestration technique in SAs where we enable data feeding on the principal diagonal followed by bi-directional propagation. This improves the runtime by up to 2 × at minimal hardware overhead. In addition, the proposed data orchestration enables convolution lowering (known as im2col) using a simple hardware support to fully exploit input feature map reuse opportunity and significantly lower the off-chip memory traffic resulting in 1.2 ×throughput improvement and 2.17 × inference energy reduction during YOLOv3 and RESNET50 workload on average. In contrast, conventional data orchestration would require more elaborate hardware and control signals to implement im2col in hardware because of the data skew. We have synthesized and conducted place and route for 16×16 systolic arrays based on the novel and conventional orchestrations using ASAP 7nm PDK and found that our proposed approach results in 0.211% area and 1.6% power overheads.
Md Mizanur Rahaman Nayan, Ritik Raj, Shaik Gouse Basha, Tushar Krishna, Azad Naeemi
DATE2
2025 CogSys: Efficient and Scalable Neurosymbolic Cognition System via Algorithm-Hardware Co-Design
abstract
Neurosymbolic AI is an emerging compositional paradigm that fuses neural learning with symbolic reasoning to enhance the transparency, interpretability, and trustworthiness of AI. It also exhibits higher data efficiency making it promising for edge deployments. Despite the algorithmic promises and demonstrations, unfortunately executing neurosymbolic workloads on current hardware (CPU/GPU/TPU) is challenging due to higher memory intensity, greater compute heterogeneity and access pattern irregularity, leading to severe hardware underutilization. This work proposes CogSys, a characterization and co-design framework dedicated to neurosymbolic AI system acceleration, aiming to win both reasoning efficiency and scalability. On the algorithm side, CogSys proposes an efficient factorization technique to alleviate compute and memory overhead. On the hardware side, CogSys proposes a scalable neurosymbolic architecture with reconfigurable neuro/symbolic processing elements ($n s P E$) and bubble streaming (BS) dataflow with spatial-temporal (ST) mapping for highly parallel and efficient neurosymbolic computation. On the system side, CogSys features an adaptive workload-aware scheduler (adSCH) to orchestrate heterogeneous kernels and enhance resource utilization. Evaluated across cognitive workloads, CogSys enables reconfigurable support for neural and symbolic kernels and exhibits $\gt75 \times$ speedup over TPU-like systolic array with only $\lt5 \%$ area overhead, as benchmarked under the TSMC 28nm technology node. CogSys achieves $4 \times$ $96 \times$ speedup compared to desktop and edge GPUs. For the first time, CogSys enables real-time abduction reasoning towards human fluid intelligence, requiring only 0.3 s per reasoning task with $4 \mathrm{~mm}^{2}$ area and 1.48 W power consumption.
Zishen Wan, Hanchen Yang 0001, Ritik Raj, Che-Kai Liu, Ananda Samajdar, Arijit Raychowdhury, Tushar Krishna
HPCA3
2025 SCALE-Sim V3: a Modular Cycle-Accurate Systolic Accelerator Simulator for End-To-End System Analysis
abstract
The rapid advancements in AI, scientific computing, and high-performance computing (HPC) have driven the need for versatile and efficient hardware accelerators. Existing tools like SCALE-Sim v2 provide valuable cycle-accurate simulations for systolic-array-based architectures but fall short in supporting key modern features such as sparsity, multi-core scalability, and comprehensive memory analysis. To address these limitations, we present SCALE-Sim v3 (GitHub Repository), a modular, cycle-accurate simulator that extends the capabilities of its predecessor. SCALE-Sim v3 introduces five significant enhancements: multi-core simulation with spatio-temporal partitioning and hierarchical memory structures, support for sparse matrix multiplications (SpMM) with layer-wise and row-wise sparsity, integration with Ramulator for detailed DRAM analysis, precise data layout modeling to minimize memory stalls, and energy and power estimation via Accelergy. These improvements enable deeper end-to-end system analysis for modern AI accelerators, accommodating a wide variety of systems and workloads and providing detailed full-system insights into latency, bandwidth, and power efficiency. A$128 \times 128$array is$6.53 \times$faster than a$32 \times 32$array for ViTbase, using only latency as a metric. However, SCALE-Sim v3 finds that$32 \times 32$is$2.86 \times$more energy-efficient due to better utilization and lower leakage energy. For EdP,$64 \times 64$outperforms both$128 \times 128$and$32 \times 32$for ViT-base. SCALE-Sim v2 shows a 21 % reduction in compute cycles for six ResNet18 layers using weight-stationary (WS) dataflow compared to outputstationary (OS). However, when factoring in DRAM stalls, OS dataflow exhibits 30.1% lower execution cycles compared to WS, highlighting the critical role of detailed DRAM analysis.
Ritik Raj, Sarbartha Banerjee, Nikhil Chandra, Zishen Wan, Jianming Tong, Ananda Samajdar, Tushar Krishna
ISPASS1
2025 Cloudy With a Chance of JSON
abstract
Couchbase Capella is a scalable document-oriented database service in the cloud. Its existing Capella Operational service is based on a shared-nothing architecture and supports high volumes of low-latency queries and updates for JSON documents. Its new Capella Columnar cloud service complements the Operational service. The Capella Columnar service supports complex analytical queries (e.g., ad hoc joins and aggregations) over large collections of JSON documents that can originate from a variety of Couchbase and non-Couchbase data sources and formats and can either be stored and managed by the Capella Columnar service or externally stored and accessed on demand at query time. This paper describes the new Capella Columnar service, looking both over and under the hood.
Murtadha Al Hubail, Ali Alsuliman, Wail Y. Alkowaileet, Michael Blow, Michael J. Carey 0001, Savyasach Enukonda, Peeyush Gupta, Santosh Hegde, Kamini Jagtiani, Abhishek Jindal, Nawazish Kahn, Mehnaz Tabassum Mahin, Ian Maxon, M. Muralikrishna, Keshav Murthy, Preetham Poluparthi, Ankit Prabhu, Ritik Raj, Vijay Sarathy, Shahrzad Shirazi, Utsav Singh, Hussain Towaileb, Ayush Tripathi, Janhavi Tripurwar, Bo-Chun Wang, Till Westmann
Proc. VLDB Endow.19
2024 A 475 MHz Manycore FPGA Accelerator for RTL Simulation
abstract
This paper presents the implementation of Manticore: a manycore accelerator for parallel RTL simulation. Manticore packs up to 225 custom soft processors running at 475 MHz on a large FPGA. Implementing manycore accelerators on FPGAs is challenging as designers must reconcile the conflicting goals of maximizing the number of cores on the chip and clocking them at the highest possible frequency. Designers face two classes of constraints: (1) architectural constraints imposed by a large FPGA's multi-die structure, and (2) physical constraints imposed by the FPGA shell's size and placement. Physical design therefore plays a critical role in the implementation of manycore accelerators. We present physical design challenges faced during Manticore's implementation on the AMD Alveo U200 card---a large FPGA with a poorly-placed, wide shell that challenges physical implementation.
Sahand Kashani, Mahyar Emami, Keisuke Kamahori, Mohammad Sepehr Pourghannad, Ritik Raj, James R. Larus
FPGA5
2024 Towards Cognitive AI Systems: Workload and Characterization of Neuro-Symbolic AI
abstract
The remarkable advancements in artificial intel-ligence (AI), primarily driven by deep neural networks, are facing challenges surrounding unsustainable computational tra-jectories, limited robustness, and a lack of explainability. To develop next-generation cognitive AI systems, neuro-symbolic AI emerges as a promising paradigm, fusing neural and symbolic approaches to enhance interpretability, robustness, and trustwor-thiness, while facilitating learning from much less data. Recent neuro-symbolic systems have demonstrated great potential in collaborative human-AI scenarios with reasoning and cognitive capabilities. In this paper, we aim to understand the workload characteristics and potential architectures for neuro-symbolic AI. We first systematically categorize neuro-symbolic AI algorithms, and then experimentally evaluate and analyze them in terms of runtime, memory, computational operators, sparsity, and system characteristics on CPUs, GPUs, and edge SoCs. Our studies reveal that neuro-symbolic models suffer from inefficiencies on off-the-shelf hardware, due to the memory-bound nature of vector-symbolic and logical operations, complex flow control, data dependencies, sparsity variations, and limited scalability. Based on profiling insights, we suggest cross-layer optimization solutions to improve the performance, efficiency, and scalability of neuro-symbolic computing. Finally, we discuss the challenges and potential future directions of neuro-symbolic AI from both system and architectural perspectives.
Zishen Wan, Che-Kai Liu, Hanchen Yang 0001, Ritik Raj, Chaojian Li, Haoran You, Yonggan Fu, Cheng Wan 0005, Ananda Samajdar, Yingyan (Celine) Lin, Tushar Krishna, Arijit Raychowdhury
ISPASS4
2023 Manticore: Hardware-Accelerated RTL Simulation with Static Bulk-Synchronous Parallelism
abstract
The demise of Moore's Law and Dennard Scaling has revived interest in specialized computer architectures and accelerators. Verification and testing of this hardware depend heavily upon cycle-accurate simulation of register-transfer-level (RTL) designs. The fastest software RTL simulators can simulate designs at 1--1000 kHz, i.e., more than three orders of magnitude slower than hardware. Improved simulators can increase designers' productivity by speeding design iterations and permitting more exhaustive exploration.
Mahyar Emami, Sahand Kashani, Keisuke Kamahori, Mohammad Sepehr Pourghannad, Ritik Raj, James R. Larus
ASPLOS (4)5
2022 A 65nm Compute-In-Memory 7T SRAM Macro Supporting 4-bit Multiply and Accumulate Operation by Employing Charge Sharing
abstract
In this work, we propose an energy-efficient 64$\times $ 64 compute-in-memory (CIM) SRAM macro using a 7T bit-cell in 65nm CMOS UMC PDK. It supports 4-bit inputs, 4-bit weights & 4-bit outputs and performs 4-bit MAC operations. It also supports multiple row activations performing 1024 4b$\times $4b multiply and accumulate (MAC) operations in one clock cycle. Inputs are realized by the number of pulses on the read wordline (RWL), which discharges read bitline (RBL) according to bitwise multiplication of weights & inputs. Outputs of 4 columns storing 4-bit weights are then combined via charge sharing to perform a binary-weighted average representing MAC operation, further quantized by a flash analog to digital converter (ADC) giving 4-bit output. The proposed CIM macro achieves an energy efficiency of 28.9 TOPS/W and throughput of 212.9 GOPS operating at supply voltage 1 V with a 2 GHz clock frequency.
Dinesh Kushwaha, Ritik Raj, Ashish Joshi, Jwalant Mishra, Rajat Kohli, Sandeep Miryala, Rajiv V. Joshi, Sudeb Dasgupta, Bulusu Anand
ISCAS4
2021 AutIS: Artificial Intelligent Based Automated Interviewing System
Rupesh Kumar Dewang, Arpit Gupta, Anisha Kumari, Ritik Raj, Raj Nath Shah, Tanmay Jaiswal, Arvind Mewada
HIS4