Browsing by Author "ACM, publisher"
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Item Open Access A framework for profiling spatial variability in the performance of classification models(Colorado State University. Libraries, 2024-04-03) Warushavithana, Menuka, author; Barram, Kassidy, author; Carlson, Caleb, author; Mitra, Saptashwa, author; Ghosh, Sudipto, author; Breidt, Jay, author; Pallickara, Sangmi Lee, author; Pallickara, Shrideep, author; ACM, publisherScientists use models to further their understanding of phenomena and inform decision-making. A confluence of factors has contributed to an exponential increase in spatial data volumes. In this study, we describe our methodology to identify spatial variation in the performance of classification models. Our methodology allows tracking a host of performance measures across different thresholds for the larger, encapsulating spatial area under consideration. Our methodology ensures frugal utilization of resources via a novel validation budgeting scheme that preferentially allocates observations for validations. We complement these efforts with a browser-based, GPU-accelerated visualization scheme that also incorporates support for streaming to assimilate validation results as they become available.Item Open Access A methodology for evaluating multimodal referring expression generation for embodied virtual agents(Colorado State University. Libraries, 2023-10-09) Alalyani, Nada, author; Krishnaswamy, Nikhil, author; ACM, publisherRobust use of definite descriptions in a situated space often involves recourse to both verbal and non-verbal modalities. For IVAs, virtual agents designed to interact with humans, the ability to both recognize and generate non-verbal and verbal behavior is a critical capability. To assess how well an IVA is able to deploy multimodal behaviors, including language, gesture, and facial expressions, we propose a methodology to evaluate the agent's capacity to generate object references in a situational context, using the domain of multimodal referring expressions as a use case. Our contributions include: 1) developing an embodied platform to collect human referring expressions while communicating with the IVA. 2) comparing human and machine-generated references in terms of evaluable properties using subjective and objective metrics. 3) reporting preliminary results from trials that aimed to check whether the agent can retrieve and disambiguate the object the human referred to, if the human has the ability to correct misunderstanding using language, deictic gesture, or both; and human ease of use while interacting with the agent.Item Open Access Algorithm parallelism for improved extractive summarization(Colorado State University. Libraries, 2023-08-22) Villanueva, Arturo N., Jr., author; Simske, Steven J., author; ACM, publisherWhile much work on abstractive summarization has been conducted in recent years, including state-of-the-art summarizations from GPT-4, extractive summarization's lossless nature continues to provide advantages, preserving the style and often key phrases of the original text as meant by the author. Libraries for extractive summarization abound, with a wide range of efficacy. Some do not perform much better or perform even worse than random sampling of sentences extracted from the original text. This study breathes new life to using classical algorithms by proposing parallelism through an implementation of a second order meta-algorithm in the form of the Tessellation and Recombination with Expert Decisioner (T&R) pattern, taking advantage of the abundance of already-existing algorithms and dissociating their individual performance from the implementer's biases. Resulting summaries obtained using T&R are better than any of the component algorithms.Item Open Access Algorithms for parallel generic hp-adaptive finite element software(Colorado State University. Libraries, 2023-09-19) Fehling, Marc, author; Bangerth, Wolfgang, author; ACM, publisherThe hp-adaptive finite element method—where one independently chooses the mesh size (h) and polynomial degree (p) to be used on each cell—has long been known to have better theoretical convergence properties than either h- or p-adaptive methods alone. However, it is not widely used, owing at least in part to the difficulty of the underlying algorithms and the lack of widely usable implementations. This is particularly true when used with continuous finite elements. Herein, we discuss algorithms that are necessary for a comprehensive and generic implementation of hp-adaptive finite element methods on distributed-memory, parallel machines. In particular, we will present a multistage algorithm for the unique enumeration of degrees of freedom suitable for continuous finite element spaces, describe considerations for weighted load balancing, and discuss the transfer of variable size data between processes. We illustrate the performance of our algorithms with numerical examples and demonstrate that they scale reasonably up to at least 16,384 message passage interface processes. We provide a reference implementation of our algorithms as part of the open source library deal.II.Item Open Access An artists' perspectives on natural interactions for virtual reality 3D sketching(Colorado State University. Libraries, 2024-05-11) Rodriguez, Richard, author; Sullivan, Brian T., author; Machuca, Mayra Donaji Barrera, author; Batmaz, Anil Ufuk, author; Tornatzky, Cyane, author; Ortega, Francisco R., author; ACM, publisherVirtual Reality (VR) applications like OpenBrush offer artists access to 3D sketching tools within the digital 3D virtual space. These 3D sketching tools allow users to "paint" using virtual digital strokes that emulate real-world mark-making. Yet, users paint these strokes through (unimodal) VR controllers. Given that sketching in VR is a relatively nascent field, this paper investigates ways to expand our understanding of sketching in virtual space, taking full advantage of what an immersive digital canvas offers. Through a study conducted with the participation of artists, we identify potential methods for natural multimodal and unimodal interaction techniques in 3D sketching. These methods demonstrate ways to incrementally improve existing interaction techniques and incorporate artistic feedback into the design.Item Open Access Character relationship mapping in major fictional works using text analysis methods(Colorado State University. Libraries, 2023-08-22) Wolyn, Sam, author; Simske, Steven, author; ACM, publisherDetermining the relationships between characters is an important step in analyzing fictional works. Knowing character relationships can be useful when summarizing a work and may also help to determine authorship. In this paper, scores are generated for pairs of characters in fictional works, which can be used for classification tasks if characters have a relationship or not. An SVM is used to predict relationships between characters. Characters farther from the decision boundary often had stronger relationships than those closer to the boundary. The relative rank of the relationships may have additional literary and authorship related purposes.Item Open Access Claim extraction and dynamic stance detection in COVID-19 tweets(Colorado State University. Libraries, 2023-04-30) Faramarzi, Noushin Salek, author; Chaleshtori, Fateme Hashemi, author; Shirazi, Hossein, author; Ray, Indrakshi, author; Banerjee, Ritwik, author; ACM, publisherThe information ecosystem today is noisy, and rife with messages that contain a mix of objective claims and subjective remarks or reactions. Any automated system that intends to capture the social, cultural, or political zeitgeist, must be able to analyze the claims as well as the remarks. Due to the deluge of such messages on social media, and their tremendous power to shape our perceptions, there has never been a greater need to automate these analyses, which play a pivotal role in fact-checking, opinion mining, understanding opinion trends, and other such downstream tasks of social consequence. In this noisy ecosystem, not all claims are worth checking for veracity. Such a check-worthy claim, moreover, must be accurately distilled from subjective remarks surrounding it. Finally, and especially for understanding opinion trends, it is important to understand the stance of the remarks or reactions towards that specific claim. To this end, we introduce a COVID-19 Twitter dataset, and present a three-stage process to (i) determine whether a given Tweet is indeed check-worthy, and if so, (ii) which portion of the Tweet ought to be checked for veracity, and finally, (iii) determine the author's stance towards the claim in that Tweet, thus introducing the novel task of topic-agnostic stance detection.Item Open Access Computational modeling for the computer animation of legged figures(Colorado State University. Libraries, 1985) Girard, Michael, author; Maciejewski, Anthony A., author; ACM, publisherModeling techniques for animating legged figures are described which are used in the PODA animation system. PODA utilizes pseudoinverse control in order to solve the problems associated with manipulating kinematically redundant limbs. PODA builds on this capability to synthesize a kinematic model of legged locomotion which allows animators to control the complex relationships between the motion of the body of a figure and the coordination of its legs. Finally, PODA provides for the integration of a simple model of legged locomotion dynamics which insures that the accelerations of a figure's body are synchronized with the timing of the forces applied by its legs.Item Open Access Constant depth circuit complexity for generating quasigroups(Colorado State University. Libraries, 2024-07-16) Collins, Nathaniel A., author; Grochow, Joshua A., author; Levet, Michael, author; Weiß, Armin, author; ACM, publisherWe investigate the constant-depth circuit complexity of the Isomorphism Problem, Minimum Generating Set Problem (MGS), and Sub(qasi)group Membership Problem (Membership) for groups and quasigroups (=Latin squares), given as input in terms of their multiplication (Cayley) tables. Despite decades of research on these problems, lower bounds for these problems even against depth-2 AC circuits remain unknown. Perhaps surprisingly, Chattopadhyay, Torán, and Wagner (FSTTCS 2010; ACM Trans. Comput. Theory, 2013) showed that Quasigroup Isomorphism could be solved by AC circuits of depth O(log log n) using O(log2 n) nondeterministic bits, a class we denote ∃log2 nFOLL. We narrow this gap by improving the upper bound for these problems to quasiAC0, thus decreasing the depth to constant. In particular, we show that Membership can be solved in NTIME(polylog(n)) … Our results suggest that understanding the constant-depth circuit complexity may be key to resolving the complexity of problems concerning (quasi)groups in the multiplication table model.Item Open Access Cross-layer design for AI acceleration with non-coherent optical computing(Colorado State University. Libraries, 2023-06-05) Sunny, Febin, author; Nikdast, Mahdi, author; Pasricha, Sudeep, author; ACM, publisherEmerging AI applications such as ChatGPT, graph convolutional networks, and other deep neural networks require massive computational resources for training and inference. Contemporary computing platforms such as CPUs, GPUs, and TPUs are struggling to keep up with the demands of these AI applications. Non-coherent optical computing represents a promising approach for light-speed acceleration of AI workloads. In this paper, we show how cross-layer design can overcome challenges in non-coherent optical computing platforms. We describe approaches for optical device engineering, tuning circuit enhancements, and architectural innovations to adapt optical computing to a variety of AI workloads. We also discuss techniques for hardware/ software co-design that can intelligently map and adapt AI software to improve performance on non-coherent platforms.Item Open Access Design space exploration for PCM-based photonic memory(Colorado State University. Libraries, 2023-06-05) Shafiee, Amin, author; Charbonnier, Benoit, author; Pasricha, Sudeep, author; Nikdast, Mahdi, author; ACM, publisherThe integration of silicon photonics (SiPh) and phase change materials (PCMs) has created a unique opportunity to realize adaptable and reconfigurable photonic systems. In particular, the nonvolatile programmability in PCMs has made them a promising candidate for implementing optical memory systems. In this paper, we describe the design of an optical memory cell based on PCMs while exploring the design space of the cell in terms of PCM material choice (e.g., GST, GSST, Sb2Se3), cell bit capacity, latency, and power consumption. Leveraging this design-space exploration for the design of efficient optical memory cells, we present the design and implementation of an optical memory array and explore its scalability and power consumption when using different optical memory cells. We also identify performance bottlenecks that need to be alleviated to further scale optical memory arrays with competitive latency and energy consumption, compared to their electronic counterparts.Item Open Access Ethics in computing education: challenges and experience with embedded ethics(Colorado State University. Libraries, 2023-06-05) Pasricha, Sudeep, author; ACM, publisherThe next generation of computer engineers and scientists must be proficient in not just the technical knowledge required to analyze, optimize, and create computing systems, but also with the skills required to make ethical decisions during design. Teaching computer ethics in computing curricula is therefore becoming an important requirement with significant ramifications for our increasingly connected and computing-reliant society. In this paper, we reflect on the many challenges and questions with effectively integrating ethics into modern computing curricula. We describe a case study of integrating ethics modules into the computer engineering curricula at Colorado State University.Item Open Access Exploring unimodal notification interaction and display methods in augmented reality(Colorado State University. Libraries, 2023-10-09) Plabst, Lucas, author; Raikwar, Aditya, author; Oberdörfer, Sebastian, author; Ortega, Francisco, author; Niebling, Florian, author; ACM, publisherAs we develop computing platforms for augmented reality (AR) head-mounted display (HMDs) technologies for social or workplace environments, understanding how users interact with notifications in immersive environments has become crucial. We researched effectiveness and user preferences of different interaction modalities for notifications, along with two types of notification display methods. In our study, participants were immersed in a simulated cooking environment using an AR-HMD, where they had to fulfill customer orders. During the cooking process, participants received notifications related to customer orders and ingredient updates. They were given three interaction modes for those notifications: voice commands, eye gaze and dwell, and hand gestures. To manage multiple notifications at once, we also researched two different notification list displays, one attached to the user's hand and one in the world. Results indicate that participants preferred using their hands to interact with notifications and having the list of notifications attached to their hands. Voice and gaze interaction was perceived as having lower usability than touch.Item Open Access Fast and scalable monitoring for value-freeze operator augmented signal temporal logic(Colorado State University. Libraries, 2024-05-14) Ghorbel, Bassem, author; Prabhu, Vinayak S., author; ACM, publisherSignal Temporal Logic (STL) is a timed temporal logic formalism that has found widespread adoption for rigorous specification of properties in Cyber-Physical Systems. However, STL is unable to specify oscillatory properties commonly required in engineering design. This limitation can be overcome by the addition of additional operators, for example, signal-value freeze operators, or with first order quantification. Previous work on augmenting STL with such operators has resulted in intractable monitoring algorithms. We present the first efficient and scalable offline monitoring algorithms for STL augmented with independent freeze quantifiers. Our final optimized algorithm has a |ρ|log(|ρ|) dependence on the trace length |ρ| for most traces ρ arising in practice, and a |ρ|2 dependence in the worst case. We also provide experimental validation of our algorithms – we show the algorithms scale to traces having 100k time samples.Item Open Access FedHIL: heterogeneity resilient federated learning for robust indoor localization with mobile devices(Colorado State University. Libraries, 2023-09-09) Gufran, Danish, author; Pasricha, Sudeep, author; ACM, publisherIndoor localization plays a vital role in applications such as emergency response, warehouse management, and augmented reality experiences. By deploying machine learning (ML) based indoor localization frameworks on their mobile devices, users can localize themselves in a variety of indoor and subterranean environments. However, achieving accurate indoor localization can be challenging due to heterogeneity in the hardware and software stacks of mobile devices, which can result in inconsistent and inaccurate location estimates. Traditional ML models also heavily rely on initial training data, making them vulnerable to degradation in performance with dynamic changes across indoor environments. To address the challenges due to device heterogeneity and lack of adaptivity, we propose a novel embedded ML framework called FedHIL. Our framework combines indoor localization and federated learning (FL) to improve indoor localization accuracy in device-heterogeneous environments while also preserving user data privacy. FedHIL integrates a domain-specific selective weight adjustment approach to preserve the ML model's performance for indoor localization during FL, even in the presence of extremely noisy data. Experimental evaluations in diverse real-world indoor environments and with heterogeneous mobile devices show that FedHIL outperforms state-of-the-art FL and non-FL indoor localization frameworks. FedHIL is able to achieve 1.62 × better localization accuracy on average than the best performing FL-based indoor localization framework from prior work.Item Open Access Formal verification of source-to-source transformations for HLS(Colorado State University. Libraries, 2024-04-02) Pouchet, Louis-Noël, author; Tucker, Emily, author; Zhang, Niansong, author; Chen, Hongzheng, author; Pal, Debjit, author; Rodríguez, Gabriel, author; Zhang, Zhiru, author; ACM, publisherHigh-level synthesis (HLS) can greatly facilitate the description of complex hardware implementations, by raising the level of abstraction up to a classical imperative language such as C/C++, usually augmented with vendor-specific pragmas and APIs. Despite productivity improvements, attaining high performance for the final design remains a challenge, and higher-level tools like source-to-source compilers have been developed to generate programs targeting HLS toolchains. These tools may generate highly complex HLS-ready C/C++ code, reducing the programming effort and enabling critical optimizations. However, whether these HLS-friendly programs are produced by a human or a tool, validating their correctness or exposing bugs otherwise remains a fundamental challenge. In this work we target the problem of efficiently checking the semantics equivalence between two programs written in C/C++ as a means to ensuring the correctness of the description provided to the HLS toolchain, by proving an optimized code version fully preserves the semantics of the unoptimized one. We introduce a novel formal verification approach that combines concrete and abstract interpretation with a hybrid symbolic analysis. Notably, our approach is mostly agnostic to how control-flow, data storage, and dataflow are implemented in the two programs. It can prove equivalence under complex bufferization and loop/syntax transformations, for a rich class of programs with statically interpretable control-flow. We present our techniques and their complete end-to-end implementation, demonstrating how our system can verify the correctness of highly complex programs generated by source-to-source compilers for HLS, and detect bugs that may elude co-simulation.Item Open Access GHOST: a graph neural network accelerator using silicon photonics(Colorado State University. Libraries, 2023-09-09) Afifi, Salma, author; Sunny, Febin, author; Shafiee, Amin, author; Nikdast, Mahdi, author; Pasricha, Sudeep, author; ACM, publisherGraph neural networks (GNNs) have emerged as a powerful approach for modelling and learning from graph-structured data. Multiple fields have since benefitted enormously from the capabilities of GNNs, such as recommendation systems, social network analysis, drug discovery, and robotics. However, accelerating and efficiently processing GNNs require a unique approach that goes beyond conventional artificial neural network accelerators, due to the substantial computational and memory requirements of GNNs. The slowdown of scaling in CMOS platforms also motivates a search for alternative implementation substrates. In this paper, we present GHOST, the first silicon-photonic hardware accelerator for GNNs. GHOST efficiently alleviates the costs associated with both vertex-centric and edge-centric operations. It implements separately the three main stages involved in running GNNs in the optical domain, allowing it to be used for the inference of various widely used GNN models and architectures, such as graph convolution networks and graph attention networks. Our simulation studies indicate that GHOST exhibits at least 10.2 × better throughput and 3.8 × better energy efficiency when compared to GPU, TPU, CPU and multiple state-of-the-art GNN hardware accelerators.Item Open Access Improving block management in 3D NAND flash SSDs with sub-block first write sequencing(Colorado State University. Libraries, 2024-06-12) Buddhanoy, Matchima, author; Khan, Kamil, author; Milenkovic, Aleksandar, author; Pasricha, Sudeep, author; Ray, Biswajit, author; ACM, publisherContinual vertical scaling in 3D NAND flash solid-state drives (SSDs) results in larger memory blocks, causing performance degradation due to big-block management issues. Pages within a 3D NAND flash block are traditionally written using layer first write sequencing. This paper introduces and explores the benefits of an alternative sub-block first write sequence. This method when coupled with sub-block erase operations promises to alleviate the big-block problem. Our evaluation on a commercial 32-layer 3D NAND flash SSD chip shows that though the proposed method increases the raw bit error rate (RBER), it remains below the threshold that can be corrected by error correction codes (ECCs). Simulation analysis further shows that our proposed method reduces garbage collection overhead, resulting in 36.0% lower response time and 9.6% reduction in additional writes due to garbage collection compared to traditional 3D NAND flash SSDs.Item Open Access Life-after-death: exploring thermal annealing conditions to enhance 3D NAND SSD endurance(Colorado State University. Libraries, 2024-07-08) Buddhanoy, Matchima, author; Pasricha, Sudeep, author; Ray, Biswajit, author; ACM, publisherIn this paper, we evaluate thermal annealing effects on the endurance of commercial off-the-shelf (COTS) 3D NAND flash memory beyond its end-of-life. We systematically evaluate the effects of anneal duration, anneal temperature, and state of the memory cells during annealing on the endurance enhancement. Interestingly, we find that endurance enhancement critically depends on the state of flash memory cells during annealing, with programmed cells showing significantly larger improvements than erased cells. Our experimental evaluation indicates that the post-cycle data retention property of an annealed chip significantly improves after thermal annealing, resulting in ∼30% endurance recovery. Our results have significant implications for the future wear-leveling algorithms of SSD-based storage systems.Item Open Access Methodology for resiliency analysis of mission-critical systems(Colorado State University. Libraries, 2024-05-21) Abdelgawad, Mahmoud, author; Ray, Indrakshi, author; ACM, publisherMission-critical systems ensure the safety and security of any nation. Attacks on mission-critical systems can have devastating consequences. We need to design missions that can prevent, detect, survive, recover, and respond to faults and cyber attacks. In other words, we must design missions that are cyber-resilient. System engineering techniques must be used to specify, analyze, and understand where adverse events are possible and how to mitigate them while a mission-critical system is deployed. This work introduces an end-to-end methodology for designing cyber-resilient mission-critical systems. The methodology first specifies a mission in the form of a workflow. It then converts the mission workflow into formal representation using Coloured Petri Nets (CPN). The methodology also derives threat models from the mission specification. The threat models are used to form a formal specification of attacks that can be represented in CPN. These CPN attacks are plugged into potential places in the CPN mission to design various attack scenarios. The methodology finally verifies the state transitions of the CPN mission attached to attacks to analyze the resiliency of the mission. It identifies in which state transition the mission succeeds, fails, and is incomplete. The methodology is applied to a drone surveillance system as a motivating example. The result shows that the methodology is practical for resiliency analysis of mission-critical systems. The methodology demonstrates how to restrict a mission to improve the resiliency of mission-critical systems. The methodology provides crucial insights in the early stages of mission specification to achieve cyber resiliency.