Yu David Liu

Online data services have stringent performance requirement and must tolerate workload fluctuation. This paper introduces P it S top , a new query language runtime design built on the idea of interruptible query processing : the time-consuming task of data inspection for processing each query or update may be interrupted and resumed later at the boundary of fine-grained data partitions. This counter-intuitive idea enables a novel form of fine-grained concurrency while preserving sequential consistency . We build P it S top through modifying the language runtime of Cypher, the query language of a state-of-the-art graph database, Neo4j. Our evaluation on the Google Cloud shows that P it S top can outperform unmodified Neo4j during workload fluctuation, with reduced latency and increased throughput.

Visual SLAM systems are concurrent, performance-critical systems that respond to real-time environmental conditions and are frequently deployed on resource-constrained hardware. Previous work has identified three interconnected systems challenges to building consistent, accurate, and robust SLAM systems— timeliness , concurrency , and context awareness . In this article, we analyze three popular, state-of-the-art frameworks with varying system designs and optimization techniques, and we quantify the extent to which they are affected by the aforementioned system challenges. We find that all SLAM systems must balance the interconnected nature of timeliness and accuracy, and different system designs and optimization techniques uniquely address this tension. Global-map-based SLAM systems typically achieve the best performance but suffer in resource-constrained scenarios with increased concurrency . Across all SLAM systems, incorporating context awareness into decision-making would mitigate the impact of timeliness and concurrency on accuracy in resource-constrained scenarios.

Power modeling is an essential building block for computer systems in support of energy optimization, energy profiling, and energy-aware application development. We introduce Vesta , a novel approach to modeling the power consumption of applications with one key insight: language runtime events are often correlated with a sustained level of power consumption. When compared with the established approach of power modeling based on hardware performance counters (HPCs), Vesta has the benefit of solely requiring application-scoped information and enabling a higher level of explainability, while achieving comparable or even higher precision. Through experiments performed on 37 real-world applications on the Java Virtual Machine (JVM), we find the power model built by Vesta is capable of predicting energy consumption with a mean absolute percentage error of 1.56 % , while the monitoring of language runtime events incurs small performance and energy overhead.

With the rapid growth of Artificial Intelligence (AI) applications supported by deep learning (DL), the energy efficiency of these applications has an increasingly large impact on sustainability. We introduce Smaragdine, a new energy accounting system for tensor-based DL programs implemented with TensorFlow. At the heart of Smaragdine is a novel white-box methodology of energy accounting: Smaragdine is aware of the internal structure of the DL program, which we call tensor-aware energy accounting. With Smaragdine, the energy consumption of a DL program can be broken down into units aligned with its logical hierarchical decomposition structure. We apply Smaragdine for understanding the energy behavior of BERT, one of the most widely used language models. Layer-by-layer and tensor-by-tensor, Smaragdine is capable of identifying the highest energy/power-consuming components of BERT. Furthermore, we conduct two case studies on how Smaragdine supports downstream toolchain building, one on the comparative energy impact of hyperparameter tuning of BERT, the other on the energy behavior evolution when BERT evolves to its next generation, ALBERT.

The current techniques and tools for collecting, aggregating, and reporting verifiable sustainability data are vulnerable to cyberattacks and misuse, requiring new security and privacy-preserving solutions. This article outlines security challenges and research directions for addressing these requirements.

The use of large language models with chatbots like ChatGPT has become increasingly popular among students, especially in Computer Science education. However, significant debates exist in the education community on the role of ChatGPT in learning. Therefore, it is critical to understand the potential impact of ChatGPT on the learning, engagement, and overall success of students in classrooms. In this empirical study, we report on a controlled experiment with 182 participants in a first-year undergraduate course on object-oriented programming. Our differential study divided students into two groups, one using ChatGPT and the other not using it for practical programming assignments. The study results showed that the students’ performance is not influenced by ChatGPT usage (no statistical significance between groups with a p-value of 0.730), nor are the grading results of practical assignments (p-value 0.760) and midterm exams (p-value 0.856). Our findings from the controlled experiment suggest that it is safe for novice programmers to use ChatGPT if specific measures and adjustments are adopted in the education process.

Data processing systems are a fundamental component of the modern computing stack. These systems are routinely deployed online: they continuously receive the requests of data processing operations, and continuously return the results to end users or client applications. Online data processing systems have unique features beyond conventional data processing, and the optimizations designed for them are complex, especially when data themselves are structured and dynamic. This paper describes DON Calculus, the first rigorous foundation for online data processing. It captures the essential behavior of both the backend data processing engine and the frontend application, with the focus on two design dimensions essential yet unique to online data processing systems: incremental operation processing (IOP) and temporal locality optimization (TLO). A novel design insight is that the operations continuously applied to the data can be defined as an operation stream flowing through the data structure, and this abstraction unifies diverse designs of IOP and TLO in one calculus. DON Calculus is endowed with a mechanized metatheory centering around a key observable equivalence property: despite the significant non-deterministic executions introduced by IOP and TLO, the observable result of DON Calculus data processing is identical to that of conventional data processing without IOP and TLO. Broadly, DON Calculus is a novel instance in the active pursuit of providing rigorous guarantees to the software system stack. The specification and mechanization of DON Calculus provide a sound base for the designers of future data processing systems to build upon, helping them embrace rigorous semantic engineering without the need of developing from scratch.

UAVs are deployed in various applications including disaster search-and-rescue, precision agriculture, law enforcement and first response. As UAV software systems grow more complex, the drawbacks of developing them in low-level languages become more pronounced. For example, the lack of memory safety in C implies poor isolation between the UAV autopilot and other concurrent tasks. As a result, the most crucial aspect of UAV reliability-timely control of the flight-could be adversely impacted by other tasks such as perception or planning. We introduce JCopter, an autopilot framework for UAVs developed in a managed language, i.e., a high-level language with built-in safe memory and timing management. Through detailed simulation as well as flight testing, we demonstrate how JCopter retains the timeliness of C-based autopilots while also providing the reliability of managed languages.