290 research outputs found

    Natural and Technological Hazards in Urban Areas

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    Natural hazard events and technological accidents are separate causes of environmental impacts. Natural hazards are physical phenomena active in geological times, whereas technological hazards result from actions or facilities created by humans. In our time, combined natural and man-made hazards have been induced. Overpopulation and urban development in areas prone to natural hazards increase the impact of natural disasters worldwide. Additionally, urban areas are frequently characterized by intense industrial activity and rapid, poorly planned growth that threatens the environment and degrades the quality of life. Therefore, proper urban planning is crucial to minimize fatalities and reduce the environmental and economic impacts that accompany both natural and technological hazardous events

    IPASIR-UP: User Propagators for CDCL

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    Modern SAT solvers are frequently embedded as sub-reasoning engines into more complex tools for addressing problems beyond the Boolean satisfiability problem. Examples include solvers for Satisfiability Modulo Theories (SMT), combinatorial optimization, model enumeration and counting. In such use cases, the SAT solver is often able to provide relevant information beyond the satisfiability answer. Further, domain knowledge of the embedding system (e.g., symmetry properties or theory axioms) can be beneficial for the CDCL search, but cannot be efficiently represented in clausal form. In this paper, we propose a general interface to inspect and influence the internal behaviour of CDCL SAT solvers. Our goal is to capture the most essential functionalities that are sufficient to simplify and improve use cases that require a more fine-grained interaction with the SAT solver than provided via the standard IPASIR interface. For our experiments, we extend CaDiCaL with our interface and evaluate it on two representative use cases: enumerating graphs within the SAT modulo Symmetries framework (SMS), and as the main CDCL(T) SAT engine of the SMT solver cvc5

    Towards A Practical High-Assurance Systems Programming Language

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    Writing correct and performant low-level systems code is a notoriously demanding job, even for experienced developers. To make the matter worse, formally reasoning about their correctness properties introduces yet another level of complexity to the task. It requires considerable expertise in both systems programming and formal verification. The development can be extremely costly due to the sheer complexity of the systems and the nuances in them, if not assisted with appropriate tools that provide abstraction and automation. Cogent is designed to alleviate the burden on developers when writing and verifying systems code. It is a high-level functional language with a certifying compiler, which automatically proves the correctness of the compiled code and also provides a purely functional abstraction of the low-level program to the developer. Equational reasoning techniques can then be used to prove functional correctness properties of the program on top of this abstract semantics, which is notably less laborious than directly verifying the C code. To make Cogent a more approachable and effective tool for developing real-world systems, we further strengthen the framework by extending the core language and its ecosystem. Specifically, we enrich the language to allow users to control the memory representation of algebraic data types, while retaining the automatic proof with a data layout refinement calculus. We repurpose existing tools in a novel way and develop an intuitive foreign function interface, which provides users a seamless experience when using Cogent in conjunction with native C. We augment the Cogent ecosystem with a property-based testing framework, which helps developers better understand the impact formal verification has on their programs and enables a progressive approach to producing high-assurance systems. Finally we explore refinement type systems, which we plan to incorporate into Cogent for more expressiveness and better integration of systems programmers with the verification process

    Synthetic Aperture Radar (SAR) Meets Deep Learning

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    This reprint focuses on the application of the combination of synthetic aperture radars and depth learning technology. It aims to further promote the development of SAR image intelligent interpretation technology. A synthetic aperture radar (SAR) is an important active microwave imaging sensor, whose all-day and all-weather working capacity give it an important place in the remote sensing community. Since the United States launched the first SAR satellite, SAR has received much attention in the remote sensing community, e.g., in geological exploration, topographic mapping, disaster forecast, and traffic monitoring. It is valuable and meaningful, therefore, to study SAR-based remote sensing applications. In recent years, deep learning represented by convolution neural networks has promoted significant progress in the computer vision community, e.g., in face recognition, the driverless field and Internet of things (IoT). Deep learning can enable computational models with multiple processing layers to learn data representations with multiple-level abstractions. This can greatly improve the performance of various applications. This reprint provides a platform for researchers to handle the above significant challenges and present their innovative and cutting-edge research results when applying deep learning to SAR in various manuscript types, e.g., articles, letters, reviews and technical reports

    Capacity: Cryptographically-Enforced In-Process Capabilities for Modern ARM Architectures (Extended Version)

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    In-process compartmentalization and access control have been actively explored to provide in-place and efficient isolation of in-process security domains. Many works have proposed compartmentalization schemes that leverage hardware features, most notably using the new page-based memory isolation feature called Protection Keys for Userspace (PKU) on x86. Unfortunately, the modern ARM architecture does not have an equivalent feature. Instead, newer ARM architectures introduced Pointer Authentication (PA) and Memory Tagging Extension (MTE), adapting the reference validation model for memory safety and runtime exploit mitigation. We argue that those features have been underexplored in the context of compartmentalization and that they can be retrofitted to implement a capability-based in-process access control scheme. This paper presents Capacity, a novel hardware-assisted intra-process access control design that embraces capability-based security principles. Capacity coherently incorporates the new hardware security features on ARM that already exhibit inherent characteristics of capability. It supports the life-cycle protection of the domain's sensitive objects -- starting from their import from the file system to their place in memory. With intra-process domains authenticated with unique PA keys, Capacity transforms file descriptors and memory pointers into cryptographically-authenticated references and completely mediates reference usage with its program instrumentation framework and an efficient system call monitor. We evaluate our Capacity-enabled NGINX web server prototype and other common applications in which sensitive resources are isolated into different domains. Our evaluation shows that Capacity incurs a low-performance overhead of approximately 17% for the single-threaded and 13.54% for the multi-threaded webserver.Comment: Accepted at ACM CCS 202

    Guiding Quality Assurance Through Context Aware Learning

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    Software Testing is a quality control activity that, in addition to finding flaws or bugs, provides confidence in the software’s correctness. The quality of the developed software depends on the strength of its test suite. Mutation Testing has shown that it effectively guides in improving the test suite’s strength. Mutation is a test adequacy criterion in which test requirements are represented by mutants. Mutants are slight syntactic modifications of the original program that aim to introduce semantic deviations (from the original program) necessitating the testers to design tests to kill these mutants, i.e., to distinguish the observable behavior between a mutant and the original program. This process of designing tests to kill a mutant is iteratively performed for the entire mutant set, which results in augmenting the test suite, hence improving its strength. Although mutation testing is empirically validated, a key issue is that its application is expensive due to the large number of low-utility mutants that it introduces. Some mutants cannot be even killed as they are functionally equivalent to the original program. To reduce the application cost, it is imperative to limit the number of mutants to those that are actually useful. Since it requires manual analysis and test executions to identify such mutants, there is a lack of an effective solution to the problem. Hence, it remains unclear how to mutate and test a code efficiently. On the other hand, with the advancement in deep learning, several works in the literature recently focused on using it on source code to automate many nontrivial tasks including bug fixing, producing code comments, code completion, and program repair. The increasing utilization of deep learning is due to a combination of factors. The first is the vast availability of data to learn from, specifically source code in open-source repositories. The second is the availability of inexpensive hardware able to efficiently run deep learning infrastructures. The third and the most compelling is its ability to automatically learn the categorization of data by learning the code context through its hidden layer architecture, making it especially proficient in identifying features. Thus, we explore the possibility of employing deep learning to identify only useful mutants, in order to achieve a good trade-off between the invested effort and test effectiveness. Hence, as our first contribution, this dissertation proposes Cerebro, a deep learning approach to statically select subsuming mutants based on the mutants’ surrounding code context. As subsuming mutants reside at the top of the subsumption hierarchy, test cases designed to only kill this minimal subset of mutants kill all the remaining mutants. Our evaluation of Cerebro demonstrates that it preserves the mutation testing benefits while limiting the application cost, i.e., reducing all cost factors such as equivalent mutants, mutant executions, and the mutants requiring analysis. Apart from improving test suite strength, mutation testing has been proven useful in inferring software specifications. Software specifications aim at describing the software’s intended behavior and can be used to distinguish correct from incorrect software behaviors. Specification inference techniques aim at inferring assertions by generating and filtering candidate assertions through dynamic test executions and mutation testing. Due to the introduction of a large number of mutants during mutation testing such techniques are also computationally expensive, hence establishing a need for the selection of mutants that fit best for assertion inference. We refer to such mutants as Assertion Inferring Mutants. In our analysis, we find that the assertion inferring mutants are significantly different from the subsuming mutants. Thus, we explored the employability of deep learning to identify Assertion Inferring Mutants. Hence, as our second contribution, this dissertation proposes Seeker, a deep learning approach to statically select Assertion Inferring Mutants. Our evaluation demonstrates that Seeker enables an assertion inference capability comparable to the full mutation analysis while significantly limiting the execution cost. In addition to testing software in general, a few works in the literature attempt to employ mutation testing to tackle security-related issues, due to the fault-based nature of the technique. These works propose mutation operators to convert non-vulnerable code to vulnerable by mimicking common security bugs. However, these pattern-based approaches have two major limitations. Firstly, the design of security-specific mutation operators is not trivial. It requires manual analysis and comprehension of the vulnerability classes. Secondly, these mutation operators can alter the program semantics in a manner that is not convincing for developers and is perceived as unrealistic, thereby hindering the usability of the method. On the other hand, with the release of powerful language models trained on large code corpus, e.g. CodeBERT, a new family of mutation testing tools has arisen with the promise to generate natural mutants. We study the extent to which the mutants produced by language models can semantically mimic the behavior of vulnerabilities aka Vulnerability-mimicking Mutants. Designed test cases failed by these mutants will also tackle mimicked vulnerabilities. In our analysis, we found that a very small subset of mutants is vulnerability-mimicking. Though, this set mimics more than half of the vulnerabilities in our dataset. Due to the absence of any defined features to identify vulnerability-mimicking mutants, as our third contribution, this dissertation introduces Mystique, a deep learning approach that automatically extracts features to identify vulnerability-mimicking mutants. Despite the scarcity, Mystique predicts vulnerability-mimicking mutants with a high prediction performance, demonstrating that their features can be automatically learned by deep learning models to statically predict these without the need of investing any effort in defining features. Since our vulnerability-mimicking mutants cannot mimic all the vulnerabilities, we perceive that these mutants are not a complete representation of all the vulnerabilities and there exists a need for actual vulnerability prediction approaches. Although there exist many such approaches in the literature, their performance is limited due to a few factors. Firstly, vulnerabilities are fewer in comparison to software bugs, limiting the information one can learn from, which affects the prediction performance. Secondly, the existing approaches learn on both, vulnerable, and supposedly non-vulnerable components. This introduces an unavoidable noise in training data, i.e., components with no reported vulnerability are considered non-vulnerable during training, and hence, results in existing approaches performing poorly. We employed deep learning to automatically capture features related to vulnerabilities and explored if we can avoid learning on supposedly non-vulnerable components. Hence, as our final contribution, this dissertation proposes TROVON, a deep learning approach that learns only on components known to be vulnerable, thereby making no assumptions and bypassing the key problem faced by previous techniques. Our comparison of TROVON with existing techniques on security-critical open-source systems with historical vulnerabilities reported in the National Vulnerability Database (NVD) demonstrates that its prediction capability significantly outperforms the existing techniques

    Distributed Multi-writer Multi-reader Atomic Register with Optimistically Fast Read and Write

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    A distributed multi-writer multi-reader (MWMR) atomic register is an important primitive that enables a wide range of distributed algorithms. Hence, improving its performance can have large-scale consequences. Since the seminal work of ABD emulation in the message-passing networks [JACM '95], many researchers study fast implementations of atomic registers under various conditions. "Fast" means that a read or a write can be completed with 1 round-trip time (RTT), by contacting a simple majority. In this work, we explore an atomic register with optimal resilience and "optimistically fast" read and write operations. That is, both operations can be fast if there is no concurrent write. This paper has three contributions: (i) We present Gus, the emulation of an MWMR atomic register with optimal resilience and optimistically fast reads and writes when there are up to 5 nodes; (ii) We show that when there are > 5 nodes, it is impossible to emulate an MWMR atomic register with both properties; and (iii) We implement Gus in the framework of EPaxos and Gryff, and show that Gus provides lower tail latency than state-of-the-art systems such as EPaxos, Gryff, Giza, and Tempo under various workloads in the context of geo-replicated object storage systems

    Arena: Multi-leader Synchronous Byzantine Fault Tolerance

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    Byzantine fault-tolerant state machine replication (BFT-SMR) replicates a state machine across a set of replicas, and processes requests as a single machine even in the presence of Byzantine faults. Recently, synchronous BFT-SMRs have received tremendous attention due to their simple design and high fault-tolerance threshold. In this paper, we propose Arena, the first multi-leader synchronous BFT-SMR. Thanks to the synchrony assumption, Arena gains the performance benefit from multi-leader with a much simpler design (compared to other partially synchronous multi-leader designs). Furthermore, it is more robust: ``no progress\u27\u27 of a leader will not trigger a view-change. Our experimental results show that Arena achieves a peak throughput of up to 7.7Ă—\times higher than the state-of-the-art

    Adaptive Automated Machine Learning

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    The ever-growing demand for machine learning has led to the development of automated machine learning (AutoML) systems that can be used off the shelf by non-experts. Further, the demand for ML applications with high predictive performance exceeds the number of machine learning experts and makes the development of AutoML systems necessary. Automated Machine Learning tackles the problem of finding machine learning models with high predictive performance. Existing approaches incorporating deep learning techniques assume that all data is available at the beginning of the training process (offline learning). They configure and optimise a pipeline of preprocessing, feature engineering, and model selection by choosing suitable hyperparameters in each model pipeline step. Furthermore, they assume that the user is fully aware of the choice and, thus, the consequences of the underlying metric (such as precision, recall, or F1-measure). By variation of this metric, the search for suitable configurations and thus the adaptation of algorithms can be tailored to the user’s needs. With the creation of a vast amount of data from all kinds of sources every day, our capability to process and understand these data sets in a single batch is no longer viable. By training machine learning models incrementally (i.ex. online learning), the flood of data can be processed sequentially within data streams. However, if one assumes an online learning scenario, where an AutoML instance executes on evolving data streams, the question of the best model and its configuration remains open. In this work, we address the adaptation of AutoML in an offline learning scenario toward a certain utility an end-user might pursue as well as the adaptation of AutoML towards evolving data streams in an online learning scenario with three main contributions: 1. We propose a System that allows the adaptation of AutoML and the search for neural architectures towards a particular utility an end-user might pursue. 2. We introduce an online deep learning framework that fosters the research of deep learning models under the online learning assumption and enables the automated search for neural architectures. 3. We introduce an online AutoML framework that allows the incremental adaptation of ML models. We evaluate the contributions individually, in accordance with predefined requirements and to state-of-the- art evaluation setups. The outcomes lead us to conclude that (i) AutoML, as well as systems for neural architecture search, can be steered towards individual utilities by learning a designated ranking model from pairwise preferences and using the latter as the target function for the offline learning scenario; (ii) architectual small neural networks are in general suitable assuming an online learning scenario; (iii) the configuration of machine learning pipelines can be automatically be adapted to ever-evolving data streams and lead to better performances

    Analysing and Reducing Costs of Deep Learning Compiler Auto-tuning

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    Deep Learning (DL) is significantly impacting many industries, including automotive, retail and medicine, enabling autonomous driving, recommender systems and genomics modelling, amongst other applications. At the same time, demand for complex and fast DL models is continually growing. The most capable models tend to exhibit highest operational costs, primarily due to their large computational resource footprint and inefficient utilisation of computational resources employed by DL systems. In an attempt to tackle these problems, DL compilers and auto-tuners emerged, automating the traditionally manual task of DL model performance optimisation. While auto-tuning improves model inference speed, it is a costly process, which limits its wider adoption within DL deployment pipelines. The high operational costs associated with DL auto-tuning have multiple causes. During operation, DL auto-tuners explore large search spaces consisting of billions of tensor programs, to propose potential candidates that improve DL model inference latency. Subsequently, DL auto-tuners measure candidate performance in isolation on the target-device, which constitutes the majority of auto-tuning compute-time. Suboptimal candidate proposals, combined with their serial measurement in an isolated target-device lead to prolonged optimisation time and reduced resource availability, ultimately reducing cost-efficiency of the process. In this thesis, we investigate the reasons behind prolonged DL auto-tuning and quantify their impact on the optimisation costs, revealing directions for improved DL auto-tuner design. Based on these insights, we propose two complementary systems: Trimmer and DOPpler. Trimmer improves tensor program search efficacy by filtering out poorly performing candidates, and controls end-to-end auto-tuning using cost objectives, monitoring optimisation cost. Simultaneously, DOPpler breaks long-held assumptions about the serial candidate measurements by successfully parallelising them intra-device, with minimal penalty to optimisation quality. Through extensive experimental evaluation of both systems, we demonstrate that they significantly improve cost-efficiency of autotuning (up to 50.5%) across a plethora of tensor operators, DL models, auto-tuners and target-devices
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