1. |
- Wilhelmsson, Kenneth, 1976
(författare)
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Huvudansatser för parsningsmetoder. Om programutvecklingens förutsättningar i en svensk kontext
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Syftet med denna text var att ge en inblick i området (syntaktisk) parsning. Tanken var att ge en bild av utvecklingen som var 1) fri från alltför tekniska detaljer, då området är programmeringstekniskt, och 2) beskriven ur ett svenskt perspektiv. Bakgrunden till valet av ämne till texten, som var tänkt att finnas med i antologin Text och kontext, var att parsning är relativt okänt för många personer verksamma inom närliggande områden, samtidigt som det är ett absolut nyckelbegrepp för den som ägnar sig åt datorlingvistik eller språkteknologi. Målet var alltså att ge en ganska allmän utifrånblick på några centrala sidor av utvecklingen, samtidigt som det tydligt är så att den som själv arbetat med utveckling kan ha starka åsikter och preferenser rörande metodval, något som i ärlighetens namn kanske inte heller denna text är lösgjord från. Hur ska det göras? Konsten att utveckla automatisk syntaxanalys av naturlig text kan läras ut från ett flertal perspektiv. Det kan t.ex. ske med fokus på användandet av en viss grammatikformalism, med fokus på beräkningssnabbhet, med fokus på entydiggörande av möjliga ambiguiteter. Tolkningsval kan göras med hjälp av antingen handskrivna regler eller inhämtad statistik. En sorts huvudtema i denna text är hur metoder för parsning på senare år uppvisar förändringar som kanske kan förklaras med att programmen har fått andra användningsområden och att metoderna har anpassats därefter (en annan tolkning är att flera senare system inte längre gör parsning i strikt mening). När detta tänkta ”kapitel” var färdigt fick det kommentaren att det inte var anpassat för antologins målgrupp. Det fick skrivas en annan kapiteltext, men det kom samtidigt ett förslag att publicera texten om parsning här som denna rapport.
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2. |
- Chatterjee, Bapi, 1982
(författare)
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Lock-free Concurrent Search
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The contemporary computers typically consist of multiple computing cores with high compute power. Such computers make excellent concurrent asynchronous shared memory system. On the other hand, though many celebrated books on data structure and algorithm provide a comprehensive study of sequential search data structures, unfortunately, we do not have such a luxury if concurrency comes in the setting. The present dissertation aims to address this paucity. We describe novel lock-free algorithms for concurrent data structures that target a variety of search problems. (i) Point search (membership query, predecessor query, nearest neighbour query) for 1-dimensional data: Lock-free linked-list; lock-free internal and external binary search trees (BST). (ii) Range search for 1-dimensional data: A range search method for lock-free ordered set data structures - linked-list, skip-list and BST. (iii) Point search for multi-dimensional data: Lock-free kD-tree, specially, a generic method for nearest neighbour search. We prove that the presented algorithms are linearizable i.e. the concurrent data structure operations intuitively display their sequential behaviour to an observer of the concurrent system. The lock-freedom in the introduced algorithms guarantee overall progress in an asynchronous shared memory system. We present the amortized analysis of lock-free data structures to show their efficiency. Moreover, we provide sample implementations of the algorithms and test them over extensive micro-benchmarks. Our experiments demonstrate that the implementations are scalable and perform well when compared to related existing alternative implementations on common multi-core computers. Our focus is on propounding the generic methodologies for efficient lock-free concurrent search. In this direction, we present the notion of help-optimality, which captures the optimization of amortized step complexity of the operations. In addition to that, we explore the language-portable design of lock-free data structures that aims to simplify an implementation from programmer’s point of view. Finally, our techniques to implement lock-free linearizable range search and nearest neighbour search are independent of the underlying data structures and thus are adaptive to similar data structures.
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3. |
- Liu, Yuanhua, 1971, et al.
(författare)
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Considering the importance of user profiles in interface design
- 2009
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Ingår i: User Interfaces. ; , s. 23-
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- User profile is a popular term widely employed during product design processes by industrial companies. Such a profile is normally intended to represent real users of a product. The ultimate purpose of a user profile is actually to help designers to recognize or learn about the real user by presenting them with a description of a real user’s attributes, for instance; the user’s gender, age, educational level, attitude, technical needs and skill level. The aim of this chapter is to provide information on the current knowledge and research about user profile issues, as well as to emphasize the importance of considering these issues in interface design. In this chapter, we mainly focus on how users’ difference in expertise affects their performance or activity in various interaction contexts. Considering the complex interaction situations in practice, novice and expert users’ interactions with medical user interfaces of different technical complexity will be analyzed as examples: one focuses on novice and expert users’ difference when interacting with simple medical interfaces, and the other focuses on differences when interacting with complex medical interfaces. Four issues will be analyzed and discussed: (1) how novice and expert users differ in terms of performance during the interaction; (2) how novice and expert users differ in the perspective of cognitive mental models during the interaction; (3) how novice and expert users should be defined in practice; and (4) what are the main differences between novice and expert users’ implications for interface design. Besides describing the effect of users’ expertise difference during the interface design process, we will also pinpoint some potential problems for the research on interface design, as well as some future challenges that academic researchers and industrial engineers should face in practice.
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4. |
- Rumman, Nadine Abu, et al.
(författare)
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Skin deformation methods for interactive character animation
- 2017
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Ingår i: Communications in Computer and Information Science. - Cham : Springer International Publishing. - 1865-0937 .- 1865-0929. ; 693, s. 153-174, s. 153-174
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Konferensbidrag (refereegranskat)abstract
- Character animation is a vital component of contemporary computer games, animated feature films and virtual reality applications. The problem of creating appealing character animation can best be described by the title of the animation bible: “The Illusion of Life”. The focus is not on completing a given motion task, but more importantly on how this motion task is performed by the character. This does not necessarily require realistic behavior, but behavior that is believable. This of course includes the skin deformations when the character is moving. In this paper, we focus on the existing research in the area of skin deformation, ranging from skeleton-based deformation and volume preserving techniques to physically based skinning methods. We also summarize the recent contributions in deformable and soft body simulations for articulated characters, and discuss various geometric and example-based approaches. © Springer International Publishing AG 2017.
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5. |
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6. |
- Bainomugisha, Engineer, et al.
(författare)
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Message from Chairs of SEiA 2018
- 2018
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Ingår i: Proceedings - International Conference on Software Engineering. - New York, NY, USA : ACM. - 0270-5257. ; 2018, s. x-xi
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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7. |
- Laaber, C., et al.
(författare)
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An Evaluation of Open-Source Software Microbenchmark Suites for Continuous Performance Assessment
- 2018
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Ingår i: MSR '18 Proceedings of the 15th International Conference on Mining Software Repositories. - New York, NY, USA : ACM Digital Library. - 9781450357166 ; , s. 119-130, s. 119-130
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Continuous integration (CI) emphasizes quick feedback to developers. This is at odds with current practice of performance testing, which predominantely focuses on long-running tests against entire systems in production-like environments. Alternatively, software microbenchmarking attempts to establish a performance baseline for small code fragments in short time. This paper investigates the quality of microbenchmark suites with a focus on suitability to deliver quick performance feedback and CI integration. We study ten open-source libraries written in Java and Go with benchmark suite sizes ranging from 16 to 983 tests, and runtimes between 11 minutes and 8.75 hours. We show that our study subjects include benchmarks with result variability of 50% or higher, indicating that not all benchmarks are useful for reliable discovery of slow-downs. We further artificially inject actual slowdowns into public API methods of the study subjects and test whether test suites are able to discover them. We introduce a performance-test quality metric called the API benchmarking score (ABS). ABS represents a benchmark suite's ability to find slowdowns among a set of defined core API methods. Resulting benchmarking scores (i.e., fraction of discovered slowdowns) vary between 10% and 100% for the study subjects. This paper's methodology and results can be used to (1) assess the quality of existing microbenchmark suites, (2) select a set of tests to be run as part of CI, and (3) suggest or generate benchmarks for currently untested parts of an API.
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8. |
- Laaber, C., et al.
(författare)
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Applying test case prioritization to software microbenchmarks
- 2021
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Ingår i: Empirical Software Engineering. - : Springer Science and Business Media LLC. - 1382-3256 .- 1573-7616. ; 26:6
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Tidskriftsartikel (refereegranskat)abstract
- Regression testing comprises techniques which are applied during software evolution to uncover faults effectively and efficiently. While regression testing is widely studied for functional tests, performance regression testing, e.g., with software microbenchmarks, is hardly investigated. Applying test case prioritization (TCP), a regression testing technique, to software microbenchmarks may help capturing large performance regressions sooner upon new versions. This may especially be beneficial for microbenchmark suites, because they take considerably longer to execute than unit test suites. However, it is unclear whether traditional unit testing TCP techniques work equally well for software microbenchmarks. In this paper, we empirically study coverage-based TCP techniques, employing total and additional greedy strategies, applied to software microbenchmarks along multiple parameterization dimensions, leading to 54 unique technique instantiations. We find that TCP techniques have a mean APFD-P (average percentage of fault-detection on performance) effectiveness between 0.54 and 0.71 and are able to capture the three largest performance changes after executing 29% to 66% of the whole microbenchmark suite. Our efficiency analysis reveals that the runtime overhead of TCP varies considerably depending on the exact parameterization. The most effective technique has an overhead of 11% of the total microbenchmark suite execution time, making TCP a viable option for performance regression testing. The results demonstrate that the total strategy is superior to the additional strategy. Finally, dynamic-coverage techniques should be favored over static-coverage techniques due to their acceptable analysis overhead; however, in settings where the time for prioritzation is limited, static-coverage techniques provide an attractive alternative.
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9. |
- Mallozzi, Piergiuseppe, 1990, et al.
(författare)
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A runtime monitoring framework to enforce invariants on reinforcement learning agents exploring complex environments
- 2019
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Ingår i: RoSE 2019, IEEE/ACM 2nd International Workshop on Robotics Software Engineering, p.5-12. - : IEEE. - 9781728122496
-
Konferensbidrag (refereegranskat)abstract
- © 2019 IEEE. Without prior knowledge of the environment, a software agent can learn to achieve a goal using machine learning. Model-free Reinforcement Learning (RL) can be used to make the agent explore the environment and learn to achieve its goal by trial and error. Discovering effective policies to achieve the goal in a complex environment is a major challenge for RL. Furthermore, in safety-critical applications, such as robotics, an unsafe action may cause catastrophic consequences in the agent or in the environment. In this paper, we present an approach that uses runtime monitoring to prevent the reinforcement learning agent to perform 'wrong' actions and to exploit prior knowledge to smartly explore the environment. Each monitor is de?ned by a property that we want to enforce to the agent and a context. The monitors are orchestrated by a meta-monitor that activates and deactivates them dynamically according to the context in which the agent is learning. We have evaluated our approach by training the agent in randomly generated learning environments. Our results show that our approach blocks the agent from performing dangerous and safety-critical actions in all the generated environments. Besides, our approach helps the agent to achieve its goal faster by providing feedback and shaping its reward during learning.
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10. |
- Pir Muhammad, Amna, 1990
(författare)
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Managing Human Factors and Requirements in Agile Development of Automated Vehicles: An Exploration
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Context: Automated Vehicle (AV) technology has evolved significantly in complexity and impact; it is expected to ultimately change urban transporta- tion. However, research shows that vehicle automation can only live up to this expectation if it is defined with human capabilities and limitations in mind. Therefore, it is necessary to bring human factors knowledge to AV developers. Objective: This thesis aims to empirically study how we can effectively bring the required human factors knowledge into large-scale agile AV develop- ment. The research goals are 1) to explore requirements engineering and human factors in agile AV development, 2) to investigate the problems of requirements engineering, human factors, and agile way of working in AV development, and 3) to demonstrate initial solutions to existing problems in agile AV development. Method: We conducted this research in close collaboration with industry, using different empirical methodologies to collect data—including interviews, workshops, and document analysis. To gain in-depth insights, we did a qualita- tive exploratory study to investigate the problem and used a design science approach to develop initial solution in several iterations. Findings and Conclusions: We found that applying human factors knowledge effectively is one of the key problem areas that need to be solved in agile development of artificial intelligence (AI)-intense systems. This motivated us to do an in-depth interview study on how to manage human factors knowl- edge during AV development. From our data, we derived a working definition of human factors for AV development, discovered the relevant properties of agile and human factors, and defined implications for agile ways of working, managing human factors knowledge, and managing requirements. The design science approach allowed us to identify challenges related to agile requirements engineering in three case companies in iterations. Based on these three case studies, we developed a solution strategy to resolve the RE challenges in agile AV development. Moreover, we derived building blocks and described guide- lines for the creation of a requirements strategy, which should describe how requirements are structured, how work is organized, and how RE is integrated into the agile work and feature flow. Future Outlook: In future work, I plan to define a concrete requirement strategy for human factors knowledge in large-scale agile AV development. It could help establishing clear communication channels and practices for incorporating explicit human factors knowledge into AI-based large-scale agile AV development.
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11. |
- Sundell, Håkan, 1968, et al.
(författare)
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NOBLE: non-blocking programming support via lock-free shared abstract data types
- 2009
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Ingår i: SIGARCH Computer Architecture News. - : ACM, Association for Computing Machinery, Inc.. - 0163-5964 .- 1943-5851. ; 36:5, s. 80-87
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Tidskriftsartikel (refereegranskat)abstract
- An essential part of programming for multi-core and multi-processor includes ef cient and reliable means for sharing data. Lock-free data structures are known as very suitable for this purpose, although experienced to be very complex to design. In this paper, we present a software library of non-blocking abstract data types that have been designed to facilitate lock-free programming for non-experts. The system provides: i) ef cient implementations of the most commonly used data types in concurrent and sequential software design, ii) a lock-free memory management system, and iii) a run time-system. The library provides clear semantics that are at least as strong as those of corresponding lock-based implementations of the respective data types. Our software library can be used for facilitating lockfree programming; its design enables the programmer to: i) replace lock-based components of sequential or parallel code easily and ef ciently , ii) use well-tuned concurrent algorithms inside a software or hardware transactional system. In the paper we describe the design and functionality of the system. We also provide experimental results that show that the library can considerably improve the performance of software systems.
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12. |
- Gerken, Jan, 1991, et al.
(författare)
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Equivariance versus augmentation for spherical images
- 2022
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Ingår i: Proceedings of Machine Learning Resaerch. ; , s. 7404-7421
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Konferensbidrag (refereegranskat)abstract
- We analyze the role of rotational equivariance in convolutional neural networks (CNNs) applied to spherical images. We compare the performance of the group equivariant networks known as S2CNNs and standard non-equivariant CNNs trained with an increasing amount of data augmentation. The chosen architectures can be considered baseline references for the respective design paradigms. Our models are trained and evaluated on single or multiple items from the MNIST- or FashionMNIST dataset projected onto the sphere. For the task of image classification, which is inherently rotationally invariant, we find that by considerably increasing the amount of data augmentation and the size of the networks, it is possible for the standard CNNs to reach at least the same performance as the equivariant network. In contrast, for the inherently equivariant task of semantic segmentation, the non-equivariant networks are consistently outperformed by the equivariant networks with significantly fewer parameters. We also analyze and compare the inference latency and training times of the different networks, enabling detailed tradeoff considerations between equivariant architectures and data augmentation for practical problems.
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13. |
- Memedi, Mevludin, 1983-, et al.
(författare)
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Automatic Spiral Analysis for Objective Assessment of Motor Symptoms in Parkinson's Disease
- 2015
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 15:9, s. 23727-23744
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Tidskriftsartikel (refereegranskat)abstract
- A challenge for the clinical management of advanced Parkinson's disease (PD) patients is the emergence of fluctuations in motor performance, which represents a significant source of disability during activities of daily living of the patients. There is a lack of objective measurement of treatment effects for in-clinic and at-home use that can provide an overview of the treatment response. The objective of this paper was to develop a method for objective quantification of advanced PD motor symptoms related to off episodes and peak dose dyskinesia, using spiral data gathered by a touch screen telemetry device. More specifically, the aim was to objectively characterize motor symptoms (bradykinesia and dyskinesia), to help in automating the process of visual interpretation of movement anomalies in spirals as rated by movement disorder specialists. Digitized upper limb movement data of 65 advanced PD patients and 10 healthy (HE) subjects were recorded as they performed spiral drawing tasks on a touch screen device in their home environment settings. Several spatiotemporal features were extracted from the time series and used as inputs to machine learning methods. The methods were validated against ratings on animated spirals scored by four movement disorder specialists who visually assessed a set of kinematic features and the motor symptom. The ability of the method to discriminate between PD patients and HE subjects and the test-retest reliability of the computed scores were also evaluated. Computed scores correlated well with mean visual ratings of individual kinematic features. The best performing classifier (Multilayer Perceptron) classified the motor symptom (bradykinesia or dyskinesia) with an accuracy of 84% and area under the receiver operating characteristics curve of 0.86 in relation to visual classifications of the raters. In addition, the method provided high discriminating power when distinguishing between PD patients and HE subjects as well as had good test-retest reliability. This study demonstrated the potential of using digital spiral analysis for objective quantification of PD-specific and/or treatment-induced motor symptoms.
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14. |
- Elmqvist, Niklas, 1977, et al.
(författare)
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Employing Dynamic Transparency for 3D Occlusion Management: Design Issues and Evaluation
- 2007
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Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - 1611-3349 .- 0302-9743. - 9783540747949 ; 4662, s. 532 - 545
-
Konferensbidrag (refereegranskat)abstract
- Recent developments in occlusion management for 3D environments often involve the use of dynamic transparency, or virtual “X-ray vision”, to promote target discovery and access in complex 3D worlds. However, there are many different approaches to achieving this effect and their actual utility for the user has yet to be evaluated. Furthermore, the introduction of semi-transparent surfaces adds additional visual complexity that may actually have a negative impact on task performance. In this paper, we report on an empirical user study comparing dynamic transparency to standard viewpoint controls. Our implementation of the technique is an image-space algorithm built using modern programmable shaders to achieve real-time performance and visually pleasing results. Results from the user study indicate that dynamic transparency is superior for perceptual tasks in terms of both efficiency and correctness.
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15. |
- Blanch, Krister, 1991
(författare)
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Beyond-application datasets and automated fair benchmarking
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Beyond-application perception datasets are generalised datasets that emphasise the fundamental components of good machine perception data. When analysing the history of perception datatsets, notable trends suggest that design of the dataset typically aligns with an application goal. Instead of focusing on a specific application, beyond-application datasets instead look at capturing high-quality, high-volume data from a highly kinematic environment, for the purpose of aiding algorithm development and testing in general. Algorithm benchmarking is a cornerstone of autonomous systems development, and allows developers to demonstrate their results in a comparative manner. However, most benchmarking systems allow developers to use their own hardware or select favourable data. There is also little focus on run time performance and consistency, with benchmarking systems instead showcasing algorithm accuracy. By combining both beyond-application dataset generation and methods for fair benchmarking, there is also the dilemma of how to provide the dataset to developers for this benchmarking, as the result of a high-volume, high-quality dataset generation is a significant increase in dataset size when compared to traditional perception datasets. This thesis presents the first results of attempting the creation of such a dataset. The dataset was built using a maritime platform, selected due to the highly dynamic environment presented on water. The design and initial testing of this platform is detailed, as well as as methods of sensor validation. Continuing, the thesis then presents a method of fair benchmarking, by utilising remote containerisation in a way that allows developers to present their software to the dataset, instead of having to first locally store a copy. To test this dataset and automatic online benchmarking, a number of reference algorithms were required for initial results. Three algorithms were built, using the data from three different sensors captured on the maritime platform. Each algorithm calculates vessel odometry, and the automatic benchmarking system was utilised to show the accuracy and run-time performance of these algorithms. It was found that the containerised approach alleviated data management concerns, prevented inflated accuracy results, and demonstrated precisely how computationally intensive each algorithm was.
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16. |
- Lv, Zhihan, Dr. 1984-, et al.
(författare)
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Deep Learning for Security in Digital Twins of Cooperative Intelligent Transportation Systems
- 2022
-
Ingår i: IEEE transactions on intelligent transportation systems (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1524-9050 .- 1558-0016. ; 23:9, s. 16666-16675
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Tidskriftsartikel (refereegranskat)abstract
- The purpose is to solve the security problems of the Cooperative Intelligent Transportation System (CITS) Digital Twins (DTs) in the Deep Learning (DL) environment. The DL algorithm is improved; the Convolutional Neural Network (CNN) is combined with Support Vector Regression (SVR); the DTs technology is introduced. Eventually, a CITS DTs model is constructed based on CNN-SVR, whose security performance and effect are analyzed through simulation experiments. Compared with other algorithms, the security prediction accuracy of the proposed algorithm reaches 90.43%. Besides, the proposed algorithm outperforms other algorithms regarding Precision, Recall, and F1. The data transmission performances of the proposed algorithm and other algorithms are compared. The proposed algorithm can ensure that emergency messages can be responded to in time, with a delay of less than 1.8s. Meanwhile, it can better adapt to the road environment, maintain high data transmission speed, and provide reasonable path planning for vehicles so that vehicles can reach their destinations faster. The impacts of different factors on the transportation network are analyzed further. Results suggest that under path guidance, as the Market Penetration Rate (MPR), Following Rate (FR), and Congestion Level (CL) increase, the guidance strategy's effects become more apparent. When MPR ranges between 40% similar to 80% and the congestion is level III, the ATT decreases the fastest, and the improvement effect of the guidance strategy is more apparent. The proposed DL algorithm model can lower the data transmission delay of the system, increase the prediction accuracy, and reasonably changes the paths to suppress the sprawl of traffic congestions, providing an experimental reference for developing and improving urban transportation.
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17. |
- Nguyen, Björnborg, 1992, et al.
(författare)
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Systematic benchmarking for reproducibility of computer vision algorithms for real-time systems: The example of optic flow estimation
- 2019
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Ingår i: IEEE International Conference on Intelligent Robots and Systems. - : IEEE. - 2153-0858 .- 2153-0866. ; , s. 5264-5269
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Konferensbidrag (refereegranskat)abstract
- Until now there have been few formalized methods for conducting systematic benchmarking aiming at reproducible results when it comes to computer vision algorithms. This is evident from lists of algorithms submitted to prominent datasets, authors of a novel method in many cases primarily state the performance of their algorithms in relation to a shallow description of the hardware system where it was evaluated. There are significant problems linked to this non-systematic approach of reporting performance, especially when comparing different approaches and when it comes to the reproducibility of claimed results. Furthermore how to conduct retrospective performance analysis such as an algorithm's suitability for embedded real-time systems over time with underlying hardware and software changes in place. This paper proposes and demonstrates a systematic way of addressing such challenges by adopting containerization of software aiming at formalization and reproducibility of benchmarks. Our results show maintainers of broadly accepted datasets in the computer vision community to strive for systematic comparison and reproducibility of submissions to increase the value and adoption of computer vision algorithms in the future.
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18. |
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19. |
- Casado, Lander, 1985, et al.
(författare)
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ContikiSec: A Secure Network Layer for Wireless Sensor Networks under the Contiki Operating System
- 2009
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Ingår i: Proceedings of the 14th Nordic Conference on Secure IT Systems (NordSec 2009), Lecture Notes in Computer Science. - 1611-3349. - 9783642047657 ; 5838, s. 133 - 147
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Konferensbidrag (refereegranskat)abstract
- In this paper we introduce ContikiSec, a secure network layer forwireless sensor networks, designed for the Contiki Operating System. ContikiSechas a configurable design, providing three security modes starting fromconfidentiality and integrity, and expanding to confidentiality, authentication,and integrity. ContikiSec has been designed to balance low energy consumptionand security while conforming to a small memory footprint. Our design wasbased on performance evaluation of existing security primitives and is part ofthe contribution of this paper. Our evaluation was performed in the ModularSensor Board hardware platform for wireless sensor networks, running Contiki.Contiki is an open source, highly portable operating system for wireless sensornetworks (WSN) that is widely used in WSNs.
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20. |
- Chatterjee, Bapi, 1982
(författare)
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Efficient Implementation of Concurrent Data Structures on Multi-core and Many-core Architectures
- 2015
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Synchronization of concurrent threads is the central problem in order to design efficient concurrent data-structures. The compute systems widely available in market are increasingly becoming heterogeneous involving multi-core Central Processing Units (CPUs) and many-core Graphics Processing Units (GPUs). This thesis contributes to the research of efficient synchronization in concurrent data-structures in more than one way. It is divided into two parts. In the first part, a novel design of a Set Abstract Data Type (ADT) based on an efficient lock-free Binary Search Tree (BST) with improved amortized bounds of the time complexity of set operations - Add, Remove and Contains, is presented. In the second part, a comprehensive evaluation of concurrent Queue implementations on multi-core CPUs as well as many-core GPUs are presented. Efficient Lock-free BST -To the best of our knowledge, the lock-free BST presented in this thesis is the first to achieve an amortized complexity of O(H(n)+c) for all Set operations where H(n) is the height of a BST on n nodes and c is the contention measure. Also, the presented lock-free algorithm of BST comes with an improved disjoint-access-parallelism compared to the previously existing concurrent BST algorithms. This algorithm uses single-word compare-and-swap (CAS) primitives. The presented algorithm is linearizable. We implemented the algorithm in Java and it shows good scalability. Evaluation of concurrent data-structures - We have evaluated the performance of a number of concurrent FIFO Queue algorithms on multi-core CPUs and many-core GPUs. We studied the portability of existing design of concurrent Queues from CPUs to GPUs which are inherently designed for SIMD programs. We observed that in general concurrent queues offer them to efficient implementation on GPUs with faster cache memory and better performance support for atomic synchronization primitives such as CAS. To the best of our knowledge, this is the first attempt to evaluate a concurrent data-structure on GPUs.
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21. |
- Ha, Phuong, 1976, et al.
(författare)
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The Synchronization Power of Coalesced Memory Accesses
- 2008
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Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 9783540877783 ; 5218, s. 320-334
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Konferensbidrag (refereegranskat)abstract
- Multicore processor architectures have established themselves as the new generation of processor architectures. As part of the one core to many cores evolution, memory access mechanisms have advanced rapidly. Several new memory access mechanisms have been implemented in many modern commodity multicore processors. Memory access mechanisms, by devising how processing cores access the shared memory, directly influence the synchronization capabilities of the multicore processors. Therefore, it is crucial to investigate the synchronization power of these new memory access mechanisms.This paper investigates the synchronization power of coalesced memory accesses, a family of memory access mechanisms introduced in recent large multicore architectures like the CUDA graphics processors. We first design three memory access models to capture the fundamental features of the new memory access mechanisms. Subsequently, we prove the exact synchronization power of these models in terms of their consensus numbers. These tight results show that the coalesced memory access mechanisms can facilitate strong synchronization between the threads of multicore processors, without the need of synchronization primitives other than reads and writes. In the case of the contemporary CUDA processors, our results imply that the coalesced memory access mechanisms have consensus numbers up to sixteen.
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22. |
- Ha, Phuong, 1976, et al.
(författare)
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Wait-free Programming for General Purpose Computations on Graphics Processors
- 2008
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Ingår i: the Proceedings of the 22th International Parallel and Distributed Symposium (IPDPS 2008). - 1530-2075. - 9781424416936 ; , s. 1-12
-
Konferensbidrag (refereegranskat)abstract
- The fact that graphics processors (GPUs) are today’s most powerful computational hardware for the dollar has motivated researchers to utilize the ubiquitous and powerful GPUs for general-purpose computing. Recent GPUs feature the single-program multiple-data (SPMD) multicore architecture instead of the single-instruction multiple-data (SIMD). However, unlike CPUs, GPUs devote their transistors mainly to data processing rather than data caching and flow control, and consequently most of the powerful GPUs with many cores do not support any synchronization mechanisms between their cores. This prevents GPUs from being deployed more widely for general-purpose computing. This paper aims at bridging the gap between the lack of synchronization mechanisms in recent GPU architectures and the need of synchronization mechanisms in parallel applications. Based on the intrinsic features of recent GPU architectures, we construct strong synchronization objects like wait-free and t-resilient read-modify-write objects for a general model of recent GPU architectures without strong hardware synchronization primitives like test-and-set and compare-and-swap. Accesses to the wait-free objects have time complexity O(N), whether N is the number of processes. Our result demonstrates that it is possible to construct wait-free synchronization mechanisms for GPUs without the need of strong synchronization primitives in hardware and that wait-free programming is possible for GPUs.
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23. |
- Ali, Muhaddisa Barat, 1986
(författare)
-
Deep Learning Methods for Classification of Gliomas and Their Molecular Subtypes, From Central Learning to Federated Learning
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The most common type of brain cancer in adults are gliomas. Under the updated 2016 World Health Organization (WHO) tumor classification in central nervous system (CNS), identification of molecular subtypes of gliomas is important. For low grade gliomas (LGGs), prediction of molecular subtypes by observing magnetic resonance imaging (MRI) scans might be difficult without taking biopsy. With the development of machine learning (ML) methods such as deep learning (DL), molecular based classification methods have shown promising results from MRI scans that may assist clinicians for prognosis and deciding on a treatment strategy. However, DL requires large amount of training datasets with tumor class labels and tumor boundary annotations. Manual annotation of tumor boundary is a time consuming and expensive process. The thesis is based on the work developed in five papers on gliomas and their molecular subtypes. We propose novel methods that provide improved performance. The proposed methods consist of a multi-stream convolutional autoencoder (CAE)-based classifier, a deep convolutional generative adversarial network (DCGAN) to enlarge the training dataset, a CycleGAN to handle domain shift, a novel federated learning (FL) scheme to allow local client-based training with dataset protection, and employing bounding boxes to MRIs when tumor boundary annotations are not available. Experimental results showed that DCGAN generated MRIs have enlarged the original training dataset size and have improved the classification performance on test sets. CycleGAN showed good domain adaptation on multiple source datasets and improved the classification performance. The proposed FL scheme showed a slightly degraded performance as compare to that of central learning (CL) approach while protecting dataset privacy. Using tumor bounding boxes showed to be an alternative approach to tumor boundary annotation for tumor classification and segmentation, with a trade-off between a slight decrease in performance and saving time in manual marking by clinicians. The proposed methods may benefit the future research in bringing DL tools into clinical practice for assisting tumor diagnosis and help the decision making process.
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24. |
- Amundin, Mats, et al.
(författare)
-
A proposal to use distributional models to analyse dolphin vocalisation
- 2017
-
Ingår i: Proceedings of the 1st International Workshop on Vocal Interactivity in-and-between Humans, Animals and Robots, VIHAR 2017. - 9782956202905 ; , s. 31-32
-
Konferensbidrag (refereegranskat)abstract
- This paper gives a brief introduction to the starting points of an experimental project to study dolphin communicative behaviour using distributional semantics, with methods implemented for the large scale study of human language.
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25. |
- Lv, Zhihan, Dr. 1984-, et al.
(författare)
-
5G for mobile augmented reality
- 2022
-
Ingår i: International Journal of Communication Systems. - : John Wiley & Sons. - 1074-5351 .- 1099-1131. ; 35:5
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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26. |
- Lv, Zhihan, Dr. 1984-, et al.
(författare)
-
Editorial : 5G for Augmented Reality
- 2022
-
Ingår i: Mobile Networks and Applications. - : Springer. - 1383-469X .- 1572-8153.
-
Tidskriftsartikel (refereegranskat)
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27. |
- Ge, Chenjie, 1991, et al.
(författare)
-
Co-Saliency-Enhanced Deep Recurrent Convolutional Networks for Human Fall Detection in E-Healthcare
- 2018
-
Ingår i: Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS. - 1557-170X. ; 2018-July, s. 1572-1575
-
Konferensbidrag (refereegranskat)abstract
- This paper addresses the issue of fall detection from videos for e-healthcare and assisted-living. Instead of using conventional hand-crafted features from videos, we propose a fall detection scheme based on co-saliency-enhanced recurrent convolutional network (RCN) architecture for fall detection from videos. In the proposed scheme, a deep learning method RCN is realized by a set of Convolutional Neural Networks (CNNs) in segment-levels followed by a Recurrent Neural Network (RNN), Long Short-Term Memory (LSTM), to handle the time-dependent video frames. The co-saliency-based method enhances salient human activity regions hence further improves the deep learning performance. The main contributions of the paper include: (a) propose a recurrent convolutional network (RCN) architecture that is dedicated to the tasks of human fall detection in videos; (b) integrate a co-saliency enhancement to the deep learning scheme for further improving the deep learning performance; (c) extensive empirical tests for performance analysis and evaluation under different network settings and data partitioning. Experiments using the proposed scheme were conducted on an open dataset containing multicamera videos from different view angles, results have shown very good performance (test accuracy 98.96%). Comparisons with two existing methods have provided further support to the proposed scheme.
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28. |
- Liu, Yuqi, et al.
(författare)
-
Integration of Multi-scale Spatial Digital Twins in Metaverse Based on Multi-dimensional Hash Geocoding
- 2024
-
Ingår i: IMX '24. - : Association for Computing Machinery (ACM). - 9798400705038 ; , s. 56-63
-
Konferensbidrag (refereegranskat)abstract
- With the popularization of the metaverse, virtual reality mapping technology based on digital twins has generated a large amount of spatial data. These data are multidimensional, multi-scale, mobile, and distributed. In order to fully utilize these data, we propose a non mutation multidimensional hash geocoding that can organize and store data with geographic features, and achieve data mapping at different scales from macro to micro. The mapping between them can achieve joint utilization of data of various scales. On this basis, we propose a block network secure storage mapping model for spatial digital twins, which can securely and reliably organize and map spatial data. This article also looks forward to the possible emergence of digital twins of different dimensions and scales in the future metaverse, and proposes an adaptive 3D reconstruction method based on this to adapt to digital twins models of different scales in the metaverse. On the basis of our work, we will further promote the development of the spatial digital twin metaverse.
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29. |
- Atalar, Aras, 1985
(författare)
-
Throughput and energy efficiency of lock-free data structures: Execution Models and Analyses
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Concurrent data structures are key program components to harness the available parallelism in multi-core processors. Lock-free algorithmic implementations of concurrent data structures offer high scalability and possess desirable properties such as immunity to deadlocks, convoying and priority inversion. In this thesis, we develop analytical tools to model and analyze the throughput and energy consumption of concurrent lock-free data structures. We start our study with a general class of lock-free data structures. Then, we target more specialized designs for lock-free queues. Finally, we focus on the search data structures that possess different characteristics compared to previously mentioned data structures. Performance of lock-free data structures: This thesis contributes to the problem of making ends meet between theoretical bounds and actual measured throughput. As the first step, we consider a general class of lock-free data structures and propose three analytical frameworks with different flavors. Analyses of this class also cover efficient implementations of a set of fundamental data structures that suffer from inherent sequential bottlenecks. We model the executions and examine the impact of contention on the throughput of these algorithms. Our analyses lead to optimization methods on memory management and back-off strategies. Performance and energy efficiency of lock-free queues: We take a step further to model the throughput of lock-free operations and their interaction. Considering shared queues, as a key paradigm for data sharing, operations (En- queue, Dequeue) access the opposite ends of a queue. Same type of operations might contend with each other on a non-empty queue. However, all types of operations are subject to interaction when the queue is empty. We first decorrelate the throughput of dequeuers’ and enqueuers’ into several uncorrelated basic throughputs, and reconstruct the main throughputs as a function of these basic throughputs. Besides, we model the power dissipation and integrate it with the throughput estimations to extract the energy consumption of applications that utilize lock-free queues. Performance of lock-free search data structures: Lock-free designs that utilize fine-grained synchronization have produced efficient implementations of search data structures. These designs reveal different characteristics compared to the previous set of lock-free data structures with inherent sequential bottlenecks. We introduce a new way of modeling and analyzing the throughput of search data structures under stationary and memoryless access patterns..
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30. |
- Bernhard, David, et al.
(författare)
-
Security proofs for Participation privacy, receipt-freeness and ballot privacy for the helios voting scheme
- 2017
-
Ingår i: ARES '17 Proceedings of the 12th International Conference on Availability, Reliability and Security. - New York : Association for Computing Machinery (ACM). - 9781450352574
-
Konferensbidrag (refereegranskat)abstract
- The Helios voting scheme is well studied including formal proofs for verifiability and ballot privacy. However, depending on its version, the scheme provides either participation privacy (hiding who participated in the election) or verifiability against malicious bulletin board (preventing election manipulation by ballot stuffing), but not both at the same time. It also does not provide receipt-freeness, thus enabling vote buying by letting the voters construct receipts proving how they voted. Recently, an extension to Helios, further referred to as KTV-Helios, has been proposed that claims to provide these additional security properties. However, the authors of KTV-Helios did not prove their claims. Our contribution is to provide formal definitions for participation privacy and receipt-freeness that we applied to KTV-Helios. In order to evaluate the fulfillment of participation privacy and receipt-freeness, we furthermore applied the existing definition of ballot privacy, which was also used for evaluating the security of Helios, in order to show that ballot privacy also holds for KTV-Helios
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31. |
- Bonneau, Charlotte, et al.
(författare)
-
Deconstruction of Crystalline Networks into Underlying Nets: Relevance for Terminology Guidelines and Crystallographic Databases
- 2018
-
Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7505 .- 1528-7483. ; 18:6, s. 3411-3418
-
Tidskriftsartikel (refereegranskat)abstract
- This communication briefly reviews why network topology is an important tool (for understanding, comparing, communicating, designing, and solving crystal structures from powder diffraction data) and then discusses the terms of an IUPAC project dealing with various aspects of network topology. One is the ambiguity in node assignment, and this question is addressed in more detail. First, we define the most important approaches: the "all node" deconstruction considering all branch points of the linkers, the "single node" deconstruction considering only components mixed, and the ToposPro "standard representation" also considering linkers as one node but, if present, takes each metal atom as a separate node. These methods are applied to a number of metal-organic framework structures (MOFs, although this is just one example of materials this method is applicable on), and it is concluded that the "all node" method potentially yields more information on the structure in question but cannot be recommended as the only way of reporting the network topology. In addition, several terms needing definitions are discussed.
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32. |
- Brunetta, Carlo, 1992
(författare)
-
Cryptographic Tools for Privacy Preservation and Verifiable Randomness
- 2018
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Our society revolves around communication. The Internet is the biggest, cheapest and fastest digital communication channel used nowadays. Due to the continuous increase of daily communication among people worldwide, more and more data might be stolen, misused or tampered. We require to protect our communications and data by achieving privacy and confidentiality. Despite the two terms, "privacy" and "confidentiality",are often used as synonymous, in cryptography they are modelled in very different ways. Intuitively, cryptography can be seen as a tool-box in which every scheme, protocol or primitive is a tool that can be used to solve specific problems and provide specific communication security guarantees such as confidentiality. Privacy is instead not easy to describe and capture since it often depends on "which" information is available, "how" are these data used and/or "who" has access to our data. This licentiate thesis raises research questions and proposes solutions related to: the possibility of defining encryption schemes that provide both strong security and privacy guarantees; the importance of designing cryptographic protocols that are compliant with real-life privacy-laws or regulations; and the necessity of defining a post-quantum mechanism to achieve the verifiability of randomness. In more details, the thesis achievements are: (a) defining a new class of encryption schemes, by weakening the correctness property, that achieves Differential Privacy (DP), i.e., a mathematically sound definition of privacy; (b) formalizing a security model for a subset of articles in the European General Data Protection Regulation (GDPR), designing and implementing a cryptographic protocol based on the proposed GDPR-oriented security model, and; (c) proposing a methodology to compile a post-quantum interactive protocol for proving the correct computation of a pseudorandom function into a non-interactive one, yielding a post-quantum mechanism for verifiable randomness.
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33. |
- Dolonius, Dan, 1985
(författare)
-
Sparse Voxel DAGs for Shadows and for Geometry with Colors
- 2018
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Triangles are probably the most common format for shapes in computer graphics. Nevertheless, when high detail is desired, Sparse Voxel Octrees (SVO) and Sparse Voxel Directed Acyclic Graphs (DAG) can be considerably more memory efficient. One of the first practical use cases for DAGs was to use the structure to represent precomputed shadows. However, previous methods were very time consuming in building the DAG and did not support any other attributes than discretized geometry. Furthermore, when used for scene object representation, the DAGs lacked proper support for properties such as object colors. The focus on this thesis is to speed up the build times of the DAG and to allow other, important, attributes such as colors to be encoded. This thesis is a collection of three papers where we in Paper I solve the problem with slow construction times while also further compressing the DAG, allowing much faster feedback to an artist making changes to a scene and also opening up the possibility to recompute the DAG in run time for slowly moving shadows. If a unique color per voxel is desired, which uncompressed would require 3 bytes per voxel, we realize that the benefit from compressing the geometry (down to or even below one bit per voxel) is rendered practically useless. We thus need to find a way to compress the colors as well. In Paper IIA, we solve this issue by mapping the voxel colors to a texture, allowing for the use of conventional compression algorithms, as well as a novel format designed for real-time performance. In Paper IIB, we further significantly improve the compression.
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34. |
- Ebadi Tavallaei, Hamid, 1987, et al.
(författare)
-
Sampling and Partitioning for Differential Privacy
- 2016
-
Ingår i: Privacy Security & Trust Conference 2016. - 9781509043798 ; , s. 664-673
-
Konferensbidrag (refereegranskat)abstract
- Differential privacy enjoys increasing popularity thanks to both a precise semantics for privacy and effective enforcement mechanisms. Many tools have been proposed to spread its use and ease the task of the concerned data scientist. The most promising among them completely discharge the user of the privacy concerns by transparently taking care of the privacy budget. However, their implementation proves to be delicate, and introduce flaws by falsifying some of the theoretical assumptions made to guarantee differential privacy. Moreover, such tools rely on assumptions leading to over-approximations which artificially reduce utility. In this paper we focus on a key mechanism that tools do not support well: sampling. We demonstrate an attack on PINQ (McSherry, SIGMOD 2009), one of these tools, relying on the difference between its internal mechanics and the formal theory for the sampling operation, and study a range of sampling methods and show how they can be correctly implemented in a system for differential privacy.
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35. |
- Elowsson, Anders
(författare)
-
Deep Layered Learning in MIR
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Deep learning has boosted the performance of many music information retrieval (MIR) systems in recent years. Yet, the complex hierarchical arrangement of music makes end-to-end learning hard for some MIR tasks – a very deep and structurally flexible processing chain is necessary to extract high-level features from a spectrogram representation. Mid-level representations such as tones, pitched onsets, chords, and beats are fundamental building blocks of music. This paper discusses how these can be used as intermediate representations in MIR to facilitate deep processing that generalizes well: each music concept is predicted individually in learning modules that are connected through latent representations in a directed acyclic graph. It is suggested that this strategy for inference, defined as deep layered learning (DLL), can help generalization by (1) – enforcing the validity of intermediate representations during processing, and by (2) – letting the inferred representations establish disentangled structures that support high-level invariant processing. A background to DLL and modular music processing is provided, and relevant concepts such as pruning, skip connections, and layered performance supervision are reviewed.
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36. |
- Elowsson, Anders
(författare)
-
Modeling Music : Studies of Music Transcription, Music Perception and Music Production
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation presents ten studies focusing on three important subfields of music information retrieval (MIR): music transcription (Part A), music perception (Part B), and music production (Part C).In Part A, systems capable of transcribing rhythm and polyphonic pitch are described. The first two publications present methods for tempo estimation and beat tracking. A method is developed for computing the most salient periodicity (the “cepstroid”), and the computed cepstroid is used to guide the machine learning processing. The polyphonic pitch tracking system uses novel pitch-invariant and tone-shift-invariant processing techniques. Furthermore, the neural flux is introduced – a latent feature for onset and offset detection. The transcription systems use a layered learning technique with separate intermediate networks of varying depth. Important music concepts are used as intermediate targets to create a processing chain with high generalization. State-of-the-art performance is reported for all tasks.Part B is devoted to perceptual features of music, which can be used as intermediate targets or as parameters for exploring fundamental music perception mechanisms. Systems are proposed that can predict the perceived speed and performed dynamics of an audio file with high accuracy, using the average ratings from around 20 listeners as ground truths. In Part C, aspects related to music production are explored. The first paper analyzes long-term average spectrum (LTAS) in popular music. A compact equation is derived to describe the mean LTAS of a large dataset, and the variation is visualized. Further analysis shows that the level of the percussion is an important factor for LTAS. The second paper examines songwriting and composition through the development of an algorithmic composer of popular music. Various factors relevant for writing good compositions are encoded, and a listening test employed that shows the validity of the proposed methods.The dissertation is concluded by Part D - Looking Back and Ahead, which acts as a discussion and provides a road-map for future work. The first paper discusses the deep layered learning (DLL) technique, outlining concepts and pointing out a direction for future MIR implementations. It is suggested that DLL can help generalization by enforcing the validity of intermediate representations, and by letting the inferred representations establish disentangled structures supporting high-level invariant processing. The second paper proposes an architecture for tempo-invariant processing of rhythm with convolutional neural networks. Log-frequency representations of rhythm-related activations are suggested at the main stage of processing. Methods relying on magnitude, relative phase, and raw phase information are described for a wide variety of rhythm processing tasks.
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37. |
- Rukundo, Adones, 1986, et al.
(författare)
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Monotonically relaxing concurrent data-structure semantics for increasing performance: An efficient 2D design framework
- 2019
-
Ingår i: Leibniz International Proceedings in Informatics, LIPIcs. - 1868-8969. ; 146
-
Konferensbidrag (refereegranskat)abstract
- There has been a significant amount of work in the literature proposing semantic relaxation of concurrent data structures for improving scalability and performance. By relaxing the semantics of a data structure, a bigger design space, that allows weaker synchronization and more useful parallelism, is unveiled. Investigating new data structure designs, capable of trading semantics for achieving better performance in a monotonic way, is a major challenge in the area. We algorithmically address this challenge in this paper. We present an efficient, lock-free, concurrent data structure design framework for out-of-order semantic relaxation. We introduce a new two dimensional algorithmic design, that uses multiple instances of a given data structure. The first dimension of our design is the number of data structure instances operations are spread to, in order to benefit from parallelism through disjoint memory access; the second dimension is the number of consecutive operations that try to use the same data structure instance in order to benefit from data locality. Our design can flexibly explore this two-dimensional space to achieve the property of monotonically relaxing concurrent data structure semantics for better performance within a tight deterministic relaxation bound, as we prove in the paper. We show how our framework can instantiate lock-free out-of-order queues, stacks, counters and dequeues. We provide implementations of these relaxed data structures and evaluate their performance and behaviour on two parallel architectures. Experimental evaluation shows that our two-dimensional design significantly outperforms the respected previous proposed designs with respect to scalability and performance. Moreover, our design increases performance monotonically as relaxation increases.
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38. |
- Ahrendt, Wolfgang, 1967, et al.
(författare)
-
Verification of Smart Contract Business Logic: Exploiting a Java Source Code Verifier
- 2019
-
Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - Cham : Springer International Publishing. - 1611-3349 .- 0302-9743. ; 11761 LNCS, s. 228-243
-
Konferensbidrag (refereegranskat)abstract
- Smart contracts have been argued to be a means of building trust between parties by providing a self-executing equivalent of legal contracts. And yet, code does not always perform what it was originally intended to do, which resulted in losses of millions of dollars. Static verification of smart contracts is thus a pressing need. This paper presents an approach to verifying smart contracts written in Solidity by automatically translating Solidity into Java and using KeY, a deductive Java verification tool. In particular, we solve the problem of rolling back the effects of aborted transactions by exploiting KeY’s native support of JavaCard transactions. We apply our approach to a smart contract which automates a casino system, and discuss how the approach addresses a number of known shortcomings of smart contract development in Solidity.
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39. |
- Arshad, Hamed, 1987, et al.
(författare)
-
Attribute-based encryption with enforceable obligations
- 2023
-
Ingår i: Journal of Cryptographic Engineering. - Heidelberg : Springer. - 2190-8508 .- 2190-8516. ; 13, s. 343-371
-
Tidskriftsartikel (refereegranskat)abstract
- Attribute-based encryption (ABE) is a cryptographic mechanism that provides fine-grained access control to encrypted data, which can thus be stored in, e.g., public clouds. However, ABE schemes lack the notion of obligations, which is common in attribute-based access control systems such as eXtensible Access Control Markup Language and Usage Control. Obligations are used to define and enforce extra constraints that happen before approving or denying an access request. In this paper, we propose OB-ABE, a system for extending any classical ABE with enforceable obligations. Our system architecture has as core component trusted hardware enclaves, implemented with SGX, used for enforcing obligations. We employ ProVerif to formally model OB-ABE and verify its main property called "enforceable obligations," i.e., if a message is encrypted along with an obligation, then the message can be decrypted only after enforcing the attached obligation. OB-ABE has two more properties: (i) OB-ABE is a "conservative extension" of the underlying ABE scheme, preserving its security properties; (ii) OB-ABE is "backward compatible" in the sense that any ciphertext produced by an ABE scheme can be decrypted by its extended OB-ABE version, and moreover, a ciphertext produced by an OB-ABE scheme can be decrypted by its underlying ABE scheme provided that the ciphertext does not have obligations attached. We also implement in C using Intel SGX a prototype of an OB-ABE extending the well-known ciphertext-policy ABE.
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40. |
- Butun, Ismail, 1981, et al.
(författare)
-
A Review of Distributed Access Control for Blockchain Systems towards Securing the Internet of Things
- 2021
-
Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 9, s. 5428-5441
-
Forskningsöversikt (refereegranskat)abstract
- As the Internet of Things (IoT) paradigm gets more attention from academia and industry, implementation tools of IoT will be explored more and more. One example is the applicability of blockchain systems to provide security and privacy of IoT networks, which is the topic of this article. Blockchain systems are on the rise, as crypto-currency payment systems (such as Bitcoin, Litecoin, etc.) boomed in the last few years due to their attractive de-centralized and anonymous features. As in every transaction, access of the users to IoT systems needs to be controlled. However, these systems are peer-to-peer systems and do not have centralized control, which means that traditional access control techniques will not be optimal. As a result, distributed access control schemes are needed and this paper aims at providing the state of the art in the literature. Thereby, we introduce and discuss the details and applicability of centralized (rolebased) and distributed (threshold-signature, reputation, trusted-computing, identity, capability, ACL, groupsignature, and hybrid) access control schemes to blockchain systems under the IoT ecosystems. Moreover, permissioned vs. permissionless blockchain systems are also discussed. Finally, challenges and research directions related to the application of all those presented blockchain systems to IoT are discussed.
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41. |
- Ciric, Rastko, et al.
(författare)
-
TemplateFlow: FAIR-sharing of multi-scale, multi-species brain models.
- 2022
-
Ingår i: Nature methods. - : Springer Science and Business Media LLC. - 1548-7105 .- 1548-7091. ; 19:12, s. 1568-1571
-
Tidskriftsartikel (refereegranskat)abstract
- Reference anatomies of the brain ('templates') and corresponding atlases are the foundation for reporting standardized neuroimaging results. Currently, there is no registry of templates and atlases; therefore, the redistribution of these resources occurs either bundled within existing software or in ad hoc ways such as downloads from institutional sites and general-purpose data repositories. We introduce TemplateFlow as a publicly available framework for human and non-human brain models. The framework combines an open database with software for access, management, and vetting, allowing scientists to share their resources under FAIR-findable, accessible, interoperable, and reusable-principles. TemplateFlow enables multifaceted insights into brains across species, and supports multiverse analyses testing whether results generalize across standard references, scales, and in the long term, species.
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42. |
- Fersman, Elena, et al.
(författare)
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Task Automata : Schedulability, Decidability and Undecidability
- 2007
-
Ingår i: Information and Computation. - : Elsevier. - 0890-5401 .- 1090-2651. ; 205:8, s. 1149-1172
-
Tidskriftsartikel (refereegranskat)abstract
- We present a model, task automata, for real time systems with non-uniformly recurring computation tasks. It is an extended version of timed automata with asynchronous processes that are computation tasks generated (or triggered) by timed events. Compared with classical task models for real time systems, task automata may be used to describe tasks (1) that are generated non-deterministically according to timing constraints in timed automata, (2) that may have interval execution times representing the best case and the worst case execution times, and (3) whose completion times may influence the releases of task instances. We generalize the classical notion of schedulability to task automata. A task automaton is schedulable if there exists a scheduling strategy such that all possible sequences of events generated by the automaton are schedulable in the sense that all associated tasks can be computed within their deadlines. Our first technical result is that the schedulability for a given scheduling strategy can be checked algorithmically for the class of task automata when the best case and the worst case execution times of tasks are equal. The proof is based on a decidable class of suspension automata: timed automata with bounded subtraction in which clocks may be updated by subtractions within a bounded zone. We shall also study the borderline between decidable and undecidable cases. Our second technical result shows that the schedulability checking problem will be undecidable if the following three conditions hold: (1) the execution times of tasks are intervals, (2) the precise finishing time of a task instance may influence new task releases, and (3) a task is allowed to preempt another running task.
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43. |
- Linnusson, Henrik, et al.
(författare)
-
Efficient conformal predictor ensembles
- 2020
-
Ingår i: Neurocomputing. - : Elsevier BV. - 0925-2312 .- 1872-8286. ; 397, s. 266-278
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we study a generalization of a recently developed strategy for generating conformal predictor ensembles: out-of-bag calibration. The ensemble strategy is evaluated, both theoretically and empirically, against a commonly used alternative ensemble strategy, bootstrap conformal prediction, as well as common non-ensemble strategies. A thorough analysis is provided of out-of-bag calibration, with respect to theoretical validity, empirical validity (error rate), efficiency (prediction region size) and p-value stability (the degree of variance observed over multiple predictions for the same object). Empirical results show that out-of-bag calibration displays favorable characteristics with regard to these criteria, and we propose that out-of-bag calibration be adopted as a standard method for constructing conformal predictor ensembles.
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44. |
- Magnusson, Peter S., et al.
(författare)
-
SimICS/sun4m : A virtual workstation
- 2019
-
Ingår i: USENIX 1998 Annual Technical Conference. - New Orleans, LA, USA : USENIX Association.
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Konferensbidrag (refereegranskat)abstract
- System level simulators allow computer architects and system software designers to recreate an accurate and complete replica of the program behavior of a target system, regardless of the availability, existence, or instrumentation support of such a system. Applications include evaluation of architectural design alternatives as well as software engineering tasks such as traditional debugging and performance tuning. We present an implementation of a simulator acting as a virtual workstation fully compatible with the sun4m architecture from Sun Microsystems. Built using the system-level SPARC V8 simulator SimICS, SimICS/sun4m models one or more SPARC V8 processors, supports user-developed modules for data cache and instruction cache simulation and execution profiling of all code, and provides a symbolic and performance debugging environment for operating systems. SimICS/sun4m can boot unmodified operating systems, including Linux 2.0.30 and Solaris 2.6, directly from snapshots of disk partitions. To support essentially arbitrary code, we implemented binary-compatible simulators for several devices, including SCSI, console, interrupt, timers, EEPROM, and Ethernet. The Ethernet simulation hooks into the host and allows the virtual workstation to appear on the local network with full services available (NFS, NIS, rsh, etc). Ethernet and console traffic can be recorded for future playback. The performance of SimICS/sun4m is sufficient to run realistic workloads, such as the database benchmark TPC-D, scaling factor 1/100, or an interactive network application such as Mozilla. The slowdown in relation to native hardware is in the range of 25 to 75 (measured using SPECint95). We also demonstrate some applications, including modeling an 8-processor sun4m version (which does not exist), modeling future memory hierarchies, and debugging an operating system.
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45. |
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46. |
- Michel, Mathieu, et al.
(författare)
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Load-Balanced Data Collection through Opportunistic Routing
- 2015. - 9
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Ingår i: 2015 International Conference on Distributed Computing in Sensor Systems. - 9781479988563 ; , s. 62-70
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Konferensbidrag (refereegranskat)abstract
- Wireless Sensor Networks performing low-power data collection often suffer from uneven load distribution among nodes. Nodes close to the network root typically face a higher load, see their battery deplete first, and become prematurely unable to operate (both sensing and relaying other nodes' data). We argue that opportunistic routing, by making forwarding decision on a per-packet basis and at the receiver rather than the sender, has the potential to better balance the load across nodes. We extend ORPL, an opportunistic version of the standard routing protocol RPL, with support for load-balancing. In our protocol, ORPL-LB, nodes continuously adapt their wake-up interval in order to adjust their availability and attain a deployment-specific target duty cycle. We implement our protocol in Contikiand present our experimental validation in Indriya, a 93-nodestestbed. Our results show that ORPL-LB reduces significantly(by approximately 40%) the worst node's duty cycle, with little or no impact on packet delivery ratio and latency.
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47. |
- Nazari, N., et al.
(författare)
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Multi-level Binarized LSTM in EEG Classification for Wearable Devices
- 2020
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Ingår i: Proceedings - 2020 28th Euromicro International Conference on Parallel, Distributed and Network-Based Processing, PDP 2020. - : Institute of Electrical and Electronics Engineers Inc.. - 9781728165820 ; , s. 175-181
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Konferensbidrag (refereegranskat)abstract
- Long Short-Term Memory (LSTM) is widely used in various sequential applications. Complex LSTMs could be hardly deployed on wearable and resourced-limited devices due to the huge amount of computations and memory requirements. Binary LSTMs are introduced to cope with this problem, however, they lead to significant accuracy loss in some applications such as EEG classification which is essential to be deployed in wearable devices. In this paper, we propose an efficient multi-level binarized LSTM which has significantly reduced computations whereas ensuring an accuracy pretty close to full precision LSTM. By deploying 5-level binarized weights and inputs, our method reduces area and delay of MAC operation about 31× and 27× in 65nm technology, respectively with less than 0.01% accuracy loss. In contrast to many compute-intensive deep-learning approaches, the proposed algorithm is lightweight, and therefore, brings performance efficiency with accurate LSTM-based EEG classification to realtime wearable devices.
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48. |
- Nguyen, Dang Nhan, 1983, et al.
(författare)
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Brief Announcement: ParMarkSplit: A Parallel Mark-Split Garbage Collector Based on a Lock-Free Skip-List
- 2013
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Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - : Springer. - 1611-3349 .- 0302-9743. - 9783642415265 ; 8205, s. 557-558
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Konferensbidrag (refereegranskat)abstract
- This brief announcement provides a high level overview of a parallel mark-split garbage collector. Our parallel design introduces and makes use of an efficient concurrency control mechanism based on a lock-free skip-list design for handling the list of free memory intervals. We have implemented the parallel mark-split garbage collector in OpenJDK HotSpot as a parallel and concurrent garbage collector for the old generation. We experimentally evaluate the collector and compare it with the default concurrent mark-sweep garbage collector in OpenJDK HotSpot, using the DaCapo benchmarks.
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49. |
- Nguyen, Dang Nhan, 1983, et al.
(författare)
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ParMarkSplit : A Parallel Mark-Split Garbage Collector Based on a Lock-Free Skip-List
- 2014
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Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - Cham : Springer. - 1611-3349 .- 0302-9743. - 9783319144719 - 9783319144726 ; 8878, s. 372-387
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Konferensbidrag (refereegranskat)abstract
- Mark-split is a garbage collection algorithm that combines advantages of both the mark-sweep and the copying collection algorithms. In this paper, we present a parallel mark-split garbage collector (GC). Our parallel design introduces and makes use of an efficient concurrency control mechanism for handling the list of free memory intervals. This mechanism is based on a lock-free skip-list design which supports an extended set of operations. Beside basic operations, it can perform a composite one that can search and remove and also insert two elements atomically. We have implemented the parallel mark-split GC in OpenJDK’s HotSpot virtual machine. We experimentally evaluate our collector and compare it with the default concurrent mark-sweep GC in HotSpot, using the DaCapo benchmarks, on two contemporary multiprocessor systems; one has 12 Intel Nehalem cores with HyperThreading and the other has 48 AMD Bulldozer cores. The evaluation shows that our parallel mark-split keeps the characteristics of the sequential mark-split, that it performs better than the concurrent mark-sweep in applications that have low live/garbage ratio, and have live objects locating contiguously, therefore being marked consecutively. Our parallel mark-split performs significantly better than a trivial parallelization based on locks in terms of both collection time and scalability.
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50. |
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Reliable Smart Contracts
- 2020
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Proceedings (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- The rise of smart contracts executed on blockchain and other distributed ledger technologies enabled trustless yet decentralised computation. Various applications take advantage of this computational model, including enforced financial contracts, self-sovereign identity and voting. But smart contracts are nothing but software running on a blockchain, with risks of malfunction due to bugs in the code. Compared to traditional systems, there is an additional risk in that erroneous computation or transactions triggered by a smart contract cannot be easily rolled back due to the immutability of the underlying execution model. This ISoLA track brings together a number of experts in the field of smart contract reliability and verification to discuss the state-of-the-art in smart contract dependability and discuss research challenges and future directions.
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