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  • 301.
    Horga, Adrian
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Chattopadhyay, Sudipta
    Singapore University of Technology and Design (SUTD), Information Systems Technology and Design (ISTD), Singapore.
    Eles, Petru Ion
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Measurement Based Execution Time Analysis of GPGPU Programs via SE+GA2018Conference paper (Refereed)
    Abstract [en]

    Understanding the execution time is critical for embedded, real-time applications. Worst-case execution time (WCET) is an important metric to check the real-time constraints imposed on embedded applications. For complex execution platforms, such as graphics processing units (GPUs), analysis of WCET imposes great challenges due to the complex characteristics of GPU architecture as well as GPU program semantics. In this paper, we propose GDivAn, a measurement-based WCET analysis tool for arbitrary GPU kernels. GDivAn systematically combines the strength of symbolic execution (SE) and genetic algorithm (GA) to maintain both the scalability and the effectiveness of the analysis process. Our evaluation with several open-source GPU kernels reveals the efficiency of GDivAn.

  • 302.
    Horga, Adrian
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Chattopadhyay, Sudipta
    Centre for IT-Security, Privacy and Accountability, Saarland University, Germany.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Systematic detection of memory related performance bottlenecks in GPGPU programs2016In: Journal of systems architecture, ISSN 1383-7621, E-ISSN 1873-6165, Vol. 71, p. 73-87Article in journal (Refereed)
    Abstract [en]

    Graphics processing units (GPUs) pose an attractive choice for designing high-performance and energy-efficient software systems. This is because GPUs are capable of executing massively parallel applications. However, the performance of GPUs is limited by the contention in memory subsystems, often resulting in substantial delays and effectively reducing the parallelism. In this paper, we propose GRAB, an automated debugger to aid the development of efficient GPU kernels. GRAB systematically detects, classifies and discovers the root causes of memory-performance bottlenecks in GPUs. We have implemented GRAB and evaluated it with several open-source GPU kernels, including two real-life case studies. We show the usage of GRAB through improvement of GPU kernels on a real NVIDIA Tegra K1 hardware – a widely used GPU for mobile and handheld devices. The guidance obtained from GRAB leads to an overall improvement of up to 64%.

  • 303.
    Hu, X. Sharon
    et al.
    Univ Notre Dame, IN 46556 USA.
    Ernst, Rolf
    Tech Univ Brunswick, ME USA.
    Eles, Petru Ion
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Heiser, Gernot
    Univ New South Wales Sydney, Australia.
    Keutzer, Kurt
    Univ Calif Berkeley, CA 94720 USA.
    Kim, Daehyun
    Samsung, South Korea.
    Tohdo, Tetsuya
    DENSO CORP, Japan.
    Machine Learning for Embedded Systems: Hype or Lasting Impact? A Panel at ESWEEK 20172018In: IEEE design & test, ISSN 2168-2356, E-ISSN 2168-2364, Vol. 35, no 6, p. 86-93Article in journal (Other academic)
    Abstract [en]

    n/a

  • 304.
    Hultman, Tim
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Signal-Aware Route Planning2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Modern vehicles have an increasing number of advanced features requiring network coverage in order to function properly. In order to facilitate the requirements of such features and allow more advanced applications, we consider the possibility of planning routes that take signal strength into consideration. Previous work have shown the relationship between TCP throughput/goodput and signal strength. In this thesis signal-aware route planning is presented, implemented, and validated. Crowd-sourced map and signal data (3G) from two sources is used for building a signal coverage map. The signal and map data is validated in a field experiment, where routes were travelled while measuring the signal strength. The field experiment showed gains in signal characteristics when deviating from the shortest possible path. The average signal strength increased by 11 dBm between algorithms and the shortest possible path. Lastly, routes were planned for all possible sources and destinations in a given urban area. The results of this calculation confirms the patterns found in the field experiment.

  • 305.
    Hultman, Tim
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Boudjadar, Abdeldjalil
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Asplund, Mikael
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Connectivity-optimal Shortest Paths Using Crowdsourced Data2016In: 2016 IEEE International Conference on Pervasive Computing and Communication Workshops (PerCom Workshops), IEEE Computer Society, 2016, p. 1-6Conference paper (Refereed)
    Abstract [en]

    With the increasing dependency of ubiquitous connectivity for applications ranging from multimedia entertainment to intelligent transportation systems, having good signal coverage becomes vital. Therefore, route planners and navigation systems should take into account not only the physical distance, but also the characteristics and availability of the cellular network on the potential routes. In this paper we present a route planning tool that finds the connectivity-aware shortest paths based on crowdsourced data from OpenStreetMap and OpenSignal. The tool calculates optimal paths and allows physical distance tobe traded against signal quality. The evaluation shows that a 15% increase of the physical path length can achieve an 8.7dBm improvement of worst-case signal strength.

  • 306.
    Hussain, Sajjad
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Investigating Architecture Description Languages (ADLs) A Systematic Literature Review2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Context: Over the last two decades, software architecture has introduced a new trend insoftware development. This new trend has completely changed the normal methods andpractices of software engineering. The focus has become the architectural elements ratherthan code and sub-routines. Architecture description languages (ADLs) have been proposedfor this kind of architecture based software development. There are a number of differentADLs both in academia and industry; they are not totally adopted by the software engineeringcommunity, but they are not avoided either. In this research work, an investigation has beenperformed based on the ADLs evaluation in practice.

    Objectives: The main aim of this study is to investigate evaluation of ADLs in academia andindustry. To explore the benefits and drawbacks of ADLs in practice. The study also exploresthe different quality factors improved by ADLs. Further different methods used to buildarchitecture with ADLs and then how to use architecture described with an ADL in softwaredevelopment and maintenance have also been reported.

    Methods: This research study has been carried out using the systematic literature reviewmethod. The systematic literature review follows the guidelines suggested by Kitchenham[21].

    Results: This research review has resulted in total of 102 different ADLs. It has been foundthat out of the 102 different ADLs, 69 ADLs have been evaluated in academia and only 33ADLs have been evaluated in industry. ADLs have also been classified based on theirindustrial and academia evaluation. There are total 31 different benefits and 19 differentdrawbacks of ADLs have been identified. This review also extracted 20 different qualityfactors from literature that are improved by using ADLs in practice. Further 13 differentmethods used to build architecture with ADL have also been reported. Finally 9 differentmethods of ADLs used in software development and maintenance have been identified.

    Conclusions: The Large number of ADLs with little evaluation in industry suggests thatmore work needs to be done in order to improve ADLs evaluation in practice. ADLs providemore benefits compared to their drawbacks which suggests that ADLs can be very beneficial.Knowledge gained during this research study, suggests that ADLs are mostly unrecognized.More awareness about ADLs should be provided in education and practice.

  • 307.
    Hussain, Shahbaz
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Finding Correlation and Predicting System Behavior in Large IT Infrastructure2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Modern IT development infrastructure has a large number of components that must be monitored, for instance servers and network components. Various system-metrics (build time, CPU utilization, queries time etc.) are gathered to monitor system performance. In practice, it is extremely difficult for a system administrator to observe a correlation between several systemmetrics and predict a target system-metric based on highly correlated system-metrics without machine learning support.

    The experiments were performed on development logs at Ericsson. There were many system-metrics available in the system. Our goal is use machine learning techniques to find correlation between buildtime and other system-metrics and predict its trends in the future.

  • 308.
    Hyun Kim, Jin
    et al.
    University of Penn, PA 19104 USA.
    Kang, Inhye
    University of Seoul, South Korea.
    Kang, Sungwon
    Korea Adv Institute Science and Technology, South Korea.
    Boudjadar, Abdeldjalil
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    A Process Algebraic Approach to Resource-Parameterized Timing Analysis of Automotive Software Architectures2016In: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, Vol. 12, no 2, p. 655-671Article in journal (Refereed)
    Abstract [en]

    Modern automotive software components are often first developed by different suppliers and then integrated under limited resources by a manufacturer. The integration of software components under various resource configurations is prone to timing errors because the components are resources independently designed by the supplier and viewed by the manufacturer as black boxes during the integration stage, so that imposing resource constraints/requirements on their behavior is a challenge. This paper introduces an engineering awareness environment for the analysis of automotive systems with respect to two perspectives: 1) time-aware design models that correspond to the supplier perspective; and 2) resource-aware design models imposed by the manufacturer during integration. To this end, first we propose two timed behavioral models, a time-constrained model (TcM) and a resource-constrained model (RcM) that are extended from a functional model (FM). A timing analysis of applications can hence be conducted incrementally by adopting the separation of concerns principle coming from the model-driven architectures (MDAs). Second, given a basic application component description of AUTomotive Open System Architecture with timing properties, we specify how to define the behavior of the basic components as process terms using a process algebra, algebra of communicating shared resources with value passing (ACSR-VP), in order to exploit the description capability of the language for both timing aspects and resource-constrained aspects of a system. As a result, a timed behavioral model of a system can be seamlessly refined by various resource configurations, and both platform-independent and platform-dependent timing properties of real-time systems can be analyzed in a consistent and efficient manner.

  • 309.
    Härlin, Magnus
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Testing and Gherkin in agile projects2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Testing in agile software development is important to ensure that the rightproduct is being developed. Is it possible to include everyone in agilesoftware development by using a business readable DSL and also createtest cases based directly on that DSL?Observations, interviews, a study of literature, third degree collectedartifacts and an implementation has been performed to analyse the processof introducing Gherkin as a tool in agile software development projects.The process of performing and conducting tests has been examined at Accedoto understand how Gherkin together with CucumberJS can be usedin projects, with the purpose of increasing collaboration between dierentroles and create a ubiquitous way of referring to the same piece of softwarewithout the need to specifying implementation details.To include the entire project team in the whole process of developingsoftware is essential for a usage of Gherkin to be successful. Since thepurpose is that everyone should be able to contribute as well as understandthe progress of development in projects and share an agreement on whatis being developed. A business readable DSL provides a uniform formatto specifying tasks causing the internal communication to be improved inprojects.

  • 310.
    Hätty, Niklas
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Representing attacks in a cyber range2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Trained security experts can be a mitigating factor to sophisticated cyberattacks that aim to violate the confidentiality, integrity, and availability of information. Reproducible sessions in a safe training environment is an effective way of increasing the excellence of security experts. One approach to achieving this is by using cyber ranges, which essentially is a set of hardware nodes that can virtually represent a large organization or system. The Swedish Defense Research Agency (FOI) develops and maintains a fully functioning cyber range and has the ability to automatically deploy sophisticated attacks against organizations and systems represented in this cyber range through a system called SVED.

    In this thesis, the capability to deploy different types of cyberattacks through SVED against virtual organizations in a cyber range, CRATE, is investigated. This is done by building a dataset of publicly disclosed security incidents from a database and attempting to represent each of them in SVED, and subsequently instantiating these attack representations against organizations in CRATE.

    The results show that the prevalence of at least one CVE-entry (Common Vulnerabilities and Exposures) in the incident description is a key factor to be able to represent an attack in SVED. When such an entry does exist, SVED is likely able to implement a representation of the attack. However, for certain type of attacks a CVE-entry is not enough to determine how an attack was carried out, which is why some attacks are harder to implement in SVED. This was the case for Denial of Service (DoS) attacks, which are too reliant on infrastructure rather than one or more vulnerabilities, and SQL injections, which are more reliant on the implementation of database access.

    Finally, CRATE is able to handle almost all attacks implemented in SVED, given that the correct vulnerable application software is installed on at least one machine in one of the organizations in CRATE.

  • 311.
    Högberg, Marcus
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    A Cross-platform Picture Transfer Protocol for Linux-based Camera2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Universal Serial Bus, USB, is widely used for connecting peripheral devices to a computer. Through the years devices that use USB has evolved and more and more complicated communication protocols have been developed using the USB standard. There are many different ways to set up communication between a USB device and a host computer. The USB standard does not include any security and this poses risks when designing communication over such a connection.

    This thesis investigates how a USB-based picture transfer protocol can be designed between a small camera running embedded Linux and a host computer. The USB functionality in Windows and Mac OS/X operating systems are investigated. Solutions to create a secure USB communication are also investigated. One of three the methods of creating a USB connection with a USB device running embedded Linux are chosen based on the investigations. A protocol is then designed and an implementation developed. The protocol designed in the thesis uses existing USB functionality in the host computer operating systems Windows and Mac OS/X.

    The designed protocol is evaluated for performance and security. The evaluation is made on an evaluation platform for the camera. The transfer speed of the protocol is measured to around 18 MB/s in an ideal environment. The designed protocol could be improved by using one of the security methods found in the investigations.

  • 312.
    Islam, Md. Zahidul
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    A Cloud Based Platform for Big Data Science2014Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    With the advent of cloud computing, resizable scalable infrastructures for data processing is now available to everyone. Software platforms and frameworks that support data intensive distributed applications such as Amazon Web Services and Apache Hadoop enable users to the necessary tools and infrastructure to work with thousands of scalable computers and process terabytes of data. However writing scalable applications that are run on top of these distributed frameworks is still a demanding and challenging task. The thesis aimed to advance the core scientific and technological means of managing, analyzing, visualizing, and extracting useful information from large data sets, collectively known as “big data”. The term “big-data” in this thesis refers to large, diverse, complex, longitudinal and/or distributed data sets generated from instruments, sensors, internet transactions, email, social networks, twitter streams, and/or all digital sources available today and in the future. We introduced architectures and concepts for implementing a cloud-based infrastructure for analyzing large volume of semi-structured and unstructured data. We built and evaluated an application prototype for collecting, organizing, processing, visualizing and analyzing data from the retail industry gathered from indoor navigation systems and social networks (Twitter, Facebook etc). Our finding was that developing large scale data analysis platform is often quite complex when there is an expectation that the processed data will grow continuously in future. The architecture varies depend on requirements. If we want to make a data warehouse and analyze the data afterwards (batch processing) the best choices will be Hadoop clusters and Pig or Hive. This architecture has been proven in Facebook and Yahoo for years. On the other hand, if the application involves real-time data analytics then the recommendation will be Hadoop clusters with Storm which has been successfully used in Twitter. After evaluating the developed prototype we introduced a new architecture which will be able to handle large scale batch and real-time data. We also proposed an upgrade of the existing prototype to handle real-time indoor navigation data.

  • 313.
    Izosimov, Viacheslav
    et al.
    Embedded Intelligent Solutions (EIS) by Semcon AB, Linköping, Sweden.
    Di Guglielmo, Giuseppe
    University of Verona, Italy.
    Lora, Michele
    University of Verona, Italy.
    Pravadelli, Graziano
    University of Verona, Italy.
    Fummi, Franco
    University of Verona, Italy.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Fujita, Masahiro
    University of Tokyo, Japan; Japan Scence and Technology Agency, Japan.
    Time-Constraint-Aware Optimization of Assertions in Embedded Software2012In: Journal of electronic testing, ISSN 0923-8174, E-ISSN 1573-0727, Vol. 28, no 4, p. 469-486Article in journal (Refereed)
    Abstract [en]

    Technology shrinking and sensitization have led to more and more transient faults in embedded systems. Transient faults are intermittent and non-predictable faults caused by external events, such as energetic particles striking the circuits. These faults do not cause permanent damages, but may affect the running applications. One way to ensure the correct execution of these embedded applications is to keep debugging and testing even after shipping of the systems, complemented with recovery/restart options. In this context, the executable assertions that have been widely used in the development process for design validation can be deployed again in the final product. In this way, the application will use the assertion to monitor itself under the actual execution and will not allow erroneous out-of-the-specification behavior to manifest themselves. This kind of software-level fault tolerance may represent a viable solution to the problem of developing commercial off-the-shelf embedded systems with dependability requirements. But software-level fault tolerance comes at a computational cost, which may affect time-constrained applications. Thus, the executable assertions shall be introduced at the best possible points in the application code, in order to satisfy timing constraints, and to maximize the error detection efficiency. We present an approach for optimization of executable assertion placement in time-constrained embedded applications for the detection of transient faults. In this work, assertions have different characteristics such as tightness, i.e., error coverage, and performance degradation. Taking into account these properties, we have developed an optimization methodology, which identifies candidate locations for assertions and selects a set of optimal assertions with the highest tightness at the lowest performance degradation. The set of selected assertions is guaranteed to respect the real-time deadlines of the embedded application. Experimental results have shown the effectiveness of the proposed approach, which provides the designer with a flexible infrastructure for the analysis of time-constrained embedded applications and transient-fault-oriented executable assertions.

  • 314.
    Jain, Rahul
    et al.
    Indian Inst Technol, India.
    Nayak, Priyam
    Indian Inst Technol, India.
    Rahul, A. S.
    Indian Inst Technol, India.
    Dalve, Pravin
    Indian Inst Technol, India.
    Moudgalya, Kannan M.
    Indian Inst Technol, India.
    Naren, P. R.
    SASTRA Deemed Univ, India.
    Wagner, Daniel
    Independent Researcher, Manaus, Brazil.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Implementation of a Property Database and Thermodynamic Calculations in OpenModelica for Chemical Process Simulation2019In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 58, no 18, p. 7551-7560Article in journal (Refereed)
    Abstract [en]

    An attempt has been made to enhance the thermodynamic capability of the general purpose modeling and simulation environment OpenModelica. The property database ChemSep and the thermodynamic algorithms of DWSIM are made available in OpenModelica. The following three approaches, listed in the order of increasing computational efficiency, are attempted in this work: Python-C API, socket programming, and a native port. The most efficient method of native port is adopted to make available NRTL, Peng-Robinson, UNIFAC, and UNIQUAC algorithms in OpenModelica. Through several examples, OpenModelica results are compared with Aspen Plus, indicating a good match in all cases. This work is released as an open source to enhance the collaboration among chemical engineers.

  • 315.
    Jensen, Henrik
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Industry Foundation Classes: A study of its requested use in Configura2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Configura Sverige AB is developing the software solutions Configura and CET Designer for companies dealing with highly configurable and complex products that also require space planning. The aim is to simplify the selling process. Configura Sverige AB has received requests from their customers to be able to read and write files according to an ISO standard called Industry Foundation Classes (IFC). IFC is an open international standard within Building Information Modeling (BIM) to exchange data between different software applications used for projects in the building industry and facility management. To assist Configura Sverige AB in a decision on how to further proceed, questions why users request IFC, how they need to work with IFC, and about possible workflows with IFC are considered in this thesis. To answer the questions, an interpretive case study method was used to view the questions from different perspectives. A qualitative approach was used to collect and analyze data, involving for example a survey among users requesting IFC and input from two different contractors requesting IFC files from these users. The results show that users have been requested by architects and contractors to supply IFC files, and a conclusion is that demands on the use of BIM and IFC within the public sector in certain countries is a major reason to these requests. The results has much focus on import and export of IFC files and on possible workflows using IFC files. With IFC files, users may be a part of a collaboration between several different disciplines within the building industry. Users need to base their work on other disciplines models, which in many cases will be the architect's IFC file. An IFC export shall only include the user's products, it will be up to another application to integrate these products in a coordination BIM. The IFC export will be used for interdisciplinary coordination, visualization and collision detection and it is important to use simple graphical representation of the products.

  • 316.
    Jiang, Ke
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Security-Driven Design of Real-Time Embedded Systems2015Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Real-time embedded systems (RTESs) have been widely used in modern society. And it is also very common to find them in safety and security critical applications, such as transportation and medical equipment. There are, usually, several constraints imposed on a RTES, for example, timing, resource, energy, and performance, which must be satisfied simultaneously. This makes the design of such systems a difficult problem.

    More recently, the security of RTESs emerges as a major design concern, as more and more attacks have been reported. However, RTES security, as a parameter to be considered during the design process, has been overlooked in the past. This thesis approaches the design of secure RTESs focusing on aspects that are particularly important in the context of RTES, such as communication confidentiality and side-channel attack resistance.

    Several techniques are presented in this thesis for designing secure RTESs, including hardware/software co-design techniques for communication confidentiality on distributed platforms, a global framework for secure multi-mode real-time systems, and a scheduling policy for thwarting differential power analysis attacks. 

    All the proposed solutions have been extensively evaluated in a large amount of experiments, including two real-life case studies, which demonstrate the efficiency of the presented techniques.

  • 317.
    Jiang, Ke
    et al.
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Batina, Lejla
    Institute for Computing and Information Sciences, Radboud University Nijmegen, The Netherlands.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Robustness Analysis of Real-Time Scheduling Against Differential Power Analysis Attacks2014In: IEEE Computer Society Annual Symposium on VLSI, IEEE Computer Society, 2014, p. 450-455Conference paper (Refereed)
    Abstract [en]

    Embedded systems (ESs) have been a prominent solution for enhancing system performance and reliability in recent years. ESs that are required to ensure functional correctness under timing constraints are referred to as real-time embedded systems (RTESs). With the emerging trend of utilizing RTESs in safety and reliability critical areas, security of RTESs, especially confidentiality of the communication, becomes of great importance. More recently, side-channel attacks (SCAs) posed serious threats to confidentiality protection mechanisms, namely, cryptographic algorithms. In this work, we present the first analytical framework for quantifying the influence of real-time scheduling policies on the robustness of secret keys against differential power analysis (DPA) attacks, one of the most popular type of SCAs. We validated the proposed concept on two representative scheduling algorithms, earliest deadline first scheduling (EDF) and rate-monotonic scheduling (RMS), via extensive experiments.

  • 318.
    Jiang, Ke
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Eles, Petru Ion
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Power-Aware Design Techniques of Secure Multimode Embedded Systems2016In: ACM Transactions on Embedded Computing Systems, ISSN 1539-9087, E-ISSN 1558-3465, Vol. 15, no 1, p. 6-Article in journal (Refereed)
    Abstract [en]

    Nowadays, embedded systems have been widely used in all types of application areas, some of which belong to the safety and reliability critical domains. The functional correctness and design robustness of the embedded systems involved in such domains are crucial for the safety of personal/enterprise property or even human lives. Thereby, a holistic design procedure that considers all the important design concerns is essential. In this article, we approach embedded systems design from an integral perspective. We consider not only the classic real-time and quality of service requirements, but also the emerging security and power efficiency demands. Modern embedded systems are not any more developed for a fixed purpose, but instead designed for undertaking various processing requests. This leads to the concept of multimode embedded systems, in which the number and nature of active tasks change during runtime. Under dynamic situations, providing high performance along with various design concerns becomes a really difficult problem. Therefore, we propose a novel power-aware secure embedded systems design framework that efficiently solves the problem of runtime quality optimization with security and power constraints. The efficiency of our proposed techniques are evaluated in extensive experiments.

  • 319.
    Jiang, Ke
    et al.
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    A Design Framework for Dynamic Embedded Systems with Security Constraints2013In: The 12th Swedish System-on-Chip Conference (SSoCC 2013), Ystad, Sweden, May 6-7, 2013 (not reviewed, not printed)., 2013Conference paper (Other academic)
  • 320.
    Jiang, Ke
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Optimization of Secure Embedded Systems with Dynamic Task Sets2013In: Design, Automation & Test in Europe (DATE 2013), IEEE , 2013, p. 1765-1770Conference paper (Refereed)
    Abstract [en]

    In this paper, we approach embedded systems design from a new angle that considers not only quality of service but also security as part of the design process. Moreover, we also take into consideration the dynamic aspect of modern embedded systems in which the number and nature of active tasks are variable during run-time. In this context, providing both high quality of service and guaranteeing the required level of security becomes a difficult problem. Therefore, we propose a novel secure embedded systems design framework that efficiently solves the problem of run-time quality optimization with security constraints. Experiments demonstrate the efficiency of our proposed techniques.

  • 321.
    Jiang, Ke
    et al.
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Performance Comparison of Simulated Annealing and Tabu Search on Block Cipher Optimization in Distributed Embedded Systems2011In: The 11th Swedish System-on-Chip Conference, Varberg, Sweden, May 2-3, 2011, 2011Conference paper (Other academic)
    Abstract [en]

    In this paper, we consider distributed embedded systems in which privacy or confidentiality of the internal communication is critical, and present an approach to optimize cryptographic algorithms under strict timing constraints. We have developed a technique searching for the best system-affordable cryptographic protection for the messages transmitted over the internal communication bus. On account of the complexity of the problem, finding the optimal solution is only feasible for very small systems. Therefore, we formulate the technique in two efficient metaheuristics, and study their performance from extensive experiments.

  • 322.
    Jiang, Ke
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Chattopadhyay, Sudipta
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Batina, Lejla
    Radboud University Nijmegen, The Netherlands.
    SPARTA: A scheduling policy for thwarting differential power analysis attacks2016In: 2016 21ST ASIA AND SOUTH PACIFIC DESIGN AUTOMATION CONFERENCE (ASP-DAC), IEEE Press, 2016, p. 667-672Conference paper (Refereed)
    Abstract [en]

    Embedded systems (ESs) have been widely used in various application domains. It is very important to design ESs that guarantee functional correctness of the system under strict timing constraints. Such systems are known as the real-time embedded systems (RTESs). More recently, RTESs started to be utilized in safety and reliability critical areas, which made the overlooked security issues, especially confidentiality of the communication, a serious problem. Differential power analysis attacks (DPAs) pose serious threats to confidentiality protection mechanisms, i.e., implementations of cryptographic algorithms, on embedded platforms. In this work, we present a scheduling policy, SPARTA, that thwarts DPAs. Theoretical guarantees and preliminary experimental results are presented to demonstrate the efficiency of the SPARTA scheduler.

  • 323.
    Jiang, Ke
    et al.
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Lifa, Adrian Alin
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Jiang, Wei
    University of Electronic Science and Technology of China, Chengdu.
    Energy-Aware Design of Secure Multi-Mode Real-Time Embedded Systems with FPGA Co-Processors2013In: Proceedings of the 21st International conference on Real-Time Networks and Systems / [ed] Michel Auguin, Robert de Simone, Robert Davis, Emmanuel Grolleau, New York: Association for Computing Machinery (ACM), 2013, p. 109-118Conference paper (Refereed)
    Abstract [en]

    We approach the emerging area of energy efficient, secure real-time embedded systems design. Many modern embedded systems have to fulfill strict security constraints and are often required to meet stringent deadlines in different operation modes, where the number and nature of active tasks vary (dynamic task sets). In this context, the use of dynamic voltage/frequency scaling (DVFS) techniques and onboard field-programmable gate array (FPGA) co-processors offer new dimensions for energy savings and performance enhancement. We propose a novel design framework that provides the best security protection consuming the minimal energy for all operation modes of a system. Extensive experiments demonstrate the efficiency of our techniques.

  • 324.
    Jiang, Wei
    et al.
    School of Computer Science and Technology, University of Electronic Science and Technology of China.
    Jiang, Ke
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Ma, Yue
    School of Computer Science and Technology, University of Electronic Science and Technology of China.
    Resource Allocation of Security-Critical Tasks with Statistically Guaranteed Energy Constraint2012In: International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA 2012), Seoul, Korea, August 19-22, 2012., IEEE , 2012, p. 330-339Conference paper (Other academic)
    Abstract [en]

    In this paper, we are interested in resourceallocation for energy constrained and security-criticalembedded systems. Tasks in such systems need to besuccessfully executed under certain energy budget and berobust against serious security threatens. Different to formerenergy minimal scheduling problem, we introduce a newoptimization problem for a set of tasks with energyconstraint and multiple security choices. We present adynamic programming based approximation algorithm tominimize the security risk of the system while statisticallyguaranteeing energy consumption constraints for givenenergy slack ratio. The proposed algorithm is very efficientin both time and space dimensions, and achieves goodsolutions. Extensive simulations demonstrate the superiorityof our algorithm over other approaches.

  • 325.
    Jiang, Wei
    et al.
    School of Computer Science and Engineering, University of Electronic Science and Technology of China, China School of Information and Software Engineering, University of Electronic Science and Technology of China, China .
    Jiang, Ke
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Zhang, Xia
    School of Information and Software Engineering, University of Electronic Science and Technology of China, China .
    Ma, Yue
    Department of Computer Science and Engineering, University of Notre Dame, United States .
    Energy Aware Real-Time Scheduling Policy with Guaranteed Security Protection2014In: 2014 19TH ASIA AND SOUTH PACIFIC DESIGN AUTOMATION CONFERENCE (ASP-DAC), IEEE conference proceedings, 2014, p. 317-322Conference paper (Refereed)
    Abstract [en]

    In this work, we address the emerging scheduling problem existed in the design of secure and energy-efficient real-time embedded systems. The objective is to minimize the energy consumption subject to security and schedulability constraints. Due to the complexity of the problem, we propose a dynamic programming based approximation approach to find the near-optimal solutions with respect to predefined security constraint. The proposed technique has polynomial time complexity which is about half of traditional approximation approaches. The efficiency of our algorithm is validated by extensive experiments.

  • 326.
    Jiang, Wei
    et al.
    University of Elect Science and Technology China, Peoples R China.
    Jiang, Ke
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Zhang, Xia
    University of Texas Dallas, TX 75230 USA.
    Ma, Yue
    University of Notre Dame, IN 46556 USA.
    Energy Optimization of Security-Critical Real-Time Applications with Guaranteed Security Protection2015In: Journal of systems architecture, ISSN 1383-7621, E-ISSN 1873-6165, Vol. 61, no 7, p. 282-292Article in journal (Refereed)
    Abstract [en]

    Designing energy-efficient applications has become of critical importance for embedded systems, especially for battery-powered systems. Additionally, the emerging requirements on both security and real-time make it much more difficult to produce ideal solutions. In this work, we address the emerging scheduling problem existed in the design of secure and energy-efficient real-time embedded systems. The objective is to minimize the system energy consumption subject to security and schedulability constraints. Due to the complexity of the problem, we propose a dynamic programming based approximation approach to find efficient solutions under given constraints. The proposed technique has polynomial time complexity which is half of existing approximation approaches. The efficiency of our algorithm is validated by extensive experiments and a real-life case study. Comparing with other approaches, the proposed approach achieves energy-saving up to 37.6% without violating the real-time and security constraints of the system.

  • 327.
    Jianqiang, Cheng
    et al.
    Univ. Paris Sud, France.
    Kosuch, Stefanie
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Lisser, Abdel
    Univ. Paris Sud, France.
    Stochastic Shortest Path Problem with Uncertain Delays2012In: Proceedings of the 1st International Conference on Operations Research and Enterprise Systems (ICORES-2012 / [ed] Carlos J. Luz, Fernando Valente, 2012, p. 256-264Conference paper (Other academic)
  • 328.
    Johansson, Marcus
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Generating SkePU Code from Automatically Detected Algorithmic Patterns in C Source Programs2016Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Modern heterogeneous multi-core architectures containing one or multiple GPU de- vices require expert knowledge in order to be fully utilized through parallelization by the programmer. Software written for one hardware setup might not easily be portable to work as efficiently on a differing architecture. Automatic parallelization of sequential C code to make efficient use of such architecture in an extensible man- ner would facilitate the porting of legacy code and provide a non-expert programmer with a tool granting access to modern hardware architectures.

    We present an early prototype of such an extensible tool-chain and attempt to apply it on domain-specific C source code. It is based on a generic tool for hierarchical pattern matching in C source codes, where the user can define own patterns and recognition rules, and a code generation back-end. We show how it, combined with existing libraries, can be used to automatically port sequential legacy code to different multicore architectures, such as multicore CPUs and GPUs. Our tool is an attempt to do this and yields valid parallelized code, but fails to reach speedup for most implemented patterns. The tool is applied on one test case, a legacy ODE implementation in C, with similar results. A reason for slowdown is discussed in the concluding section.

  • 329.
    Johansson, Viktor
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Vallén, Alexander
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Random testing with sanitizers to detect concurrency bugs in embedded avionics software2018Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Fuzz testing is a random testing technique that is effective at finding bugs in large software programs and protocols. We investigate if the technology can be used to find bugs in multi-threaded applications by fuzzing a real-time embedded avionics platform together with a tool specialized at finding data races between multiple threads. We choose to fuzz an API (available to applications executing on top) of the platform. This thesis evaluates aspects of integrating a fuzzing program, AFL and a sanitizer, ThreadSanitizer with an embedded system. We investigate the modifications needed to create a correct run-time environment for the system, including supplying test data in a safe manner and we discuss hardware dependencies. We present a setup where we show that the tools can be used to find planted data races, however slowdown introduced by the tools is significant and the fuzzer only managed to find very simple planted data races during the test runs. Our findings also indicate what appear to be conflicts in instrumentation between the fuzzer and the sanitizer.  

  • 330.
    Jonsson, Alexander
    Linköping University, Department of Computer and Information Science, Software and Systems.
    The Usefulness of Programming Languages Beyond Java2019Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Beyond Java, new programming languages running on the Java virtual machine (JVM) have been developed, such as Kotlin, Scala, JRuby and Clojure amongst others. Since all those languages compile to Java bytecode, they should theoretically be able to be used together in a project. This paper investigates if it is possible and what benefits it gives using those programming languages together in a project. The languages chosen to be used together were Jython, Scala and Kotlin.

    An experiment was conducted where in a single project, each programming language was assigned a problem to be solved. The experiment was then conducted in two iterations where in each iteration, the problems to be solved was assigned to a different programming language.

    From the experiment it was shown that using those languages together in a project was possible but resulted in some complications needed to be solved. It was also shown that the following division amongst the languages worked best in the present use case: Jython for graphical handling, Scala for calculating and computing and Kotlin for data-handling.

  • 331.
    Jonsson, Anders
    et al.
    University of Pompeu Fabra, Spain .
    Jonsson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Lööw, Tomas
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Limitations of acyclic causal graphs for planning2014In: Artificial Intelligence, ISSN 0004-3702, E-ISSN 1872-7921, Vol. 210, p. 36-55Article in journal (Refereed)
    Abstract [en]

    Causal graphs are widely used in planning to capture the internal structure of planning instances. Researchers have paid special attention to the subclass of planning instances with acyclic causal graphs, which in the past have been exploited to generate hierarchical plans, to compute heuristics, and to identify classes of planning instances that are easy to solve. This naturally raises the question of whether planning is easier when the causal graph is acyclic. In this article we show that the answer to this question is no, proving that in the worst case, the problem of plan existence is PSPACE-complete even when the causal graph is acyclic. Since the variables of the planning instances in our reduction are propositional, this result applies to STRIPS planning with negative preconditions. We show that the reduction still holds if we restrict actions to have at most two preconditions. Having established that planning is hard for acyclic causal graphs, we study two subclasses of planning instances with acyclic causal graphs. One such subclass is described by propositional variables that are either irreversible or symmetrically reversible. Another subclass is described by variables with strongly connected domain transition graphs. In both cases, plan existence is bounded away from PSPACE, but in the latter case, the problem of bounded plan existence is hard, implying that optimal planning is significantly harder than satisficing planning for this class.

  • 332.
    Jonsson, Anders
    et al.
    Universitat Pompeu Fabra, Barcelona, Spain.
    Jonsson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Lööw, Tomas
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    When Acyclicity is not Enough: Limitations of the Causal Graph2013In: Proceedings of the Twenty-Third International Conference on Automated Planning and Scheduling, AAAI Press, 2013, p. 117-125Conference paper (Refereed)
    Abstract [en]

    Causal graphs are widely used in planning to capture the internal  structure of planning instances. In the past, causal graphs have been exploited to generate hierarchical plans, to compute heuristics, and  to identify classes of planning instances that are easy to solve. It  is generally believed that planning is easier when the causal graph is acyclic. In this paper we show that this is not true in the worst  case, proving that the problem of plan existence is PSPACE-complete  even when the causal graph is acyclic. Since the variables of the  planning instances in our reduction are propositional, this result  applies to STRIPS planning with negative pre-conditions. Having  established that planning is hard for acyclic causal graphs, we study  a subclass of planning instances with acyclic causal graphs whose  variables have strongly connected domain transition graphs. For this  class, we show that plan existence is easy, but that bounded plan  existence is hard, implying that optimal planning is significantly  harder than satisficing planning for this class.

  • 333.
    Jonsson, Leif
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering. Ericsson AB, Sweden.
    Borg, Markus
    Lund University, Sweden.
    Broman, David
    KTH Royal Institute Technology, Sweden; University of Calif Berkeley, CA 94720 USA.
    Sandahl, Kristian
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Eldh, Sigrid
    Ericsson AB, Sweden.
    Runeson, Per
    Lund University, Sweden.
    Automated bug assignment: Ensemble-based machine learning in large scale industrial contexts2016In: Journal of Empirical Software Engineering, ISSN 1382-3256, E-ISSN 1573-7616, Vol. 21, no 4, p. 1533-1578Article in journal (Refereed)
    Abstract [en]

    Bug report assignment is an important part of software maintenance. In particular, incorrect assignments of bug reports to development teams can be very expensive in large software development projects. Several studies propose automating bug assignment techniques using machine learning in open source software contexts, but no study exists for large-scale proprietary projects in industry. The goal of this study is to evaluate automated bug assignment techniques that are based on machine learning classification. In particular, we study the state-of-the-art ensemble learner Stacked Generalization (SG) that combines several classifiers. We collect more than 50,000 bug reports from five development projects from two companies in different domains. We implement automated bug assignment and evaluate the performance in a set of controlled experiments. We show that SG scales to large scale industrial application and that it outperforms the use of individual classifiers for bug assignment, reaching prediction accuracies from 50 % to 89 % when large training sets are used. In addition, we show how old training data can decrease the prediction accuracy of bug assignment. We advice industry to use SG for bug assignment in proprietary contexts, using at least 2,000 bug reports for training. Finally, we highlight the importance of not solely relying on results from cross-validation when evaluating automated bug assignment.

  • 334.
    Jonsson, Leif
    et al.
    Linköping University, Department of Computer and Information Science, PELAB - Programming Environment Laboratory. Ericsson AB, Sweden.
    Broman, David
    KTH Royal Institute Technology, Sweden; University of Calif Berkeley, CA USA.
    Magnusson, Måns
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Science & Engineering.
    Sandahl, Kristian
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Villani, Mattias
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Eldh, Sigrid
    Ericsson AB, Sweden.
    Automatic Localization of Bugs to Faulty Components in Large Scale Software Systems using Bayesian Classification2016In: 2016 IEEE INTERNATIONAL CONFERENCE ON SOFTWARE QUALITY, RELIABILITY AND SECURITY (QRS 2016), IEEE , 2016, p. 425-432Conference paper (Refereed)
    Abstract [en]

    We suggest a Bayesian approach to the problem of reducing bug turnaround time in large software development organizations. Our approach is to use classification to predict where bugs are located in components. This classification is a form of automatic fault localization (AFL) at the component level. The approach only relies on historical bug reports and does not require detailed analysis of source code or detailed test runs. Our approach addresses two problems identified in user studies of AFL tools. The first problem concerns the trust in which the user can put in the results of the tool. The second problem concerns understanding how the results were computed. The proposed model quantifies the uncertainty in its predictions and all estimated model parameters. Additionally, the output of the model explains why a result was suggested. We evaluate the approach on more than 50000 bugs.

  • 335.
    Jonsson, Marcus
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Resource planning in a multi-project organization: A case study at Sanmina in Örnsköldsvik2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    To plan resources for multiple parallel projects is not an easy task, this has been experienced at a contract manufacturing company called Sanmina in Örnsköldsvik where this thesis work was performed. The aim of this thesis was to identify the problems with the resource planning process used today and to come up with a feasible solution. Different factors such as routines, formalization, time resources and opportunities for recuperation was also investigated to see if a solution to the identified problems could be used to decrease the amount of perceived psychological stress reactions. The thesis was divided into three phases, a pre-study phase, an implementation phase and an evaluation phase. In the pre-study phase a series of interviews was performed to get a better understanding of the current problems and this knowledge was then used to see if any existing tool for resource planning could be used. No tool was found that fulfilled all the requirements. In the implementation phase a new tool was developed with the requirements found in the pre-study. In the evaluation phase this new tool was tested in workshops on faked projects and then evaluated in the form of interviews with the attendees. The conclusion from this evaluation is that this new tool will in fact reduce the perceived amount of stress in the studied case at Sanmina in Örnsköldsvik. To be able to verify that this is the case for any multi-project organization a much more extensive evaluation would have to be done with real projects in different companies in different trades.

  • 336.
    Jonsson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Constants and finite unary relations in qualitative constraint reasoning2018In: Artificial Intelligence, ISSN 0004-3702, E-ISSN 1872-7921, Vol. 257Article in journal (Refereed)
    Abstract [en]

    Extending qualitative CSPs with the ability of restricting selected variables to finite sets of possible values has been proposed as an interesting research direction with important applications, cf. "Qualitative constraint satisfaction problems: an extended framework with landmarks" by Li, Liu, and Wang (2013) [48]. Previously presented complexity results for this kind of extended formalisms have typically focused on concrete examples and not on general principles. We propose three general methods. The first two methods are based on analysing the given CSP from a model-theoretical perspective, while the third method is based on directly analysing the growth of the representation of solutions. We exemplify the methods on temporal and spatial formalisms including Allens algebra and RCC-5. (C) 2017 Elsevier B.V. All rights reserved.

  • 337.
    Jonsson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Finite Unary Relations and Qualitative Constraint Satisfaction2016In: ECAI 2016: 22ND EUROPEAN CONFERENCE ON ARTIFICIAL INTELLIGENCE, IOS PRESS , 2016, Vol. 285, p. 37-45Conference paper (Refereed)
    Abstract [en]

    Extending qualitative CSPs with the ability of restricting selected variables to finite sets of possible values has been proposed as an important research direction with important applications. Complexity results for this kind of formalisms have appeared in the literature but they focus on concrete examples and not on general principles. We propose three general methods. The first two methods are based on analysing the given CSP from a model-theoretical perspective, while the third method is based on directly analysing the growth of the representation of solutions. We exemplify our methods on temporal and spatial formalisms including Allens algebra and RCC5.

  • 338.
    Jonsson, Peter
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Lagerkvist, Victor
    Technical University of Dresden, Germany.
    An initial study of time complexity in infinite-domain constraint satisfaction2017In: Artificial Intelligence, ISSN 0004-3702, E-ISSN 1872-7921, Vol. 245, p. 115-133Article in journal (Refereed)
    Abstract [en]

    The constraint satisfaction problem (CSP) is a widely studied problem with numerous applications in computer science and artificial intelligence. For infinite-domain CSPs, there are many results separating tractable and NP-hard cases while upper and lower bounds on the time complexity of hard cases are virtually unexplored, Hence, we initiate a study of the worst-case time complexity of such CSPs, We analyze backtracking algorithms and determine upper bounds on their time complexity. We present asymptotically faster algorithms based on enumeration techniques and we show that these algorithms are applicable to well-studied problems in, for instance, temporal reasoning. Finally, we prove non-trivial lower bounds applicable to many interesting CSPs, under the assumption that certain complexity-theoretic assumptions hold. The gap between upper and lower bounds is in many cases surprisingly small, which suggests that our upper bounds cannot be significantly improved. (C) 2017 Elsevier B.V. All rights reserved.

  • 339.
    Jonsson, Peter
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Lagerkvist, Victor
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Upper and Lower Bounds on the Time Complexity of Infinite-domain CSPs2015In: Principles and Practice of Constraint Programming - 21st International Conference, CP 2015, Cork, Ireland, August 31 - September 4, 2015, Proceedings / [ed] Pesant, Gilles, Springer Berlin/Heidelberg, 2015, Vol. 9255, p. 183-199Conference paper (Refereed)
    Abstract [en]

    The constraint satisfaction problem (CSP) is a widely studied problem with numerous applications in computer science. For infinite-domain CSPs, there are many results separating tractable and NP-hard cases while upper bounds on the time complexity of hard cases are virtually unexplored. Hence, we initiate a study of the worst-case time cmplexity of such CSPs. We analyse backtracking algorithms and show that they can be improved by exploiting sparsification. We present even faster algorithms based on enumerating finite structures. Last, we prove non-trivial lower bounds applicable to many interesting CSPs, under the assumption that the strong exponential-time hypothesis is true.

  • 340.
    Jonsson, Peter
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Lagerkvist, Victor
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nordh, Gustav
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Blowing Holes in Various Aspects of Computational Problems, with Applications to Constraint Satisfaction2013In: Principles and Practice of Constraint Programming / [ed] Christian Schulte, Springer Berlin/Heidelberg, 2013, p. 398-414Conference paper (Refereed)
    Abstract [en]

    We consider methods for constructing NP-intermediate problems under the assumption that P ≠ NP. We generalize Ladner’s original method for obtaining NP-intermediate problems by using parameters with various characteristics. In particular, this generalization allows us to obtain new insights concerning the complexity of CSP problems. We begin by fully characterizing the problems that admit NP-intermediate subproblems for a broad and natural class of parameterizations, and extend the result further such that structural CSP restrictions based on parameters that are hard to compute (such as tree-width) are covered. Hereby we generalize a result by Grohe on width parameters and NP-intermediate problems. For studying certain classes of problems, including CSPs parameterized by constraint languages, we consider more powerful parameterizations. First, we identify a new method for obtaining constraint languages Γ such that CSP(Γ) are NP-intermediate. The sets Γ can have very different properties compared to previous constructions (by, for instance, Bodirsky & Grohe) and provides insights into the algebraic approach for studying the complexity of infinite-domain CSPs. Second, we prove that the propositional abduction problem parameterized by constraint languages admits NP-intermediate problems. This settles an open question posed by Nordh & Zanuttini.

  • 341.
    Jonsson, Peter
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Lagerkvist, Victor
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nordh, Gustav
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Constructing NP-intermediate problems by blowing holes with parameters of various properties2015In: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 581, p. 67-82Article in journal (Refereed)
    Abstract [en]

    The search for natural NP-intermediate problems is one of the holy grails within computational complexity. Ladners original diagonalization technique for generating NP-intermediate problems, blowing holes, has a serious shortcoming: it creates problems with a highly artificial structure by arbitrarily removing certain problem instances. In this article we limit this problem by generalizing Ladners method to use parameters with various characteristics. This allows one to define more fine-grained parameters, resulting in NP-intermediate problems where we only blow holes in a controlled subset of the problem. We begin by fully characterizing the problems that admit NP-intermediate subproblems for a broad and natural class of parameterizations, and extend the result further such that structural CSP restrictions based on parameters that are hard to compute (such as tree-width) are covered, thereby generalizing a result by Grohe. For studying certain classes of problems, including CSPs parameterized by constraint languages, we consider more powerful parameterizations. First, we identify a new method for obtaining constraint languages Gamma such that CSP(Gamma) are NP-intermediate. The sets Gamma can have very different properties compared to previous constructions (by, for instance, Bodirsky and Grohe) and provides insights into the algebraic approach for studying the complexity of infinite-domain CSPs. Second, we prove that the propositional abduction problem parameterized by constraint languages admits NP-intermediate problems. This settles an open question posed by Nordh and Zanuttini. (C) 2015 Elsevier B.V. All rights reserved.

  • 342.
    Jonsson, Peter
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Lagerkvist, Victor
    Technical University of Dresden, Germany.
    Nordh, Gustav
    Kvarnvagen 6, Sweden.
    Zanuttini, Bruno
    Normandie University, France.
    Strong partial clones and the time complexity of SAT problems2017In: Journal of computer and system sciences (Print), ISSN 0022-0000, E-ISSN 1090-2724, Vol. 84, p. 52-78Article in journal (Refereed)
    Abstract [en]

    Improving exact exponential-time algorithms for NP-complete problems is an expanding research area. Unfortunately, general methods for comparing the complexity of such problems are sorely lacking. In this article we study the complexity of SAT(S) with reductions increasing the amount of variables by a constant (CV-reductions) or a constant factor (LV-reductions). Using clone theory we obtain a partial order amp;lt; on languages such that SAT(S) is CV-reducible to SAT(S) if S amp;lt; S. With this ordering we identify the computationally easiest NP-complete SAT(S) problem (SAT({R})), which is strictly easier than 1-in-3-SAT. We determine many other languages in amp;lt; and bound their complexity in relation to SAT({R}). Using LV-reductions we prove that the exponential-time hypothesis is false if and only if all SAT(S) problems are subexponential. This is extended to cover degree-bounded SAT(S) problems. Hence, using clone theory, we obtain a solid understanding of the complexity of SAT(S) with CV-and LV-reductions. (C) 2016 Elsevier Inc. All rights reserved.

  • 343.
    Jonsson, Peter
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Lagerkvist, Victor
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Schmidt, Johannes
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Uppman, Hannes
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Relating the Time Complexity of Optimization Problems in Light of the Exponential-Time Hypothesis2014In: Mathematical Foundations of Computer Science 2014: 39th International Symposium, MFCS 2014, Budapest, Hungary, August 25-29, 2014. Proceedings, Part II / [ed] Erzsébet Csuhaj-Varjú, Martin Dietzfelbinger, Zoltán Ésik, Springer Berlin/Heidelberg, 2014, p. 408-419Conference paper (Refereed)
    Abstract [en]

    Obtaining lower bounds for NP-hard problems has for a long time been an active area of research. Recent algebraic techniques introduced by Jonsson et al. (SODA 2013) show that the time complexity of the parameterized SAT(·) problem correlates to the lattice of strong partial clones. With this ordering they isolated a relation R such that SAT(R) can be solved at least as fast as any other NP-hard SAT(·) problem. In this paper we extend this method and show that such languages also exist for the max ones problem (Max-Ones(Γ)) and the Boolean valued constraint satisfaction problem over finite-valued constraint languages (VCSP(Δ)). With the help of these languages we relate Max-Ones and VCSP to the exponential time hypothesis in several different ways.

  • 344.
    Jonsson, Peter
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Lagerkvist, Viktor
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nordh, Gustav
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Zanuttini, Bruno
    Université de Caen Basse-Normandie, France.
    Complexity of SAT problems, Clone Theory and the Exponential Time Hypothesis2013In: SODA-2013, SIAM , 2013, p. 1264-1277Conference paper (Refereed)
  • 345.
    Jonsson, Peter
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Lööw, Tomas
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Computational complexity of linear constraints over the integers2013In: Artificial Intelligence, ISSN 0004-3702, E-ISSN 1872-7921, Vol. 195, p. 44-62Article in journal (Refereed)
    Abstract [en]

    Temporal reasoning problems arise in many areas of Al, including planning, natural language understanding, and reasoning about physical systems. The computational complexity of continuous-time temporal constraint reasoning is fairly well understood. There are, however, many different cases where discrete time must be considered; various scheduling problems and reasoning about sampled physical systems are two examples. Here, the complexity of temporal reasoning is not as well-studied nor as well-understood. In order to get a better understanding, we consider the powerful Horn disjunctive linear relations (Horn DLR) formalism adapted for discrete time and study its computational complexity. We show that the full formalism is NP-hard and identify several maximal tractable subclasses. We also lift the maximality results to obtain hardness results for other families of constraints. Finally, we discuss how the results and techniques presented in this paper can be used for studying even more expressive classes of temporal constraints.

  • 346.
    Jonsson, Peter
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Thapper, Johan
    Université Paris-Sud 11, Laboratoire de Recherche en Informatique (LRI) .
    Affine Consistency and the Complexity of Semilinear Constraints2014In: Mathematical Foundations of Computer Science 2014 / [ed] Ersébet Csuhaj-Varjú,Martin Dietzfelbinger,Zoltán Ésik, Berlin/Heidelberg, 2014, p. 420-431Conference paper (Refereed)
    Abstract [en]

    A semilinear relation is a finite union of finite intersections of open and closed half-spaces over, for instance, the reals, the rationals or the integers. Semilinear relations have been studied in connection with algebraic geometry, automata theory, and spatiotemporal reasoning, just to mention a few examples. We concentrate on relations over the reals and rational numbers. Under this assumption, the computational complexity of the constraint satisfaction problem (CSP) is known for all finite sets Γ of semilinear relations containing the relations R +={(x,y,z) | x+y=z}, ≤ and {1}. These problems correspond to extensions of LP feasibility. We generalise this result as follows. We introduce an algorithm, based on computing affine hulls, which solves a new class of semilinear CSPs in polynomial time. This allows us to fully determine the complexity of CSP(Γ) for semilinear Γ containing R+ and satisfying two auxiliary conditions. Our result covers all semilinear Γ such that {R+,{1}}⊆Γ. We continue by studying the more general case when Γ contains R+ but violates either of the two auxiliary conditions. We show that each such problem is equivalent to a problem in which the relations are finite unions of homogeneous linear sets and we present evidence that determining the complexity of these problems may be highly non-trivial.

  • 347.
    Jonsson, Peter
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Thapper, Johan
    University of Paris Est Marne la Vallee, France.
    Constraint satisfaction and semilinear expansions of addition over the rationals and the reals2016In: Journal of computer and system sciences (Print), ISSN 0022-0000, E-ISSN 1090-2724, Vol. 82, no 5, p. 912-928Article in journal (Refereed)
    Abstract [en]

    A semilinear relation is a finite union of finite intersections of open and closed half spaces over, for instance, the reals, the rationals, or the integers. Semilinear relations have been studied in connection with algebraic geometry, automata theory, and spatiotemporal reasoning. We consider semilinear relations over the rationals and the reals. Under this assumption, the computational complexity of the constraint satisfaction problem (CSP) is known for all finite sets containing R+ = {(x, y, z) vertical bar x y = z}, <=, and {1}. These problems correspond to expansions of the linear programming feasibility problem. We generalise this result and fully determine the complexity for all finite sets of semilinear relations containing R+. This is accomplished in part by introducing an algorithm, based on computing affine hulls, which solves a new class of semilinear CSPs in polynomial time. We further analyse the complexity of linear optimisation over the solution set and the existence of integer solutions. (C) 2016 Elsevier Inc. All rights reserved.

  • 348.
    Jonsson, Peter
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Thapper, Johan
    Univ Paris Est Marne la Vallee, France.
    Tractability conditions for numeric CSPs2018In: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 715, p. 21-34Article in journal (Refereed)
    Abstract [en]

    The computational complexity of the constraint satisfaction problem (CSP) with semilinear relations over the reals has gained recent attraction. As a result, its complexity is known for all finite sets of semilinear relations containing the relation R+ = {(x, y, z) is an element of R-3 vertical bar x + y = z}. We consider larger and more expressive classes of relations such as semialgebraic and o-minimal relations. We present a general result for characterising computationally hard fragments and, under certain side conditions, this result implies that polynomial-time solvable fragments are only to be found within two limited families of sets of relations. In the setting of semialgebraic relation, our result takes on a simplified form and we provide a full complexity classification for constraint languages that consist of algebraic varieties. Full classifications like the one obtained here for algebraic varieties or the one for semilinear relations appear to be rare and we discuss several barriers for obtaining further such results. These barriers have strong connections with well-known open problems concerning the complexity of various restrictions of convex programming. (c) 2018 Elsevier B.V. All rights reserved.

  • 349.
    Joshi, Prachi
    et al.
    Virginia Tech, VA 24061 USA.
    Ravi, S. S.
    Virginia Tech, VA 24061 USA; SUNY Albany, NY 12222 USA.
    Samii, Soheil
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Gen Motors, MI USA.
    Bordoloi, Unmesh D.
    Gen Motors, MI USA.
    Shukla, Sandeep K.
    IIT Kanpur, India.
    Zeng, Haibo
    Virginia Tech, VA 24061 USA.
    Offset Assignment to Signals for Improving Frame Packing in CAN-FD2017In: 2017 IEEE REAL-TIME SYSTEMS SYMPOSIUM (RTSS), IEEE , 2017, p. 167-177Conference paper (Refereed)
    Abstract [en]

    Controller Area Network (CAN) is a widely used protocol that allows communication among Electronic Control Units (ECUs) in automotive electronics. It was extended to CAN-FD (CAN with Flexible Data-rate) to meet the increasing demand for bandwidth utilization caused by the growing number of features in modern automobiles. The signal-to-frame packing problem has been studied in literature for both CAN and CAN-FD. In this work, we propose and formulate, for the first time, the signal offset assignment problem (SOAP) in a frame in order to improve the bus bandwidth utilization. We prove that SOAP is NP-complete. We propose a general approximation framework (GAF) for SOAP which can use any approximation algorithm for the makespan minimization problem (MMP) in multiprocessor systems. We derive the performance guarantee provided by GAF as a function of the performance guarantee of the approximation algorithm for MMP and the number of signal periods in the frame. We demonstrate the efficacy of our approach through experiments using three different algorithms (two approximation algorithms and an integer linear programming formulation) for MMP in GAF. Our results indicate that by using offsets for signals in frame packing schemes, one can achieve about 10.54% improvement in bandwidth utilization (on a single bus) in CAN-FD systems.

  • 350.
    Joshi, Prachi
    et al.
    Virginia Tech, Blacksburg, VA, USA.
    Zeng, Haibo
    Virginia Tech, Blacksburg, VA, USA.
    Bordoloi, Unmesh D.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. General Motors, USA.
    Samii, Soheil
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. General Motors, USA.
    Ravi, S. S.
    Virginia Tech,Blacksburg, VA, USA.
    Shukla, Sandeep K.
    IT Kanpur, Kanpur, India.
    The Multi-Domain Frame Packing Problem for CAN-FD2017In: 29th Euromicro Conference on Real-Time Systems (ECRTS 2017), Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik , 2017Conference paper (Refereed)
    Abstract [en]

    The Controller Area Network with Flexible Data-Rate (CAN-FD) is a new communication protocol to meet the bandwidth requirements for the constantly growing volume of data exchanged in modern vehicles. The problem of frame packing for CAN-FD, as studied in the literature, assumes a single sub-system where one CAN-FD bus serves as the communication medium among several Electronic Control Units (ECUs). Modern automotive electronic systems, on the other hand, consist of several sub-systems, each facilitating a certain functional domain such as powertrain, chassis and suspension. A substantial fraction of all signals is exchanged across sub-systems. In this work, we study the frame packing problem for CAN-FD with multiple sub-systems, and propose a two-stage optimization framework. In the first stage, we pack the signals into frames with the objective of minimizing the bandwidth utilization. In the second stage, we extend Audsley's algorithm to assign priorities/identifiers to the frames. In case the resulting solution is not schedulable, our framework provides a potential repacking method. We propose two solution approaches: (a) an Integer Linear Programming (ILP) formulation that provides an optimal solution but is computationally expensive for industrial-size problems; and (b) a greedy heuristic that scales well and provides solutions that are comparable to optimal solutions. Experimental results show the efficiency of our optimization framework in achieving feasible solutions with low bandwidth utilization. The results also show a significant improvement over the case when there is no cross-domain consideration (as in prior work).

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