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  • 401.
    Li, Lu
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Kessler, Christoph
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Lazy Allocation and Transfer Fusion Optimization for GPU-based Heterogeneous Systems2018In: 2018 26TH EUROMICRO INTERNATIONAL CONFERENCE ON PARALLEL, DISTRIBUTED, AND NETWORK-BASED PROCESSING (PDP 2018), IEEE , 2018, p. 311-315Conference paper (Refereed)
    Abstract [en]

    We present two memory optimization techniques which improve the efficiency of data transfer over PCIe bus for GPU-based heterogeneous systems, namely lazy allocation and transfer fusion optimization. Both are based on merging data transfers so that less overhead is incurred, thereby increasing transfer throughput and making accelerator usage profitable also for smaller operand sizes. We provide the design and prototype implementation of the two techniques in CUDA. Microbench-marking results show that especially for smaller and medium-sized operands significant speedups can be achieved. We also prove that our transfer fusion optimization algorithm is optimal.

  • 402.
    Li, Lu
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Kessler, Christoph
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    MeterPU: A Generic Measurement Abstraction API Enabling Energy-tuned Skeleton Backend Selection2015In: Trustcom/BigDataSE/ISPA, 2015 IEEE, IEEE Press, 2015, Vol. 3, p. 154-159Conference paper (Refereed)
    Abstract [en]

    We present MeterPU, an easy-to-use, generic and low-overhead abstraction API for taking measurements of various metrics (time, energy) on different hardware components (e.g. CPU, DRAM, GPU), using pluggable platform-specific measurement implementations behind a common interface in C++. We show that with MeterPU, not only legacy (time) optimization frameworks, such as autotuned skeleton back-end selection, can be easily retargeted for energy optimization, but also switching different optimization goals for arbitrary code sections now becomes trivial. We apply MeterPU to implement the first energytunable skeleton programming framework, based on the SkePU skeleton programming library.

  • 403.
    Li, Lu
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Kessler, Christoph
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    MeterPU: a generic measurement abstraction API: Enabling energy-tuned skeleton backend selection2018In: Journal of Supercomputing, ISSN 0920-8542, E-ISSN 1573-0484, Vol. 74, no 11, p. 5643-5658Article in journal (Refereed)
    Abstract [en]

    We present MeterPU, an easy-to-use, generic and low-overhead abstraction API for taking measurements of various metrics (time, energy) on different hardware components (e.g., CPU, DRAM, GPU) in a heterogeneous computer system, using pluggable platform-specific measurement implementations behind a common interface in C++. We show that with MeterPU, not only legacy (time) optimization frameworks, such as autotuned skeleton back-end selection, can be easily retargeted for energy optimization, but also switching between measurement metrics or techniques for arbitrary code sections now becomes trivial. We apply MeterPU to implement the first energy-tunable skeleton programming framework, based on the SkePU skeleton programming library.

  • 404.
    Lianjie, Shen
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Optimization and Search in Model-Based Automotive SW/HW Development2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis two case studies are performed about solving two design problems we face during the design phase of new Volvo truck. One is to solve the frame packing problem on CAN bus. The other is to solve the LDC allocation problem. Both solutions are targeted to meet as many end-to-end latency requirements as possible. Now the solution is obtained through manually approach and based on the designer experience. But it is still not satisfactory enough. With the development of artificial intelligence method we propose two methods based on genetic algorithm to solve our design problem we face today. In first case study about frame packing we perform one single genetic algorithm process to find the optimal solution. In second case study about LDC allocation we proposed how to handle two genetic algorithm processes together to reach the optimal solution. In this thesis we show the feasibility of adopting artificial intelligence concept in some activities of the truck design phases like we do in both case studies.  

  • 405.
    Lifa, Adrian Alin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Hardware/Software Codesign of Embedded Systems with Reconfigurable and Heterogeneous Platforms2015Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Modern applications running on today's embedded systems have very high requirements. Most often, these requirements have many dimensions: the applications need high performance as well as exibility, energy-eciency as well as real-time properties, fault tolerance as well as low cost. In order to meet these demands, the industry is adopting architectures that are more and more heterogeneous and that have reconguration capabilities. Unfortunately, this adds to the complexity of designing streamlined applications that can leverage the advantages of such architectures.

    In this context, it is very important to have appropriate tools and design methodologies for the optimization of such systems. This thesis addresses the topic of hardware/software codesign and optimization of adaptive real-time systems implemented on recongurable and heterogeneous platforms. We focus on performance enhancement for dynamically recongurable FPGA-based systems, energy minimization in multi-mode real-time systems implemented on heterogeneous platforms, and codesign techniques for fault-tolerant systems.

    The solutions proposed in this thesis have been validated by extensive experiments, ranging from computer simulations to proof of concept implementations on real-life platforms. The results have conrmed the importance of the addressed aspects and the applicability of our techniques for design optimization of modern embedded systems.

  • 406.
    Lifa, Adrian Alin
    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.
    Context-Aware Speculative Prefetch for Soft Real-Time Applications2012In: International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA 2012), Seoul, Korea, August 19-22, 2012, IEEE, 2012Conference paper (Refereed)
    Abstract [en]

    Dynamically reconfigurable computing devices have the ability to adapt their hardware to application demands, providing the performance of hardware acceleration, as well as high flexibility, at competitive costs. For these reasons, FPGA-based reconfigurable systems are becoming popular in many application domains, including soft real-time computing. Unfortunately, one of their biggest limitations is the high reconfiguration overhead. One method to overcome this problem is configuration prefetching, which tries to reduce the reconfiguration penalty by preloading modules on the FPGA before they are needed, and overlapping the reconfiguration with useful computation. In this paper we present a speculative approach to context-aware inter-procedural configuration prefetching that provides statistical guarantees by minimizing the alpha-percentile of the execution time distribution of a soft real-time application. Our method uses profile information and takes into account the calling context of a procedure in order to generate better prefetch solutions. We also propose a middleware needed to apply the context-dependent prefetches at run-time. Our experiments show that the developed algorithm outperforms the previous state-of-art.

  • 407.
    Lifa, Adrian Alin
    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.
    Dynamic Configuration Prefetching Based on Piecewise Linear Prediction2013In: Design, Automation & Test in Europe (DATE 2013), IEEE , 2013, p. 815-820Conference paper (Refereed)
    Abstract [en]

    Modern systems demand high performance, as well as high degrees of flexibility and adaptability. Many current applications exhibit a dynamic and nonstationary behavior, having certain characteristics in one phase of their execution, that will change as the applications enter new phases, in a manner unpredictable at design-time. In order to meet the performance requirements of such systems, it is important to have on-line optimization algorithms, coupled with adaptive hardware platforms, that together can adjust to the run-time conditions. We propose an optimization technique that minimizes the expected execution time of an application by dynamically scheduling hardware prefetches. We use a piecewise linear predictor in order to capture correlations and predict the hardware modules to be reached. Experiments show that the proposed algorithm outperforms the previous state-of-art in reducing the expected execution time by up to 27% on average.

  • 408.
    Lifa, Adrian Alin
    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.
    Execution Time Minimization Based on Hardware/Software Partitioning and Speculative Prefetch2012Report (Other academic)
    Abstract [en]

    This report addresses the problem of minimizing the average execution time of an application, based on speculative FPGA configuration prefetch. Dynamically reconfigurable systems (like FPGAs) provide both the performance of hardware acceleration and the flexibility and adaptability that modern applications require. Unfortunately, one of their main drawbacks that significantly impacts performance is the high reconfiguration overhead. Configuration prefetching is one method to reduce this penalty by overlapping FPGA reconfigurations with useful computations. In order to make it effective and to avoid very high misprediction penalties, it is important to prefetch the configurations that provide the highest performance improvement, and to do this early enough to hide the reconfiguration overhead. In this report we propose a speculative approach that schedules prefetches at design time and simultaneously performs HW/SW partitioning, in order to minimize the expected execution time of an application. Our method prefetches and executes in hardware those configurations that provide the highest performance improvement. The algorithm takes into consideration profiling information (such as branch probabilities and execution time distributions), correlated with the application characteristics. We demonstrate the effectiveness of our approach compared to the previous state-of-art using extensive experiments, including real-life case studies.

  • 409.
    Lifa, Adrian Alin
    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.
    Minimization of Average Execution Time Based on Speculative FPGA Configuration Prefetch2012In: International Conference on ReConFigurable Computing and FPGAs, 2012, IEEE, 2012Conference paper (Refereed)
    Abstract [en]

    One of the main drawbacks that significantly impacts the performance of dynamically reconfigurable systems (like FPGAs), is their high reconfiguration overhead. Configuration prefetching is one method to reduce this penalty by overlapping FPGA reconfigurations with useful computations. In this paper we propose a speculative approach that schedules prefetches at design time and simultaneously performs HW/SW partitioning, in order to minimize the expected execution time of an application. Our method prefetches and executes in hardware those configurations that provide the highest performance improvement. The algorithm takes into consideration profiling information (such as branch probabilities and execution time distributions), correlated with the application characteristics. Compared to the previous state-of-art, we reduce the reconfiguration penalty with 34% on average, and with up to 59% for particular case studies.

  • 410.
    Lifa, Adrian
    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.
    A Reconfigurable Framework for Performance Enhancement with Dynamic FPGA Configuration Prefetching2016In: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, ISSN 0278-0070, E-ISSN 1937-4151, Vol. 35, no 1, p. 100-113Article in journal (Refereed)
    Abstract [en]

    Many modern applications exhibit a dynamic and nonstationary behavior, with certain characteristics in one phase of their execution, which change as the application enters new phases, in a manner unpredictable at design-time. In order to meet the demands of such applications, it is important to have adaptive and self-reconfiguring hardware platforms, coupled with intelligent on-line optimization algorithms, that together can adjust to the run-time requirements. Partially dynamically reconfigurable field programmable gate array architectures offer both high performance and flexibility. Despite these potential advantages, the challenges faced by designers trying to set-up a functioning system are still significant, mainly because of the still immature design tools and limited device drivers. We propose a complete framework, based on Xilinx’s commercial design suite, that enables an application designer to leverage the advantages of partial dynamic reconfiguration with minimal effort. Our IP-based architecture, together with the comprehensive application programming interface, can be employed to accelerate an application by dynamically scheduling hardware prefetches. Moreover, a piecewise linear predictor is used to capture correlations and predict the hardware modules that will generate the highest performance improvement. Our evaluation comprises of extensive simulations, as well as a complete implementation of the smallest univalue segment assimilating nucleus image processing application on the ML605 board from Xilinx. The measurements show a significant reduction of the expected execution time compared to previous state-of-the-art prefetching algorithms, with only a minor energy overhead.

  • 411.
    Lifa, Adrian
    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.
    On-the-fly Energy Minimization for Multi-Mode Real-Time Systems on Heterogeneous Platforms2015In: 2015 13th IEEE Symposium on Embedded Systems For Real-time Multimedia (ESTIMedia), IEEE , 2015, p. 75-84Conference paper (Refereed)
    Abstract [en]

    The increasing computational demands of next generation multimedia systems require innovative optimization methods. Modern heterogeneous architectures bring together multiple general-purpose CPUs and multiple GPUs and FPGAs, in an attempt to answer the performance, energy-efficiency and flexibility requirements of today???s complex multimedia applications. However, in order to leverage the advantages of such architectures, careful optimization is essential. In modern systems, more and more multimedia applications need real-time support (e.g. automotive systems that use image processing for active safety features). Real-time multi-mode systems are a good model for a wide range of applications that dynamically change their computational requirements over time. In this context, intelligent on-line resource management is needed, such that the heterogeneous resources are used in an energy-efficient manner, while meeting the real-time constraints. This paper proposes a resource manager that implements run-time policies to decide on-the-fly task admission and the mapping of active tasks to resources, such that the energy consumption of the system is minimized and all task deadlines are met.

  • 412.
    Lin, Chih-Yuan
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Understanding IEC-60870-5-104 Traffic Patterns in SCADA Networks2018In: Proceedings of the 4th ACM Workshop on Cyber-Physical System Security, NY, USA: ACM , 2018, p. 51-60Conference paper (Refereed)
    Abstract [en]

    The IEC-60870-5-104 (IEC-104) protocol is commonly used in Supervisory Control and Data Acquisition (SCADA) networks to operate critical infrastructures, such as power stations. As the importance of SCADA security is growing, characterization and modeling of SCADA traffic for developing defense mechanisms based on the regularity of the polling mechanism used in SCADA systems has been studied, whereas the characterization of traffic caused by non-polling mechanisms, such as spontaneous events, has not been well-studied. This paper provides a first look at how the traffic flowing between SCADA components changes over time. It proposes a method built upon Probabilistic Suffix Tree (PST) to discover the underlying timing patterns of spontaneous events. In 11 out of 14 tested data sequences, we see evidence of existence of underlying patterns. Next, the prediction capability of the approach, useful for devising anomaly detection mechanisms, is studied. While some data patterns enable an 80% prediction possibility, more work is needed to tune the method for higher accuracy.

  • 413.
    Lin, Chih-Yuan
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    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.
    Timing-Based Anomaly Detection in SCADA Networks2018In: Critical Information Infrastructures Security, Springer, 2018, p. 48-59Conference paper (Refereed)
    Abstract [en]

    Supervisory Control and Data Acquisition (SCADA) systems that operate our critical infrastructures are subject to increased cyber attacks. Due to the use of request-response communication in polling, SCADA traffic exhibits stable and predictable communication patterns. This paper provides a timing-based anomaly detection system that uses the statistical attributes of the communication patterns. This system is validated with three datasets, one generated from real devices and two from emulated networks, and is shown to have a False Positive Rate (FPR) under 1.4%. The tests are performed in the context of three different attack scenarios, which involve valid messages so they cannot be detected by whitelisting mechanisms. The detection accuracy and timing performance are adequate for all the attack scenarios in request-response communications. With other interaction patterns (i.e. spontaneous communications), we found instead that 2 out of 3 attacks are detected.

  • 414.
    Lindberg, Emil
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Measuring the effect of memory bandwidth contention in applications on multi-core processors2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis we design and implement a benchmarking tool for applications' sensitivity to main memory bandwidth contention, in a multi-core environment, on an ARM Cortex-A15 CPU. The tool is supposed to minimize usage of shared resources, except for the main memory bandwidth, allowing it to isolate the effects of the bandwidth contention only. The difficulty in doing this lies in using a correct memory access pattern for this purpose, i.e. which memory addresses to access, in which order and at what rate in order to minimize cache usage while generating a high and controllable main memory bandwidth usage.

    We manage to implement a tool with low cache memory usage while still being able to saturate the main memory bandwidth. The tool uses a proportional-integral controller to control the amount of bandwidth it uses. We then use the tool to investigate the memory behaviour of the platform and of some applications when the tool is using a variable amount of bandwidth. However, we have some difficulties in analyzing the results due to the lack of support for hardware performance counters in the operating system we are using and are forced to rely on hardware timers for our data gathering. Another difficulty is the platform's limited L2 cache bandwidth, which leads to a heavy impact on L2 cache read latency by the tool. Despite this, we are able to draw some conclusions on the bandwidth usage of other applications in optimal cases with the help of the tool.

  • 415.
    Lindell, Patrick
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nilsson, Daniel
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Providing visualisation of wood industry data with a user centred design2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    When developing a new system, it is a good idea to involve the end users from the start to prevent usability issues. This thesis has evaluated how one can develop a data visualisation system for the sawmill industry with a focus on user experience. 

    Semi-structured interviews with a snowball sample approach were used to acquire the demands of the end users. From these demands, paper prototypes were developed and then evaluated. Data on these prototypes were collected iteratively with the help of usability tests. This was done to understand how pleased users were when using the product but also to evaluate how efficiently they used it. Metrics have been used to measure the user experience of the product with both the paper prototypes and a hi-fi prototype, also described as the alpha prototype. 

    The conclusion answers the two research questions asked in this thesis. It concludes that the interview technique used in this thesis gave a good understanding of what information the users were interested in. Regarding measuring user experience, usability issues have been detected and reduced for each iteration, which indirectly results in a higher efficiency since the number of confusions are reduced. Something that can be seen from the system usability scale tests is that the high scores (about 89) they generated indicate that the users are pleased. With the different metrics used in this thesis, the conclusions are that the fewer the obstacles are for the user, the less annoyed they are when using the product and in turn perform their goals faster.

  • 416.
    Lindgren, Simon
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Efficient Software Integration Process for the automotive industry with Jenkins2015Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    In this thesis an overlook of the software process for a car has been made. Two design choices have been proposed to enhance the scalability and improve the time it takes to build a software application. In these design choices, Jenkins has been used as a tool to make the implementations possible and to distribute work over different computers. Measurements show that distributing the workload on multiple computers would improve the utilization and reduce the time for building software.

  • 417.
    Lindholm, David
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Economics of Test Automation: Test case selection for automation2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis a method for selecting test cases for test automation is developed and evaluated. Existing methods from the literature has been reviewed and modified resulting in the proposed method, a decision tree containing 23 factors grouped into 8 decision points. The decision tree has been used and evaluated in an industrial setting. The economic benefits were calculated with return on investment and the organisational benefits were measured in a survey at a software producing company. The result was that automated tests, selected with the decision tree, provided economic benefits after 0.5 to 4 years, these tests were also found leading to 3 organisational benefits: less human effort when testing, reduction in cost and allowing for shorter release cycles.

  • 418.
    Lindmark, Fanny
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Master Data Management: Creating a Common Language for Master Data Across an Extended and Complex Supply Chain2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Connectivity provided by technology and liberation of trade have led to a globalization of organizations, affecting supply chains to expand in complexity. As a result, many organizations today have challenges of managing information in a consistent manner throughout a complex system environment. This study aims to identify the most valuable attributes of a solution for managing master data, in an efficient and consistent manner, across an extended and complex supply chain. Master data, such as products, customers and suppliers, can be defined as valuable core business information, since it is vital for supporting business operations. A requirements elicitation was performed, including interviews conducted internally with employees at IFS and externally with customers. Furthermore, a requirements analysis resulted in a specification of requirements including the most desirable attributes of a future Master Data Management (MDM) solution. Five main themes of the attributes were identified; architecture, availability and integration, governance, user interface and lifecycle management. The study contributes to the area of research, by identifying challenges and valuable attributes to consider when developing or investing in a solution for MDM.

  • 419.
    Lindskog Hedström, David
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Assessing Needs for Visualizations in Continuous Integration: A Multiple Case Study2017Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Many organizations are moving towards agile software development and practices such as continuous integration. Being significantly different from traditional development, agile development has unique new challenges to be dealt with. This report is exploring challenges that large-scale organizations adopting continuous integration are experiencing related to their integration process. Challenges that are focused on are those that relate to understanding information about what the continuous integration system does. Two types of challenges were found: those that call for a need of understanding information and those that hinders information from being used. The report also suggests how visualizations can be used to help solving the former of the two.

  • 420.
    Lindén, Erik
    Linköping University, Department of Computer and Information Science, Software and Systems.
    A latency comparison of IoT protocols in MES2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Many industries are now moving several of their processes into the cloud computing sphere. One important process is to collect machine data in an effective way. Moving signal collection processes to the cloud instead of on premise raises many questions about performance, scalability, security and cost.This thesis focuses on some of the market leading and cutting edge protocols appropriate for industrial production data collection. It investigates and compares the pros and cons of the protocols with respect to the demands of industrial systems. The thesis also presents examples of how the protocols can be used to collect data all the way to a higher-level system such as ERP or MES.The protocols focused on are MQTT and AMQP (in OPC-UA). The possibilities of OPC-UA in cloud computing is of extra interest to investigate in this thesis due to its increasing usage and development.

  • 421.
    Lingfors, Anders
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Software download over DoIP in Android2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Android operating system, originally intended for smartphone devices, is now finding its way into cars and other vehicles. While the Android system already implements support for system updates, it is not suitable for use in the automotive domain. It is not compatible with modern automotive standards for diagnostic communication such as ISO 14229: Unified Diagnostic Services (UDS). This means that new tools, procedures and software would be needed to allow an Android device to be updated by a service technician in a repair shop or on the field. A better approach would be to add support for automotive diagnostic communication in Android. This way, the tools and supporting infrastructure that already exist can still be used.

    We have developed a solution for diagnostic communication on Android that is both modular and compatible with existing automotive standards. By using the standard ISO 13400: Diagnostic communication over Internet Protocol (DoIP), this solution enables both updating the system software on the Android device itself, as well as diagnostic communication with the ECUs on the vehicle’s internal CAN network. Thus, an existing diagnostic port based on a slower communication protocol such as CAN or J1587 could theoretically be replaced completely by the Android device’s Ethernet port.

    Finally, we have evaluated the performance of our implementation under various settings and conditions. These include varying the maximum size of a diagnostic message, different network settings, downloading software over a Wi-Fi link, and downloading data to multiple devices simultaneously.

  • 422.
    Ljung, Dennis
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Das, Ruben
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Isaksson, Johan
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Yngve, Alexander
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Sestorp, Adam
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Söderén, Martin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Fast, Sebastian
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Erfarenheter från utveckling av kvadratisk optimeringsalgoritm för prediktionsreglering2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna kandidatrapport studerar en projektuppgift som har utförts av en grupp studenter på Linköpings universitet. Uppgiften har givits av en industridoktorand på Saab och härstammar från reglering av styrsystem i stridsflygplan. Det som har tagits fram av kandidatgruppen är en kvadratisk optimeringslösare som även kan köras från MATLAB. Undersökningar har gjorts om det går att implementera optimeringsalgoritmen i programspråket C med projektets tidsbegränsning, om lösaren kan bli lika snabb som den kommersiella produkten Gurobi och om projektet går att utföra utan någon speciell utvecklingsmetodik. I resultat går det att se att det gick att implementera optimeringsalgoritmen, att lösaren inte kunde bli lika snabb som Gurobi och att kandidatgruppen inte använde någon speciell utvecklingsmetodik.

    Slutsatser kandidatgruppen har dragit ar att valet av optimeringsalgoritm inte var helt genomtänkt, att mer mer tid och resurser hade lösaren kanske kunnat blivit lika snabb som Gurobi och att arbetet fungerade tillfredsställande utan någon speciell utvecklingsmetod.

  • 423.
    Lofwenmark, Andreas
    et al.
    Saab Aeronaut, Linkoping, Sweden.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Fault and timing analysis in critical multi-core systems: A survey with an avionics perspective2018In: Journal of systems architecture, ISSN 1383-7621, E-ISSN 1873-6165, Vol. 87, p. 1-11Article, review/survey (Refereed)
    Abstract [en]

    With more functionality added to future safety-critical avionics systems, new platforms are required to offer the computational capacity needed. Multi-core processors offer a potential that is promising, but they also suffer from two issues that are only recently being addressed in the safety-critical contexts: lack of methods for assuring timing determinism, and higher sensitivity to permanent and transient faults due to shrinking transistor sizes. This paper reviews major contributions that assess the impact of fault tolerance on worst-case execution time of processes running on a multi-core platform. We consider the classic approach for analyzing the impact of faults in such systems, namely fault injection. The review therefore explores the area in which timing effects are studied when fault injection methods are used. We conclude that there are few works that address the intricate timing effects that appear when inter-core interferences due to simultaneous accesses of shared resources are combined with fault tolerance techniques. We assess the applicability of the methods to currently available multi-core processors used in avionics. Dark spots on the research map of the integration problem of hardware reliability and timing predictability for multi-core avionics systems are identified.

  • 424.
    Log, Natanael
    Linköping University, Department of Computer and Information Science, Software and Systems.
    A Study on the Performance and Architectural Characteristics of an Internet of Things Gateway2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study focuses on the Internet of Things (IoT) gateway; a common middleware solution that bridges the gap between physical sensors and devices to internet applications. There is a shown interest in understanding the characteristics of different types of gateway architectures both from the research field and the industry, particularly the IT-consulting firm Attentec in Linköping, Sweden. A study has also been made on the open source C library libuv, used in the common web runtime engine NodeJS. The library has been used to study how asynchronous I/O operations can be used to improve the IoT gateway performance. A set of three general architectural approaches are identified. Common internal and external properties are identified based on state-of-the-art gateway implementations found in the industry. All of these properties are taken into account when a general gateway implementation is developed that is proposed to mimic any architectural level implementation of the gateway. A set of performance tests are conducted on the implementation to observe how different configurations of the gateway affect throughput and response time of data transmitted from simulated devices. The results show that the properties of the gateway do affect throughput and response time significantly and that libuv overall helps implement one of the best performing gateway configurations.

  • 425.
    Luckey, Christian
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Evaluating Clojure Spec2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The objective of this thesis is to evaluate whether or not Clojure Spec meets the goals it sets out to meet with regards to easy data validation, performance and automatically generated tests in comparison to existing specification systems in the Clojure ecosystem.

    A specification for a real-world data format was implemented in the three currently popular specification systems used in Clojure. They were then compared on merits in terms of performance, code size and additional capabilities.

    The results show that Spec shines with complex data, both in expressivity and validation performance, but has an API more complex than its competitors. For complex enough use cases where expressing regular data structures and generative testing is desired the time investment of learning Spec pays off, in simpler situations an assertions library like Truss can be recommended.

  • 426.
    Lundberg, Elina
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Gavefalk, Erica
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Investigating the impact on subjective satisfaction and learnability when adopting cloud in an SME2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cloud services and solutions have served as a shift in the computer industry and create new opportunities for users. Clouds have been described as easily usable and fluid in terms of expansion and contraction depending on the real-time needs. Although the cloud is promoted with several benefits, it is not always apparent for the users that this is the case. Understanding both the benefits and challenges that exist is substantial for a successful adoption to cloud. This master’s thesis is conducted in collaboration with Exsitec ABand aims to investigate how the adoption of the cloud service Microsoft Azure will affect the development process. Also, it aims to provide a best practice for potentially needed updated working procedures, in terms of satisfaction and learnability. The investigation was performed through interviews and the System Usability Scale, to assess how the end users experienced development in a cloud environment. The thesis revealed that the Azure portal has low overall usability, but that there also exists an inconsistency of that perception. Two major factors that contributed to the satisfaction and learnability was the lack of documentation and that the Azure portal was considered hard to master. The SUS score revealed that the mean value was below an acceptable level, and thus changes in the company’s working procedures need to be implemented. Internal documentation regarding how the company should use both cloud in general, as well as the portal in particular, are required in order to increase the learnability and subjective satisfaction.

  • 427.
    Lundberg, Jonas
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Törnqvist, Eva
    Linköping University, The Tema Institute, Technology and Social Change. Linköping University, Faculty of Arts and Sciences.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Establishing conversation spaces in hastily formed networks: the worst fire in modern Swedish history2014In: Disasters. The Journal of Disaster Studies, Policy and Management, ISSN 0361-3666, E-ISSN 1467-7717, Vol. 38, no 4, p. 790-807Article in journal (Refereed)
    Abstract [en]

    In presenting examples from the most extensive and demanding fire in modern Swedish history, this paper describes challenges facing hastily formed networks in exceptional situations. Two concepts that have been used in the analysis of the socio-technical systems that make up a response are conversation space and sensemaking. This paper argues that a framework designed to promote understanding of the sensemaking process must take into consideration the time at which as well as the location in which an individual is engaged in an event. In hastily formed networks, location is partly mediated through physical systems that form conversation spaces of players and their interaction practices. This paper identifies and discusses four challenges to the formation of shared conversation spaces. It is based on the case study of the 2006 Bodträskfors forest fire in Sweden and draws on the experiences of organised volunteers and firefighters who participated in a hastily formed network created to combat the fire. 

  • 428.
    Lundberg, Jonas
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Törnqvist, Eva
    Linköping University, The Tema Institute, Technology and Social Change. Linköping University, Faculty of Arts and Sciences.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Resilience in Sensemaking and Control of Emergency Response2012In: International Journal of Emergency Management, ISSN 1471-4825, E-ISSN 1741-5071, Vol. 8, no 2, p. 99-122Article in journal (Refereed)
    Abstract [en]

    This paper proposes a model for describing resilience in emergency management of irregular events. The purpose of our model is to describe three parallel developments in an emergency response scenario. Namely, changes in the ongoing events processes, the actors' sensemaking and control functions, and the technologies used for sensemaking and control. Focusing on the three separate developments enables identifying resilience in the choice of control functions and technologies in response to foreseen and actual process changes, their consequences and new disturbances. Our model was created following an emergency exercise that proved to be difficult to analyse with respect to resilience using existing models. We use the exercise to illustrate and apply our model through a qualitative analysis.

  • 429.
    Lundberg, Martin
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Automatic parameter tuning in localization algorithms2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Many algorithms today require a number of parameters to be set in order to perform well in a given application. The tuning of these parameters is often difficult and tedious to do manually, especially when the number of parameters is large. It is also unlikely that a human can find the best possible solution for difficult problems. To be able to automatically find good sets of parameters could both provide better results and save a lot of time.

    The prominent methods Bayesian optimization and Covariance Matrix Adaptation Evolution Strategy (CMA-ES) are evaluated for automatic parameter tuning in localization algorithms in this work. Both methods are evaluated using a localization algorithm on different datasets and compared in terms of computational time and the precision and recall of the final solutions. This study shows that it is feasible to automatically tune the parameters of localization algorithms using the evaluated methods. In all experiments performed in this work, Bayesian optimization was shown to make the biggest improvements early in the optimization but CMA-ES always passed it and proceeded to reach the best final solutions after some time. This study also shows that automatic parameter tuning is feasible even when using noisy real-world data collected from 3D cameras.

  • 430.
    Lundholm, Jonathan
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Plattformsoberoende widgets med giljotinpackade bakgrundstexturer2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    We have in this work created an widgets API on Android and iOS for Visiarcs development platform CoffeeMaker. CoffeeMaker uses the multiplattform-API Cocos2dx and tries to use the reactive programming paradigm as much as possible. We used design patterns to try to smoothen out the differences between Android and iOS and implemented functionality for buttons, checkboxes, radiobuttons and textfields on these platforms. These widgets are themeble with a JSON-like format and uses a texture atlas to be sparse on system resources. We needed a texture packer which was suited to be run during runtime of a userspace application. We found a quick heurustic, O(n2), with good density, approximately 94% according to our test method.

  • 431.
    Löfwenmark, Andreas
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Saab Aeronautics.
    Timing Predictability in Future Multi-Core Avionics Systems2017Licentiate thesis, monograph (Other academic)
    Abstract [en]

    With more functionality added to safety-critical avionics systems, new platforms are required to offer the computational capacity needed. Multi-core platforms offer a potential that is now being explored, but they pose significant challenges with respect to predictability due to shared resources (such as memory) being accessed from several cores in parallel. Multi-core processors also suffer from higher sensitivity to permanent and transient faults due to shrinking transistor sizes.

    This thesis addresses several of these challenges. First, we review major contributions that assess the impact of fault tolerance on worst-case execution time of processes running on a multi-core platform. In particular, works that evaluate the timing effects using fault injection methods. We conclude that there are few works that address the intricate timing effects that appear when inter-core interferences due to simultaneous accesses of shared resources are combined with the fault tolerance techniques. We assess the applicability of the methods to COTS multi-core processors used in avionics. We identify dark spots on the research map of the joint problem of hardware reliability and timing predictability for multi-core avionics systems.

    Next, we argue that the memory requests issued by the real-time operating systems (RTOS) must be considered in resource-monitoring systems to ensure proper execution on all cores.

    We also adapt and extend an existing method for worst-case response time analysis to fulfill the specific requirements of avionics systems. We relax the requirement of private memory banks to also allow cores to share memory banks.

  • 432.
    Löfwenmark, Andreas
    et al.
    Saab Aeronaut, Avion Equipment, Linkoping, Sweden.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Challenges in Future Avionic Systems on Multi-core Platforms2014In: 2014 IEEE International Symposium on Software Reliability Engineering Workshops, IEEE, 2014, p. 115-119Conference paper (Refereed)
    Abstract [en]

    Modern avionic system development is undergoing a major transition, from federated systems to Integrated Modular Avionics (IMA) where several applications with mixed criticality will reside on the same platform. Moreover, there is a departure from today’s single core computing, and we need to address the problem of how to guarantee determinism (in time and space) for application tasks running on multiple cores and interacting through shared memory. This paper summarizes the main challenges and briefly describes some active directions in research regarding temporal partitioning. It also outlines the forthcoming research that we will pursue for quantifying time bounds on memory access related interference, to ensure determinism and comply with certification requirements.

  • 433.
    Löfwenmark, Andreas
    et al.
    Saab Aeronautics, Sweden.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Experience Report: Memory Accesses for Avionic Applications and Operating Systems on a Multi-core Platform2015In: 2015 IEEE 26TH INTERNATIONAL SYMPOSIUM ON SOFTWARE RELIABILITY ENGINEERING (ISSRE), Institute of Electrical and Electronics Engineers (IEEE), 2015, p. 153-160Conference paper (Refereed)
    Abstract [en]

    The deployment of multi-core platforms in safety-critical avionic applications is hampered by the lack of means to ensure predictability when processes running on different cores can create interference effects, affecting worst-case execution time, due to shared memory accesses. One way to restrict these interferences is to allocate a budget for different processes prior to run-time and to monitor the adherence to this budget during run-time. While earlier works in adopting this approach seem promising, they focus on application level (user mode) accesses to shared memory and not the operating system accesses. In this paper we construct experiments for studying a multi-core platform running an ARINC 653 compliant operating system, and measure the impact of both application processes and operating system (supervisor mode) activities. In particular, as opposed to earlier works that considered networking applications, we select four avionic processes that exhibit different memory access patterns, namely, a navigation process, a matrix multiplication process, a math library process and an image processing one. The benchmarking on a set of avionic-relevant application processes shows that (a) the potential interference by the operating system cannot be neglected when allocating budgets that are to be monitored at run-time, and (b) the bounds for the allowed number of memory accesses should not always be based on the maximum measured count during profiling, which would lead to overly pessimistic budgets.

  • 434.
    Löfwenmark, Andreas
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Saab Aeronautics.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Understanding Shared Memory Bank Access Interference in Multi-Core Avionics2016Conference paper (Refereed)
    Abstract [en]

    Deployment of multi-core platforms in safety-critical applications requires reliable estimation of worst-case response time (WCRT) for critical processes. Determination of WCRT needs to accurately estimate and measure the interferences arising from multiple processes and multiple cores. Earlier works have proposed frameworks in which CPU, shared cache, and shared memory (DRAM) interferences can be estimated using some application and platform-dependent parameters. In this work we examine a recent work in which single core equivalent (SCE) worst case execution time is used as a basis for deriving WCRT. We describe the specific requirements in an avionics context including the sharing of memory banks by multiple processes on multiple cores, and adapt the SCE framework to account for them. We present the needed adaptations to a real-time operating system to enforce the requirements, and present a methodology for validating the theoretical WCRT through measurements on the resulting platform. The work reveals that the framework indeed creates a (pessimistic) bound on the WCRT. It also discloses that the maximum interference for memory accesses does not arise when all cores share the same memory bank.

  • 435.
    Lövgren, Viktor
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Reducing Regression Testing Feedback Cycle Times Through Improved Testing Techniques2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Software is continually and rapidly evolving with constant risk of introducing faults. Software testing has long been used to aid in the detection of faults, and agile development strategies have been driving the use of automated tests and regression testing specifically. As development continues, test suites eventually grow in the number of test cases to the extent that the execution time is extensive. When it has increased to the point that it prevents efficient software engineering, a regression testing technique is required to reduce the feedback cycle times - the times for receiving feedback from tests on changes.

    This thesis has investigated regression testing techniques presented in previous research. The focus has been on test case selection techniques - for selecting a subset of all test cases for execution - and test case prioritization techniques - for determining the execution order of test cases. With some evaluation criteria in mind, a safe modification-based selection and prioritization technique was chosen and a proof-of-concept implementation was developed. First, the implemented technique was evaluated for robustness using an example application. Following, a case study was conducted on an existing software development project, where the perceived problems with regression testing were documented by interviewing a software developer. The technique was then integrated with the project's existing regression testing and its efficiency was evaluated.

    It was concluded that a regression testing technique is, to some extent, practical to implement, although difficult to verify for complete correctness. Empirical evaluations in the case study showcased reduced feedback cycle times of 60% or more compared to when not using the technique - assuming a uniform distribution of failing test cases. However, it was stated as important to evaluate the efficiency of the technique on a per-project basis.

  • 436.
    Lööw, Andreas
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    A Functional-Level Simulator for the Configurable (Many-Core) PRAM-Like REPLICA Architecture2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master's thesis discusses the design and implementation of a simulator for the REPLICA architecture, a many-core PRAM-like machine. REPLICA provides a programming model that seemingly cannot be provided by mainstream hardware without significant slowdown compared to traditional models. This also implies that it is difficult to simulate REPLICA's programming model on mainstream hardware. Simulator design decisions are described and the resulting simulator is evaluated and compared to existing simulators, where we see that the simulator presented in this thesis is the fastest of them. As seen from the discussion focus in the thesis, most efforts were directed towards simulator execution speed rather than user-facing features.

  • 437.
    Maddison, John
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Automatisk validering av skärmgrafik med OpenCV och Tesseract2018Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [sv]

    I dagens flygplan finns det mycket information som på ett snabbt och pålitligt sätt behöver förmedlas till piloten via instrument på flera skärmar i cockpit. Att verifiera att skärmarna visar korrekt data för olika indata är ett tidskrävande och monotont arbete. Därför undersöker Saab möjligheten att automatisera delar av arbetet. Examensarbetet undersöker genom praktiskt implementation ifall det är möjligt att automatisera bildanalysen med hjälp av programmen OpenCV och Tesseract. Resultatet visade att det går att enkelt konstruera tester för att automatiskt identifiera oönskade förändringar i den implementerade instrumentingen.

  • 438.
    Maghazeh, Arian
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    System-Level Design of GPU-Based Embedded Systems2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Modern embedded systems deploy several hardware accelerators, in a heterogeneous manner, to deliver high-performance computing. Among such devices, graphics processing units (GPUs) have earned a prominent position by virtue of their immense computing power. However, a system design that relies on sheer throughput of GPUs is often incapable of satisfying the strict power- and time-related constraints faced by the embedded systems.

    This thesis presents several system-level software techniques to optimize the design of GPU-based embedded systems under various graphics and non-graphics applications. As compared to the conventional application-level optimizations, the system-wide view of our proposed techniques brings about several advantages: First, it allows for fully incorporating the limitations and requirements of the various system parts in the design process. Second, it can unveil optimization opportunities through exposing the information flow between the processing components. Third, the techniques are generally applicable to a wide range of applications with similar characteristics. In addition, multiple system-level techniques can be combined together or with application-level techniques to further improve the performance.

    We begin by studying some of the unique attributes of GPU-based embedded systems and discussing several factors that distinguish the design of these systems from that of the conventional high-end GPU-based systems. We then proceed to develop two techniques that address an important challenge in the design of GPU-based embedded systems from different perspectives. The challenge arises from the fact that GPUs require a large amount of workload to be present at runtime in order to deliver a high throughput. However, for some embedded applications, collecting large batches of input data requires an unacceptable waiting time, prompting a trade-off between throughput and latency. We also develop an optimization technique for GPU-based applications to address the memory bottleneck issue by utilizing the GPU L2 cache to shorten data access time. Moreover, in the area of graphics applications, and in particular with a focus on mobile games, we propose a power management scheme to reduce the GPU power consumption by dynamically adjusting the display resolution, while considering the user's visual perception at various resolutions. We also discuss the collective impact of the proposed techniques in tackling the design challenges of emerging complex systems.

    The proposed techniques are assessed by real-life experimentations on GPU-based hardware platforms, which demonstrate the superior performance of our approaches as compared to the state-of-the-art techniques.

  • 439.
    Maghazeh, Arian
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Bordoloi, Unmesh D.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Dastgeer, Usman
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Ericsson Sweden.
    Andrei, Alexandru
    Ericsson Sweden.
    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.
    Latency-Aware Packet Processing on CPU-GPU Heterogeneous Systems2017In: DAC '17 Proceedings of the 54th Annual Design Automation Conference 2017, New York, NY, USA: Association for Computing Machinery (ACM), 2017Conference paper (Refereed)
    Abstract [en]

    In response to the tremendous growth of the Internet, towards what we call the Internet of Things (IoT), there is a need to move from costly, high-time-to-market specific-purpose hardware to flexible, low-time-to-market general-purpose devices for packet processing. Among several such devices, GPUs have attracted attention in the past, mainly because the high computing demand of packet processing applications can, potentially, be satisfied by these throughput-oriented machines. However, another important aspect of such applications is the packet latency which, if not handled carefully, will overshadow the throughput benefits. Unfortunately, until now, this aspect has been mostly ignored. To address this issue, we propose a method that considers the variable bit rate of the traffic and, depending on the current rate, minimizes the latency, while meeting the rate demand. We propose a persistent kernel based software architecture to overcome the challenges inherent in GPU implementation like kernel invocation overhead, CPU-GPU communication and memory access overhead. We have chosen packet classification as the packet processing application to demonstrate our technique. Using the proposed approach, we are able to reduce the packet latency on average by a factor of 3.5, compared to the state-of-the-art solutions, without any packet drop.

  • 440.
    Maghazeh, Arian
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Bordoloi, Unmesh D.
    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.
    General Purpose Computing on Low-Power Embedded GPUs: Has It Come of Age?2013In: 13th International Conference on Embedded Computer Systems: Architectures, Modeling, and Simulation (SAMOS 2013), Samos, Greece, July 15-18, 2013., IEEE Press, 2013Conference paper (Refereed)
    Abstract [en]

    In this paper we evaluate the promise held by low power GPUs for non-graphic workloads that arise in embedded systems. Towards this, we map and implement 5 benchmarks, that find utility in very different application domains, to an embedded GPU. Our results show that apart from accelerated performance, embedded GPUs are promising also because of their energy efficiency which is an important design goal for battery-driven mobile devices. We show that adopting the same optimization strategies as those used for programming high-end GPUs might lead to worse performance on embedded GPUs. This is due to restricted features of embedded GPUs, such as, limited or no user-defined memory, small instruction-set, limited number of registers, among others. We propose techniques to overcome such challenges, e.g., by distributing the workload between GPUs and multi-core CPUs, similar to the spirit of heterogeneous computation.

  • 441.
    Maghazeh, Arian
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Bordoloi, Unmesh D.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Horga, Adrian
    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.
    Saving Energy without Defying Deadlines on Mobile GPU-based Heterogeneous Systems2014In: 2014 International Conference on Hardware/Software Codesign and System Synthesis, Association for Computing Machinery (ACM), 2014Conference paper (Refereed)
    Abstract [en]

    With the advent of low-power programmable compute cores based on GPUs, GPU-equipped heterogeneous platforms are becoming common in a wide spectrum of industries including safety-critical domains like the automotive industry. While the suitability of GPUs for throughput oriented applications is well-accepted, their applicability for real-time applications remains an open issue. Moreover, in mobile/embedded systems, energy-efficient computing is a major concern and yet, there has been no systematic study on the energy savings that GPUs may potentially provide. In this paper, we propose an approach to utilize both the GPU and the CPU in a heterogeneous fashion to meet the deadlines of a real-time application while ensuring that we maximize the energy savings. We note that GPUs are inherently built to maximize the throughput and this poses a major challenge when deadlines must be satisfied. The problem becomes more acute when we consider the fact that GPUs are more energy efficient than CPUs and thus, a naive approach that is based on maximizing GPU utilization might easily lead to infeasible solutions from a deadline perspective.

  • 442.
    Maghazeh, Arian
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Bordoloi, Unmesh D.
    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 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.
    Perception-aware power management for mobile games via dynamic resolution scaling2015In: 2015 IEEE/ACM INTERNATIONAL CONFERENCE ON COMPUTER-AIDED DESIGN (ICCAD), IEEE , 2015, p. 613-620Conference paper (Refereed)
    Abstract [en]

    Modern mobile devices provide ultra-high resolutions in their display panels. This imposes ever increasing workload on the GPU leading to high power consumption and shortened battery life. In this paper, we first show that resolution scaling leads to significant power savings. Second, we propose a perception-aware adaptive scheme that sets the resolution during game play. We exploit the fact that game players are often willing to trade quality for longer battery life. Our scheme uses decision theory, where the predicted user perception is combined with a novel asymmetric loss function that encodes users' alterations in their willingness to save power.

  • 443.
    Maghazeh, Arian
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Chattopadhyay, Sudipta
    Singapore Univ Technol and Design, 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.
    Cache-Aware Kernel Tiling: An Approach for System-Level Performance Optimization of GPU-Based Applications2019In: 2019 DESIGN, AUTOMATION and TEST IN EUROPE CONFERENCE and EXHIBITION (DATE), IEEE , 2019, p. 570-575Conference paper (Refereed)
    Abstract [en]

    We present a software approach to address the data latency issue for certain GPU applications. Each application is modeled as a kernel graph, where the nodes represent individual GPU kernels and the edges capture data dependencies. Our technique exploits the GPU L2 cache to accelerate parameter passing between the kernels. The key idea is that, instead of having each kernel process the entire input in one invocation, we subdivide the input into fragments (which fit in the cache) and, ideally, process each fragment in one continuous sequence of kernel invocations. Our proposed technique is oblivious to kernel functionalities and requires minimal source code modification. We demonstrate our technique on a full-fledged image processing application and improve the performance on average by 30% over various settings.

  • 444.
    Magnusson, Filip
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Evaluating Deep Learning Algorithms for Steering an Autonomous Vehicle2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With self-driving cars on the horizon, vehicle autonomy and its problems is a hot topic. In this study we are using convolutional neural networks to make a robot car avoid obstacles. The robot car has a monocular camera, and our approach is to use the images taken by the camera as input, and then output a steering command. Using this method the car is to avoid any object in front of it.

    In order to lower the amount of training data we use models that are pretrained on ImageNet, a large image database containing millions of images. The model are then trained on our own dataset, which contains of images taken directly by the robot car while driving around. The images are then labeled with the steering command used while taking the image. While training we experiment with using different amounts of frozen layers. A frozen layer is a layer that has been pretrained on ImageNet, but are not trained on our dataset.

    The Xception, MobileNet and VGG16 architectures are tested and compared to each other.

    We find that a lower amount of frozen layer produces better results, and our best model, which used the Xception architecture, achieved 81.19% accuracy on our test set. During a qualitative test the car avoid collisions 78.57% of the time.

  • 445.
    Mahfouzi, Rouhollah
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Aminifar, Amir
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. École Polytechnique Fédérale de Lausanne (EPFL), Switzerland.
    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.
    Villani, Mattias
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Intrusion-Damage Assessment and Mitigation in Cyber-Physical Systems for Control Applications2016In: RTNS '16 Proceedings of the 24th International Conference on Real-Time Networks and Systems, New York: ACM Press, 2016, p. 141-150Conference paper (Refereed)
    Abstract [en]

    With cyber-physical systems opening to the outside world, security can no longer be considered a secondary issue. One of the key aspects in security of cyber-phyiscal systems is to deal with intrusions. In this paper, we highlight the several unique properties of control applications in cyber-physical systems. Using these unique properties, we propose a systematic intrusion-damage assessment and mitigation mechanism for the class of observable and controllable attacks.

    On the one hand, in cyber-physical systems, the plants follow certain laws of physics and this can be utilized to address the intrusion-damage assessment problem. That is, the states of the controlled plant should follow those expected according to the physics of the system and any major discrepancy is potentially an indication of intrusion. Here, we use a machine learning algorithm to capture the normal behavior of the system according to its dynamics. On the other hand, the control performance strongly depends on the amount of allocated resources and this can be used to address the intrusion-damage mitigation problem. That is, the intrusion-damage mitigation is based on the idea of allocating more resources to the control application under attack. This is done using a feedback-based approach including a convex optimization.

  • 446.
    Mahfouzi, Rouhollah
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Aminifar, Amir
    Ecole Polytech Fed Lausanne, Switzerland.
    Samii, Soheil
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Gen Motors RandD, MI USA.
    Rezine, Ahmed
    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.
    Stability-Aware Integrated Routing and Scheduling for Control Applications in Ethernet Networks2018In: PROCEEDINGS OF THE 2018 DESIGN, AUTOMATION and TEST IN EUROPE CONFERENCE and EXHIBITION (DATE), IEEE , 2018, p. 682-687Conference paper (Refereed)
    Abstract [en]

    Real-time communication over Ethernet is becoming important in various application areas of cyber-physical systems such as industrial automation and control, avionics, and automotive networking. Since such applications are typically time critical, Ethernet technology has been enhanced to support time driven communication through the IEEE 802.1 TSN standards. The performance and stability of control applications is strongly impacted by the timing of the network communication. Thus, in order to guarantee stability requirements, when synthesizing the communication schedule and routing, it is needed to consider the degree to which control applications can tolerate message delays and jitters. In this paper we jointly solve the message scheduling and routing problem for networked cyber-physical systems based on the time-triggered Ethernet TSN standards. Moreover, we consider this communication synthesis problem in the context. of control applications and guarantee their worst-case stability, taking explicitly into consideration the impact of communication delay and jitter on control quality. Considering the inherent complexity of the network communication synthesis problem, we also propose new heuristics to improve synthesis efficiency without any major loss of quality. Experiments demonstrate the effectiveness of the proposed solutions.

  • 447.
    Majeed, Mudassar
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Dastgeer, Usman
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Kessler, Christoph
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Cluster-SkePU: A Multi-Backend Skeleton Programming Library for GPU Clusters2013In: Proceedings of the International Conference on Parallel and Distributed Processing Techniques and Applications (PDPTA-2013),, 2013Conference paper (Refereed)
    Abstract [en]

    SkePU is a C++ template library with a simple and unified interface for expressing data parallel computations in terms of generic components, called skeletons, on multi-GPU systems using CUDA and OpenCL. The smart containers in SkePU, such as Matrix and Vector, perform data management with a lazy memory copying mechanism that reduces redundant data communication. SkePU provides programmability, portability and even performance portability, but up to now application written using SkePU could only run on a single multi-GPU node. We present the extension of SkePU for GPU clusters without the need to modify the SkePU application source code. With our prototype implementation, we performed two experiments. The first experiment demonstrates the scalability with regular algorithms for N-body simulation and electric field calculation over multiple GPU nodes. The results for the second experiment show the benefit of lazy memory copying in terms of speedup gained for one level of Strassen’s algorithm and another synthetic matrix sum application.

  • 448.
    Malmberg, Erik
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Visualization of Internet of Things Data from a District Heating System2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One application of the Internet of Things that is currently developed is the collection of data from district heating systems. This development leads to the problem of how the collected data should be used to operate the systems in a manner that reduces the dependency on fossil fuels. This thesis proposes a characterization of this problem into visualization tasks and requirements, as well as a visualization application, based on the tool Power BI, for gaining insight into how to operate a district heating system. The tasks and requirements were elicited during collaborative meetings and prototyping together with district heating experts. The perceived effectiveness of the visualization application was validated with a usability evaluation, including the usability metric for user experience questionnaire, with four district heating experts. The perceived efficiency was, however, found to be lacking compared to the other usability aspects. A redesign of one of the Power BI components, which according to the evaluation should improve the application, is also suggested.

  • 449.
    Mangaraj, Swadhin K
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Extension of the SkePU Skeleton ProgrammingFramework for Multi-core CPU and Multi-GPU Systems for MPI-based Clusters2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    SkePU (Skeleton Programming Framework for Multi-core CPU and Multi-GPU Systems) is a parallel computing framework developed by Johan Enmyren and Christoph Kessler at Linköpings Universitet. This C++ template library provides a simple and unified interface for specifying data-parallel computations with the help of skeletons and is targeted to multiple backends e.g. for a sequential CPU, parallel CPUs using MPI and OpenMP or GPUs using CUDA and OpenCL. SkePU is comprised of seven data-parallel skeletons and one task-parallel skeleton and these skeletons use two types of containers: vector and matrix to model real-life parallel applications. In this thesis, we address the extension of the SkePU framework by extending the matrix container (which stores 2-D data values) that can efficiently use the existing skeletons to develop parallel scientific applications on large-scale clusters using MPI. This piece of work focuses on the distribution of the matrix among the participating processes which after receiving their share of data can execute the application in parallel. This work covers all of the seven data-parallel skeletons. Each skeleton has been tested with a small application program. In addition to measurement of performance improvement from the application program’s execution time, we have also done a communication cost analysis for all skeletons with MPI using the LogGP model. In order to evaluate and test the operational efficiency of the extension, we have considered a PDE solver application. Through this application, we have demonstrated the performance gain and scalability of the extended framework. The performance improvement was more when computational load dominates the memory I/O operations. The results show that using the extension can serve as a viable approach while implementing real-life parallel applications on large-scale clusters.

  • 450.
    Marián Santos, Javier
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Monkey Gamer: Automatic Profiling of Android Games2013Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Due to the huge amount of smart-phone applications available nowadays,there is a need to check them in order to know if they are trustworthy, efficientand reliable. Furthermore, research on smart-phones is really intensive,so it is important to be able to easily profile applications and collect datathat researchers can use. In this thesis we have focused on Android gamesas they represent a big portion of Android applications and Android is themost used mobile operative system nowadays.

    The thesis work can be divided in two main tasks. The first task consistsof research on Android games in order to know how they are developed,which game design engines are used nowadays and how can we automatisethe execution of Android applications and, in particular, games. The secondstep consists of development of a program called Monkey Gamer that canplay Android games automatically and collect execution traces of the game. The Monkey Gamer analyses the screen shown on a device, recognises theplaces where the user should touch, and interacts with them. Then, consideringeach screen as a state of a state machine, the program tries to coverthe whole game, generating the highest possible number of execution traces.

    In order to test our solution we have compared the traces generated bythe Monkey Gamer with the ones obtained by some real players, achievinga significant similarity. The tests were executed on three games, coveringdifferent categories and implementation solutions.

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