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  • 201.
    Drabent, Wlodzimierz
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Logic + control: On program construction and verification2018In: Theory and Practice of Logic Programming, ISSN 1471-0684, E-ISSN 1475-3081, Vol. 18, no 1, p. 1-29Article in journal (Refereed)
    Abstract [en]

    This paper presents an example of formal reasoning about the semantics of a Prolog program of practical importance (the SAT solver of Howe and King). The program is treated as a definite clause logic program with added control. The logic program is constructed by means of stepwise refinement, hand in hand with its correctness and completeness proofs. The proofs are declarative – they do not refer to any operational semantics. Each step of the logic program construction follows a systematic approach to constructing programs which are provably correct and complete. We also prove that correctness and completeness of the logic program is preserved in the final Prolog program. Additionally, we prove termination, occur-check freedom and non-floundering.

    Our example shows how dealing with “logic” and with “control” can be separated. Most of the proofs can be done at the “logic” level, abstracting from any operational semantics.

    The example employs approximate specifications; they are crucial in simplifying reasoning about logic programs. It also shows that the paradigm of semantics-preserving program transformations may be not sufficient.  We suggest considering transformations which preserve correctness and completeness with respect to an approximate specification.

  • 202.
    Drabent, Wlodzimierz
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    On completeness of logic programs2015In: Logic-Based Program Synthesis and Transformation - 24th International Symposium, (LOPSTR-2014), 2015, Vol. 8981, p. 261-278Conference paper (Refereed)
    Abstract [en]

    Program correctness (in imperative and functional programming) splits in logic programming into correctness and completeness. Completeness means that a program produces all the answers required by its specification. Little work has been devoted to reasoning about completeness. This paper presents a few sufficient conditions for completeness of definite programs. We also study preserving completeness under some cases of pruning of SLD-trees (e.g. due to using the cut). We treat logic programming as a declarative paradigm, abstracting from any operational semantics as far as possible. We argue that the proposed methods are simple enough to be applied, possibly at an informal level, in practical Prolog programming. We point out importance of approximate specifications.

  • 203.
    Drabent, Wlodzimierz
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Institute of Computer Science, Polish Academy of Sciences.
    On definite program answers and least Herbrand models2016In: Theory and Practice of Logic Programming, ISSN 1471-0684, E-ISSN 1475-3081, Vol. 16, no 4, p. 498-508Article in journal (Refereed)
    Abstract [en]

    A sufficient and necessary condition is given under which least Herbrand models exactlycharacterize the answers of definite clause programs.

  • 204.
    Drabent, Wlodzimierz
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Polish Academic Science, Poland.
    Proving completeness of logic programs with the cut2017In: Formal Aspects of Computing, ISSN 0934-5043, E-ISSN 1433-299X, Vol. 29, no 1, p. 155-172Article in journal (Refereed)
    Abstract [en]

    Completeness of a logic program means that the program produces all the answers required by its specification. The cut is an important construct of programming language Prolog. It prunes part of the search space, this may result in a loss of completeness. This paper proposes a way of proving completeness of programs with the cut. The semantics of the cut is formalized by describing how SLD-trees are pruned. A sufficient condition for completeness is presented, proved sound, and illustrated by examples.

  • 205.
    Drabent, Włodzimierz
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Institute of Computer Science, Polish Academy of Sciences, Warzawa, Poland.
    Correctness and Completeness of Logic Programs2016In: ACM Transactions on Computational Logic, ISSN 1529-3785, E-ISSN 1557-945X, Vol. 17, no 3, article id 18Article in journal (Refereed)
    Abstract [en]

    We discuss proving correctness and completeness of definite clause logic programs.  We propose a method for proving completeness, while for proving correctness we employ a method which should be well known but is often neglected.  Also, we show how to prove completeness and correctness in the presence of SLD-tree pruning, and point out that approximate specifications simplify specifications and proofs.

    We compare the proof methods to declarative diagnosis (algorithmic debugging), showing that approximate specifications eliminate a major drawback of the latter.  We argue that our proof methods reflect natural declarative thinking about programs, and that they can be used, formally or informally, in every-day programming.

  • 206.
    Durairaj, Selva Ganesh
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Parallelize Automated Tests in a Build and Test Environment2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis investigates the possibilities of finding solutions, in order to reduce the total time spent for testing and waiting times for running multiple automated test cases in a test framework. The “Automated Test Framework”, developed by Axis Communications AB, is used to write the functional tests to test both hardware and software of a resource. The functional tests that tests the software is considered in this thesis work. In the current infrastructure, tests are executed sequentially and resources are allocated using First In First Out scheduling algorithm. From the user’s point of view, it is inefficient to wait for many hours to run their tests that take few minutes to execute. The thesis consists of two main parts: (1) identify a plugin that suits the framework and executes the tests in parallel, which reduces the overall execution time of tests and (2) analyze various scheduling algorithms in order to address the resource allocation problem, which arose due to limited resource availability, while the tests were run in parallel. By distributing multiple tests across several resources and executing them in parallel, help in improving the test strategy, thereby reducing the overall execution times of test suites. The case studies were created to emulate the problematic scenarios in the company and sample tests were written that reflect the real tests in the framework. Due to the complexity of the current architecture and the limited resources available for running the test in parallel, a simulator was developed with the identified plugin in a multi-core computer, with each core simulating a resource. Multiple tests were run using the simulator in order to explore, check and assess if the overall execution time of the tests can be reduced. While achieving parallelism in running the automated tests, resource allocation became a problem, since limited resources are available to run parallel tests. In order to address this problem, scheduling algorithms were considered. A prototype was developed to mimic the behaviour of a scheduling plugin and the scheduling algorithms were implemented in the prototype. The set of values were given as input to the prototype and tested with scenarios described under case studies. The results from the prototype are used to analyze the impact caused by various scheduling algorithms on reducing the waiting times of the tests. The combined usage of simulator along with scheduler prototype helped in understanding how to minimize the total time spent for testing and improving the resource allocation process.

  • 207.
    Eilert, Rickard
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Development of a framework for creating cross-platform TV HTML5 applications2015Independent thesis Basic level (professional degree), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    When developing HTML5 applications for TV platforms, the TV platforms provide, in addition to standardHTML5 functionality, also extra APIs for TV-specific features. These extra APIs differ between TVplatforms, and that is a problem when developing an application targeting several platforms. This thesis hasexamined if it is possible to design a framework which provides the developer with one API that works formany platforms by wrapping their platform-specific code. The answer is yes. With success, platform-specificfeatures including: TV remote control input, video, volume, Internet connection status, TV channel streamsand EPG data have been harmonised under an API in a JavaScript library. Furthermore, a build systempackages the code in the way the platforms expect. The framework eases the development of TV platformHTML5 applications. At the moment, the framework supports the Pace, PC and Samsung Smart TVplatforms, but it can be extended with more TV platform back-ends.

  • 208.
    Einarson, Carl
    Linköping University, Department of Computer and Information Science, Software and Systems.
    An extension of the PPSZ Algorithm to Infinite-Domain Constraint Satisfaction Problems2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The PPSZ algorithm (Paturi et al., FOCS 1998) is the fastest known algorithm for solving k-SAT when k >= 4. Hertli et al. recently extended the algorithm to solve (d, k)-Clause Satisfaction problems ((d,k)-ClSP) for which it is the fastest known algorithm for all k >= 3 (Hertli et al. CP 2016). We analyze their algorithm and extend it to solve problems over an infinite domain. More specifically we show how the extended algorithm can solve problems that have an infinite domain but where we can, for each instance of the problem, find a finite subset of the domain which has the following properties: If there exists a solution to the problem instance, then there exists a solution using only values from this subset and the size of this subset is polynomial in the size of the problem instance. We show numerically that our algorithm is the fastest known for problems over bounded disjunction languages for some values of k <= 500 and we look at the branching time temporal language, which is a bounded disjunction language, to show how to transform a specific problem to (d,k)-ClSP. We also look at Allen's interval algebra but conclude that there is already a faster algorithm for solving this problem.

  • 209.
    Enberg, Cecilia
    et al.
    Linköping University, Department of Management and Engineering, Business Administration. Linköping University, Faculty of Arts and Sciences.
    Leifler, Ola
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Rapport: Lärande för hållbar utveckling vid utbildningsprogram vid IEI, LiU2018Report (Other academic)
    Abstract [sv]

     

     Denna rapport beskriver en studie vars syfte har varit att undersöka vilka utmaningar och möjligheter som finns med att på ett systematiskt sätt arbeta för att främja ett lärande för hållbar utveckling vid LiU. Vår utgångspunkt har varit universitetskanslerämbetets tematiska utvärdering från 2017 av lärosätenas arbete med att främja en hållbar utveckling genom sina utbildningar. Vi har genomfört en studie med programansvariga vid utbildningar som ges vid institutionen för ekonomisk och industriell utveckling, IEI varav en del på filosofisk och andra på teknisk fakultet. Dels har vi gått igenom utbildningsplanerna för programmen, dels har vi genomfört en enkätundersökning och en uppsättning fokusgruppsdiskussioner med programansvariga.

    Ett mindre antal av programmen och specifikt civilingenjörsutbildningen i Energi, Miljö & Management (EMM) har i utbildningsplaner referenser till specifika mål för en hållbar utveckling som man avser förbereda sina studenter att kunna bidra till. De flesta programs primära fokus ligger dock på anställningsbarhet för sina studenter. Från enkäten och fokusgruppsdiskussioner har vi förstått att det för många programansvariga har varit det första tillfället de fått att fundera över hur deras utbildningar eventuellt bidrar till att förbereda studenter för att hantera utmaningar kopplade till en hållbar utveckling. I våra resultat märks också en tydlig ambivalens och tveksamhet inför både vad man gör just nu, vad man vill göra och vilken sorts drivkrafter och styrning man önskar i det arbetet. Flera programansvariga hävdar å ena sidan att begreppet är svårdefinierat, men att man å andra sidan är säker på att man arbetar i en riktning som gör att utbildningarna bidrar till att främja en hållbar utveckling. Man hävdar att en del lärare vid de egna programmen kan sakna kompetens att hantera problem med flera dimensioner, men anser samtidigt att de egna lärarna har den kompetens som behövs för utbildnings-programmen. Man ser positivt på studenters och externa finansiärers önskemål om förändringar av utbildningarna, men är samtidigt tveksam till många av de sätt som LiU skulle kunna använda för att stödja arbetet med för-ändringar.

    Baserat på vår analys av programansvarigas respons och universitetskanslersämbetets rekommendationer ger vi avslutningsvis rekommendationer för fortsatt arbete med frågan om lärande för hållbar utveckling på LiU.

  • 210.
    Enblom, Gustav
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Eskebaek, Hannes
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Real Time Vehicle Diagnostics Using Head Mounted Displays2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis evaluates how a head mounted display (HMD) can be used to increase usability compared to existing computer programs that are used during maintenance work on vehicles. Problems identified during a case study in a vehicle workshop are first described. As an attempt to solve some of the identified problems a prototype application using a HMD was developed. The prototype application aids the user during troubleshooting of systems on the vehicle by leading the mechanic with textual information and augmented reality (AR). Assessment of the prototype application was done by comparing it to the existing computer program and measuring error rate and time to completion for a predefined task. Usability was also measured using the System Usability Scale. The assessment showed that HMDs can provide higher usability in terms of efficiency and satisfaction. Furthermore, the thesis describes and discusses other possibilities and limitations that usage of HMDs and AR can lead to that were identified both from theory and during implementation.

  • 211.
    Englund, Albin
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Suther, Magnus
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Bluetooth Low Energy som trådlös standard för hemautomation2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The public has a great demand of products in the field of home automation. The latest Bluetooth standard, Bluetooth Low Energy creates new opportunities for interesting products that simplifies everyday life. Solutions such as infraredand Wi-Fi do not qualify for an energy efficient and practical way to o↵er such products, which Bluetooth Low Energy does. In this report, the standard is discussed in order to account for how it can be used to automate a home.

    For this thesis a power switch prototype and an iOSapplication where implemented, which where used to investigate and to demonstrate a concept for how the technology can be applied for home automation. Results shows that the range is the main limitation of the technology. It is also shown how the signal strength may be used as a trigger to control a power switch.

    This report also describes how the system achieves interoperability by implementing a custom profile.

  • 212. Engstrom, Robert
    et al.
    Färnqvist, Tommy
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Jonsson, Peter
    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.
    An Approximability-related Parameter on Graphs - Properties and Applications2015In: DISCRETE MATHEMATICS AND THEORETICAL COMPUTER SCIENCE, ISSN 1462-7264, Vol. 17, no 1, p. 33-66Article in journal (Refereed)
    Abstract [en]

    We introduce a binary parameter on optimisation problems called separation. The parameter is used to relate the approximation ratios of different optimisation problems; in other words, we can convert approximability (and non-approximability) result for one problem into (non)-approximability results for other problems. Our main application is the problem (weighted) maximum H-colourable subgraph (MAX H-COL), which is a restriction of the general maximum constraint satisfaction problem (MAX CSP) to a single, binary, and symmetric relation. Using known approximation ratios for MAX k-CUT, we obtain general asymptotic approximability results for MAX H-COL for an arbitrary graph H. For several classes of graphs, we provide near-optimal results under the unique games conjecture. We also investigate separation as a graph parameter. In this vein, we study its properties on circular complete graphs. Furthermore, we establish a close connection to work by Samal on cubical colourings of graphs. This connection shows that our parameter is closely related to a special type of chromatic number. We believe that this insight may turn out to be crucial for understanding the behaviour of the parameter, and in the longer term, for understanding the approximability of optimisation problems such as MAX H-COL.

  • 213.
    Engström, Adam
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Strömsparande arkitektur för inbyggnadslinux2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The objective of this work was to evaluate and implement a number of energy saving functions for a specific embedded system. The functions were then grouped into a number of energy levels with known properties in terms of functionality, energy consumption, and transition time between the levels.

    The embedded system consisted of an AT91 ARM9 processor, GSM/GPRS modem, display, Ethernet and other peripheral units. Some energy saving methods that were considered were suspend to RAM, suspend to disk, frequency scaling, and methods for saving energy in the modem, Ethernet, USB and display backlight. The functions were grouped into levels and an interface was specified for controlling the energy level.

    It proved possible to get known properties within the defined energy levels, even though the paritioning of functions into these levels proved to be sub-optimal in a typical application usage scenario because it was designed for mainly energy consumption, not usage.

    The final result is a number of energy saving functions grouped into levels, which are controllable via an application interface. Each of the levels have a known energy consumption in both loaded and un-loaded mode.

  • 214.
    Eriksson, Björn
    Linköping University, Department of Computer and Information Science, Software and Systems.
    A study of Bitcoin as a currency for email-based micro-transactions2016Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Bitcoin is a cryptocurrency that has been the focus of a lot of discussions lately and has attracted a large number of users. Its offers many possibilities for cheap transactions and unregulated finances which has been realized in numerous sites and applications on the web and in mobile phones. One medium that seem to have been neglected when it comes to Bitcoins development is email. This is curious since Bitcoin by its nature seem to have many properties that would work well with texted messages. The purpose of this study it to analyze the current papers about Bitcoin to find the current status of email based Bitcoin services,  and try to analyze if email as a tool is a suitable medium to be used with Bitcoin. This analyze is done through a systematic literature review of current papers, followed by an examination of past and current Bitcoin companies that has used email as part of their service. In the end the results suggested that the low security in email, and the apparent lack of services that would benefit from an email based Bitcoin service suggest that a service like that would be hard to develop today and not very useful to the public.

  • 215.
    Eriksson, Joakim
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Representation of asynchronous communication protocols in Scala and Akka2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis work investigates how to represent protocols for asynchronous communication in the Scala programming language and the Akka actor framework, to be run on Java Virtual Machine (JVM). Further restrictions from the problem domain - the coexistence of multiple protocol instances sharing the same Java thread - imply that neither an asynchronous call waiting for response nor anything else can block the underlying Java threads.

    A common way to represent asynchronous communication protocols is to use state machines. This thesis seeks a way to shrink the size of and to reduce the complexity of the protocol implementations by representing sequences of asynchronous communication calls (i.e. sequences of sent and received messages) as a type of procedure. The idea is find a way to make the procedures that contain asynchronous calls look like synchronous communication procedures by hiding the asynchronous details. In other words, the resulting procedure code should show what to do and not so much focus on how to overcome the impediment of the asynchronous calls.

    With the help of an asynchronous communication protocol toy example, this report shows how such an protocol can be implemented with a combination of a state machine and a procedure representation in Scala and Akka. The procedure representation hides away the asynchronous details by using the Scala capability to use CPS-transformed delimited continuations. As a sub-problem, this thesis also shows how to safely schedule asynchronous communication timeouts with help of Scala and Akka within the restrictions of the thesis problem domain.

  • 216.
    Eriksson, Jonas
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Partitioning methodology validation for embedded systems design2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As modern embedded systems are becoming more sophisticated the demands on their applications significantly increase. A current trend is to utilize the advances of heterogeneous platforms (i.e. platform consisting of different computational units (e.g. CPU, FPGA or GPU)) where different parts of the application can be distributed among the different computational units as software and hardware implementations. This technology can improve the application characteristics to meet requirements (e.g. execution time, power consumption and design cost), but it leads to a new challenge in finding the best combination of hardware and software implementation (referred as system configuration). The decisions whether a part of the application should be implemented in software (e.g. as C code) or hardware (e.g. as VHDL code) affect the entire product life-cycle. This is traditionally done manually by the developers in the early stage of the design phase. However, due to the increasing complexity of the application the need of a systematic process that aids the developer when making these decisions to meet the demands rises. Prior to this work a methodology called MULTIPAR has been designed to address this problem. MULTIPAR applies component-/model-based techniques to design the application, i.e. the application is modeled as a number of interconnected components, where some of the components will be implemented as software and the remaining ones as hardware. To perform the partitioning decisions, i.e. determining for each component whether it should be implemented as software or hardware, MULTIPAR proposes a set of formulas to calculate the properties of the entire system based on the properties for each component working in isolation.

    This thesis aims to show to what extent the proposed system formulas are valid. In particular it focuses on validating the formulas that calculate the system response time, system power consumption, system static memory and system FPGA area. The formulas were validated trough an industrial case study, where the system properties for different system configurations were measured and calculated by applying these formulas. The measured values and calculated values for the system properties were compared by conducting a statistical analysis. The case study demonstrated that the system properties can be accurately calculated by applying the system formulas.

  • 217.
    Eriksson, Mattias
    et al.
    Linköping University, Department of Computer and Information Science, PELAB - Programming Environment Laboratory. 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.
    Integrated Code Generation for Loops2012In: ACM Transactions on Embedded Computing Systems, ISSN 1539-9087, E-ISSN 1558-3465, Vol. 11, no 1Article in journal (Refereed)
    Abstract [en]

    Code generation in a compiler is commonly divided into several phases: instruction selection, scheduling, register allocation, spill code generation, and, in the case of clustered architectures, cluster assignment. These phases are interdependent; for instance, a decision in the instruction selection phase affects how an operation can be scheduled We examine the effect of this separation of phases on the quality of the generated code. To study this we have formulated optimal methods for code generation with integer linear programming; first for acyclic code and then we extend this method to modulo scheduling of loops. In our experiments we compare optimal modulo scheduling, where all phases are integrated, to modulo scheduling, where instruction selection and cluster assignment are done in a separate phase. The results show that, for an architecture with two clusters, the integrated method finds a better solution than the nonintegrated method for 27% of the instances.

  • 218.
    Eriksson, Mattias
    et al.
    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.
    Integrated Offset Assignment2011In: Proceedings 9th Workshop on Optimizations for DSP and Embedded Systems (ODES-9) / [ed] George Cai and Tom van der Aa, 2011, p. 47-54Conference paper (Refereed)
    Abstract [en]

    One important part of generating code for DSP processors is to make good use of the address generation unit (AGU). In this paper we divide the code generation into three parts: (1) scheduling, (2) address register assignment, and (3) storage layout. The goal is to nd out if solving these three subproblems as one big integrated problem gives better results compared to when scheduling or address register assignment is solved separately. We present optimal dynamic programming algorithms for both integrated and non-integrated code generation for DSP processors. In our experiments we nd that integrationis benecial when the AGU has 1 or 2 address registers; for the other cases existing heuristics are near optimal. We also nd that integrating address register assignment and storage layout gives slightly better results than integrating scheduling and storage layout. I.e. address register assignment is more important than scheduling.

  • 219.
    Eriksson, Oskar
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Evaluation of BizTalk360: From a business value perspective2019Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    This thesis was requested by Solution Xperts in Linköping and is an evaluation of the software BizTalk360, which is a add-on to the very well known application integration software BizTalk Server. One problem that many face with BizTalk Server is how to handle the post-implementation operations of their implementation. Referring to such factors as monitoring and security for instance. The built-in tools are very limited and lack a variety of functions that are very desirable. BizTalk360 tries to solve this. In order to evaluate the value that BizTalk360 brings to its users, two factors were taken into account. How important are the functions provided for the company? And how difficult would these be to implement independently?. After testing the BizTalk360 core functions and features and also implementing a representative function of BizTalk360, everything learnt were presented to group of experienced BizTalk Sever developers in order to receive estimates regarding their individual importance and theoretical implementation time. The importance of the functions proved quite minor. The platform offers a lot of smart solutions to various problems but these wont see enough use to justify the cost. The difficulty of implementing a similar platform were also estimated to be quite low, only time consuming. Estimated to take (through average) 653 man hours.

  • 220.
    Eriksson, Oskar
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Rydkvist, Emil
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    An in-depth analysis of dynamically rendered vector-based maps with WebGL using Mapbox GL JS2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The regular way of displaying maps in a web browser is by downloading raster images from a server and lay them side by side to make up a map. If any information on the map is changed, new images has to be downloaded, it cannot be done on the client. The introduction of WebGL opens up a whole new world of delivering advanced graphics content to the end user in a web browser. Utilizing this technology for displaying maps means only the source data is sent to the web browser where the map gets rendered using the device's GPU. This adds a number of benefits such as the ability of changing map appearance on the client, add new features to the map and often less data transfer. It however sets higher expectations of the client device's hardware as it needs to render the map at a high enough frame rate to not appear slow and unresponsive. This thesis investigates a framework for client side map rendering in a web browser, Mapbox GL JS, with focus on performance. It shows how map source data can be generated as well as its corresponding style rules are constructed with performance in mind. It provides benchmarking results of different map data sets with different detail intensity and shows that a device with good GPU performance is needed for an acceptable user experience. It also shows that lowering the amount of rendered detail does not necessarily result in better performance.

  • 221.
    Eriksson, Simon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Andersson, Patrik
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Efficient IR for the OpenModelica Compiler2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The OpenModelica compiler currently generates code directly from a syntax tree representation, which leads to inefficient code in several cases. This thesis work introduces a lower-level intermediate representation for the compiler which aims to simplify the compiler back end and enable more optimizations. The resulting design of the representation features flat primitive operations and control flow using basic blocks and terminators. Variables are mutable, unlike SSA-based representations. Introducing the IR did not significantly change the runtime performance of the test programs. The number of lines of code compared to the old back end was reduced to a quarter, this and the simpler representation will help future work on optimization passes and implementing an LLVM-based back end.

  • 222.
    Ernfridsson, Alexander
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Sammansättning av ett privat moln som infrastruktur för utveckling2017Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [sv]

    Idag är det vanligt att hantera, beskriva och konfigurera sin datainfrastruktur såsom processer, serverar och miljöer i maskinläsbara konfigurationsfiler istället för fysisk hårdvara eller interaktiva konfigureringsverktyg. Automatiserad datainfrastruktur blir mer och mer vanligt för att kunna fokusera mer på utveckling och samtidigt få ett stabilare system. Detta har gjort att antalet verktyg för automatisering av datainfrastruktur skjutit i höjden det senaste årtiondet. Lösningar för automatisering av olika typer av datainfrastrukturer har blivit mer komplexa och innehåller ofta många verktyg som interagerar med varandra.

    Det här kandidatarbetet jämför, väljer ut och sätter ihop existerande plattformar och verktyg och skapar ett privat moln som infrastruktur för utveckling. Detta för att effektivera livscykeln för en serverbaserad runtime-miljö. En jämförelse av molnplattformarna OpenStack, OpenNebula, CloudStack och Eucalyptus baserad på litteratur, lägger grunden för molnet. Molnplattformen kompletteras därefter med andra verktyg och lösningar för att fullborda livscykelautomatiseringen av runtime-miljöer. En prototyp av lösningen skapades för att analysera praktiska problem.

    Arbetet visar att en kombination av OpenStack, Docker, containerorkestrering samt konfigureringsverktyg är en lovande lösning. Lösningen skalar efter behov, automatiserar och hanterar verksamhetens konfigurationer för runtime-miljöer.

  • 223.
    Ernstsson, August
    Linköping University, Department of Computer and Information Science, Software and Systems.
    SkePU 2: Language Embedding and Compiler Support for Flexible and Type-Safe Skeleton Programming2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis presents SkePU 2, the next generation of the SkePU C++ framework for programming of heterogeneous parallel systems using the skeleton programming concept. SkePU 2 is presented after a thorough study of the state of parallel programming models, frameworks and tools, including other skeleton programming systems. The advancements in SkePU 2 include a modern C++11 foundation, a native syntax for skeleton parameterization with user functions, and an entirely new source-to-source translator based on Clang compiler front-end libraries.

    SkePU 2 extends the functionality of SkePU 1 by embracing metaprogramming techniques and C++11 features, such as variadic templates and lambda expressions. The results are improved programmability and performance in many situations, as shown in both a usability survey and performance evaluations on high-performance computing hardware. SkePU’s skeleton programming model is also extended with a new construct, Call, unique in the sense that it does not impose any predefined skeleton structure and can encapsulate arbitrary user-defined multi-backend computations.

    We conclude that SkePU 2 is a promising new direction for the SkePU project, and a solid basis for future work, for example in performance optimization.

  • 224.
    Ernstsson, August
    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.
    Extending smart containers for data locality-aware skeleton programming2019In: Concurrency and Computation, ISSN 1532-0626, E-ISSN 1532-0634, Vol. 31, no 5, article id e5003Article in journal (Refereed)
    Abstract [en]

    We present an extension for the SkePU skeleton programming framework to improve the performance of sequences of transformations on smart containers. By using lazy evaluation, SkePU records skeleton invocations and dependencies as directed by smart container operands. When a partial result is required by a different part of the program, the run-time system will process the entire lineage of skeleton invocations; tiling is applied to keep chunks of container data in the working set for the whole sequence of transformations. The approach is inspired by big data frameworks operating on large clusters where good data locality is crucial. We also consider benefits other than data locality with the increased run-time information given by the lineage structures, such as backend selection for heterogeneous systems. Experimental evaluation of example applications shows potential for performance improvements due to better cache utilization, as long as the overhead of lineage construction and management is kept low.

  • 225.
    Ernstsson, August
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Li, Lu
    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.
    SkePU 2: Flexible and Type-Safe Skeleton Programming for Heterogeneous Parallel Systems2018In: International journal of parallel programming, ISSN 0885-7458, E-ISSN 1573-7640, Vol. 46, no 1, p. 62-80Article in journal (Refereed)
    Abstract [en]

    In this article we present SkePU 2, the next generation of the SkePU C++ skeleton programming framework for heterogeneous parallel systems. We critically examine the design and limitations of the SkePU 1 programming interface. We present a new, flexible and type-safe, interface for skeleton programming in SkePU 2, and a source-to-source transformation tool which knows about SkePU 2 constructs such as skeletons and user functions. We demonstrate how the source-to-source compiler transforms programs to enable efficient execution on parallel heterogeneous systems. We show how SkePU 2 enables new use-cases and applications by increasing the flexibility from SkePU 1, and how programming errors can be caught earlier and easier thanks to improved type safety. We propose a new skeleton, Call, unique in the sense that it does not impose any predefined skeleton structure and can encapsulate arbitrary user-defined multi-backend computations. We also discuss how the source-to-source compiler can enable a new optimization opportunity by selecting among multiple user function specializations when building a parallel program. Finally, we show that the performance of our prototype SkePU 2 implementation closely matches that of SkePU 1.

  • 226.
    Faur, Andrei
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Memory Profiling Techniques2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Memory profiling is an important technique which aids program optimization and can even help tracking down bugs. The main problem with the current memory profiling techniques and tools is that they slow down the target software considerably therefore making them inadequate for mainline integration. Ideally, the user would be able to monitor memory consumption without having to worry about the rest of the software being affected in any way. This thesis provides a comparison of existing techniques and tools along with the description of a memory profiler implementation which tries to provide a balance between the information it is able to retrieve and the influence it has on the target software.

  • 227.
    Ferretti, Gianni
    et al.
    Politecn Milan, Italy.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Editorial Material: Special issue on object-oriented modelling and simulation in MATHEMATICAL AND COMPUTER MODELLING OF DYNAMICAL SYSTEMS, vol 23, issue 3, pp 240-2422017In: Mathematical and Computer Modelling of Dynamical Systems, ISSN 1387-3954, E-ISSN 1744-5051, Vol. 23, no 3, p. 240-242Article in journal (Other academic)
    Abstract [en]

    n/a

  • 228.
    Fischer, Benjamin
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Vehicular Group Membership Resilient to Malicious Attacks2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    There is a range of tools and techniques in the realm of information security that can be used to enhance the security of a distributed network protocol and some of them introduce new problems. A security analysis of the distributed network protocol SLMP is made and three vulnerabilities are identified; messages can be intercepted and tampered with, nodes can fake id, and leader nodes can do a lot of harm if they are malicious. Three versions of SLMP that aims to remedy these vulnerabilities are implemented and the results show that while they remedy the vulnerabilities some of them introduce new problems. 

  • 229.
    Fleming, Theodor
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Decentralized Identity Management for a Maritime Digital Infrastructure: With focus on usability and data integrity2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    When the Internet was created it did not include any protocol for identifying the person behind the computer. Instead, the act of identification has primarily been established by trusting a third party. But, the rise of Distributed Ledger Technology has made it possible to authenticate a digital identity and build trust without the need of a third party. The Swedish Maritime Administration are currently validating a new maritime digital infrastructure for the maritime transportation industry. The goal is to reduce the number of accidents, fuel consumption and voyage costs. Involved actors has their identity stored in a central registry that relies on the trust of a third party. This thesis investigates how a conversion from the centralized identity registry to a decentralized identity registry affects the usability and the risk for compromised data integrity. This is done by implementing a Proof of Concept of a decentralized identity registry that replaces the current centralized registry, and comparing them. The decentralized Proof of Concept’s risk for compromised data integrity is 95.1% less compared with the centralized registry, but this comes with a loss of 53% in efficiency.

  • 230.
    Fors Johansson, Christoffer
    Linköping University, Department of Computer and Information Science, Software and Systems.
    OpenModelica Interactive Simulation using an OPC UA client2017Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Simulating a model of a complex physical system can beuseful in order to obtain a deeper understanding of the system.OpenModelica is an open-source, modeling and simulation environmentin which such a simulation could be performed. This thesispresents a design and implementation of an interactive simulationprototype for the OpenModelica Connection Editor. After aninvestigation of the possibilities in the current OpenModelicaenvironment, several requirements were determined about howinteractive simulation should look and work. A prototype wasdeveloped based on these requirements. As a result, the prototypecan act as a base for applying further functionality to theinteractive simulation in both parallel and future works.

  • 231.
    Forsell, Martti
    et al.
    Platform Architectures Team, VTT Technical Research Centre of Finland, Finland.
    Hansson, Erik
    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.
    Mäkelä, Jari-Matti
    Information Technology, University of Turku, Finland.
    Leppänen, Ville
    Information Technology, University of Turku, Finland.
    Hardware and Software Support for NUMA Computing on Configurable Emulated Shared Memory Architectures2013In: 2013 IEEE 27th International Parallel and Distributed Processing Symposium Workshops & PhD Forum (IPDPSW), IEEE conference proceedings, 2013, p. 640-647Conference paper (Refereed)
    Abstract [en]

    The emulated shared memory (ESM) architectures are good candidates for future general purpose parallel computers due to their ability to provide easy-to-use explicitly parallel synchronous model of computation to programmers as well as avoid most performance bottlenecks present in current multicore architectures. In order to achieve full performance the applications must, however, have enough thread-level parallelism (TLP). To solve this problem, in our earlier work we have introduced a class of configurable emulated shared memory (CESM) machines that provides a special non-uniform memory access (NUMA) mode for situations where TLP is limited or for direct compatibility for legacy code sequential computing or NUMA mechanism. Unfortunately the earlier proposed CESM architecture does not integrate the different modes of the architecture well together e.g. by leaving the memories for different modes isolated and therefore the programming interface is non-integrated. In this paper we propose a number of hardware and software techniques to support NUMA computing in CESM architectures in a seamless way. The hardware techniques include three different NUMA-shared memory access mechanisms and the software ones provide a mechanism to integrate NUMA computation into the standard parallel random access machine (PRAM) operation of the CESM. The hardware techniques are evaluated on our REPLICA CESM architecture and compared to an ideal CESM machine making use of the proposed software techniques.

  • 232.
    Forsell, Martti
    et al.
    Platform Architectures Team, VTT Technical Research Centre of Finland, Finland.
    Hansson, Erik
    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.
    Mäkelä, Jari-Matti
    Department of Information Technology, University of Turku, Finland.
    Leppänen, Ville
    Department of Information Technology, University of Turku, Finland.
    NUMA Computing with Hardware and Software Co-Support on Configurable Emulated Shared Memory Architectures2014In: International Journal of Networking and Computing, ISSN 2185-2839, E-ISSN 2185-2847, Vol. 4, no 1, p. 189-206Article in journal (Refereed)
    Abstract [en]

    The emulated shared memory (ESM) architectures are good candidates for future general purpose parallel computers due to their ability to provide an easy-to-use explicitly parallel synchronous model of computation to programmers as well as avoid most performance bottlenecks present in current multicore architectures. In order to achieve full performance the applications must, however, have enough thread-level parallelism (TLP). To solve this problem, in our earlier work we have introduced a class of configurable emulated shared memory (CESM) machines that provides a special non-uniform memory access (NUMA) mode for situations where TLP is limited or for direct compatibility for legacy code sequential computing and NUMA mechanism. Unfortunately the earlier proposed CESM architecture does not integrate the different modes of the architecture well together e.g. by leaving the memories for different modes isolated and therefore the programming interface is non-integrated. In this paper we propose a number of hardware and software techniques to support NUMA computing in CESM architectures in a seamless way. The hardware techniques include three different NUMA shared memory access mechanisms and the software ones provide a mechanism to integrate and optimize NUMA computation into the standard parallel random access machine (PRAM) operation of the CESM. The hardware techniques are evaluated on our REPLICA CESM architecture and compared to an ideal CESM machine making use of the proposed software techniques.

  • 233.
    Forsgren, Mikael
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Dahlström, Nils
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Karlsson, Markus
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology. Linköping University, Department of Clinical and Experimental Medicine, Division of Neuroscience.
    Dahlqvist Leinhard, Olof
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Smedby, Örjan
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Cedersund, Gunnar
    Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Whole Body Mechanistic Minimal Model for Gd-EOB-DTPA Contrast Agent Pharmacokinetics in Evaluation of Diffuse Liver Disease2014Conference paper (Other academic)
    Abstract [en]

    Purpose: Aiming for non-invasive diagnostic tools to decrease the need for biopsy in diffuse liver disease and to quantitatively describe liver function, we applied a mechanistic pharmacokinetic modelling analysis of liver MRI with Gd-EOB-DTPA. This modelling method yields physiologically relevant parameters and was compared to previously developed methods in a patient group with diffuse liver disease. Materials and Methods: Using data from healthy volunteers undergoing liver MRI, an identifiable mechanistic model was developed, based on compartments described by ordinary differential equations and kinetic expressions, and validated with independent data including Gd-EOB-DTPA concentration measurements in blood samples. Patients (n=37) with diffuse liver disease underwent liver biopsy and MRI with Gd-EOB-DTPA. The model was used to derive pharmacokinetic parameters which were then compared with other quantitative estimates in their ability to separate mild from severe liver fibrosis. Results: The estimations produced by the mechanistic model allowed better separation between mild and severe fibrosis than previously described methods for quantifying hepatic Gd-EOB-DTPA uptake. Conclusions: With a mechanistic pharmacokinetic modelling approach, the estimation of liver uptake function and its diagnostic information can be improved compared to current methods.

  • 234.
    Foster, Simon
    et al.
    University of York, England.
    Thiele, Bernhard Amadeus
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Cavalcanti, Ana
    University of York, England.
    Woodcock, Jim
    University of York, England.
    Towards a UTP Semantics for Modelica2017In: UNIFYING THEORIES OF PROGRAMMING, UTP 2016, SPRINGER INTERNATIONAL PUBLISHING AG , 2017, Vol. 10134, p. 44-64Conference paper (Refereed)
    Abstract [en]

    We describe our work on a UTP semantics for the dynamic systems modelling language Modelica. This is a language for modelling a systems continuous behaviour using a combination of differential-algebraic equations and an event-handling system. We develop a novel UTP theory of hybrid relations, inspired by Hybrid CSP and Duration Calculus, that is purely relational and provides uniform handling of continuous and discrete variables. This theory is mechanised in our Isabelle implementation of the UTP, Isabelle/UTP, with which we verify some algebraic properties. Finally, we show how a subset of Modelica models can be given semantics using our theory. When combined with the wealth of existing UTP theories for discrete system modelling, our work enables a sound approach to heterogeneous semantics for Cyber-Physical systems by leveraging the theory linking facilities of the UTP.

  • 235.
    Fouladi, Amir Hossein
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Zafari Khorvaj, Omid
    Linköping University, Department of Computer and Information Science, Software and Systems.
    TryMyLanguage: An Extensible, Web-based Software Development Environment2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Introducing a new programming language can be a challenge to languagedesigners and developers. This is usually due to diculties related to settingup the environment and going through the documentation for people whowant to start using and learning the language. In this thesis, we developeda web-based software system called TryMyLanguage which can be used toalleviate this issue by eliminating the need for users to install and congurerelated software tools such as compiler, interpreter, etc., on their computers.TryMyLanguage can be congured with dierent programming languagesand it is not limited to a set of predened languages. We evaluated thesystem by simulating a production environment and showing how it wouldbehave in such an environment. At the end a case study is presented to showhow the system can be used with a programming language named Modelyzeas an example.

  • 236.
    French, Kimberley
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Energy Consumption of In-Vehicle Communication in Electric Vehicles: A comparison between CAN, Ethernet and EEE2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As a step towards decreasing the greenhouse gas emissions caused by the transport sector, electrical vehicles (EVs) have become more and more popular. Two major problem areas the EV industry is currently facing are range limitations, i.e. being restricted by the capacity of the battery, as well as a demand for higher bandwidth as the in-vehicle communication increases. In this thesis, an attempt is made to address these problem areas by examining the energy consumption required by Controller Area Network (CAN) and Ethernet. In addition, the effects of Energy-Efficient Ethernet (EEE) are reviewed. The protocols are examined by performing a theoretical analysis over CAN, Ethernet and EEE, physical tests over CAN and Ethernet, as well as simulations of EEE. The results show that Ethernet requires 2.5 to four times more energy than CAN in theory, and 4.5 to six times more based on physical measurements. The energy consumption of EEE depends on usage, ranging from energy levels of 40 \% less than CAN when idle, and up to equal amounts as regular Ethernet at high utilisation. By taking full advantage of the traits of Time-Sensitive Networking, EEE has the potential of significantly decreasing the amount of energy consumed compared to standard Ethernet while still providing a much higher bandwidth than CAN, at the cost of introducing short delays. This thesis provides insight into the behaviour of a transmitter for each of the three protocols, discusses the energy implications of replacing CAN with Ethernet and highlights the importance of understanding how to use Ethernet and EEE efficiently.

  • 237.
    Fridell, Emil
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Architectural Rules Conformance with ArCon and Open-SourceModeling Tools2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In software development it is often crucial that the system implementationfollows the architecture dened through design patterns and a constraint set.In Model-Driven development most artefacts are created using models, butthe architectural design rules is one area where no standard to model therules exists. ArCon, Architecture Conformance Checker, is a tool to checkconformance of architectural design rules on a system model, dened in UML,that implements the system or application. The architectural design rules aredened in a UML model but with a specic meaning, dierent from standardUML, proposed by the authors of ArCon. Within this thesis ArCon wasextended to be able to check models created by the Open-Source modelingtool Papyrus, and integrated as a plugin on the Eclipse platform. The methodused by ArCon, to dene architectural rules, was also given a short evaluationduring the project to get a hint of its potential and future use. The case-studyshowed some problems and potential improvements of the used implementationof ArCon and its supported method.

  • 238.
    Frimodig, Johan
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Utvärdering och förslag för att skapa ett effektivare administrationsverktyg i AES2018Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
  • 239.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Urquía Moraleda, Alfonso (Translator)
    Universidad Nacional de Educación a Distancia, Madrid, España.
    Villa Ramírez, José Luis (Translator)
    Campus Tecnológico Km 1, Via Turbaco Cartagena de Indias, Colombia.
    Introducción al Modelado y Simulación de Sistemas Técnicos y Físicos con Modelica2015Book (Other academic)
    Abstract [en]

    Master modeling and simulation using Modelica, the new powerful, highly versatile object-based modeling language

    Modelica, the new object-based software/hardware modeling language that is quickly gaining popularity around the world, offers an almost universal approach to high-level computational modeling and simulation. It handles a broad range of application domains, for example mechanics, electrical systems, control, and thermodynamics, and facilitates general notation as well as powerful abstractions and efficient implementations. Using the versatile Modelica language and its associated technology, this text presents an object-oriented, component-based approach that makes it possible for readers to quickly master the basics of computer-supported equation-based object-oriented (EOO) mathematical modeling and simulation.

    Throughout the text, Modelica is used to illustrate the various aspects of modeling and simulation. At the same time, a number of key concepts underlying the Modelica language are explained with the use of modeling and simulation examples. This book:

    • Examines basic concepts such as systems, models, and simulations

    • Guides readers through the Modelica language with the aid of several step-by-step examples

    • Introduces the Modelica class concept and its use in graphical and textual modeling

    • Explores modeling methodology for continuous, discrete, and hybrid systems

    • Presents an overview of the Modelica Standard Library and key Modelica model libraries

    Readers will find plenty of examples of models that simulate distinct application domains as well as examples that combine several domains. All the examples and exercises in the text are available via DrModelica. This electronic self-teaching program, freely available on the text's companion website, guides readers from simple, introductory examples and exercises to more advanced ones.

    Written by the Director of the Open Source Modelica Consortium, Introduction to Modeling and Simulation of Technical and Physical Systems with Modelica is recommended for engineers and students interested in computer-aided design, modeling, simulation, and analysis of technical and natural systems. By building on basic concepts, the text is ideal for students who want to learn modeling, simulation, and object orientation.

    This book is aimed at teaching Modelica modeling and simulation to beginners, or in courses where there is only limited time for an introduction to Modelica. For more in-dept coverage of this topic, the book Principles of Object-Oriented Modeling and Simulation with Modelica 3.3: A Cyber-Physical Approach is recommended. That book also includes the introductory material of the small book.

    This book is aimed at teaching Modelica modeling and simulation to beginners, or in courses where there is only limited time for an introduction to Modelica.

    For more in-dept coverage of this topic, the book Principles of Object-Oriented Modeling and Simulation with Modelica 3.3: A Cyber-Physical Approach is recommended. That book also includes the introductory material of the small book.

  • 240.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Model-based development of sustainable cyber-physical systems including requirement formalization using the OpenModelica Model-based Development Toolkit2016In: ACM PROCCEDINGS OF THE 10TH EUROPEAN CONFERENCE ON SOFTWARE ARCHITECTURE WORKSHOPS (ECSA-W), ASSOC COMPUTING MACHINERY , 2016Conference paper (Refereed)
    Abstract [en]

    Large-scale and increasingly software-defined systems in power and factory automation are very long-lived. Longevity requires sustainability-economically, environmentally and last but not least in terms of usability. Sustainability therefore requires continuous change. In this talk we look at handling requirements, models, and implementations in a model-driven formal way that lends itself to a more systematic change tracking than traditional software development approaches and languages, but that also crosses boundaries of software-controlled physical equipment models (so-called cyber-physical systems), distributed digital control (networked systems) and software services. The industry is currently seeing a rapid development of cyber-physical system products. The systems that are developed have increasing demands of sustainability, dependability and usability. Moreover, lead time and cost efficiency continue to be essential for industry competitiveness. Extensive use of modeling and simulation - Model-Based Systems Engineering (MBSE) tools - throughout the value chain and system life-cycle is one of the most important ways to effectively target these challenges. Simultaneously there is an increased interest in open source tools that allow more control of tool features and support, and increased cooperation and shared access to knowledge and innovations between organizations. In this talk we briefly present technology and open source tooling for MBSE based on the Modelica and UML standards, supported by tools such as OpenModelica and Papyrus respectively. Modelica is a modern, strongly typed, declarative, equation-based, and object-oriented language for modeling and simulation of complex cyber-physical systems, whereas UML is a wide-spread industrial standard for software modeling. We present the OpenModelica open source MBSE environment including the ModelicaML Eclipse plug-in integrating Modelica and UML, covering the development process starting from business processes, via requirements, to models, which can be compiled to simulations or to product code. An important question is whether a particular system design fulfills or violates requirements that are imposed on the system under development. We give examples of case studies starting with natural-language requirements and show briefly how they are translated into models. Then, designs and verification scenarios are modeled, and simulation models are composed and simulated automatically. The simulation results produced can then be used to draw conclusions on requirement fulfillment. Other features of the environment are meta modeling for efficient model transformations, the Functional Mockup Interface for general tool integration, model-based optimization, as well as generation of parallel code for multi-core architectures.

  • 241.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Principles of object-oriented modeling and simulation with Modelica 3.3: a cyber-physical approach2015 (ed. 2)Book (Other academic)
    Abstract [en]

    The second edition features improvements and updates of the Modelica language including synchronous clocked constructs, examines basic concepts of cyber-physical, equation-based, object-oriented system modeling and simulation. Prof. Fritzson introduces the Modelica class concept and its use in graphical and textual modeling with several hundred examples from many application areas and explores modeling methodology for continuous, discrete, and hybrid systems; and more.

    This text is aimed at System Modeling and Simulation engineers, control engineers, mechanical engineers, those working with CAD (Computer Aided Design), virtual reality, biochemistry, embedded systems, and data communication.

    Fritzson covers the Modelica language in impressive depth from the basic concepts such as cyber-physical, equation-base, object-oriented, system, model, and simulation, while also incorporating over a hundred exercises and their solutions for a tutorial, easy-to-read experience.

    • The only book with complete Modelica 3.3 coverage
    • Over one hundred exercises and solutions
    • Examines basic concepts such as cyber-physical, equation-based, object-oriented, system, model, and simulation

  • 242.
    Fritzson, Peter
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Elmqvist, HildingDassault Systémes AB, Sweden.
    Proceedings of the 11th International Modelica Conference, Versailles, France, September 21-23, 20152015Conference proceedings (editor) (Refereed)
    Abstract [en]

    Welcome The 11th International Modelica Conference, which takes place at Palais des Congrès de Versailles, is the main event for the Modelica community. Users, library developers, tool vendors, and language designers gather to share their knowledge and learn about the latest scientific and industrial progress related to Modelica and FMI (Functional Mockup Interface). The fundamental idea behind Modelica is to allow storing modeling knowhow in a high-level formally defined format, i.e., to collect information which you otherwise would find in engineering books only accessible by humans. By allowing convenient reuse of this knowhow by definition of component model libraries, enormous saving in man-hours for setting up simulation studies is achieved. Furthermore, by proper validation of such model libraries, much more reliable conclusions can be made from simulation studies leading to better products and user experience. These considerations lead to the equation-based object-oriented formalism of Modelica. Since the start of the collaborative design work for Modelica in 1996, Modelica has matured from an idea among a small number of dedicated enthusiasts to a widely accepted standard language for the modeling and simulation of cyber-physical systems. In addition, the standardization of the language by the non-profit organization Modelica Association enables Modelica models to be portable between a growing number of tools. Modelica is now used in many industries including automotive, energy and process, aerospace, and industrial equipment. Modelica is the language of choice for model-based systems engineering. The FMI standard has been added to the project portfolio of the Modelica Association. FMI provides a complementary standard that enables deployment of pre-compiled high quality models originating from different model formats to a larger number of engineers working with system design and verification.

  • 243.
    Fritzson, Peter
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Pop, Adrian
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Sjölund, Martin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Asghar, Adeel
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    MetaModelica – A Symbolic-Numeric Modelica Language and Comparison to Julia2019In: Proceedings of the 13th International Modelica Conference, Regensburg, Germany, March 4–6, 2019 / [ed] Anton Haumer: OTH Regensburg, Germany, Linköping, 2019Conference paper (Refereed)
    Abstract [en]

    The need for integrating system modeling with advanced tool capabilities is becoming increasingly pronounced. For example, a set of simulation experiments may give rise to new data that are used to systematically construct a series of new models, e.g. for further simulation and design optimization. Such combined symbolic-numeric capabilities have been pioneered by dynamically typed interpreted languages such as Lisp and Mathematica. Such capabilities are also relevant for advanced modeling and simulation applications but lacking in the standard Modelica language. Therefore, this is a topic of long-running design discussions in the Modelica Design group. One contribution in this direction is MetaModelica, that has been developed to extend Modelica with symbolic operations and advanced data structures, while preserving safe engineering practices through static type checking and a compilation-based efficient implementation. Another recent effort is Modia, implemented using the Julia macro mechanism, making it dynamically typed but also adding new capabilities. The Julia language has appeared rather recently and has expanded into a large and fast-growing ecosystem. It is dynamically typed, provides both symbolic and numeric operations, advanced data structures, and has a just-intime compilation-based efficient implementation. Despite independent developments there are surprisingly many similarities between Julia and MetaModelica. This paper presents MetaModelica and its environment as a large case study, together with a short comparison to Julia. Since Julia may be important for the future Modelica, some integration options between Modelica tools and Julia are also discussed, including a possible approach for implementing MetaModelica (and OpenModelica) in Julia.

  • 244.
    Färnqvist, Tommy
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Constraint Optimization Problems and Bounded Tree-width Revisited2012Conference paper (Other academic)
    Abstract [en]

    The valued constraint satisfaction problem (VCSP) is an optimization framework originating from artificial intelligence which generalizes the classical constraint satisfaction problem (CSP). In this paper, we are interested in structural properties that can make problems from the VCSP framework, as well as other CSP variants, solvable to optimality in polynomial time. So far, the largest structural class that is known to be polynomial-time solvable to optimality is the class of bounded hypertree width instances introduced by Gottlob et al. Here, larger classes of tractable instances are singled out by using dynamic programming and structural decompositions based on a hypergraph invariant proposed by Grohe and Marx. In the second part of the paper, we take a different view on our optimization problems; instead of considering fixed arbitrary values for some structural invariant of the (hyper)graph structure of the constraints, we consider the problems parameterized by the tree-width of primal, dual, and incidence graphs, combined with several other basic parameters such as domain size and arity. Such parameterizations of plain CSPs have been studied by Samer and Szeider. Here, we extend their framework to encompass our optimization problems, by coupling it with further non-trivial machinery and new reductions. By doing so, we are able to determine numerous combinations of the considered parameters that make our optimization problems admit fixed-parameter algorithms.

  • 245.
    Färnqvist, Tommy
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Counting Homomorphisms via Hypergraph-based Structural Restrictions2012Conference paper (Refereed)
    Abstract [en]

    The way in which the graph structure of the constraints influences the computational complexity of counting constraint satisfaction problems (#CSPs) is well understood for constraints of bounded arity. The situation is less clear if there is no bound on the arities. Here we initiate the systematic study of these problems and identify new classes of polynomial time solvable instances based on dynamic programming over tree decompositions, in a way generalizing well-known approaches to combinatorial optimization problems on bounded treewidth graphs, but basing the decompositions on various hypergraph width measures from the literature on plain CSPs.

  • 246.
    Färnqvist, Tommy
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Exploiting Structure in CSP-related Problems2013Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In this thesis we investigate the computational complexity and approximability of computational problems from the constraint satisfaction framework. An instance of a constraint satisfaction problem (CSP) has three components; a set V of variables, a set D of domain values, and a set of constraints C. The constraints specify a set of variables and associated local conditions on the domain values allowed for each variable, and the objective of a CSP is to assign domain values to the variables, subject to these constraints.

    The first main part of the thesis is concerned with studying restrictions on the structure induced by the constraints on the variables for different computational problems related to the CSP. In particular, we examine how to exploit various graph, and hypergraph, acyclicity measures from the literature to find classes of relational structures for which our computational problems become efficiently solvable. Among the problems studied are, such where, in addition to the constraints of a CSP, lists of allowed domain values for each variable are specified (LHom). We also study variants of the CSP where the objective is changed to: counting the number of possible assignments of domain values to the variables given the constraints of a CSP (#CSP), minimising or maximising the cost of an assignment satisfying all constraints given various different ways of assigning costs to assignments (MinHom, Max Sol, and CSP), or maximising the number of satisfied constraints (Max CSP). In several cases, our investigations uncover the largest known (or possible) classes of relational structures for which our problems are efficiently solvable. Moreover, we take a different view on our optimisation problems MinHom and VCSP; instead of considering fixed arbitrary values for some (hyper)graph acyclicity measure associated with the underlying CSP, we consider the problems parameterised by such measures in combination with other basic parameters such as domain size and maximum arity of constraints. In this way, we identify numerous combinations of the considered parameters which make these optimisation problems admit fixed-parameter algorithms.

    In the second part of the thesis, we explore the approximability properties of the (weighted) Max CSP problem for graphs. This is a problem which is known to be approximable within some constant ratio, but not believed to be approximable within an arbitrarily small constant ratio. Thus it is of interest to determine the best ratio within which the problem can be approximated, or at least give some bound on this constant. We introduce a novel method for studying approximation ratios which, in the context of Max CSP for graphs, takes the form of a new binary parameter on the space of all graphs. This parameter may, informally, be thought of as a sort of distance between two graphs; knowing the distance between two graphs, we can bound the approximation ratio of one of them, given a bound for the other.

  • 247.
    Färnqvist, Tommy
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Heintz, Fredrik
    Linköping University, Department of Computer and Information Science, Artificial Intelligence and Integrated Computer Systems. Linköping University, Faculty of Science & Engineering.
    Lambrix, Patrick
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    Mannila, Linda
    Åbo Academy, Finland.
    Wang, Chunyan
    Linköping University, Department of Computer and Information Science.
    Supporting Active Learning by Introducing an Interactive Teaching Tool in a Data Structures and Algorithms Course2016In: Proceedings of the 47th ACM Technical Symposium on Computer Science Education (SIGCSE 2016), ACM Publications, 2016, p. 663-668Conference paper (Refereed)
    Abstract [en]

    Traditionally, theoretical foundations in data structures and algorithms (DSA) courses have been covered through lectures followed by tutorials, where students practise their understanding on pen-and-paper tasks. In this paper, we present findings from a pilot study on using the interactive e-book OpenDSA as the main material in a DSA course. The goal was to redesign an already existing course by building on active learning and continuous examination through the use of OpenDSA. In addition to presenting the study setting, we describe findings from four data sources: final exam, OpenDSA log data, pre and post questionnaires as well as an observation study. The results indicate that students performed better on the exam than during previous years. Students preferred OpenDSA over traditional textbooks and worked actively with the material, although a large proportion of them put off the work until the due date approaches.

  • 248.
    Färnqvist, Tommy
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Heintz, Fredrik
    Linköping University, Department of Computer and Information Science, Artificial Intelligence and Integrated Computer Systems. Linköping University, Faculty of Science & Engineering.
    Lambrix, Patrick
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    Mannila, Linda
    Åbo Academy, Finland.
    Wang, Chunyan
    Linköping University, Department of Computer and Information Science.
    Supporting Active Learning Using an Interactive Teaching Tool in a Data Structures and Algorithms Course2015In: Proceedings of 5:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar (UtvSvIng), 2015, p. 76-79Conference paper (Other academic)
    Abstract [en]

    Traditionally, theoretical foundations in data structuresand algorithms (DSA) courses have been covered throughlectures followed by tutorials, where students practise theirunderstanding on pen-and-paper tasks. In this paper, we presentfindings from a pilot study on using the interactive e-bookOpenDSA as the main material in a DSA course. The goal was toredesign an already existing course by building on active learningand continuous examination through the use of OpenDSA. Inaddition to presenting the study setting, we describe findings fromfour data sources: final exam, OpenDSA log data, pre- and postcourse questionnaires as well as an observation study. The resultsindicate that students performed better on the exam than duringprevious years. Students preferred OpenDSA over traditionaltextbooks and worked actively with the material, although alarge proportion of them put off the work until the due dateapproaches.

  • 249.
    Gallastegi, Akaitz
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Web-based Real-Time Communication for Rescue Robots2014Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    In this thesis an audio and video streaming system is implemented for its use in rescue robots. WebRTC technology is used in order to stream in real time. Implemented in an architecture based on a Web server, two pages running WebRTC and a TURN1-STUN2 server, the system has been tested in terms of CPU and bandwidth utilization. Measurements show that when WebRTC is run in an Intel Core i3, less than 10% of CPU is used, whereas on smaller tablets the performance is not enough for running the application with the desired quality of service.

  • 250.
    Ganeson, Anand
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Design and Implementation of a User Friendly OpenModelica - Python interface2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    How can Python users be empowered with the robust simulation, compilation and scripting abilities of a non-proprietary object-oriented, equation based modeling language such as Modelica? The immediate objective of this thesis work is to develop an application programming interface for the OpenModelica modeling and simulation environment that would bridge the gap between the two agile programming languages Python and Modelica.

    The Python interface to OpenModelica OMPython, is both a tool and a functional library that allows Python users to realize the full capabilities of Open- Modelica’s scripting and simulation environment requiring minimal setup actions. OMPython is designed to combine both simulation and model building. Thus domain experts (people writing the models) and computational engineers (people writing the solver code) can work on one unified tool that is industrially viable for optimization of Modelica models, while offering a flexible platform for algorithm development and research.

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