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  • 201.
    Eriksson, Joakim
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Representation of asynchronous communication protocols in Scala and Akka2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    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.

  • 202.
    Eriksson, Jonas
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Partitioning methodology validation for embedded systems design2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    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.

  • 203.
    Eriksson, Mattias
    et al.
    Linköpings universitet, Institutionen för datavetenskap, PELAB - Laboratoriet för programmeringsomgivningar. Linköpings universitet, Tekniska högskolan.
    Kessler, Christoph
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Integrated Code Generation for Loops2012Ingår i: ACM Transactions on Embedded Computing Systems, ISSN 1539-9087, E-ISSN 1558-3465, Vol. 11, nr 1Artikel i tidskrift (Refereegranskat)
    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.

  • 204.
    Eriksson, Mattias
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Kessler, Christoph
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Integrated Offset Assignment2011Ingår i: Proceedings 9th Workshop on Optimizations for DSP and Embedded Systems (ODES-9) / [ed] George Cai and Tom van der Aa, 2011, s. 47-54Konferensbidrag (Refereegranskat)
    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.

  • 205.
    Eriksson, Oskar
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Rydkvist, Emil
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    An in-depth analysis of dynamically rendered vector-based maps with WebGL using Mapbox GL JS2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    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.

  • 206.
    Ernfridsson, Alexander
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Sammansättning av ett privat moln som infrastruktur för utveckling2017Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    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.

  • 207.
    Ernstsson, August
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    SkePU 2: Language Embedding and Compiler Support for Flexible and Type-Safe Skeleton Programming2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    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.

  • 208.
    Ernstsson, August
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Li, Lu
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Kessler, Christoph
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    SkePU 2: Flexible and Type-Safe Skeleton Programming for Heterogeneous Parallel Systems2018Ingår i: International journal of parallel programming, ISSN 0885-7458, E-ISSN 1573-7640, Vol. 46, nr 1, s. 62-80Artikel i tidskrift (Refereegranskat)
    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.

  • 209.
    Faur, Andrei
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Memory Profiling Techniques2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    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.

  • 210.
    Ferretti, Gianni
    et al.
    Politecn Milan, Italy.
    Fritzson, Peter
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Editorial Material: Special issue on object-oriented modelling and simulation in MATHEMATICAL AND COMPUTER MODELLING OF DYNAMICAL SYSTEMS, vol 23, issue 3, pp 240-2422017Ingår i: Mathematical and Computer Modelling of Dynamical Systems, ISSN 1387-3954, E-ISSN 1744-5051, Vol. 23, nr 3, s. 240-242Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    n/a

  • 211.
    Fors Johansson, Christoffer
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    OpenModelica Interactive Simulation using an OPC UA client2017Självständigt arbete på grundnivå (högskoleexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    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.

  • 212.
    Forsell, Martti
    et al.
    Platform Architectures Team, VTT Technical Research Centre of Finland, Finland.
    Hansson, Erik
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Kessler, Christoph
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    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 Architectures2013Ingår i: 2013 IEEE 27th International Parallel and Distributed Processing Symposium Workshops & PhD Forum (IPDPSW), IEEE conference proceedings, 2013, s. 640-647Konferensbidrag (Refereegranskat)
    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.

  • 213.
    Forsell, Martti
    et al.
    Platform Architectures Team, VTT Technical Research Centre of Finland, Finland.
    Hansson, Erik
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Kessler, Christoph
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    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 Architectures2014Ingår i: International Journal of Networking and Computing, ISSN 2185-2839, E-ISSN 2185-2847, Vol. 4, nr 1, s. 189-206Artikel i tidskrift (Refereegranskat)
    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.

  • 214.
    Forsgren, Mikael
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Dahlström, Nils
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Karlsson, Markus
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för neurovetenskap.
    Dahlqvist Leinhard, Olof
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Smedby, Örjan
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Cedersund, Gunnar
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Hälsouniversitetet.
    Lundberg, Peter
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Whole Body Mechanistic Minimal Model for Gd-EOB-DTPA Contrast Agent Pharmacokinetics in Evaluation of Diffuse Liver Disease2014Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 215.
    Foster, Simon
    et al.
    University of York, England.
    Thiele, Bernhard Amadeus
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Cavalcanti, Ana
    University of York, England.
    Woodcock, Jim
    University of York, England.
    Towards a UTP Semantics for Modelica2017Ingår i: UNIFYING THEORIES OF PROGRAMMING, UTP 2016, SPRINGER INTERNATIONAL PUBLISHING AG , 2017, Vol. 10134, s. 44-64Konferensbidrag (Refereegranskat)
    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.

  • 216.
    Fouladi, Amir Hossein
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Zafari Khorvaj, Omid
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    TryMyLanguage: An Extensible, Web-based Software Development Environment2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    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.

  • 217.
    Fridell, Emil
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Architectural Rules Conformance with ArCon and Open-SourceModeling Tools2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    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.

  • 218.
    Frimodig, Johan
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Utvärdering och förslag för att skapa ett effektivare administrationsverktyg i AES2018Självständigt arbete på grundnivå (högskoleexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
  • 219.
    Fritzson, Peter
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Urquía Moraleda, Alfonso (Översättare)
    Universidad Nacional de Educación a Distancia, Madrid, España.
    Villa Ramírez, José Luis (Översättare)
    Campus Tecnológico Km 1, Via Turbaco Cartagena de Indias, Colombia.
    Introducción al Modelado y Simulación de Sistemas Técnicos y Físicos con Modelica2015Bok (Övrigt vetenskapligt)
    Abstract [es]

    Domine el modelamiento y simulación usando Modelica, el nuevo poderoso y altamente versátil lenguaje de modelamiento basado en objetos.

    Modelica, el nuevo lenguaje de modelamiento de software/hardware orientado a objetos que está ganando una rápida popularidad en el mundo entero, ofrece un acercamiento casi universal al modelamiento y simulación computacional de alto nivel. Modelica maneja un amplio rango de dominios de aplicación, por ejemplo, sistemas mecánicos, eléctricos, de control, y termodinámicos, y facilita el uso de notación general así como el uso de poderosas abstracciones e implementaciones eficientes. Usando el versátil lenguaje de Modelica y su tecnología asociada, este texto presenta un acercamiento orientado a objetos basado en componentes que le hace posible a los lectores dominar rápidamente las bases del modelamiento matemático basado en ecuaciones orientado a objetos (EOO por sus siglas en inglés) y simulación soportado por computadora.

    A través de este texto Modelica se usa para ilustrar los diferentes aspectos del modelamiento y la simulación. A la vez, se explican varios conceptos claves del lenguaje Modelica con el uso de ejemplos de modelamiento y simulación. Este libro:

    • Examina los conceptos básicos tales como sistemas, modelos y simulaciones
    • Guía al lector a través del lenguaje Modelica con la ayuda de varios ejemplos paso a paso
    • Introduce el concepto de la clase Modelica y su uso en el modelamiento gráfico y basado en texto.
    • Explora las metodologías de modelamiento para sistemas continuos, discretos e híbridos
    • Presenta una revisión de la Librería Estándar de Modelica y las librerías clave de modelos de Modelica

    Los lectores encontrarán una buena cantidad de ejemplos de modelos que simulan aplicaciones en distintos dominios así como ejemplos que combinan varios dominios. Todos los ejemplos y ejercicios en el texto están disponibles a través de DrModelica. Este programa de auto enseñanza electrónico, disponible gratuitamente en el sitio web  que acompaña al texto, guía a los lectores desde ejemplos introductorios y simples hasta ejercicios mas avanzados.

    Escrito por el Director del consorcio Open Source Modelica Consortium, Introducción al Modelamiento y Simulación de Sistemas Físicos y Técnicos con Modelica es un libro recomendado para ingenieros y estudiantes interesados en el diseño, modelamiento, simulación y análisis asistido por computador de sistemas técnicos y naturales. Partiendo de conceptos básicos, el texto es ideal para estudiantes quienes desean aprender del modelamiento y la simulación orientado a objetos.

    Este libro está enfocado en la enseñanza del modelamiento y simulación usando Modelica para principiantes, o en cursos donde hay limitado espacio de tiempo para una introducción a Modelica. Para un cubrimiento con mayor profundidad de este tópico se recomienda el libro Principles of Object-Oriented Modeling and Simulation with Modelica 3.3: A Cyber-Physical Approach, el cual también incluye el material introductorio de este libro.

  • 220.
    Fritzson, Peter
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Model-based development of sustainable cyber-physical systems including requirement formalization using the OpenModelica Model-based Development Toolkit2016Ingår i: ACM PROCCEDINGS OF THE 10TH EUROPEAN CONFERENCE ON SOFTWARE ARCHITECTURE WORKSHOPS (ECSA-W), ASSOC COMPUTING MACHINERY , 2016Konferensbidrag (Refereegranskat)
    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.

  • 221.
    Fritzson, Peter
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Principles of object-oriented modeling and simulation with Modelica 3.3: a cyber-physical approach2015 (uppl. 2)Bok (Övrigt vetenskapligt)
    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

  • 222.
    Fritzson, Peter
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Elmqvist, HildingDassault Systémes AB, Sweden.
    Proceedings of the 11th International Modelica Conference, Versailles, France, September 21-23, 20152015Proceedings (redaktörskap) (Refereegranskat)
    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.

  • 223.
    Färnqvist, Tommy
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Constraint Optimization Problems and Bounded Tree-width Revisited2012Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 224.
    Färnqvist, Tommy
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Counting Homomorphisms via Hypergraph-based Structural Restrictions2012Konferensbidrag (Refereegranskat)
    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.

  • 225.
    Färnqvist, Tommy
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Exploiting Structure in CSP-related Problems2013Doktorsavhandling, monografi (Övrigt vetenskapligt)
    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.

  • 226.
    Färnqvist, Tommy
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Heintz, Fredrik
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Lambrix, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Mannila, Linda
    Åbo Academy, Finland.
    Wang, Chunyan
    Linköpings universitet, Institutionen för datavetenskap.
    Supporting Active Learning by Introducing an Interactive Teaching Tool in a Data Structures and Algorithms2016Ingår i: Proceedings of the 47th ACM Technical Symposium on Computer Science Education (SIGCSE 2016), ACM Publications, 2016, s. 663-668Konferensbidrag (Refereegranskat)
    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.

  • 227.
    Färnqvist, Tommy
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Heintz, Fredrik
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Lambrix, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Mannila, Linda
    Åbo Academy, Finland.
    Wang, Chunyan
    Linköpings universitet, Institutionen för datavetenskap.
    Supporting Active Learning Using an Interactive Teaching Tool in a Data Structures and Algorithms Course2015Ingår i: Proceedings of 5:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar (UtvSvIng), 2015, s. 76-79Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 228.
    Gallastegi, Akaitz
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Web-based Real-Time Communication for Rescue Robots2014Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    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.

  • 229.
    Ganeson, Anand
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Design and Implementation of a User Friendly OpenModelica - Python interface2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    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.

  • 230.
    Ganjei, Zeinab
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Rezine, Ahmed
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Eles, Petru Ion
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Peng, Zebo
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Safety Verification of Phaser Programs2017Ingår i: PROCEEDINGS OF THE 17TH CONFERENCE ON FORMAL METHODS IN COMPUTER AIDED DESIGN (FMCAD 2017), IEEE , 2017, s. 68-75Konferensbidrag (Refereegranskat)
    Abstract [en]

    We address the problem of statically checking control state reachability (as in possibility of assertion violations, race conditions or runtime errors) and plain reachability (as in deadlock-freedom) of phaser programs. Phasers are a modern non-trivial synchronization construct that supports dynamic parallelism with runtime registration and deregistration of spawned tasks. They allow for collective and point-to-point synchronizations. For instance, phasers can enforce barriers or producer-consumer synchronization schemes among all or subsets of the running tasks. Implementations are found in modern languages such as Habanero Java. Phasers essentially associate phases to individual tasks and use their runtime values to restrict possible concurrent executions. Unbounded phases may result in infinite transition systems even in the case of programs only creating finite numbers of tasks and phasers. We introduce an exact gap-order based procedure that always terminates when checking control reachability for programs generating bounded numbers of coexisting tasks and phasers. We also show verifying plain reachability is undecidable even for programs generating few tasks and phasers. We then explain how to turn our procedure into a sound analysis for checking plain reachability (including deadlock freedom). We report on preliminary experiments with our open source tool.

  • 231.
    Ganjei, Zeinab
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Rezine, Ahmed
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Eles, Petru
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Peng, Zebo
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Abstracting and Counting Synchronizing Processes2014Rapport (Övrigt vetenskapligt)
    Abstract [en]

    We address the problem of automatically establishing synchronization dependent correctness (e.g. due to using barriers or ensuring absence of deadlocks) of programs generating an arbitrary number of concurrent processes and manipulating variables ranging over an infinite domain. Automatically checking such properties for these programs is beyond the capabilities of current verification techniques. For this purpose, we describe an original logic that mixes two sorts of variables: those shared and manipulated by the concurrent processes, and ghost variables refering to the number of processes satisfying predicates on shared and local program variables. We then combine existing works on counter, predicate, and constrained monotonic abstraction and nest two cooperating counter example based refinement loops for establishing correctness (safety expressed as non reachability of configurations satisfying formulas in our logic). We have implemented a tool (Pacman, for predicated constrained monotonic abstraction) and used it to perform parameterized verification for several programs whose correctness crucially depends on precisely capturing the number of synchronizing processes. 

  • 232.
    Ganjei, Zeinab
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Rezine, Ahmed
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Eles, Petru
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Peng, Zebo
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Counting dynamically synchronizing processes2016Ingår i: International Journal on Software Tools for Technology Transfer (STTT), ISSN 1433-2779, E-ISSN 1433-2787, Vol. 18, nr 5, s. 517-534Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We address the problem of automatically establishing correctness for programs generating an arbitrary number of concurrent processes and manipulating variables ranging over an infinite domain. The programs we consider can make use of the shared variables to count and synchronize the spawned processes. This allows them to implement intricate synchronization mechanisms, such as barriers. Automatically verifying correctness, and deadlock freedom, of such programs is beyond the capabilities of current techniques. For this purpose, we make use of counting predicates that mix counters referring to the number of processes satisfying certain properties and variables directly manipulated by the concurrent processes. We then combine existing works on counter, predicate, and constrained monotonic abstraction and build a nested counter example based refinement scheme for establishing correctness (expressed as non-reachability of configurations satisfying counting predicates formulas). We have implemented a tool (Pacman, for predicated constrained monotonic abstraction) and used it to perform parameterized verification on several programs whose correctness crucially depends on precisely capturing the number of processes synchronizing using shared variables.

  • 233.
    Ganjei, Zeinab
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Rezine, Ahmed
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Eles, Petru
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Peng, Zebo
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Lazy Constrained Monotonic Abstraction2016Ingår i: Verification, Model Checking, and Abstract Interpretation: 17th International Conference, VMCAI 2016, St. Petersburg, FL, USA, January 17-19, 2016. Proceedings / [ed] Barbara Jobstmann; K. Rustan M. Leino, Springer Berlin/Heidelberg, 2016, Vol. 9583, s. 147-165Konferensbidrag (Refereegranskat)
    Abstract [en]

    We introduce Lazy Constrained Monotonic Abstraction (lazy CMA for short) for lazily and soundly exploring well structured abstractions of infinite state non-monotonic systems. CMA makes use of infinite state and well structured abstractions by forcing monotonicity wrt. refinable orderings. The new orderings can be refined based on obtained false positives in a CEGAR like fashion. This allows for the verification of systems that are not monotonic and are hence inherently beyond the reach of classical analysis based on the theory of well structured systems. In this paper, we consistently improve on the existing approach by localizing refinements and by avoiding to trash the explored state space each time a refinement step is required for the ordering. To this end, we adapt ideas from classical lazy predicate abstraction and explain how we address the fact that the number of control points (i.e., minimal elements to be visited) is a priori unbounded. This is unlike the case of plain lazy abstraction which relies on the fact that the number of control locations is finite. We propose several heuristics and report on our experiments using our open source prototype. We consider both backward and forward explorations on non-monotonic systems automatically derived from concurrent programs. Intuitively, the approach could be regarded as using refinable upward closure operators as localized widening operators for an a priori arbitrary number of control points.

  • 234.
    Ganjei, Zeinab
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Rezine, Ahmed
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Ion Eles, Petru
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Peng, Zebo
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Abstracting and Counting Synchronizing Processes2015Ingår i: Verification, Model Checking, and Abstract Interpretation: 16th International Conference on Verification, Model Checking, and Abstract Interpretation (VMCAI 2015), Mumbai, India, Jan. 12-14, 2015., Springer, 2015, s. 227-244Konferensbidrag (Refereegranskat)
    Abstract [en]

    We address the problem of automatically establishing synchronization dependent correctness (e.g. due to using barriers or ensuring absence of deadlocks) of programs generating an arbitrary number of concurrent processes and manipulating variables ranging over an infinite domain. Automatically checking such properties for these programs is beyond the capabilities of current verification techniques. For this purpose, we describe an original logic that mixes two sorts of variables: those shared and manipulated by the concurrent processes, and ghost variables referring to the number of processes satisfying predicates on shared and local program variables. We then combine existing works on counter, predicate, and constrained monotonic abstraction and nest two cooperating counter example based refinement loops for establishing correctness (safety expressed as non reachability of configurations satisfying formulas in our logic). We have implemented a tool (Pacman, for predicated constrained monotonic abstraction) and used it to perform parameterized verification for several programs whose correctness crucially depends on precisely capturing the number of synchronizing processes.

  • 235.
    Ganty, Pierre
    et al.
    IMDEA Software Institute, Spain.
    Rezine, Ahmed
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Ordered Counter-Abstraction Refinable Subword Relations for Parameterized Verification2014Ingår i: LANGUAGE AND AUTOMATA THEORY AND APPLICATIONS (LATA 2014), Springer Berlin/Heidelberg, 2014, Vol. 8370, s. 396-408Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present an original refinable subword based symbolic representation for the verification of linearly ordered parameterized systems. Such a system consists of arbitrary many finite processes placed in an array. Processes communicate using global transitions constrained by their relative positions (i.e., priorities). The model can include binary communication, broadcast, shared variables or dynamic creation and deletion of processes. Configurations are finite words of arbitrary lengths. The successful monotonic abstraction approach uses the subword relation to define upward closed sets as symbolic representations for such systems. Natural and automatic refinements remained missing for such symbolic representations. For instance, subword based relations are simply too coarse for automatic forward verification of systems involving priorities. We remedy to this situation and introduce a symbolic representation based on an original combination of counter abstraction with subword based relations. This allows us to define an infinite family of relaxation operators that guarantee termination by a new well quasi ordering argument. The proposed automatic analysis is at least as precise and efficient as monotonic abstraction when performed backwards. It can also be successfully used in forward, something monotonic abstraction is incapable of. We implemented a prototype to illustrate the approach.

  • 236.
    Garro, Alfredo
    et al.
    Department of Informatics, Modeling, Electronics and Systems Engineering (DIMES), University of Calabria, Italy.
    Tundis, Andrea
    Department of Informatics, Modeling, Electronics and Systems Engineering (DIMES), University of Calabria, Italy.
    Bouskela, Daniel
    R&D Division, Electricité de France (EDF), France.
    Jardin, Audrey
    R&D Division, Electricité de France (EDF), France.
    Nguyen, Thuy
    R&D Division, Electricité de France (EDF), France.
    Otter, Martin
    Institute of System Dynamics and Control, DLR German Aerospace Center, Germany.
    Buffoni, Lena
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Fritzson, Peter
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Sjölund, Martin
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Schamai, Wladimir
    Airbus Group Innovations, Hamburg, Germany.
    Olsson, Hans
    Dassault Systèmes AB, Sweden.
    On formal cyber physical system properties modeling: a new temporal logic language and a Modelica-based solution2016Ingår i: 2016 IEEE International Symposium on Systems Engineering (ISSE), IEEE , 2016, s. 112-119Konferensbidrag (Refereegranskat)
    Abstract [en]

    Modeling and Simulation methods, tools and techniques aim at supporting the different phases of the lifecycle of modern systems, going from requirements analysis to system design and operation. However, their effective application requires investigating several aspects such as the formal modeling of system requirements and the binding and automated composition between heterogeneous models (e.g. requirements models, architectural models, behavioral models). In this context, the paper presents a new formal requirement modeling language based on temporal logic, called FORM-L, and a software library, based on the Modelica language, that implements the constructs provided by FORM-L so as to enable the visual modeling of system properties as well as their verification through simulation. The effectiveness of the proposal is shown on a real case study concerning an Intermediate Cooling System.

  • 237.
    Gatla, Goutham
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Validation of ModelicaML models2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In the world of modeling, Model Validation plays a crucial role. A model editor is not said to becomplete without Validation. ModelicaML is a Modeling Language extended from a subset of UMLand SysML, developed under OpenModelica Project. It is defined to provide time-discrete andtime-continuous models. Papyrus Model Editor is extended to support for ModelicaML usingModelicaML Eclipse plug-in. This plug-in comes with Modelica Code Generator.Previously, ModelicaML plug-in had a prototype of validation which provided only Batch-modevalidation. The validation is used to be done by the Modelica compiler after the code generation phase.Each time the user tried to validate the model; first Modelica code is generated and then validated. Thistype of validation misses certain validation rules to validate due to the conversion from theModelicaML model to Modelica code.The goal of this thesis is to implement Model Validation done at model editor level with both Batch andLive mode validation. This can be done by developing an Eclipse plug-in which does the ModelValidation. This plug-in uses the EMF Validation framework for implementing the constraints andvalidation on ModelicaML models.

  • 238.
    Gebremedhin, Mahder
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Automatic and Explicit Parallelization Approaches for Mathematical Simulation Models2015Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    The move from single core and processor systems to multi-core and many-processors systemscomes with the requirement of implementing computations in a way that can utilizethese multiple units eciently. This task of writing ecient multi-threaded algorithmswill not be possible with out improving programming languages and compilers to providethe mechanisms to do so. Computer aided mathematical modeling and simulationis one of the most computationally intensive areas of computer science. Even simpli-ed models of physical systems can impose a considerable amount of computational loadon the processors at hand. Being able to take advantage of the potential computationpower provided by multi-core systems is vital in this area of application. This thesis triesto address how we can take advantage of the potential computation power provided bythese modern processors to improve the performance of simulations. The work presentsimprovements for the Modelica modeling language and the OpenModelica compiler.

    Two approaches of utilizing the computational power provided by modern multi-corearchitectures are presented in this thesis: Automatic and Explicit parallelization. Therst approach presents the process of extracting and utilizing potential parallelism fromequation systems in an automatic way with out any need for extra eort from the modelers/programmers side. The thesis explains improvements made to the OpenModelicacompiler and presents the accompanying task systems library for ecient representation,clustering, scheduling proling and executing complex equation/task systems with heavydependencies. The Explicit parallelization approach explains the process of utilizing parallelismwith the help of the modeler or programmer. New programming constructs havebeen introduced to the Modelica language in order to enable modelers write parallelizedcode. the OpenModelica compiler has been improved accordingly to recognize and utilizethe information from this new algorithmic constructs and generate parallel code toimprove the performance of computations.

  • 239.
    Gebremedhin, Mahder
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Fritzson, Peter
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Automatic Task Based Analysis and Parallelization in the Context of Equation Based Languages2014Ingår i: EOOLT '14 Proceedings of the 6th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools, New York: ACM , 2014, s. 49-52Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents an automatic parallelization approach for handling complex task systems with heavy dependencies, including methods of analyzing dependencies, representing them in a convenient way, and processing the resulting task graph representation. We present a library-based task system representation, clustering, profiling, and scheduling approach to simplify the otherwise tedious process of parallelizing complex task systems. We have implemented a flexible and robust task system handling library to manipulate and parallelize these complex task systems on shared memory multi-core and multi-processor systems. The implementation has been developed as part of the OpenModelica simulation environment. We demonstrate methods of extracting and utilizing parallelism in the context of mathematical modeling languages.

  • 240.
    Gerling, Jonas
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Implementing Object and Feature Detection Without Compromising the Performance2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis will cover how some computationally heavy algorithms used in digital image processing and computer vision are implemented with WebGL and computed on the graphics processing unit by utilizing GLSL-shaders. This thesis is based on an already implemented motion detection plug-in used in web based games. This plug-in is enhanced with new features and some already implemented algorithms are improved. The motion detection is based on image subtraction and uses the delta image from previous frames to determine motion.

    The plug-in is used in web based games so the performance is of utmost importance since bad performance leads to frustration and less immersion for the players

    Techniques brought up are edge detection, Gaussian filter, features from accelerated segment test(FAST) and Harris corner detection. These techniques will be implemented by utilizing the parallel structure of the GPU. Both Harris corner detection and features from accelerated segment test can be run in real time but the result of the Harris corner detection is the better of the two. The thesis will also cover different color spaces, how they are implemented and why they were implemented

  • 241.
    Ghani Zadegan, Farrokh
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Ingelsson, Urban
    Semcon AB.
    Carlsson, Gunnar
    Ericsson AB.
    Larsson, Erik
    Lund University, Sweden .
    Access Time Analysis for IEEE P16872012Ingår i: I.E.E.E. transactions on computers (Print), ISSN 0018-9340, E-ISSN 1557-9956, Vol. 61, nr 10, s. 1459-1472Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The IEEE P1687 (IJTAG) standard proposal aims at providing a standardized interface between the IEEE Standard 1149.1 test access port (TAP) and on-chip embedded test, debug and monitoring logic (instruments), such as scan chains and temperature sensors. A key feature in P1687 is to include Segment Insertion Bits (SIBs) in the scan path to allow flexibility both in designing the instrument access network and in scheduling the access to instruments. This paper presents algorithms to compute the overall access time (OAT) for a given P1687 network. The algorithms are based on analysis for flat and hierarchical network architectures, considering two access schedules, i.e., concurrent schedule and sequential schedule. In the analysis, two types of overhead are identified, i.e., network configuration data overhead and JTAG protocol overhead. The algorithms are implemented and employed in a parametric analysis and in experiments on realistic industrial designs.

  • 242.
    Gillsjö, Lukas
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Using OpenCL to Implement Median Filtering and RSA Algorithms: Two GPGPU Application Case Studies2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Graphics Processing Units (GPU) and their development tools have advanced recently, and industry has become more interested in using them. Among several development frameworks for GPU(s), OpenCL provides a programming environment to write portable code that can run in parallel. This report describes two case studies of algorithm implementations in OpenCL. The first algorithm is Median Filtering which is a widely used image processing algorithm. The other algorithm is RSA which is a popular algorithm used in encryption. The CPU and GPU implementations of these algorithms are compared in method and speed. The GPU implementations are also evaluated by efficiency, stability, scalability and portability. We find that the GPU implementations perform better overall with some exceptions. We see that a pure GPU solution is not always the best and that a hybrid solution with both CPU and GPU may be to prefer in some cases.

  • 243.
    Girma, Robi
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Evaluation of container virtualization systems supporting Open Container Initiative images2018Självständigt arbete på grundnivå (högskoleexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Abstract

    In the Virtualization industry, container virtualization has increased in popularity with the emergence of container engines in 2013. Container engines create, remove and manage containers. They do so by utilizing container images from which containers are created. Images work as templates, are reusable and can be uploaded for others to download. Big contributors in the field of container virtualization grouped up and founded the Open Container Initiative. The project established an industry standard for the architecture of container images and how they should be run.

     

    The IT consultant company Zenon has requested a thesis to be done in the field of container virtualization as they are thinking of starting to work with one but want to learn more about modern solutions. Due to the lack of back-to-back comparisons of modern solutions supporting the standard set by the Open Container Initiative, this thesis makes an evaluation of available systems in industry standard terms of performance. The company is also interested in fields; isolation, image management and time to build an image of a Zenon application and deploy a container from it.

     

    The evaluation in this thesis was made on container engines Docker and rkt. Results showed that Docker performed better in all benchmarks. Rkt starts a container in less time than Docker but takes longer to build the specified image. Docker has much more capabilities in terms of image management with the ability to create images from scratch and to run on multiple operating systems, while rkt has limited ability for creating images, requires more configurations and is exclusive available for Linux. Both container engines offer varied isolation, where Docker has 2 security profiles and rkt lets the user implement custom isolation profiles with several provided options available.

  • 244.
    Glasser, Christian
    et al.
    University of Wurzburg, Germany.
    Jonsson, Peter
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Martin, Barnaby
    Middlesex University, England.
    Circuit Satisfiability and Constraint Satisfaction Around Skolem Arithmetic2016Ingår i: Pursuit of the Universal, SPRINGER INT PUBLISHING AG , 2016, Vol. 9709, s. 323-332Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study interactions between Skolem Arithmetic and certain classes of Circuit Satisfiability and Constraint Satisfaction Problems (CSPs). We revisit results of Gla beta er et al. [16] in the context of CSPs and settle the major open question from that paper, finding a certain satisfiability problem on circuits-involving complement, intersection, union and multiplication-to be decidable. This we prove using the decidability of Skolem Arithmetic. Then we solve a second question left open in [16] by proving a tight upper bound for the similar circuit satisfiability problem involving just intersection, union and multiplication. We continue by studying first-order expansions of Skolem Arithmetic without constants, (N; x), as CSPs. We find already here a rich landscape of problems with non-trivial instances that are in P as well as those that are NP-complete.

  • 245.
    Glasser, Christian
    et al.
    Julius Maximilian University, Germany.
    Jonsson, Peter
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Martin, Barnaby
    University of Durham, England.
    Circuit satisfiability and constraint satisfaction around Skolem Arithmetic2017Ingår i: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 703, s. 18-36Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study interactions between Skolem Arithmetic and certain classes of Circuit Satisfiability and Constraint Satisfaction Problems (CSPs). We revisit results of Glasser et al. [1] in the context of CSPs and settle the major open question from that paper, finding a certain satisfiability problem on circuits-involving complement, intersection, union and multiplication-to be decidable. This we prove using the decidability of Skolem Arithmetic. Then we solve a second question left open in [1] by proving a tight upper bound for the similar circuit satisfiability problem involving just intersection, union and multiplication. We continue by studying first-order expansions of Skolem Arithmetic without constants, (N; x), as CSPs. We find already here a rich landscape of problems with non-trivial instances that are in P as well as those that are NP-complete. (C) 2017 Elsevier B.V. All rights reserved.

  • 246.
    Gorm Larsen, Peter
    et al.
    Aarhus University, Denmark.
    Fitzgerald, John
    Newcastle University, England.
    Woodcock, Jim
    University of York, England.
    Fritzson, Peter
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Brauer, Joerg
    Verified Syst Int, Germany.
    Kleijn, Christian
    Controllab Prod, Netherlands.
    Lecomte, Thierry
    Clearsy SAS, France.
    Pfeil, Markus
    TWT Science and Innovat, Germany.
    Green, Ole
    Agro Intelligence, Denmark.
    Basagiannis, Stylianos
    United Technology Research Centre, Ireland.
    Sadovykh, Andrey
    Softeam, France.
    Integrated Tool Chain for Model-based Design of Cyber-Physical Systems: The INTO-CPS Project2016Ingår i: 2016 2ND INTERNATIONAL WORKSHOP ON MODELLING, ANALYSIS, AND CONTROL OF COMPLEX CPS (CPS DATA), IEEE , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    We describe INTO-CPS, a project that aims to realise the goal of integrated tool chains for the collaborative and multidisciplinary engineering of dependable Cyber-Physical Systems (CPSs). Challenges facing model-based CPS engineering are described, focussing on the semantic diversity of models, management of the large space of models and artefacts produced in CPS engineering, and the need to evaluate effectiveness in industrial settings. We outline the approach taken to each of these issues, particularly on the use of semantically integrated multi-models, links to architectural modelling, code generation and testing, and evaluation via industry-led studies. We describe progress on the development of a prototype tool chain from baseline tools, and discuss ongoing challenges and open research questions in this area.

  • 247.
    Grahn, Ivar
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    The Vuforia SDK and Unity3D Game Engine: Evaluating Performance on Android Devices2017Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This paper evaluates major features of PTC’s augmented reality SDK Vuforia, available for Android, iOS and the Unity3D game engine. The performance of these features are evaluated in terms of frame rate and power consumption and the testing prototypes are developed using Unity3D. Augmented reality is a rapidly growing medium and the Vuforia SDK is very popular with over 325 000 registered developers and thousands of published applications. Despite being used to such extents, there are surprisingly few works evaluating different aspects of its performance. This paper provides an introduction to augmented reality and describes the technology used by the Vuforia SDK to deliver said features. This paper shows that Vuforia is capable of maintaining sufficient performance with interactive frame rates over 20 Hz in most cases. The power consumption of these features reduces the battery lifetime to acceptable levels, suitable for hand-held devices. In some cases, however, the performance in terms of frame rate reaches levels lower than recommended. These cases should be considered by developers looking to use Vuforia.

  • 248.
    Grape, Victor
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Comparing Costs of Browser Automation Test Tools with Manual Testing2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Testing is a necessary component of software development, but it is also an expensive one, especially if performed manually. One way to mitigate the cost of testing is to implement test automation, where the test cases are run automatically. For any organisation looking to implement test automation, the most interesting cost is time. Automation takes time to implement and one of the most obvious benefits of automation is that the automated test execution time is lower than that of manual execution. This thesis contains a literature study covering testing methodology, especially in regards to the domain of web application testing. The literature covered also included three economic models that may be used to calculate the costs of automation compared to manual testing. The models can be used to calculate the time it would take, or the number of necessary executions, for the total cost of test automation to be lower than of that of manual testing. The thesis is based on a case study of test automation for the StoredSafe platform, a web application. Three sets of test automation frameworks were used to implement three different test suits and the test implementation times were collected. The data collected were then used to calculate the time it would take, using the three economic models, for the cost of automated test cases to become equal to that of with manual testing. The data showed that the estimated time to reach breakeven for the three frameworks varied between 2½ and at worst 10 years, with an average of 3½ years. The models and data presented in this thesis may be used in order to estimate the cost of test automation in comparison to manual testing over longer periods of time, but care must be taken in order to ensure that the data used is correct in regards to one’s own organisation or else the estimate may be faulty.

  • 249.
    Green Olander, Jens
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Optimizing Communication Energy Efficiency for a Multimedia Application2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Mobile devices have evolved rapidly in recent years and increased usage and performance are pushing contemporary battery technology to its limits. The constrained battery resources mean that the importance of energy-efficient application design is growing and in this regard wireless network accesses are a major contributor to a mobile device's overall energy consumption. Additionally, the energy consumption characteristics of modern cellular technologies make small volumes of poorly scheduled traffic account for a substantial share of a device's total energy consumption. However, quantifying the communication energy footprint is cumbersome, making it difficult for developers to profile applications from an energy consumption perspective and optimize traffic patterns.

    This thesis examines the traffic patterns of the Android client of the popular multimedia streaming service Spotify with the intention to reduce its energy footprint, in terms of 3G energy consumption. The application's automated test environment is extended to capture network traffic, which is used to estimate energy consumption. Automated system tests are designed and executed on a physical Android device connected to a 3G network, shedding light on the traffic patterns of different application features.

    All traffic between the Spotify client application and the backend servers is encrypted. To extract information about the traffic, the application code is instrumented to output supplementary information to the Android system log. The system log is then used as a source of information to attribute data traffic to different application modules and specific lines of code.

    Two simple traffic shaping techniques, traffic aggregation and piggybacking, are implemented in the application to provide more energy-efficient traffic patterns. As a result, 3G energy consumption during normal music playback is reduced by 22-54%, and a more contrived scenario achieves a 60% reduction. The reductions are attained by rescheduling a small class of messages, most notably data tracking application usage. These messages were found to account for a small fraction of total traffic volume, but a large portion of the application's overall 3G energy consumption.

  • 250.
    Grundström, Niklas
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    A Security Analysis of a Credit Card Payment System for Bitcoin Transactions2018Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Cryptocurrencies has become a very hot topic recently, with Bitcoin being the most

    popular. The increase in interest has led to an incentive to create payment systems for the

    currency that makes it easier to use for day-to-day shopping. A lot of companies are inves-

    tigating possible solutions for credit cards that are used for cryptocurrencies. This thesis

    aims to present and perform a security analysis on an already created concept of a credit

    card payment system for Bitcoin. The security analysis is done in a systematical approach

    where the modules were analyzed with predetermined restrictions and assumptions. The

    restricitons and assumptions are then removed one-by-one to find potential threats in the

    system. The outcome of the analysis is then evaluated in an attempt to find possible im-

    plementation methods that would mitigate or prevent the discovered threats. The possible

    implementations are also evaluated in terms of how they would affect the system.

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