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Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
• 201.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
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)

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.

• 202.
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)

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.

• 203.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Urquía Moraleda, Alfonso (Översättare)
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)

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.

• 204.
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)

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.

• 205.
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)

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

• 206.
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)

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.

• 207.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Constraint Optimization Problems and Bounded Tree-width Revisited2012Konferensbidrag (Övrigt vetenskapligt)

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.

• 208.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Counting Homomorphisms via Hypergraph-based Structural Restrictions2012Konferensbidrag (Refereegranskat)

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.

• 209.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Exploiting Structure in CSP-related Problems2013Doktorsavhandling, monografi (Övrigt vetenskapligt)

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.

• 210.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
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, 663-668 s.Konferensbidrag (Refereegranskat)

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.

• 211.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
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, 76-79 s.Konferensbidrag (Övrigt vetenskapligt)

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.

• 212.
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)

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.

• 213.
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)

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.

• 214.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Abstracting and Counting Synchronizing Processes2014Rapport (Övrigt vetenskapligt)

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.

• 215.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. 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, 517-534 s.Artikel i tidskrift (Refereegranskat)

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.

• 216.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. 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, 147-165 s.Konferensbidrag (Refereegranskat)

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.

• 217.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. 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, 227-244 s.Konferensbidrag (Refereegranskat)

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.

• 218.
IMDEA Software Institute, Spain.
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, 396-408 s.Konferensbidrag (Refereegranskat)

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.

• 219.
Department of Informatics, Modeling, Electronics and Systems Engineering (DIMES), University of Calabria, Italy.
Department of Informatics, Modeling, Electronics and Systems Engineering (DIMES), University of Calabria, Italy. R&D Division, Electricité de France (EDF), France. R&D Division, Electricité de France (EDF), France. R&D Division, Electricité de France (EDF), France. Institute of System Dynamics and Control, DLR German Aerospace Center, Germany. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. Airbus Group Innovations, Hamburg, Germany. 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, 112-119 s.Konferensbidrag (Refereegranskat)

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.

• 220.
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)

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.

• 221.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Automatic and Explicit Parallelization Approaches for Mathematical Simulation Models2015Licentiatavhandling, monografi (Övrigt vetenskapligt)

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.

• 222.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
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, 49-52 s.Konferensbidrag (Refereegranskat)

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.

• 223.
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)

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

• 224.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Semcon AB. Ericsson AB. 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, 1459-1472 s.Artikel i tidskrift (Refereegranskat)

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.

• 225.
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)

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.

• 226.
University of Wurzburg, Germany.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. Middlesex University, England.
Circuit Satisfiability and Constraint Satisfaction Around Skolem Arithmetic2016Ingår i: Pursuit of the Universal, SPRINGER INT PUBLISHING AG , 2016, Vol. 9709, 323-332 s.Konferensbidrag (Refereegranskat)

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.

• 227.
Aarhus University, Denmark.
Newcastle University, England. University of York, England. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. Verified Syst Int, Germany. Controllab Prod, Netherlands. Clearsy SAS, France. TWT Science and Innovat, Germany. Agro Intelligence, Denmark. United Technology Research Centre, Ireland. 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)

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.

• 228.
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)

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.

• 229.
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)

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.

• 230.
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)

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.

• 231.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
Fuzz testing for design assurance levels2017Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)

With safety critical software, it is important that the application is safe and stable. While this software can be quality tested with manual testing, automated testing has the potential to catch errors that manual testing will not. In addition there is also the possibility to save time and cost by automating the testing process. This matters when it comes to avionics components, as much time and cost is spent testing and ensuring the software does not crash or behave faulty. This research paper will focus on exploring the usefulness of automated testing when combining it with fuzz testing. It will also focus on how to fuzzy test applications classified into DAL-classifications.

• 232.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Zenterio.
A Comparative Study of Automated Test Explorers2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)

D ̊a v ̊ara moderna datasystem blir allt mer komplicerade,  ̈okar detta st ̈andigtbehovet av rigor ̈osa tester f ̈or att s ̈akerst ̈alla kvaliteten p ̊a den slutgiltiga pro-dukten. Det h ̈ar inneb ̈ar dock att kostnaden f ̈or att utf ̈ora testerna ocks ̊ao  ̈ kar. F ̈or att f ̈ors ̈oka hitta en l ̈osning p ̊a det h ̈ar problemet har forsknin-gen under senare tid arbetat med att ta fram automatiserade metoder atttesta mjukvarusystem. I den h ̈ar uppsatsen har olika algoritmer, f ̈or attutforska och testa ett system, implementerats och utv ̈arderats. D ̈arut ̈overhar ocks ̊a en grupp algoritmer implementerats som ska kunna isolera vilkainteraktioner med ett system som f ̊ar det att fallera.  ̈aven dessa algoritmerhar utv ̈arderats och testats mot varandra. Resultatet fr ̊an det f ̈orsta ex-perimentet var tv ̊a explorers, h ̈ar kallade DeBruijn och LStarExplorer, somvisade sig vara b ̈attre  ̈an de andra. Den f ̈orsta av dessa anv ̈ande en DeBruijn-sekvens f ̈or att hitta felen, medan den andra anv ̈ande en L*-algoritm f ̈or attbygga upp en FSM  ̈over systemet. Den h ̈ar FSM:en kunde sedan anv ̈andasf ̈or att mer precist beskriva n ̈ar felet uppstod. Resultatet fr ̊an det andraexperimentet var tv ̊a reducers, vilka b ̊ada f ̈ors ̈okte  ̊aterskapa fel genom attf ̈orst applicera interaktioner som ursprungligen utf ̈ordes percis innan feletuppstod. Om felet inte kunde  ̊aterskapas p ̊a detta s ̈att, fortsatte de medatt applicera interaktioner l ̈angre bort tills felet kunde  ̊aterskapas. Ut ̈overdetta inneh ̊aller uppsatsen ocks ̊a beskrivningar av ramverken som anv ̈andsf ̈or att k ̈ora de olika strategierna.

• 233.
Seoul National University.
Friedrich-Alexander-Universität Erlangen-Nürnberg. Universität Rostock. Ulm University. National University of Singapore. University of California, Irvine. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. Arizona State University. The University of Texas at Austin. University of Maryland, Tampere University of Technology.
Introduction to Hardware/Software Codesign2017Ingår i: Handbook of Hardware/Software Codesign / [ed] Soonhoi Ha, Jürgen Teich, Springer Netherlands, 2017Kapitel i bok, del av antologi (Refereegranskat)

Hardware/Software Codesign (HSCD) is an integral part of modern Electronic System Level (ESL) design flows. This chapter will review important aspects of hardware/software codesign flows, summarize the historical evolution of codesign techniques, and subsequently summarize each of its major branches of research and achievements that later will be presented in detail by different parts of this Handbook of Hardware/Software Codesign.

• 234.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Visuell presentation av övervakningsdata2014Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)

Systemövervakning har blivit en stor del av företags IT-strukturer eftersom företag förlitar sig mer och mer på en välfungerande och högt presterande IT- struktur. När det sker problem i företags IT-strukturer så krävs det att de löses under relativt kort tid. För att hitta problemet så krävs det en mängd olika system som skall underlätta arbetet för människor som arbetar med systemövervakning och underhåll av IT-strukturer.

För att tolka och bearbeta all den information som en IT-struktur tillhandahåller så krävs det system vars uppgift är att hjälpa människor att tolka den enorma mängd data en IT-struktur genererar. Denna rapport ger en beskrivning över hur arbetet för en systemadministratör kan förenklas med hjälp av ett integrerat övervakningssystem. Stora delar av rapporten kommer fokusera på vilken metod och protokoll som kan användas för att hämta information från olika övervakningssystem och även förslag på hur informationen kan presenteras för användaren.

• 235.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Code Generation and Global Optimization Techniques for a Reconfigurable PRAM-NUMA Multicore Architecture2014Licentiatavhandling, monografi (Övrigt vetenskapligt)

In this thesis we describe techniques for code generation and global optimization for a PRAM-NUMA multicore architecture. We specifically focus on the REPLICA architecture which is a family massively multithreaded very long instruction word (VLIW) chip multiprocessors with chained functional units that has a reconfigurable emulated shared on-chip memory. The on-ship memory system supports two execution modes, PRAM and NUMA, which can be switched between at run-time.PRAM mode is considered the standard execution mode and targets mainly applications with very high thread level parallelism (TLP). In contrast, NUMA mode is optimized for sequential legacy applications and applications with low amount of TLP. Different versions of the REPLICA architecture have different number of cores, hardware threads and functional units. In order to utilize the REPLICA architecture efficiently we have made several contributionsto the development of a compiler for REPLICA target code generation. It supports both code generation for PRAM mode and NUMA mode and can generate code for different versions of the processor pipeline (i.e. for different numbers of functional units). It includes optimization phases to increase the utilization of the available functional units. We have also contributed to quantitative the evaluation of PRAM and NUMA mode. The results show that PRAM mode often suits programs with irregular memory access patterns and control flow best while NUMA mode suites regular programs better. However, for a particular program it is not always obvious which mode, PRAM or NUMA, will show best performance. To tackle this we contributed a case study for generic stencil computations, using machine learning derived cost models in order to automatically select at runtime which mode to execute in. We extended this to also include a sequence of kernels.

• 236.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. VTT Technical Research Centre of Finland.
A Quantitative Comparison of PRAM based Emulated Shared Memory Architectures to Current Multicore CPUs and GPUs2014Ingår i: 27th International Conference on Architecture of Computing Systems (ARCS), 2014, ARCS Workshops: Proc. PASA-2014 11th Workshop on Parallel Systems and Algorithms, Lübeck, Germany, Lübeck, Germany: VDE Verlag GmbH, 2014, 27-33 s.Konferensbidrag (Refereegranskat)

The performance of current multicore CPUs and GPUs is limited in computations making frequent use of communication/synchronization between the subtasks executed in parallel. This is because the directory-based cache systems scale weakly and/or the cost of synchronization is high. The Emulated Shared Memory (ESM) architectures relying on multithreading and efficient synchronization mechanisms have been developed to solve these problems affecting both performance and programmability of current machines. In this paper, we compare preliminarily the performance of three hardware implemented ESM architectures with state-of-the-art multicore CPUs and GPUs. The benchmarks are selected to cover different patterns of parallel computation and therefore reveal the performance potential of ESM architectures with respect to current multicores.

• 237.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Optimized selection of runtime mode for the reconfigurable PRAM-NUMA architecture REPLICA using machine-learning2014Ingår i: Euro-Par 2014: Parallel Processing Workshops: Euro-Par 2014 International Workshops, Porto, Portugal, August 25-26, 2014, Revised Selected Papers, Part II / [ed] Luis Lopes et al., Springer-Verlag New York, 2014, 133-145 s.Konferensbidrag (Refereegranskat)

The massively hardware multithreaded VLIW emulated shared memory (ESM) architecture REPLICA has a dynamically reconfigurable on-chip network that offers two execution modes: PRAM and NUMA. PRAM mode is mainly suitable for applications with high amount of thread level parallelism (TLP) while NUMA mode is mainly for accelerating execution of sequential programs or programs with low TLP. Also, some types of regular data parallel algorithms execute faster in NUMA mode. It is not obvious in which mode a given program region shows the best performance. In this study we focus on generic stencil-like computations exhibiting regular control flow and memory access pattern. We use two state-of-the art machine-learning methods, C5.0 (decision trees) and Eureqa Pro (symbolic regression) to select which mode to use.We use these methods to derive different predictors based on the same training data and compare their results. The accuracy of the best derived predictors are 95% and are generated by both C5.0 and Eureqa Pro, although the latter can in some cases be more sensitive to the training data. The average speedup gained due to mode switching ranges between 1.92 to 2.23 for all generated predictors on the evaluation test cases, and using a majority voting algorithm, based on the three best predictors, we can eliminate all misclassifications.

• 238.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. KTH, Stockholm, Sweden. KTH, Stockholm, Sweden.
En jämförelse mellan programsamanhållande kurser vid KTH och LiU2015Ingår i: Proceedings of 5:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar (UtvSvIng), 2015Konferensbidrag (Övrigt vetenskapligt)

Programsammanhållande kurser där studenter från årskurs 1-3 gemensamt reflekterar över teman med koppling till deras studier och framtida yrkesliv finns på både KTH och Linköpings universitet (LiU). Syftet med kurserna är främst att skapa en helhet i utbildningen och ge förståelse för vad den leder till, genom att få studenterna att reflektera över sina studier och sin kommande yrkesroll. Detta leder förhoppningsvis till ökad genomströmning och minskade avhopp. Kurserna har gemensamt ursprung men har utvecklats i olika riktningar. Artikeln jämför tre programsammanhållande kurser för Datateknik KTH, Medieteknik KTH samt Data- och mjukvaruteknik Linköpings universitet.

• 239.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Återkoppling genom automaträttning2013Ingår i: Proceedings of 4:de Utvecklingskonferensen för Sveriges ingenjörsutbildningar (UtvSvIng), 2013Konferensbidrag (Refereegranskat)

Vi har undersökt olika former av återkoppling genom automaträttning i en kurs i datastrukturer och algoritmer. 2011 undersökte vi effekterna av tävlingsliknande moment som också använder automaträttning. 2012 införde vi automaträttning av laborationerna. Vi undersökte då hur återkoppling genom automaträttning påverkar studenternasarbetssätt, prestationsgrad och relation till den examinerande personalen. Genom automaträttning får studenterna omedelbar återkoppling om deras program är tillräckligt snabbt och ger rätt svar på testdata. När programmet är korrekt och resurseffektivt kontrollerar kursassistenterna att programmet även uppfyller andra krav som att vara välskrivet och välstrukturerat. Efter kursen undersökte vi studenternas inställning till och upplevelse av automaträttning genom en enkät. Resultaten är att studenterna är positiva till automaträttning (80% av alla som svarade) och att den påverkade studenternas sätt att arbeta huvudsakligen positivt. Till exempel svarade 50% att de ansträngde sig hårdare tack vare automaträttningen. Dessutom blir rättningen mer objektiv då den görs på exakt samma sätt för alla. Vår slutsats är att återkoppling genom automaträttning ger positiva effekter och upplevs som positiv av studenterna.

• 240.
Linköpings universitet, Institutionen för datavetenskap, KPLAB - Laboratoriet för kunskapsbearbetning. Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
Programutvecklingsstrategier för att öka kopplingen mellan programmering och matematik2015Ingår i: Proceedings of 5:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar (UtvSvIng), 2015Konferensbidrag (Refereegranskat)

Matematik och programmering är två viktiga inslag i civilingenjörsprogram inom data- och mjukvaruteknik. De studenter som klarar dessa kurser klarar sannolikt resten av utbildningen. Idag har fler studenter programmering än matematik som huvudsakligt intresse. Därför har Linköpings universitet aktivt jobbat med olika strategier för att öka kopplingen mellan programmering och matematik, främst i de inledande kurserna. För att undersöka studenternas attityder till matematik och programmering har vi genomfört flera enkätstudier som bl.a. visar att intresset för matematik är stort men intresset för programmering ännu större och att studenterna tror de kommer ha betydligt mer nytta av programmering än matematik under sin karriär. Texten är tänkt som grund för en diskussion kring hur kopplingarna mellan matematik och programmering kan göras tydligare och starkare.

• 241.
A Review of Models for Introducing Computational Thinking, Computer Science and Computing in K-12 Education.2016Ingår i: Proceedings of the 46th Frontiers in Education (FIE), IEEE , 2016Konferensbidrag (Refereegranskat)

Computing is becoming ever increasingly importantto our society. However, computing in primary and secondaryeducation has not been well developed. Computing has traditionallybeen primarily a university level discipline and there areno widely accepted general standards for what computing at K–12 level entails. Also, as the interest in this area is rather new,the amount of research conducted in the field is still limited. Inthis paper we review how 10 different countries have approachedintroducing computing into their K–12 education. The countriesare Australia, England, Estonia, Finland, New Zealand, Norway,Sweden, South Korea, Poland and USA.

The studied countries either emphasize digital competenciestogether with programming or the broader subject of computingor computer science. Computational thinking is rarely mentionedexplicitly, but the ideas are often included in some form. Themost common model is to make it compulsory in primary schooland elective in secondary school. A few countries have made itcompulsory in both. While some countries have only introducedit in secondary school.

• 242.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
Automating Text Categorization with Machine Learning: Error Responsibility in a multi-layer hierarchy2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)

The company Ericsson is taking steps towards embracing automating techniques and applying them to their product development cycle. Ericsson wants to apply machine learning techniques to automate the evaluation of a text categorization problem of error reports, or trouble reports (TRs). An excess of 100,000 TRs are handled annually.

This thesis presents two possible solutions for solving the routing problems where one technique uses traditional classifiers (Multinomial Naive Bayes and Support Vector Machines) for deciding the route through the company hierarchy where a specific TR belongs. The other solution utilizes a Convolutional Neural Network for translating the TRs into low-dimensional word vectors, or word embeddings, in order to be able to classify what group within the company should be responsible for the handling of the TR. The traditional classifiers achieve up to 83% accuracy and the Convolutional Neural Network achieve up to 71% accuracy in the task of predicting the correct class for a specific TR.

• 243.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
Naive Bayes-klassificering av förarbeteende2017Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)

Att kunna klassificera en körstil implicerar klassificering av körbeteende, vilket ligger till grunden för miljö- och säkerhetsklassificering för körningar.

I det här arbetet har vi låtit två förare köra en bil med en förhoppning att kunna klassificera vem det var som körde bilen. Målet var att kunna förutspå föraren med en korrekthet på 80-90% givet endast hastighet samt varvtal som samlas genom ODB:II-porten via CAN-bussen i fordonet. Angreppsättet på detta arbete liknar det för textklassificering, nämligen att använda två vanliga klassificeringsmetoder från just textklassificering — Multinominal och Gaussisk Naive Bayes tillsammans med N-gram samt diskretisering.

Vi fann genom att använda Multinominal Naive Bayes med 4-gram samt icke-diskretiserade respektive diskretiserade hastighet- och varvtalsvärden kunde klassificera förare med 91.48% korrekthet.

• 244.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Implementation of a real-time Fast Fourier Transform on a Graphics Processing Unit with data streamed from a high-performance digitizer2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)

In this thesis we evaluate the prospects of performing real-time digital signal processing on a graphics processing unit (GPU) when linked together with a high-performance digitizer. A graphics card is acquired and an implementation developed that address issues such as transportation of data and capability of coping with the throughput of the data stream. Furthermore, it consists of an algorithm for executing consecutive fast Fourier transforms on the digitized signal together with averaging and visualization of the output spectrum.

An empirical approach has been used when researching different available options for streaming data. For better performance, an analysis of the introduced noise of using single-precision over double-precision has been performed to decide on the required precision in the context of this thesis. The choice of graphics card is based on an empirical investigation coupled with a measurement-based approach.

An implementation in single-precision with streaming from the digitizer, by means of double buffering in CPU RAM, capable of speeds up to 3.0 GB/s is presented. Measurements indicate that even higher bandwidths are possible without overflowing the GPU. Tests show that the implementation is capable of computing the spectrum for transform sizes of $2^{21}$, however measurements indicate that higher and lower transform sizes are possible. The results of the computations are visualized in real-time.

• 245.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
Energy-Efficient Mobile Communication with Cached Signal Maps2016Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)

Data communication over cellular networks is expensive for the mobile device in terms of energy, especially when the received signal strength (RSS) is low. The mobile device needs to amplify its transmission power to compensate for noise leading to an increased energy consumption. This thesis focuses on developing a RSS map for the third generation cellular technology (3G) which can be stored locally at the mobile device, and can be used for avoiding expensive communication in low RSS areas.

The proposed signal map is created by crowdsourced information collected from several mobile devices. An application is used to collect data in the mobile device of the user and the application periodically sends the information back to the server which computes the total signal map.

The signal map is composed of three levels of information: RSS information, data rate tests and estimated energy levels. The energy level categorizes the energy consumption of an area into "High", "Medium" or "Low" based on the RSS, data rate test information and an energy model developed from physical power measurements. The coarse categorization provides an estimation of the energy consumption at each location. It is evaluated by collecting data traces on a smartphone at different locations and comparing the measured energy consumption at each location to the energy level categories of the map.

The RSS prediction is preliminarily evaluated by collecting new data along a path and comparing how well it correlates to the signal map. The evaluation in this thesis shows that with the current collected data there are not enough observations in the map to properly estimate the RSS. However, we believe that with more observations a more accurate evaluation could be done.

• 246.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Centre for IT-Security, Privacy and Accountability, Saarland University, Germany. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Systematic detection of memory related performance bottlenecks in GPGPU programs2016Ingår i: Journal of systems architecture, ISSN 1383-7621, E-ISSN 1873-6165, Vol. 71, 73-87 s.Artikel i tidskrift (Refereegranskat)

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

• 247.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
Signal-Aware Route Planning2016Självständigt arbete på grundnivå (högskoleexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)

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

• 248.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Connectivity-optimal Shortest Paths Using Crowdsourced Data2016Ingår i: 2016 IEEE International Conference on Pervasive Computing and Communication Workshops (PerCom Workshops), IEEE Computer Society, 2016, 1-6 s.Konferensbidrag (Refereegranskat)

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

• 249.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Investigating Architecture Description Languages (ADLs) A Systematic Literature Review2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)

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

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

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

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

• 250.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Finding Correlation and Predicting System Behavior in Large IT Infrastructure2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)

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

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

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