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• 251.
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, s. 133-145Konferensbidrag (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.

• 252.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Optimized variant-selection code generation for loops on heterogeneous multicore systems2016Ingår i: Parallel Computing: On the Road to Exascale / [ed] Gerhard R. Joubert, Hugh Leather, Mark Parsons, Frans Peters, Mark Sawyer, IOS Press, 2016, s. 103-112Kapitel i bok, del av antologi (Refereegranskat)

We consider the general problem of generating code for the automated selection of the expected best implementation variants for multiple subcomputations on a heterogeneous multicore system, where the program's control flow between the subcomputations is structured by sequencing and loops. A naive greedy approach as applied in previous works on multi-variant selection code generation would determine the locally best variant for each subcomputation instance but might miss globally better solutions. We present a formalization and a fast algorithm for the global variant selection problem for loop-based programs. We also show that loop unrolling can additionally improve performance, and prove an upper bound of the unroll factor which allows to keep the run-time space overhead for the variant-dispatch data structure low. We evaluate our method in case studies using an ARM big.LITTLE based system and a GPU based system where we consider optimization for both energy and performance.

• 253.
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.

• 254.
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.

• 255.
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.

• 256.
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.

• 257.
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.

• 258.
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.

• 259.
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.

• 260.
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.

• 261.
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, s. 73-87Artikel 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%.

• 262.
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.

• 263.
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, s. 1-6Konferensbidrag (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.

• 264.
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.

• 265.
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.

• 266.
University of Penn, PA 19104 USA.
University of Seoul, South Korea. Korea Adv Institute Science and Technology, South Korea. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
A Process Algebraic Approach to Resource-Parameterized Timing Analysis of Automotive Software Architectures2016Ingår i: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, Vol. 12, nr 2, s. 655-671Artikel i tidskrift (Refereegranskat)

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

• 267.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
Testing and Gherkin in agile projects2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)

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

• 268.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
A Cross-platform Picture Transfer Protocol for Linux-based Camera2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)

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

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

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

• 269.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
A Cloud Based Platform for Big Data Science2014Självständigt arbete på avancerad nivå (masterexamen), 30 poäng / 45 hpStudentuppsats (Examensarbete)

• 270.
Embedded Intelligent Solutions (EIS) by Semcon AB, Linköping, Sweden.
University of Verona, Italy. University of Verona, Italy. University of Verona, Italy. University of Verona, Italy. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. University of Tokyo, Japan; Japan Scence and Technology Agency, Japan.
Time-Constraint-Aware Optimization of Assertions in Embedded Software2012Ingår i: Journal of electronic testing, ISSN 0923-8174, E-ISSN 1573-0727, Vol. 28, nr 4, s. 469-486Artikel i tidskrift (Refereegranskat)

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

• 271.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Industry Foundation Classes: A study of its requested use in Configura2015Självständigt arbete på grundnivå (högskoleexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)

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

• 272.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Security-Driven Design of Real-Time Embedded Systems2015Doktorsavhandling, monografi (Övrigt vetenskapligt)

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

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

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

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

• 273.
Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Institute for Computing and Information Sciences, Radboud University Nijmegen, The Netherlands. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Robustness Analysis of Real-Time Scheduling Against Differential Power Analysis Attacks2014Ingår i: IEEE Computer Society Annual Symposium on VLSI, IEEE Computer Society, 2014, s. 450-455Konferensbidrag (Refereegranskat)

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

• 274.
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.
Power-Aware Design Techniques of Secure Multimode Embedded Systems2016Ingår i: ACM Transactions on Embedded Computing Systems, ISSN 1539-9087, E-ISSN 1558-3465, Vol. 15, nr 1, s. 6-Artikel i tidskrift (Refereegranskat)

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

• 275.
Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
A Design Framework for Dynamic Embedded Systems with Security Constraints2013Ingår i: The 12th Swedish System-on-Chip Conference (SSoCC 2013), Ystad, Sweden, May 6-7, 2013 (not reviewed, not printed)., 2013Konferensbidrag (Övrigt vetenskapligt)
• 276.
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.
Optimization of Secure Embedded Systems with Dynamic Task Sets2013Ingår i: Design, Automation & Test in Europe (DATE 2013), IEEE , 2013, s. 1765-1770Konferensbidrag (Refereegranskat)

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

• 277.
Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Performance Comparison of Simulated Annealing and Tabu Search on Block Cipher Optimization in Distributed Embedded Systems2011Ingår i: The 11th Swedish System-on-Chip Conference, Varberg, Sweden, May 2-3, 2011, 2011Konferensbidrag (Övrigt vetenskapligt)

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

• 278.
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.
Power-Aware Design Techniques of Secure Multimode Embedded Systems2016Ingår i: ACM Transactions on Embedded Computing Systems, ISSN 1539-9087, E-ISSN 1558-3465, Vol. 15, s. 6:1-6:29Artikel i tidskrift (Refereegranskat)

Nowadays, embedded systems have been widely used in all types of application areas, some of which belong to the safety and reliability critical domains. The functional correctness and design robustness of the embedded systems involved in such domains are crucial for the safety of personal/enterprise property or even human lives. Thereby, a holistic design procedure that considers all the important design concerns is essential.

In this article, we approach embedded systems design from an integral perspective. We consider not only the classic real-time and quality of service requirements, but also the emerging security and power efficiency demands. Modern embedded systems are not any more developed for a fixed purpose, but instead designed for undertaking various processing requests. This leads to the concept of multimode embedded systems, in which the number and nature of active tasks change during runtime. Under dynamic situations, providing high performance along with various design concerns becomes a really difficult problem. Therefore, we propose a novel power-aware secure embedded systems design framework that efficiently solves the problem of runtime quality optimization with security and power constraints. The efficiency of our proposed techniques are evaluated in extensive experiments.

• 279.
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. Radboud University Nijmegen, The Netherlands.
SPARTA: A scheduling policy for thwarting differential power analysis attacks2016Ingår i: 2016 21ST ASIA AND SOUTH PACIFIC DESIGN AUTOMATION CONFERENCE (ASP-DAC), IEEE Press, 2016, s. 667-672Konferensbidrag (Refereegranskat)

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

• 280.
Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. University of Electronic Science and Technology of China, Chengdu.
Energy-Aware Design of Secure Multi-Mode Real-Time Embedded Systems with FPGA Co-Processors2013Ingår i: Proceedings of the 21st International conference on Real-Time Networks and Systems / [ed] Michel Auguin, Robert de Simone, Robert Davis, Emmanuel Grolleau, New York: Association for Computing Machinery (ACM), 2013, s. 109-118Konferensbidrag (Refereegranskat)

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

• 281.
School of Computer Science and Technology, University of Electronic Science and Technology of China.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. School of Computer Science and Technology, University of Electronic Science and Technology of China.
Resource Allocation of Security-Critical Tasks with Statistically Guaranteed Energy Constraint2012Ingår i: International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA 2012), Seoul, Korea, August 19-22, 2012., IEEE , 2012, s. 330-339Konferensbidrag (Övrigt vetenskapligt)

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

• 282.
School of Computer Science and Engineering, University of Electronic Science and Technology of China, China School of Information and Software Engineering, University of Electronic Science and Technology of China, China .
Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. School of Information and Software Engineering, University of Electronic Science and Technology of China, China . Department of Computer Science and Engineering, University of Notre Dame, United States .
Energy Aware Real-Time Scheduling Policy with Guaranteed Security Protection2014Ingår i: 2014 19TH ASIA AND SOUTH PACIFIC DESIGN AUTOMATION CONFERENCE (ASP-DAC), IEEE conference proceedings, 2014, s. 317-322Konferensbidrag (Refereegranskat)

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

• 283.
University of Elect Science and Technology China, Peoples R China.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. University of Texas Dallas, TX 75230 USA. University of Notre Dame, IN 46556 USA.
Energy Optimization of Security-Critical Real-Time Applications with Guaranteed Security Protection2015Ingår i: Journal of systems architecture, ISSN 1383-7621, E-ISSN 1873-6165, Vol. 61, nr 7, s. 282-292Artikel i tidskrift (Refereegranskat)

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

• 284.
Univ. Paris Sud, France.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. Univ. Paris Sud, France.
Stochastic Shortest Path Problem with Uncertain Delays2012Ingår i: Proceedings of the 1st International Conference on Operations Research and Enterprise Systems (ICORES-2012 / [ed] Carlos J. Luz, Fernando Valente, 2012, s. 256-264Konferensbidrag (Övrigt vetenskapligt)
• 285.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
Generating SkePU Code from Automatically Detected Algorithmic Patterns in C Source Programs2016Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)

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

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

• 286.
University of Pompeu Fabra, Spain .
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Limitations of acyclic causal graphs for planning2014Ingår i: Artificial Intelligence, ISSN 0004-3702, E-ISSN 1872-7921, Vol. 210, s. 36-55Artikel i tidskrift (Refereegranskat)

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

• 287.
Universitat Pompeu Fabra, Barcelona, Spain.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
When Acyclicity is not Enough: Limitations of the Causal Graph2013Ingår i: Proceedings of the Twenty-Third International Conference on Automated Planning and Scheduling, AAAI Press, 2013, s. 117-125Konferensbidrag (Refereegranskat)

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

• 288.
Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten. Ericsson AB, Sweden.
Lund University, Sweden. KTH Royal Institute Technology, Sweden; University of Calif Berkeley, CA 94720 USA. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. Ericsson AB, Sweden. Lund University, Sweden.
Automated bug assignment: Ensemble-based machine learning in large scale industrial contexts2016Ingår i: Journal of Empirical Software Engineering, ISSN 1382-3256, E-ISSN 1573-7616, Vol. 21, nr 4, s. 1533-1578Artikel i tidskrift (Refereegranskat)

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

• 289.
Linköpings universitet, Institutionen för datavetenskap, PELAB - Laboratoriet för programmeringsomgivningar. Ericsson AB, Sweden.
KTH Royal Institute Technology, Sweden; University of Calif Berkeley, CA USA. Linköpings universitet, Institutionen för datavetenskap, Statistik. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för datavetenskap, Statistik. Linköpings universitet, Filosofiska fakulteten. Ericsson AB, Sweden.
Automatic Localization of Bugs to Faulty Components in Large Scale Software Systems using Bayesian Classification2016Ingår i: 2016 IEEE INTERNATIONAL CONFERENCE ON SOFTWARE QUALITY, RELIABILITY AND SECURITY (QRS 2016), IEEE , 2016, s. 425-432Konferensbidrag (Refereegranskat)

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

• 290.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
Resource planning in a multi-project organization: A case study at Sanmina in Örnsköldsvik2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)

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

• 291.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Finite Unary Relations and Qualitative Constraint Satisfaction2016Ingår i: ECAI 2016: 22ND EUROPEAN CONFERENCE ON ARTIFICIAL INTELLIGENCE, IOS PRESS , 2016, Vol. 285, s. 37-45Konferensbidrag (Refereegranskat)

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

• 292.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Technical University of Dresden, Germany.
An initial study of time complexity in infinite-domain constraint satisfaction2017Ingår i: Artificial Intelligence, ISSN 0004-3702, E-ISSN 1872-7921, Vol. 245, s. 115-133Artikel i tidskrift (Refereegranskat)

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

Publikationen är tillgänglig i fulltext från 2019-01-27 14:26
• 293.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Upper and Lower Bounds on the Time Complexity of Infinite-domain CSPs2015Ingår i: Principles and Practice of Constraint Programming - 21st International Conference, CP 2015, Cork, Ireland, August 31 - September 4, 2015, Proceedings / [ed] Pesant, Gilles, Springer Berlin/Heidelberg, 2015, Vol. 9255, s. 183-199Konferensbidrag (Refereegranskat)

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

• 294.
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.
Blowing Holes in Various Aspects of Computational Problems, with Applications to Constraint Satisfaction2013Ingår i: Principles and Practice of Constraint Programming / [ed] Christian Schulte, Springer Berlin/Heidelberg, 2013, s. 398-414Konferensbidrag (Refereegranskat)

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

• 295.
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 högskolan.
Constructing NP-intermediate problems by blowing holes with parameters of various properties2015Ingår i: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 581, s. 67-82Artikel i tidskrift (Refereegranskat)

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

• 296.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
Technical University of Dresden, Germany. Kvarnvagen 6, Sweden. Normandie University, France.
Strong partial clones and the time complexity of SAT problems2017Ingår i: Journal of computer and system sciences (Print), ISSN 0022-0000, E-ISSN 1090-2724, Vol. 84, s. 52-78Artikel i tidskrift (Refereegranskat)

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

• 297.
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.
Relating the Time Complexity of Optimization Problems in Light of the Exponential-Time Hypothesis2014Ingår i: Mathematical Foundations of Computer Science 2014: 39th International Symposium, MFCS 2014, Budapest, Hungary, August 25-29, 2014. Proceedings, Part II / [ed] Erzsébet Csuhaj-Varjú, Martin Dietzfelbinger, Zoltán Ésik, Springer Berlin/Heidelberg, 2014, s. 408-419Kapitel i bok, del av antologi (Refereegranskat)

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

• 298.
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. Université de Caen Basse-Normandie, France.
Complexity of SAT problems, Clone Theory and the Exponential Time Hypothesis2013Ingår i: SODA-2013, SIAM , 2013, s. 1264-1277Konferensbidrag (Refereegranskat)
• 299.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Computational complexity of linear constraints over the integers2013Ingår i: Artificial Intelligence, ISSN 0004-3702, E-ISSN 1872-7921, Vol. 195, s. 44-62Artikel i tidskrift (Refereegranskat)

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

• 300.
Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
Université Paris-Sud 11, Laboratoire de Recherche en Informatique (LRI) .
Affine Consistency and the Complexity of Semilinear Constraints2014Ingår i: Mathematical Foundations of Computer Science 2014 / [ed] Ersébet Csuhaj-Varjú,Martin Dietzfelbinger,Zoltán Ésik, Berlin/Heidelberg, 2014, s. 420-431Konferensbidrag (Refereegranskat)

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

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