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  • 48901.
    Zdravkovic, Jelena
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Stirna, JanisStockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.Kirikova, MariteKaragiannis, DimitrisWinter, Robert
    Advanced Enterprise Modeling2015Samlingsverk (redaktörskap) (Refereegranskat)
  • 48902.
    Zdravkovic, Jelena
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Stirna, Janis
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Kirikova, Marite
    Karagiannis, Dimitris
    Winter, Robert
    BISE – Call for Papers Issue 1/20152013Ingår i: Business & Information Systems Engineering, ISSN 1867-0202, Vol. 5, nr 5, s. 361-361Artikel i tidskrift (Refereegranskat)
  • 48903.
    Zdravkovic, Jelena
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Stirna, Janis
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Kuhr, Jan-Christian
    Koç, Hasan
    Requirements Engineering for Capability Driven Development2014Ingår i: The Practice of Enterprise Modeling: 7th IFIP WG 8.1 Working Conference, PoEM 2014, Manchester, UK, November 12-13, 2014: proceedings / [ed] Ulrich Frank, Berlin: Springer, 2014, Vol. 197, s. 193-207Konferensbidrag (Refereegranskat)
    Abstract [en]

    Lately, the notion of capability has emerged in IS engineering as an instrument to context dependent design and delivery of business services. Representing core business functionalities of an organization, capabilities, and capability driven IS development can be seen as both – a shift beyond and complement to the widely established service-oriented engineering paradigm where needs of customers form the leading modeling and design perspective. To ensure the needs of business stakeholders for variety of business contexts that an organization faces, and thus facilitate successful systems delivery, capability-driven development needs a well-defined method for requirements engineering, as well as its confirmation in practices. In this paper a process for specifying requirements capabilities and their designs is proposed. An application of the proposed approach to the area of Business Process Outsourcing (BPO) services. is carried out for the German company SIV.

  • 48904.
    Zdravkovic, Jelena
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Svee, Eric-Oluf
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Giannoulis, Constantinos
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Capturing consumer preferences as requirements for software product lines2015Ingår i: Requirements Engineering, ISSN 0947-3602, E-ISSN 1432-010X, Vol. 20, nr 1, s. 71-90Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Delivering great consumer experiences in competitive market conditions requires software vendors to move away from traditional modes of thinking to an outside- in perspective, one that shifts their business to becoming consumer-centric. Requirements engineers operating in these conditions thus need new means to both capture real preferences of consumers and then relate them to requirements for software customized in different ways to fit anyone. Additionally, because system development models require inputs that are more concrete than abstract, the indistinct values of consumers need to be classified and formalized. To address this challenge, this study aims to establish a conceptual link between preferences of consumers and system requirements, using software product line (SPL) as a means for systematically accommodating the variations within the preferences. The novelty of this study is a conceptual model of consumer preference, which integrates generic value frameworks from both psychology and marketing, and a method for its transformation to requirements for SPL using a goal-oriented RE framework as the mediator. The presented artifacts are grounded in an empirical study related to the development of a system for online education.

  • 48905.
    Zdravkovic, Jelena
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Zikra, Iyad
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Ilayperuma, Tharaka
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    An MDA Method for Service Modeling by Formalizing REA and Open-edi Business Frameworks with SBVR2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Business frameworks offer great opportunities of communication between people for working on the enterprise system engineering processes, as well as for eliciting services that the enterprise can offer in collaboration contexts. However, these kinds of frameworks, such as Resource-Event-Agent and Open-edi, recently unified in Open-edi Business Ontology (OeBTO), lack formal representations. This fact considerably limits their use in system development, particularly in model-driven development methods where the efficiency of transformations is of great importance. In this paper we suggest a formalization of OeBTO using OMG’s standard Semantics of Business Vocabulary and Business Rules (SBVR), as a method for creating a service-centric business model. This makes it possible to provide the necessary formal logic foundation to allow automatic processing of the business model and its transformation to a system-level service model. An example from the bank loan business sector is used to argument the application of the method.

  • 48906.
    Zdravkovic, Marta
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, International Science Programme (ISP).
    Chiwona-Karltun, Linley
    Swedish Univ Agr Sci, Dept Urban & Rural Dev, Uppsala, Sweden..
    Zink, Eren
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Historisk-filosofiska fakulteten, Institutionen för kulturantropologi och etnologi.
    Experiences and perceptions of South-South and North-South scientific collaboration of mathematicians, physicists and chemists from five southern African universities2016Ingår i: The Scientist (Philadelphia, Pa.), ISSN 0138-9130, E-ISSN 1588-2861, Vol. 108, nr 2, s. 717-743Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Faced with limited resources, scientists from around the world enter into collaborations to join their resources to conduct research. Like everywhere else, international co-publishing in southern African countries is increasingly on the rise. The aim of this study was to document and analyse the level of scientific productivity, collaboration patterns, scientists' experiences and attitudes towards South-South and South-North collaboration. We performed 105 interviews with scientists based at five southern African Universities, namely; University of Malawi-Chancellor College, National University of Science and Technology, the University of Botswana, the University of Zambia, and the University of Zimbabwe. We also traced 192 scientists from the various departments at these universities that had jointly published 623 scientific papers in the field of basic sciences in the period 1995-2014 in Web of Science journals. Our results show that in the majority of the cases funding from the North contributed substantially to increased scientific productivity, and international co-authorship. The results also show that collaboration with southern scientists is equally valued as that with northern scientists, but for different reasons. We conclude that supporting international and national collaboration which includes increased scientific mobility, strong scientific groups and networks, are key factors for capacity building of research in southern African Universities.

  • 48907. Zdravković, Milan
    et al.
    Zdravković, Jelena
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Aubry, Alexis
    Moalla, Néjib
    Guedria, Wided
    Sarraipa, João
    Domain framework for implementation of open IoT ecosystems2018Ingår i: International Journal of Production Research, ISSN 0020-7543, E-ISSN 1366-588X, Vol. 56, nr 7, s. 2552-2569Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The current Internet-of-things (IoT) hype, pushed by the unprecedented rate of the technological enablers’ innovation, is threatening to leave behind some major, not so obvious, unresolved issues. IoT platforms will extend existing enterprise information systems (EIS) infrastructures to encompass cross-domain sensing and actuating capabilities, thus introducing additional complexity and major risks to the implementation. Furthermore, IoT platforms are typically driven by models of the trivial complexity; they support very simple data structures and almost no business logic implementation. Finally, IoT systems are today managed centrally, which often means less openness, less flexibility and greater change management costs. In this article, we provide the overview of the scientific disciplines which could contribute to the resolution of the IoT implementation problem, namely requirements engineering, change management/continuous improvement, model-based systems engineering, system architecture design, interoperability and policy and regulatory aspects. Then, we identify the challenges of these contributions in the context of IoT and finally make an attempt to identify research directions which could have a significant impact. The discussion of the challenges and opportunities is illustrated by the proposed domain framework for implementation of open IoT ecosystems.

  • 48908.
    Zdunek, Aleksander
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Automatic error detection and switching of redundant video signals, with focus on loop detection2018Självständigt arbete på avancerad nivå (yrkesexamen), 180 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Denna rapport beskriver arbete utfört med att implementera automatisk detektion av loopande följder av bildrutor i en videosignal. Den centrala algoritmen för igenkänning av loopar beskrivs. För att förbättra beräkningshastighet tillämpas hashning av bildrutor. Två videosignaler jämförs med avseende på deras innehåller av loopar, och växling av uppspelad signal sker baserat på utvärdering av signalernas kvalitet. Upprepade följder, skilt från loopande följder, diskuteras. Tankar för vidare utveckling av en mer heltäckande paketlösning för detektion av olika typer av fel i videosignaler presenteras kort.

  • 48909.
    Zea, Elías
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Binaural Monitoring for Live Music Performances.2012Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Författare: Elías Zea

    Titel: Binaural Medhörning för Förstärkta Live-framträdanden

    Sammanfattning: Gängse medhörningssystem för livemusik förlitar sig på en ljudtekniker, som manipulerar ljudnivåer, efterklang och/eller panorering av medhörningen på scenen, för att därigenom simulera en ljudspatialisering. Denna konventionella metod försummar två av ljudfältets väsentliga aspekter: instrumentens frekvensberoende riktverkan, samt rumslokaliseringen, som intuitivt uppfattas av musiker när de spelar utan ljudförstärkning. Det här arbetet omfattar design, genomförande och utvärdering av ett medhörningssystem för livemusik som tar hänsyn till riktverkan och presenterar binauralt ljud. Systemet har fyra huvudkomponenter: musikinstrumentens riktverkan, ett rumsimpulssvar (RIR), binauralt ljud med individuella huvudrelaterade överföringsfunktioner (HRTF), och rörelseanalys av såväl musikerns huvud som av instrumentet. Systemet har utvärderats med musiker. En enkät utfördes för att bedöma musikernas första intryck av systemets noggrannhet och realism, liksom den upplevda graden av förbättring av musicerandet och utförandets konstnärliga värde. Resultaten pekar mot ytterligare forskning som kan vara av intresse.

  • 48910.
    Zeadally, Sherali
    et al.
    Univ Dist Columbia, Dept Comp Sci & Informat Technol, Network Syst Lab, Washington, DC 20008 USA..
    Hunt, Ray
    Univ Canterbury, Coll Engn, Dept Comp Sci & Software Engn, Christchurch 1, New Zealand..
    Chen, Yuh-Shyan
    Natl Taipei Univ, Dept Comp Sci & Informat Engn, San Shia, Taipei County, Taiwan..
    Irwin, Angela
    Univ S Australia, Sch Comp & Informat Sci, Mawson Lakes, SA 5095, Australia..
    Hassan, Aamir
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS).
    Vehicular ad hoc networks (VANETS): status, results, and challenges2012Ingår i: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 50, nr 4, s. 217-241Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recent advances in hardware, software, and communication technologies are enabling the design and implementation of a whole range of different types of networks that are being deployed in various environments. One such network that has received a lot of interest in the last couple of years is the Vehicular Ad-Hoc Network (VANET). VANET has become an active area of research, standardization, and development because it has tremendous potential to improve vehicle and road safety, traffic efficiency, and convenience as well as comfort to both drivers and passengers. Recent research efforts have placed a strong emphasis on novel VANET design architectures and implementations. A lot of VANET research work have focused on specific areas including routing, broadcasting, Quality of Service (QoS), and security. We survey some of the recent research results in these areas. We present a review of wireless access standards for VANETs, and describe some of the recent VANET trials and deployments in the US, Japan, and the European Union. In addition, we also briefly present some of the simulators currently available to VANET researchers for VANET simulations and we assess their benefits and limitations. Finally, we outline some of the VANET research challenges that still need to be addressed to enable the ubiquitous deployment and widespead adoption of scalable, reliable, robust, and secure VANET architectures, protocols, technologies, and services.

  • 48911.
    Zeb, Falak
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Naseem, Sajid
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Guidelines for the Deployment of Biometrics Technology in Blekinge Health Care System with the Focus on Human Perceptions and Cost Factor2010Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    Biometri Teknik är en autentisering teknik som identifierar individer från deras fysiska och beteendemässiga egenskaper. Trots att biometriska tekniken ger en robust autentisering och ökad säkerhet, har det ännu inte genomförts i många delar av världen på grund av vissa frågor som exempelvis mänskliga uppfattningar om biometriska tekniken och extra kostnader, som deltar i användningen av biometriska tekniken. Eftersom biometriska tekniken innebär identitetshantering av individer som är anledningen till att människor uppfattningar av biometriska tekniken dvs rör skyddet av privatlivet, säkerhetsfrågor och användarnas inställning fråga spelar en mycket viktig roll i spridningen av biometriska tekniken. Där för människors uppfattningar och kostnad faktor måste beaktas innan en eventuell utplacering av biometriska tekniken. Syftet med detta examensarbete är att studera och analysera hur människors uppfattning och kostnad faktor kan lösas för införande av biometri teknik i Blekinge hälsovårdssystemet. Litteraturstudie, intervjuer och undersökningar utförs av författare för identifiering och förståelse av människans förnimmelser och kostnad faktor. Baserat på dessa, är lösningar i form av riktlinjer för de frågor som berörs av biometri spridningen av tekniken i Blekinge sjukvårdssystem Sverige ges.

  • 48912.
    Zec, Milos
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för informatik (IK).
    Kajtazi, Miranda
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för informatik (IK). Örebro University.
    Examining how IT Professionals in SMEs Take Decisions About Implementing Cyber Security Strategy2015Ingår i: Proceedings of the 9th European Conference on IS Management and Evaluation (ECIME 2015), Academic Conferences Limited, 2015, s. 231-239Konferensbidrag (Refereegranskat)
    Abstract [en]

    With the significant growth of cyber space, business organizations have become more alert than ever before that cyber security must be considered seriously and that there is a need to develop up-to-date security measures. It has become an increasing trend that cyber-attackers concentrate more on small and medium than on large enterprises, due to their known vulnerability towards cyber security. In exchange of successful cyber security measures in organizations, the security risks must be taken into consideration more closely that could be helpful for re-thinking their decision-making on cyber security. This article develops a theoretical framework on cyber security with three aspects taken in consideration: organizational, technological and psychological, that deserves the attention of IT professionals while and after creating cyber security measures in their SMEs. The first two aspects (organizational and technological) focus on understanding the IT professionals' decision-making process, while the third aspect (psychological) focuses on understanding the IT professionals' post decision-making reactions. Firstly, the organizational aspect presupposes that the ones who create cyber security measures are exposed to unclear and undefined decision processes and rights that lead to system vulnerabilities. Secondly, the technological aspect focuses on disclosing how many IT professionals in their organizations fail to meet foundational technological measures, such as the existence of Internet firewall, logs of system events, existence of hardware and software inventory list, data backup, antivirus software and password rules. Lastly, the psychological aspect, explains how post cyber security decisions made by IT professionals may have a contra-effect on the organization. Our data analyses collected based on interviews with IT professionals across 6 organizations (SMEs) show that cyber security is yet to be developed among SMEs, an issue that must not be taken lightly. Results show that the IT professionals in these organizations need to strengthen and develop their security thinking, in order to decrease the vulnerability of informational assets among SMEs. We believe that a perspective on understanding decision-making processes upon the cyber security measures by IT professionals in SMEs may bring a theoretical redirection in the literature, as well as an important feedback to practice.

  • 48913.
    Zec, Milos
    et al.
    Department of Informatics, Linnaeus University, Växjö, Sweden.
    Kajtazi, Miranda
    Örebro universitet, Handelshögskolan vid Örebro Universitet. Department of Informatics, Linnaeus University, Växjö, Sweden.
    Examining how IT Professionals in SMEs Take Decisions About Implementing Cyber Security Strategy2015Ingår i: PROCEEDINGS OF 9TH EUROPEAN CONFERENCE ON IS MANAGEMENT AND EVALUATION (ECIME 2015), Academic Conferences Limited, 2015, s. 231-239Konferensbidrag (Refereegranskat)
    Abstract [en]

    With the significant growth of cyber space, business organizations have become more alert than ever before that cyber security must be considered seriously and that there is a need to develop up-to-date security measures. It has become an increasing trend that cyber-attackers concentrate more on small and medium than on large enterprises, due to their known vulnerability towards cyber security. In exchange of successful cyber security measures in organizations, the security risks must be taken into consideration more closely that could be helpful for re-thinking their decision-making on cyber security. This article develops a theoretical framework on cyber security with three aspects taken in consideration: organizational, technological and psychological, that deserves the attention of IT professionals while and after creating cyber security measures in their SMEs. The first two aspects (organizational and technological) focus on understanding the IT professionals' decision-making process, while the third aspect (psychological) focuses on understanding the IT professionals' post decision-making reactions. Firstly, the organizational aspect presupposes that the ones who create cyber security measures are exposed to unclear and undefined decision processes and rights that lead to system vulnerabilities. Secondly, the technological aspect focuses on disclosing how many IT professionals in their organizations fail to meet foundational technological measures, such as the existence of Internet firewall, logs of system events, existence of hardware and software inventory list, data backup, antivirus software and password rules. Lastly, the psychological aspect, explains how post cyber security decisions made by IT professionals may have a contra-effect on the organization. Our data analyses collected based on interviews with IT professionals across 6 organizations (SMEs) show that cyber security is yet to be developed among SMEs, an issue that must not be taken lightly. Results show that the IT professionals in these organizations need to strengthen and develop their security thinking, in order to decrease the vulnerability of informational assets among SMEs. We believe that a perspective on understanding decision-making processes upon the cyber security measures by IT professionals in SMEs may bring a theoretical redirection in the literature, as well as an important feedback to practice.

  • 48914.
    Zechner, Niklas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A novel approach to text classification2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis explores the foundations of text classification, using both empirical and deductive methods, with a focus on author identification and syntactic methods. We strive for a thorough theoretical understanding of what affects the effectiveness of classification in general. 

    To begin with, we systematically investigate the effects of some parameters on the accuracy of author identification. How is the accuracy affected by the number of candidate authors, and the amount of data per candidate? Are there differences in how methods react to the changes in parameters? Using the same techniques, we see indications that methods previously thought to be topic-independent might not be so, but that syntactic methods may be the best option for avoiding topic dependence. This means that previous studies may have overestimated the power of lexical methods. We also briefly look for ways of spotting which particular features might be the most effective for classification. Apart from author identification, we apply similar methods to identifying properties of the author, including age and gender, and attempt to estimate the number of distinct authors in a text sample. In all cases, the techniques are proven viable if not overwhelmingly accurate, and we see that lexical and syntactic methods give very similar results. 

    In the final parts, we see some results of automata theory that can be of use for syntactic analysis and classification. First, we generalise a known algorithm for finding a list of the best-ranked strings according to a weighted automaton, to doing the same with trees and a tree automaton. This result can be of use for speeding up parsing, which often runs in several steps, where each step needs several trees from the previous as input. Second, we use a compressed version of deterministic finite automata, known as failure automata, and prove that finding the optimal compression is NP-complete, but that there are efficient algorithms for finding good approximations. Third, we find and prove the derivatives of regular expressions with cuts. Derivatives are an operation on expressions to calculate the remaining expression after reading a given symbol, and cuts are an extension to regular expressions found in many programming languages. Together, these findings may be able to improve on the syntactic analysis which we have seen is a valuable tool for text classification.

  • 48915.
    Zechner, Niklas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Derivatives of regular expressions with cuts2017Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Derivatives of regular expressions are an operation which for a given expression produces an expression for what remains after a specific symbol has been read. This can be used as a step in transforming an expression into a finite string automaton. Cuts are an extension of the ordinary regular expressions; the cut operator is essentially a concatenation without backtracking, formalising a behaviour found in many programming languages. Just as for concatenation, we can also define an iterated cut operator. We show and derive expressions for the derivatives of regular expressions with cuts and iterated cuts.

  • 48916.
    Zeebari, Zangin
    Växjö universitet, Fakulteten för humaniora och samhällsvetenskap, Ekonomihögskolan, EHV.
    Developing Median Regression for SURE Models: With Application to 3-Generation Immigrants' Data in Sweden2009Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 48917.
    Zeeshan, Ahmed
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för för interaktion och systemdesign.
    Integration of Variants Handling in M-System-NT2006Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    This Master thesis proposes a solution to manage variabilities of software product line applications. The objective of the research is to support software decision makers in handling additional software complexity introduced by product line architectures. In order to fulfill this objective an approach to analyze, visualize, and measure product line specific characteristics of the C/C++ source code are proposed. The approach is validated in an empirical experiment using an open source software system. For that purpose the approach is first implemented into ®1 M-System-NT, an existing software measurement tool developed at Fraunhofer. The target hypothesis of the Institute for Experimental Software engineering research master thesis to perform static analysis of C/C++ source code, measure traditional and product line measures to identify the correlation between measures and indicate the fault proneness.

  • 48918.
    Zeeshan Iqbal, Syed Muhammad
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Törnquist Krasemann, Johanna
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    A Comparative Evaluation of Re-scheduling Strategies for Train Dispatching during Disturbances2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Railway traffic disturbances occur and train dispatchers make re-scheduling decisions in order to reduce the delays. In order to support the dispatchers, good rescheduling strategies are required that could reduce the delays. We propose and evaluate re-scheduling strategies based on: (i) earliest start time, (ii) earliest track release time, (iii) smallest buffer time, and (iv) shortest section runtime. A comparative evaluation is done for a busy part of the Swedish railway network. Our results indicate that strategies based on earliest start time and earliest track release time have the best average performance.

  • 48919.
    Zeffer, Håkan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för datorteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Hardware–Software Tradeoffs in Shared-Memory Implementations2005Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Shared-memory architectures represent a class of parallel computer systems commonly used in the commercial and technical market. While shared-memory servers typically come in a large variety of configurations and sizes, the advance in semiconductor technology have set the trend towards multiple cores per die and multiple threads per core.

    Software-based distributed shared-memory proposals were given much attention in the 90s. But their promise of short time to market and low cost could not make up for their unstable performance. Hence, these systems seldom made it to the market. However, with the trend towards chip multiprocessors, multiple hardware threads per core and increased cost of connecting multiple chips together to form large-scale machines, software coherence in one form or another might be a good intra-chip coherence solution.

    This thesis shows that data locality, software flexibility and minimal processor support for read and write coherence traps can offer good performance, while removing the hard limit of scalability. Our aggressive fine-grained software-only distributed shared-memory system exploits key application properties, such as locality and sharing patterns, to outperform a hardware-only machine on some benchmarks. On average, the software system is 11 percent slower than the hardware system when run on identical node and interconnect hardware. A detailed full-system simulation study of dual core CMPs, with multiple hardware threads per core and minimal processor support for coherence traps is on average one percent slower than its hardware-only counterpart when some flexibility is taken into account. Finally, a functional full-system simulation study of an adaptive coherence-batching scheme shows that the number of coherence misses can be reduced with up to 60 percent and bandwidth consumption reduced with up to 22 percent for both commercial and scientific applications.

  • 48920.
    Zeffer, Håkan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för datorteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Towards Low-Complexity Scalable Shared-Memory Architectures2006Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Plentiful research has addressed low-complexity software-based shared-memory systems since the idea was first introduced more than two decades ago. However, software-coherent systems have not been very successful in the commercial marketplace. We believe there are two main reasons for this: lack of performance and/or lack of binary compatibility.

    This thesis studies multiple aspects of how to design future binary-compatible high-performance scalable shared-memory servers while keeping the hardware complexity at a minimum. It starts with a software-based distributed shared-memory system relying on no specific hardware support and gradually moves towards architectures with simple hardware support.

    The evaluation is made in a modern chip-multiprocessor environment with both high-performance compute workloads and commercial applications. It shows that implementing the coherence-violation detection in hardware while solving the interchip coherence in software allows for high-performing binary-compatible systems with very low hardware complexity. Our second-generation hardware-software hybrid performs on par with, and often better than, traditional hardware-only designs.

    Based on our results, we conclude that it is not only possible to design simple systems while maintaining performance and the binary-compatibility envelope, it is often possible to get better performance than in traditional and more complex designs.

    We also explore two new techniques for evaluating a new shared-memory design throughout this work: adjustable simulation fidelity and statistical multiprocessor cache modeling.

  • 48921.
    Zeffer, Håkan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Hagersten, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    A case for low-complexity MP architectures2007Ingår i: Proc. Conference on Supercomputing: SC 2007, New York: ACM Press , 2007, s. 559-570Konferensbidrag (Refereegranskat)
  • 48922.
    Zeffer, Håkan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. dator system.
    Hagersten, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. dator system.
    Adaptive Coherence Batching for Trap-Based Memory Architectures2005Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Both software-initiated and hardware-initiated prefetching have been used to accelerate shared-memory server performance. While software-initiated prefetching require instruction set and compiler support, hardware prefetching often require additional hardware structures or extra memory state.

    The coherence batching scheme proposed in this paper keeps the system completely binary transparent and does not rely on any additional hardware. Hence, it can be implemented without additional hardware in software coherent systems and improve performance for already optimized and compiled binaries.

    We have evaluated our proposals on a trap-based memory architecture where fine-grained coherence permission checks are done in hardware but the coherence protocol is run in software on the requesting processor. Functional full-system simulation shows that our software-only coherence-batch scheme is able to reduce the number of coherence misses with up to 60 percent compared to a system without coherence batching. The average miss reduction is 37 percent while the average bandwidth usage is reduced.

  • 48923.
    Zeffer, Håkan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Datorteknik.
    Radovic, Zoran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Datorteknik.
    Grenholm, Oskar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Datorteknik.
    Hagersten, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Datorteknik.
    Evaluation, Implementation and Performance of Write Permission Caching in the DSZOOM System2004Rapport (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    Fine-grained software-based distributed shared memory (SW-DSM) systems typically maintain coherence with in-line checking code at load and store operations to shared memory. The instrumentation overhead of this added checking code can be severe. This paper (1) shows that most of the instrumentation overhead in the fine-grained DSZOOM SW-DSM system is store related, (2) introduces a new write permission cache (WPC) technique that exploits spatial store locality and batches coherence actions at runtime, (3) evaluates WPC and (4) presents WPC results when implemented in a real SW-DSM system. On average, the WPC reduces the store instrumentation overhead in DSZOOM with 42 (67) percent for benchmarks compiled with maximum (minimum) compiler optimizations.

  • 48924.
    Zeffer, Håkan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Dator System.
    Radovic, Zoran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Dator System.
    Grenholm, Oskar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Dator System.
    Hagersten, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Dator System.
    Exploiting Spatial Store Locality through Permission Caching in Software DSMs2004Ingår i: Proceedings of the 10th International Euro-Par Conference: Parallel Processing, 2004, s. 551-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fine-grained software-based distributed shared memory (SW-DSM) systems typically maintain coherence with in-line checking code at load and store operations to shared memory. The instrumentation overhead of this added checking code can be severe. This paper (1) shows that most of the instrumentation overhead in the fine-grained SW-DSM system DSZOOM is store-related, (2) introduces a new write permission cache (WPC) technique that exploits spatial store locality and batches coherence actions at runtime, (3) evaluates WPC and (4) presents WPC results when implemented in a real SW-DSM system. On average, the WPC reduces the store instrumentation overhead in DSZOOM with 42 (67) percent for benchmarks compiled with maximum (minimum) compiler optimizations.

  • 48925.
    Zeffer, Håkan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. dator system.
    Radovic, Zoran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. dator system.
    Hagersten, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. dator system.
    Flexibility Implies Performance2005Rapport (Övrigt vetenskapligt)
    Abstract [en]

    No single coherence strategy suits all applications well. Many promising adaptive protocols and coherence predictors, capable of dynamically modifying the coherence strategy, have been suggested over the years.

    While most dynamic detection schemes rely on plentiful of dedicated hardware, the customization technique suggested in this paper requires no extra hardware support for its per-application coherence strategy. Instead, each application is profiled using a low-overhead profiling tool. The appropriate coherence flag setting, suggested by the profiling, is specified when the application is launched.

    We have compared the performance of a hardware DSM (Sun WildFire) to a software DSM built with identical interconnect hardware and coherence strategy. With no support for flexibility, the software DSM runs on average 45 percent slower than the hardware DSM on the 12 studied applications, while the flexibility can get the software DSM within 11 percent. Our all-software system outperforms the hardware DSM on four applications.

  • 48926.
    Zeffer, Håkan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. dator system.
    Radovic, Zoran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Karlsson, Martin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. dator system.
    Hagersten, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. dator system.
    TMA: A Trap-Based Memory Architecture2005Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The advances in semiconductor technology have set the shared-memory server trend towards multiple cores per die and multiple threads per core. We believe that this technology shift forces a reevaluation of how to interconnect multiple such chips to form larger systems.

    This paper argues that minimal processor support for coherence traps implemented in future chip multiprocessors will provide large-scale server systems at a much lower cost in terms of engineer years, verification and time to market when compared to its traditional all-hardware counter part. In our proposal, software trap handlers are responsible for getting read/write permission, whereas the coherence trap hardware is responsible for the actual permission check.

    Detailed full-system simulation shows that a coherence-trap enabled distributed shared memory system can be performance competitive with its highly optimized hardware-only counter part. The evaluated systems use high-end processors with one or two dual-threaded cores per die as processing nodes.

  • 48927.
    Zeid Baker, Mousa
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Generation of Synthetic Images with Generative Adversarial Networks2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Machine Learning is a fast growing area that revolutionizes computer programs by providing systems with the ability to automatically learn and improve from experience. In most cases, the training process begins with extracting patterns from data. The data is a key factor for machine learning algorithms, without data the algorithms will not work. Thus, having sufficient and relevant data is crucial for the performance.

    In this thesis, the researcher tackles the problem of not having a sufficient dataset, in terms of the number of training examples, for an image classification task. The idea is to use Generative Adversarial Networks to generate synthetic images similar to the ground truth, and in this way expand a dataset. Two types of experiments were conducted: the first was used to fine-tune a Deep Convolutional Generative Adversarial Network for a specific dataset, while the second experiment was used to analyze how synthetic data examples affect the accuracy of a Convolutional Neural Network in a classification task. Three well known datasets were used in the first experiment, namely MNIST, Fashion-MNIST and Flower photos, while two datasets were used in the second experiment: MNIST and Fashion-MNIST.

    The results of the generated images of MNIST and Fashion-MNIST had good overall quality. Some classes had clear visual errors while others were indistinguishable from ground truth examples. When it comes to the Flower photos, the generated images suffered from poor visual quality. One can easily tell the synthetic images from the real ones. One reason for the bad performance is due to the large quantity of noise in the Flower photos dataset. This made it difficult for the model to spot the important features of the flowers.

    The results from the second experiment show that the accuracy does not increase when the two datasets, MNIST and Fashion-MNIST, are expanded with synthetic images. This is not because the generated images had bad visual quality, but because the accuracy turned out to not be highly dependent on the number of training examples.

    It can be concluded that Deep Convolutional Generative Adversarial Networks are capable of generating synthetic images similar to the ground truth and thus can be used to expand a dataset. However, this approach does not completely solve the initial problem of not having adequate datasets because Deep Convolutional Generative Adversarial Networks may themselves require, depending on the dataset, a large quantity of training examples.

  • 48928.
    Zeitler, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för datalogi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Scalable Parallelization of Expensive Continuous Queries over Massive Data Streams2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Numerous applications in for example science, engineering, and financial analysis increasingly require online analysis over streaming data. These data streams are often of such a high rate that saving them to disk is not desirable or feasible. Therefore, search and analysis must be performed directly over the data in motion. Such on-line search and analysis can be expressed as continuous queries (CQs) that are defined over the streams. The result of a CQ is a stream itself, which is continuously updated as new data appears in the queried stream(s). In many cases, the applications require non-trivial analysis, leading to CQs involving expensive processing. To provide scalability of such expensive CQs over high-volume streams, the execution of the CQs must be parallelized.

    In order to investigate different approaches to parallel execution of CQs, a parallel data stream management system called SCSQ was implemented for this Thesis. Data and queries from space physics and traffic management applications are used in the evaluations, as well as synthetic data and the standard data stream benchmark; the Linear Road Benchmark. Declarative parallelization functions are introduced into the query language of SCSQ, allowing the user to specify customized parallelization. In particular, declarative stream splitting functions are introduced, which split a stream into parallel sub-streams, over which expensive CQ operators are continuously executed in parallel.

    Naïvely implemented, stream splitting becomes a bottleneck if the input streams are of high volume, if the CQ operators are massively parallelized, or if the stream splitting conditions are expensive. To eliminate this bottleneck, different approaches are investigated to automatically generate parallel execution plans for stream splitting functions. This Thesis shows that by parallelizing the stream splitting itself, expensive CQs can be processed at stream rates close to network speed. Furthermore, it is demonstrated how parallelized stream splitting allows orders of magnitude higher stream rates than any previously published results for the Linear Road Benchmark.

     

  • 48929.
    Zeitler, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Datalogi. CSD.
    Working with Stella2006Ingår i: Astronnews, ISSN 1871-6644, nr 1, s. 12-13Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 48930.
    Zeitler, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Risch, Tore
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Massive scale-out of expensive continuous queries2011Ingår i: 36th International Conference on Very Large Data Bases: VLDB 2010, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Scalable execution of expensive continuous queries over massive data streams requires input streams to be split into parallel sub-streams. The query operators are continuously executed in parallel over these sub-streams. Stream splitting involves both partitioning and replication of incoming tuples, depending on how the continuous query is parallelized. We provide a stream splitting operator that enables such customized stream splitting. However, it is critical that the stream splitting itself keeps up with input streams of high volume. This is a problem when the stream splitting predicates have some costs. Therefore, to enable customized splitting of high-volume streams, we introduce a parallelized stream splitting operator, called parasplit. We investigate the performance of parasplit using a cost model and experimentally. Based on these results, a heuristic is devised to automatically parallelize the execution of parasplit. We show that the maximum stream rate of parasplit approaches network speed, and that the parallelization is resource efficient. Finally, the scalability of our approach is experimentally demonstrated on the Linear Road Benchmark, showing an order of magnitude higher stream processing rate over previously published results, allowing at least 512 expressways.

  • 48931.
    Zeitler, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Datalogi. CSD.
    Risch, Tore
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Datalogi. CSD.
    Processing High-Volume Stream Queries on a Supercomputer2006Ingår i: Processing High-Volume Stream Queries on a Supercomputer, 2006, s. 147-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Scientific instruments, such as radio telescopes, colliders, sensor networks, and simulators generate very high volumes of data streams that scientists analyze to detect and understand physical phenomena. The high data volume and the need for advanced computations on the streams require substantial hardware resources and scalable stream processing. We address these challenges by developing data stream management technology to support high-volume stream queries utilizing massively parallel computer hardware. We have developed a data stream management system prototype for state-of-the-art parallel hardware. The performance evaluation uses real measurement data from LOFAR, a radio telescope antenna array being developed in the Netherlands.

  • 48932.
    Zeitler, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Risch, Tore
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Scalable Splitting of Massive Data Streams2010Ingår i: Database Systems for Advanced Applications: Part II / [ed] Kitagawa H., Ishikawa Y., Li Q., Watanabe C., Berlin: Springer-Verlag , 2010, s. 184-198Konferensbidrag (Refereegranskat)
    Abstract [en]

    Scalable execution of continuous queries over massive data streams often requires splitting input streams into parallel sub-streams over which query operators are executed in parallel. Automatic stream splitting is in general very difficult, as the optimal parallelization may depend on application semantics. To enable application specific stream splitting, we introduce splitstream functions where the user specifies non-procedural stream partitioning and replication. For high-volume streams, the stream splitting itself becomes a performance bottleneck. A cost model is introduced that estimates the performance of splitstream functions with respect to throughput and CPU usage. We implement parallel splitstream functions, and relate experimental results to cost model estimates. Based on the results, a splitstream function called autosplit is proposed, which scales well for high degrees of parallelism, and is robust for varying proportions of stream partitioning and replication. We show how user defined parallelization using autosplit provides substantially improved scalability (L = 64) over previously published results for the Linear Road Benchmark.

  • 48933.
    Zeitler, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Risch, Tore
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Using stream queries to measure communication performance of a parallel computing environment2007Ingår i: Proc. 1st International Workshop on Distributed Event Processing, Systems and Applications (DEPSA’07), 2007Konferensbidrag (Refereegranskat)
  • 48934.
    Zeitler, Jonas
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Adaptive rendering of celestial bodies in WebGL2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This report covers theory and comparison of techniques for rendering massive scale 3D geospa- tial planet data in a web browser. It also presents implementation details of a few of these tech- niques in WebGL and Javascript, using the Three.js [1] 3D library. The thesis project is part of the implementation of Unitea, a web based education platform for interactive astronomy visualizations. Unitea is a derivative of Uniview, which is a fulldome interactive simulation of the universe. A major part of this thesis is dedicated to the implementa- tion of Hierarchical Level of Detail (HLOD) modules for Three.js based on the theory presented by T. Ulrich [2] and later generalized by Cozzi and Ring [3]. HLOD techniques are dynamic level of detail algorithms that represent the surface of objects as accurately as possible from a certain viewing angle. By using space partitioning tree-structures, view based error metrics and culling techniques detailed representations of the objects (in this case planets) can be efficiently rendered in real-time. The modules developed provide a general-purpose library for rendering planets (or other spher- ical objects) with dynamic level of detail in Three.js. The library also features connections to online web map services (WMS) and tile services.

  • 48935. Zeleznik, Michael P.
    et al.
    Maguire Jr., Gerald Q.
    Baxter, Brent S.
    University of Utah.
    PACS Data-base Design1983Ingår i: Proceedings of the Society of Photo-Optical Instrumentation Engineers, ISSN 0361-0748, Vol. 418, s. 287-295Artikel i tidskrift (Refereegranskat)
  • 48936. Zeleznik, Michael P.
    et al.
    Maguire Jr., Gerald Q.
    Baxter, Brent S.
    University of Utah.
    Noz, Marilyn E.
    New York University.
    Schimpf, James H.
    New York University.
    Horii, Steven C.
    New York University.
    PACS User Level Requirements1983Ingår i: Proceedings of the Society of Photo-Optical Instrumentation Engineers, ISSN 0361-0748, Vol. 418, s. 172-177Artikel i tidskrift (Refereegranskat)
  • 48937.
    Zeljic, Aleksandar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för datorteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Approximations and abstractions for reasoning about machine arithmetic2016Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Safety-critical systems rely on various forms of machine arithmetic to perform their tasks: integer arithmetic, fixed-point arithmetic or floating-point arithmetic. The problem with machine arithmetic is that it can exhibit subtle differences in behavior compared to the ideal mathematical arithmetic, due to fixed-size representation in memory. Failure of safety-critical systems is unacceptable, because it can cost lives or huge amounts of money, time and effort. To prevent such incidents, we want to formally prove that systems satisfy certain safety properties, or otherwise discover cases when the properties are violated. However, for this we need to be able to formally reason about machine arithmetic. The main problem with existing approaches is their inability to scale well with the increasing complexity of systems and their properties. In this thesis, we explore two alternatives to bit-blasting, the core procedure lying behind many common approaches to reasoning about machine arithmetic.

    In the first approach, we present a general approximation framework which we apply to solve constraints over floating-point arithmetic. It is built on top of an existing decision procedure, e.g., bit-blasting. Rather than solving the original formula, we solve a sequence of approximations of the formula. Initially very crude, these approximations are frequently solved very quickly. We use results from these approximations to either obtain a solution, obtain a proof of unsatisfiability or generate a new approximation to solve. Eventually, we will either have found a solution or a proof that solution does not exist. The approximation framework improves the solving time and can solve a number of formulas that the bit-blasting cannot.

    In the second approach, we present a novel method to reason about the theory of fixed-width bit-vectors. This new decision procedure is called mcBV and it is based on the model constructing satisfiability calculus (mcSAT). The procedure uses a lazy representation of bit-vectors and attempts to avoid bit-blasting altogether. It is able to reason about bit-vectors on both bit- and word-level, leveraging both Boolean constraint propagation and native arithmetic reasoning. It also features a greedy explanation generalization mechanism and is capable of more general learning compared to existing approaches. mcBV is able to reason about bit-vectors with sizes that significantly exceed the usual 32, 64 and 128 bits. Evaluation of mcBV shows an improvement in performance (compared to bit-blasting) on several classes of problems.

  • 48938.
    Zeljic, Aleksandar
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Backeman, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Wintersteiger, Christoph M.
    Microsoft Research.
    Ruemmer, Philipp
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Exploring Approximations for Floating-Point Arithmetic using UppSATManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    We consider the problem of solving floating-point constraints obtained from software verification. We present UppSAT --- a new implementation of a systematic approximation refinement framework [ZWR17] as an abstract SMT solver. Provided with an approximation and a decision procedure (implemented in an off-the-shelf SMT solver), UppSAT yields an approximating SMT solver. Additionally, UppSAT includes a library of predefined approximation components which can be combined and extended to define new encodings, orderings and solving strategies. We propose that UppSAT can be used as a sandbox for easy and flexible exploration of new approximations. To substantiate this, we explore several approximations of floating-point arithmetic. Approximations can be viewed as a composition of an encoding into a target theory, a precision ordering, and a number of strategies for model reconstruction and precision (or approximation) refinement. We present encodings of floating-point arithmetic into reduced precision floating-point arithmetic, real-arithmetic, and fixed-point arithmetic (encoded into the theory of bit-vectors in practice). In an experimental evaluation, we compare the advantages and disadvantages of approximating solvers obtained by combining various encodings and decision procedures (based on existing, state-of-the-art SMT solvers for floating-point, real, and bit-vector arithmetic).

  • 48939.
    Zeljic, Aleksandar
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Wintersteiger, Christoph M.
    Rümmer, Philipp
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    An approximation framework for solvers and decision procedures2017Ingår i: Journal of automated reasoning, ISSN 0168-7433, E-ISSN 1573-0670, Vol. 58, nr 1, s. 127-147Artikel i tidskrift (Refereegranskat)
  • 48940.
    Zeljic, Aleksandar
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Wintersteiger, Christoph M.
    Microsoft Research Cambridge.
    Rümmer, Philipp
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Approximations for Model Construction2014Ingår i: Automated Reasoning, Springer, 2014, s. 344-359Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider the problem of efficiently computing models for satisfiable constraints, in the presence of complex background theories such as floating-point arithmetic. Model construction has various applications, for instance the automatic generation of test inputs. It is well-known that naive encoding of constraints into simpler theories (for instance, bit-vectors or propositional logic) can lead to a drastic increase in size, and be unsatisfactory in terms of memory and runtime needed for model construction. We define a framework for systematic application of approximations in order to speed up model construction. Our method is more general than previous techniques in the sense that approximations that are neither under- nor over-approximations can be used, and shows promising results in practice.

  • 48941.
    Zeljic, Aleksandar
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Wintersteiger, Christoph M.
    Rümmer, Philipp
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Deciding bit-vector formulas with mcSAT2016Ingår i: Theory and Applications of Satisfiability Testing: SAT 2016, Springer, 2016, s. 249-266Konferensbidrag (Refereegranskat)
  • 48942.
    Zeljić, Aleksandar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för datorteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    From Machine Arithmetic to Approximations and back again: Improved SMT Methods for Numeric Data Types2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Safety-critical systems, especially those found in avionics and automotive industries, rely on machine arithmetic to perform their tasks: integer arithmetic, fixed-point arithmetic or floating-point arithmetic (FPA). Machine arithmetic exhibits subtle differences in behavior compared to the ideal mathematical arithmetic, due to fixed-size representation in memory. Failure of safety-critical systems is unacceptable, due to high-stakes involving human lives or huge amounts of money, time and effort. By formally proving properties of systems, we can be assured that they meet safety requirements. However, to prove such properties it is necessary to reason about machine arithmetic. SMT techniques for machine arithmetic are lacking scalability. This thesis presents approaches that augment or complement existing SMT techniques for machine arithmetic.

    In this thesis, we explore approximations as a means of augmenting existing decision procedures. A general approximation refinement framework is presented, along with its implementation called UppSAT. The framework solves a sequence of approximations. Initially very crude, these approximations are fairly easy to solve. Results of solving approximate constraints are used to either reconstruct a solution of original constraints, obtain a proof of unsatisfiability or to refine the approximation. The framework preserves soundness, completeness, and termination of the underlying decision procedure, guaranteeing that eventually, either a solution is found or a proof that solution does not exist. We evaluate the impact of approximations implemented in the UppSAT framework on the state-of-the-art in SMT for floating-point arithmetic.

    A novel method to reason about the theory of fixed-width bit-vectors called mcBV is presented. It is an instantiation of the model constructing satisfiability calculus, mcSAT, and uses a new lazy representation of bit-vectors that allows both bit- and word-level reasoning. It uses a greedy explanation generalization mechanism capable of more general learning compared to traditional approaches. Evaluation of mcBV shows that it can outperform bit-blasting on several classes of problems.

  • 48943. Zellers, M.
    et al.
    House, David
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH.
    Alexanderson, Simon
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH.
    Prosody and hand gesture at turn boundaries in Swedish2016Ingår i: Proceedings of the International Conference on Speech Prosody, International Speech Communications Association , 2016, s. 831-835Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to ensure smooth turn-taking between conversational participants, interlocutors must have ways of providing information to one another about whether they have finished speaking or intend to continue. The current work investigates Swedish speakers’ use of hand gestures in conjunction with turn change or turn hold in unrestricted, spontaneous speech. As has been reported by other researchers, we find that speakers’ gestures end before the end of speech in cases of turn change, while they may extend well beyond the end of a given speech chunk in the case of turn hold. We investigate the degree to which prosodic cues and gesture cues to turn transition in Swedish face-to-face conversation are complementary versus functioning additively. The co-occurrence of acoustic prosodic features and gesture at potential turn boundaries gives strong support for considering hand gestures as part of the prosodic system, particularly in the context of discourse-level information such as maintaining smooth turn transition.

  • 48944.
    Zellers, Margaret
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH, Tal-kommunikation.
    Perception of pitch tails at potential turn boundaries in Swedish2014Ingår i: Proceedings of the Annual Conference of the International Speech Communication Association, 2014, s. 1944-1948Konferensbidrag (Refereegranskat)
    Abstract [en]

    In a number of languages, intonational patterns at prosodic boundaries are considered to be relevant for turn transition or turn hold. A perception experiment tested the influence of fundamental frequency (F0) peak height and rising final contours on Swedish listeners’ judgment about whether a speaker wanted to hold the turn. While F0 peak height, as has been previously shown, did influence listeners’ judgments, the end height of rising pitch tails apparently did not influence listeners’ judgments about whether a speaker planned to continue talking, even though they showed sensitivity to the differences in a discrimination task. The differences in responses in the tasks, as well as the difference from results found for other languages, may indicate that listeners used comparative prominence to guide their judgments, rather than intonation playing a direct role in the turn-transition system.

  • 48945.
    Zellers, Margaret
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH, Tal-kommunikation.
    Pitch and lengthening as cues to turn transition in Swedish2013Ingår i: Proceedings of Interspeech 2013, 2013, s. 248-252Konferensbidrag (Refereegranskat)
    Abstract [en]

    In many cases of turn transition in conversation, a new speaker may respond to phonetic cues from the end of the prior turn, including variation in prosodic features such as pitch and final lengthening. Although consistent pitch and lengthening features are well-established for some languages at potential points of turn transition, this is not necessarily the case for Swedish. The current study uses a two-alternative forced choice task to investigate how variation in pitch contour and lengthening at the ends of syntactically complete turns can influence listeners’ expectations of turn hold or turn transition. Both lengthening and pitch contour features were found to influence listeners’ judgments about whether turn transition would occur, with shorter length and higher final pitch peaks associated with turn hold. Furthermore, listeners were more certain about their judgments when asked about turn-hold rather than turn-change, suggesting an imbalance in the strength of turn-hold versus turn-transition cues.

  • 48946.
    Zellers, Margaret
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH, Tal-kommunikation. University of Stuttgart, Germany.
    Prosodic Variation and Segmental Reduction and Their Roles in Cuing Turn Transition in Swedish2017Ingår i: Language and Speech, ISSN 0023-8309, E-ISSN 1756-6053, Vol. 60, nr 3, s. 454-478Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Prosody has often been identified alongside syntax as a cue to turn hold or turn transition in conversational interaction. However, evidence for which prosodic cues are most relevant, and how strong those cues are, has been somewhat scattered. The current study addresses prosodic cues to turn transition in Swedish. A perception study looking closely at turn changes and holds in cases where the syntax does not lead inevitably to a particular outcome shows that Swedish listeners are sensitive to duration variations, even in the very short space of the final unstressed syllable of a turn, and that they may use pitch cues to a lesser extent. An investigation of production data indicates that duration, and to some extent segmental reduction, demonstrate consistent variation in relation to the types of turn boundaries they accompany, while fundamental frequency and glottalization do not. Taken together, these data suggest that duration may be the primary cue to turn transition in Swedish conversation, rather than fundamental frequency, as some other studies have suggested.

  • 48947.
    Zellers, Margaret
    Department of Language and Linguistic Science, University of York, York, UK .
    Prosodic variation for topic shift and other functions in local contrasts in conversation2013Ingår i: Phonetica, ISSN 0031-8388, E-ISSN 1423-0321, Vol. 69, nr 4, s. 231-253Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Speakers and listeners have been shown to use phonetic cues to help them in tracking the ongoing structure of conversational interaction, but fragmentation between qualitative and quantitative research means that the forms and functions of these cues have been given varying characterizations. The current study explores prosodic variation in contrastive structures in conversational data, using a combined methodology adopting aspects from both qualitative (conversation analysis) and quantitative (experimental phonetics/phonology) approaches. Statistical and conversation-analytical methods used together reveal relationships between prosodic variation and interactional function, such as variations in pitch range across adjacent turns being linked to the presence of 'stepwise' topic changes.

  • 48948.
    Zellers, Margaret
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH, Tal-kommunikation.
    House, David
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH, Tal-kommunikation.
    Parallels between hand gestures and acoustic prosodic features in turn-taking2015Ingår i: 14th International Pragmatics Conference, Antwerp, Belgium, 2015, s. 454-455Konferensbidrag (Refereegranskat)
  • 48949.
    Zeltner Wolff, Johannes
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Development of software for MALTE, a system for automated testing of line current supervision andinterference monitoring devices2015Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The aim of the project is to develop software to automatically test line current supervision and interference monitoring devices for Bombardier trains. The software, called MALTE, it to replace the manual testing done by an engineer, thereby freeing up the tester to do other tasks, and increasing the test rigorousness.

    The test software, written in LabView, was developed in tandem with a hardware rack, with interfaces to the train hardware enabling communication between the two, to set test conditions and simulate the environment encountered by the hardware when on the train.

    When completed, MALTE was found to be an order of magnitude faster than a test engineer performing the tests, meaning a large save in time and cost for the engineering team.

  • 48950. Zeman, Daniel
    et al.
    Popel, Martin
    Straka, Milan
    Hajic, Jan
    Nivre, Joakim
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Språkvetenskapliga fakulteten, Institutionen för lingvistik och filologi.
    Ginter, Filip
    Luotolahti, Juhani
    Pyysalo, Sampo
    Petrov, Slav
    Potthast, Martin
    Tyers, Francis
    Badmaeva, Elena
    Gokirmak, Memduh
    Nedoluzhko, Anna
    Cinkova, Silvie
    Hajic jr., Jan
    Hlavacova, Jaroslava
    Kettnerová, Václava
    Uresova, Zdenka
    Kanerva, Jenna
    Ojala, Stina
    Missilä, Anna
    Manning, Christopher D.
    Schuster, Sebastian
    Reddy, Siva
    Taji, Dima
    Habash, Nizar
    Leung, Herman
    de Marneffe, Marie-Catherine
    Sanguinetti, Manuela
    Simi, Maria
    Kanayama, Hiroshi
    dePaiva, Valeria
    Droganova, Kira
    Martínez Alonso, Héctor
    Çöltekin, Ça\ugrı
    Sulubacak, Umut
    Uszkoreit, Hans
    Macketanz, Vivien
    Burchardt, Aljoscha
    Harris, Kim
    Marheinecke, Katrin
    Rehm, Georg
    Kayadelen, Tolga
    Attia, Mohammed
    Elkahky, Ali
    Yu, Zhuoran
    Pitler, Emily
    Lertpradit, Saran
    Mandl, Michael
    Kirchner, Jesse
    Alcalde, Hector Fernandez
    Strnadová, Jana
    Banerjee, Esha
    Manurung, Ruli
    Stella, Antonio
    Shimada, Atsuko
    Kwak, Sookyoung
    Mendonca, Gustavo
    Lando, Tatiana
    Nitisaroj, Rattima
    Li, Josie
    CoNLL 2017 Shared Task: Multilingual Parsing from Raw Text to Universal Dependencies2017Ingår i: Proceedings of the CoNLL 2017 Shared Task: Multilingual Parsing from Raw Text to Universal Dependencies, 2017, s. 1-19Konferensbidrag (Refereegranskat)
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