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  • 301.
    Elmroth, Erik
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Tordsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hernandez, Francisco
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ali-Eldin, Ahmed
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Svärd, Petter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Sedaghat, Mina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Li, Wubin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Self-management Challenges for Multi-cloud Architectures (Invited Paper)2011Inngår i: TOWARDS A SERVICE-BASED INTERNET, Berlin: Springer, 2011, Vol. 6994, s. 38-49Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Addressing the management challenges for a multitude of distributed cloud architectures, we focus on the three complementary cloud management problems of predictive elasticity, admission control, and placement (or scheduling) of virtual machines. As these problems are intrinsically intertwined we also propose an approach to optimize the overall system behavior by policy-tuning for the tools handling each of them. Moreover, in order to facilitate the execution of some of the management decisions, we also propose new algorithms for live migration of virtual machines with very high workload and/or over low-bandwidth networks, using techniques such as caching, compression, and prioritization of memory pages.

  • 302.
    Elmroth, Erik
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Tordsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hernández, Francisco
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ali-Eldin, Ahmed
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Svärd, Petter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Sedaghat, Mina
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Li, Wubin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Self-management challenges for multi-cloud architectures2011Inngår i: Towards a Service-Based Internet: 4th European Conference, ServiceWave 2011, Poznan, Poland, October 26-28, 2011. Proceedings / [ed] Witold Abramowicz, Ignacio M. Llorente, Mike Surridge, Andrea Zisman and Julien Vayssière, Springer Berlin/Heidelberg, 2011, s. 38-49Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Addressing the management challenges for a multitude of distributed cloud architectures, we focus on the three complementary cloud management problems of predictive elasticity, admission control, and placement (or scheduling) of virtual machines. As these problems are intrinsically intertwined we also propose an approach to optimize the overall system behavior by policy-tuning for the tools handling each of them. Moreover, in order to facilitate the execution of some of the management decisions, we also propose new algorithms for live migration of virtual machines with very high workload and/or over low-bandwidth networks, using techniques such as caching, compression, and prioritization of memory pages.

  • 303.
    Elmroth, Erik
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Östberg, Per-Olov
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A composable service-oriented architecture for middleware-independent and interoperable grid job management2010Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    We propose a composable, loosely coupled Service-Oriented Architecture for middleware-independent Grid job management. The architecture is designed for use in federated Grid environments and aims to decouple Grid appli- cations from Grid middlewares and other infrastructure components. The notion of an ecosystem of Grid infrastructure components is extended, and Grid job management software design is discussed in this context. Non- intrusive integration models and abstraction of Grid middleware function- ality through hierarchical aggregation of autonomous Grid job management services are emphasized, and service composition techniques facilitating this process are explored. Earlier efforts in Service-Oriented Architecture design are extended upon, and implications of these are discussed throughout the paper. A proof-of-concept implementation of the proposed architecture is presented along with a technical evaluation of the performance of the proto- type, and a details of architecture implementation are discussed along with trade-offs introduced by the service composition techniques used.

  • 304.
    Elmroth, Erik
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Östberg, Per-Olov
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Dynamic and Transparent Service Composition Techniques for Service-Oriented Grid Architectures2008Inngår i: Integrated Research in Grid Computing / [ed] S. Gorlatch and P. Fragopoulou and T. Priol, Greece: Crete University Press , 2008, s. 323-334Konferansepaper (Fagfellevurdert)
  • 305.
    Englund, Henric
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Evaluation of traffic generation tools and implementation of test system2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The purpose of this master’s thesis is to examine the possibilities to build an efficient and accurate distributed IP traffic generator based on a open source software traffic generator. The problem lies in the demand for high performance traffic generators during quality assurance of IP equipment and the high price of commercial hardware traffic generators. An evaluation is conducted to identify a suitable traffic generator, given a set of requirements that the traffic generator must fulfill to be usable in performance testing. A distributed system utilizing the most suitable traffic generator is then implemented. The result and conclusion of this report is that hardware traffic generators are superior to the software based counterpart due to the several drawbacks that software traffic generators suffers from, such as disc I/O and CPU load.

  • 306.
    Engström, Rikard
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Introducing Piclair.com to the iPhone platform2010Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    iPhone is one of the latest smartphones and it has grown in popularity ever since it was first released in 2007. The iPhone has more advanced features than a regular cell phone and is more suitable for internet related tasks because of its WiFi and 3G support. This report describes the development of a server API and a photo sharing application aimed to run on the iPhone platform. The project was issued by Piclair, the image uploading service located at http://piclair.com. Piclair already possesses efficient image uploading software for Windows and Mac OS X. The idea was to broaden the user base by entering one of the fastest growing smartphone platforms. The objective of the project was to develop a powerful but simple photo uploader dedicated to Piclair.com running on the iPhone and to create a lightweight API to handle the uploads server side. This report spans from the idea stage to a finished product. The result was a fully functional API and a non cumbersome Piclair characteristic photo uploader, suitable not only for WiFi connected devices but also 3G and EDGE.

  • 307.
    Ericson, Petter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A bottom-up automaton for tree adjoining languages2015Rapport (Annet vitenskapelig)
    Abstract [en]

    Current tree parsing algorithms for nonregular tree languages all have superlinear running times, possibly limiting their practical applicability. We present a bottom-up tree automaton that captures exactly the tree-adjoining languages in the non-deterministic case. The determinstic case captures a strict superset of the regular tree languages, while preserving running times linear in the size of the tree.

  • 308.
    Ericson, Petter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Complexity and expressiveness for formal structures in Natural Language Processing2017Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The formalized and algorithmic study of human language within the field of Natural Language Processing (NLP) has motivated much theoretical work in the related field of formal languages, in particular the subfields of grammar and automata theory. Motivated and informed by NLP, the papers in this thesis explore the connections between expressibility – that is, the ability for a formal system to define complex sets of objects – and algorithmic complexity – that is, the varying amount of effort required to analyse and utilise such systems. Our research studies formal systems working not just on strings, but on more complex structures such as trees and graphs, in particular syntax trees and semantic graphs. The field of mildly context-sensitive languages concerns attempts to find a useful class of formal languages between the context-free and context-sensitive. We study formalisms defining two candidates for this class; tree-adjoining languages and the languages defined by linear context-free rewriting systems. For the former, we specifically investigate the tree languages, and define a subclass and tree automaton with linear parsing complexity. For the latter, we use the framework of parameterized complexity theory to investigate more deeply the related parsing problems, as well as the connections between various formalisms defining the class. The field of semantic modelling aims towards formally and accurately modelling not only the syntax of natural language statements, but also the meaning. In particular, recent work in semantic graphs motivates our study of graph grammars and graph parsing. To the best of our knowledge, the formalism presented in Paper III of this thesis is the first graph grammar where the uniform parsing problem has polynomial parsing complexity, even for input graphs of unbounded node degree.

  • 309.
    Ericson, Petter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Investigating different graph representations of semantics2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Combinatory Categorial Grammar is a generic approach to the mechanical understanding of language, where movement is minimised in favour of using combinators such as B (composition) and T (type lifting) to clearly define in which ways various constituents can refer to each other. Taking the tree languages induced by the syntactic derivations and connecting the various leaves linked through the semantics, one ends up with a class of graph languages. The present work aims to point out promising avenues of research in order to investigate this class, specifically in terms of similarities with other graph-based semantic representations, such as Abstract Meaning Representations (AMR), and furthermore what graph generating or recognising formalism would be most suitable to define the class characteristics.

  • 310.
    Ericson, Petter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Order-preserving graph grammars2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The field of semantic modelling concerns formal models for semantics, that is, formal structures for the computational and algorithmic processing of meaning. This thesis concerns formal graph languages motivated by this field. In particular, we investigate two formalisms: Order-Preserving DAG Grammars (OPDG) and Order-Preserving Hyperedge Replacement Grammars (OPHG), where OPHG generalise OPDG.

    Graph parsing is the practise of, given a graph grammar and a graph, to determine if, and in which way, the grammar could have generated the graph. If the grammar is considered fixed, it is the non-uniform graph parsing problem, while if the grammars is considered part of the input, it is named the uniform graph parsing problem. Most graph grammars have parsing problems known to be NP-complete, or even exponential, even in the non-uniform case. We show both OPDG and OPHG to have polynomial uniform parsing problems, under certain assumptions.

    We also show these parsing algorithms to be suitable, not just for determining membership in graph languages, but for computing weights of graphs in graph series.

    Additionally, OPDG is shown to have several properties common to regular languages, such as MSO definability and MAT learnability. We moreover show a direct corresponcence between OPDG and the regular tree grammars.

    Finally, we present some limited practical experiments showing that real-world semantic graphs appear to mostly conform to the requirements set by OPDG, after minimal, reversible processing.

  • 311.
    Eriksson, Magnus
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Engineering Families of Software-Intensive Systems using Features, Goals and Scenarios2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Over the last decade, software has become an integral part of many products with which it is not traditionally associated (e.g., automobiles, medical equipment, home appliances, etc.). This has led to problems in many organizations, since it has proved difficult to integrate software engineering processes with other engineering processes. To address the increased complexity and to coordinate their engineering efforts, many organizations working in such domains have therefore introduced systems engineering into their business processes.

    Systems engineering is an interdisciplinary approach to system development. Teamwork is essential in developing complex systems, and systems engineering orchestrates this process throughout the lifespan of a system. The focus of systems engineering is on defining customer needs and required functionality, documenting requirements, synthesizing a design and validating the system. A problem with the traditional techniques of systems engineering is, however, that they provide inadequate support for achieving high levels of reuse between different projects.

    In this dissertation, methods and tools with the overall purpose of providing an improved reuse infrastructure for systems engineering artifacts and their resulting detailed design artifacts are proposed. The proposed methods and tools are based on the software product-line approach, a reuse strategy which focuses on families of related systems that address particular market segments.

    Studies have shown that if an empirical study does not report experiences from that which practitioners consider a “real” situation, results are likely to be ignored. Even though case studies cannot achieve the scientific rigor of formal experiments, case studies can provide enough information to decide if a specific technology will benefit a particular organization. To ensure industry-relevant research results, case studies on real development projects were chosen as the main vehicle for performing research.

    This dissertation reports experiences from four empirical studies which were performed within the Swedish defense industry. The studies indicate that the proposed methods and tools indeed provide an improved reuse infrastructure, compared to the previously used methods and tools.

  • 312.
    Eriksson, Magnus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Börstler, Jürgen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A systems product line approach2009Inngår i: Applied Software Product-Line Engineering / [ed] Kyo C. Kang, Vijayan Sugumaran, Sooyong Park, Taylor & Francis , 2009Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 313.
    Eriksson, Magnus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Börstler, Jürgen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Borg, Kjell
    BAE Systems Hägglunds AB, Örnsköldsvik, Sweden.
    Managing requirements specifications for product lines: An approach and industry case study2009Inngår i: Journal of Systems and Software, ISSN 0164-1212, E-ISSN 1873-1228, Vol. 82, nr 3, s. 435-447Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Software product line development has emerged as a leading approach for software reuse. This paper describes an approach to manage natural-language requirements specifications in a software product line context. Variability in such product line specifications is modeled and managed using a feature model. The proposed approach has been introduced in the Swedish defense industry. We present a multiple-case study covering two different product lines with in total eight product instances. These were compared to experiences from previous projects in the organization employing clone-and-own reuse. We conclude that the proposed product line approach performs better than clone-and-own reuse of requirements specifications in this particular industrial context.

  • 314. Espinoza, Angelina
    et al.
    Penya, Yoseba
    Nieves, Juan Carlos
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ortega, Mariano
    Pena, Aitor
    Rodriguez, Daniel
    Supporting Business Workflows in Smart Grids: An Intelligent Nodes-Based Approach2013Inngår i: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, Vol. 9, nr 3, s. 1384-1397Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents an application of business intelligence (BI) for electricity management systems in the context of the Smart Grid domain. Combining semantic web technologies (SWT) and elements of grid computing (GC), we have designed a distributed architecture of intelligent nodes, which are called power grid distributed nodes (PGDINs). This distributed architecture supports the majority of the grid management activities in an intelligent and collaborative way by means of distributed processing of semantic data. A node collaborative scheme is defined based on logical states that each node presents according to the events occurring in the grid. A specific BPEL business-workflow is formally defined for each logical state, based on the node's knowledge base (an electrical model) and the distributed data. The introduced core workflows allow the potential grid behavior to be predefined when a business requirement is triggered. Thus, this approach supports the grid to react and reach over again a stable state, which is defined as a working state that facilitates the provision of the required business tasks. We have validated our approach with the simulation of a well-known use case, the energy balancing verification, fed with real data from the Spanish electrical grid.

  • 315.
    Espling, Daniel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Enabling Technologies for Management of Distributed Computing Infrastructures2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Computing infrastructures offer remote access to computing power that can be employed, e.g., to solve complex mathematical problems or to host computational services that need to be online and accessible at all times. From the perspective of the infrastructure provider, large amounts of distributed and often heterogeneous computer resources need to be united into a coherent platform that is then made accessible to and usable by potential users. Grid computing and cloud computing are two paradigms that can be used to form such unified computational infrastructures.

    Resources from several independent infrastructure providers can be joined to form large-scale decentralized infrastructures. The primary advantage of doing this is that it increases the scale of the available resources, making it possible to address more complex problems or to run a greater number of services on the infrastructures. In addition, there are advantages in terms of factors such as fault-tolerance and geographical dispersion. Such multi-domain infrastructures require sophisticated management processes to mitigate the complications of executing computations and services across resources from different administrative domains.

    This thesis contributes to the development of management processes for distributed infrastructures that are designed to support multi-domain environments. It describes investigations into how fundamental management processes such as scheduling and accounting are affected by the barriers imposed by multi-domain deployments, which include technical heterogeneity, decentralized and (domain-wise) self-centric decision making, and a lack of information on the state and availability of remote resources.

    Four enabling technologies or approaches are explored and developed within this work: (I) The use of explicit definitions of cloud service structure as inputs for placement and management processes to ensure that the resulting placements respect the internal relationships between different service components and any relevant constraints. (II) Technology for the runtime adaptation of Virtual Machines to enable the automatic adaptation of cloud service contexts in response to changes in their environment caused by, e.g., service migration across domains. (III) Systems for managing meta-data relating to resource usage in multi-domain grid computing and cloud computing infrastructures. (IV) A global fairshare prioritization mechanism that enables computational jobs to be consistently prioritized across a federation of several decentralized grid installations.

    Each of these technologies will facilitate the emergence of decentralized computational infrastructures capable of utilizing resources from diverse infrastructure providers in an automatic and seamless manner.

  • 316.
    Espling, Daniel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Metadata Management in Multi-Grids and Multi-Clouds2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Grid computing and cloud computing are two related paradigms used to access and use vast amounts of computational resources. The resources are often owned and managed by a third party, relieving the users from the costs and burdens of acquiring and managing a considerably large infrastructure themselves. Commonly, the resources are either contributed by different stakeholders participating in shared projects (grids), or owned and managed by a single entity and made available to its users with charging based on actual resource consumption (clouds). Individual grid or cloud sites can form collaborations with other sites, giving each site access to more resources that can be used to execute tasks submitted by users. There are several different models of collaborations between sites, each suitable for different scenarios and each posing additional requirements on the underlying technologies.

    Metadata concerning the status and resource consumption of tasks are created during the execution of the task on the infrastructure. This metadata is used as the primary input in many core management processes, e.g., as a base for accounting and billing, as input when prioritizing and placing incoming task, and as a base for managing the amount of resources allocated to different tasks.

    Focusing on management and utilization of metadata, this thesis contributes to a better understanding of the requirements and challenges imposed by different collaboration models in both grids and clouds. The underlying design criteria and resulting architectures of several software systems are presented in detail. Each system addresses different challenges imposed by cross-site grid and cloud architectures:

    • The LUTSfed approach provides a lean and optional mechanism for filtering and management of usage data between grid or cloud sites.

    • An accounting and billing system natively designed to support cross-site clouds demonstrates usage data management despite unknown placement and dynamic task resource allocation.

    • The FSGrid system enables fairshare job prioritization across different grid sites, mitigating the problems of heterogeneous scheduling software and local management policies.

    The results and experiences from these systems are both theoretical and practical, as full scale implementations of each system has been developed and analyzed as a part of this work. Early theoretical work on structure-based service management forms a foundation for future work on structured-aware service placement in cross- site clouds. 

  • 317.
    Espling, Daniel
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Armstrong, Django
    University of Leeds.
    Tordsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Djemame, Karim
    University of Leeds.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Contextualization: Dynamic Configuration of Virtual MachinesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Virtual Machines (VMs) are commonly used as building blocks of IaaS cloud services. The number of running VM instances can be adjusted during runtime to achieve elasticity in the capacity of the service. New VM instances are based on templates that contain the basic configuration of the VM. Instance specific settings, settings unique to the infrastructure to which the instance is being deployed, are normally injected to the VM during the deployment phase through means of contextualization. In this work we present a layered approach to contextualization that supports different classes of contextualization data through the use of virtual devices. Inside each VM, data from different classes are layered on top of each other to create a unified file hierarchy using a small, custom file system. Context data can be updated during runtime by updating the contents of the virtual devices, making this approach the first contextualization approach to natively support recontextualization. Recontextualization enables run-time reconfiguration of a running service and can act as a trigger and key enabler of self-* techniques running inside the VM, allowing the service itself an unambiguous trigger for, e.g., further optimization in response to a changing environment. The runtime reconfiguration using recontextualization and its potential gains are shown in an example with a distributed file system, demonstrating the feasibility of the approach.

  • 318.
    Espling, Daniel
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Larsson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Li, Wubin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Tordsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Modeling and Placement of Cloud Services with Internal Structure2016Inngår i: IEEE Transactions on Cloud Computing, ISSN 2168-7161, Vol. 4, nr 4, s. 429-439Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Virtual machine placement is the process of mapping virtual machines to available physical hosts within a datacenter or on a remote datacenter in a cloud federation. Normally, service owners cannot influence the placement of service components beyond choosing datacenter provider and deployment zone at that provider. For some services, however, this lack of influence is a hindrance to cloud adoption. For example, services that require specific geographical deployment (due e.g. to legislation), or require redundancy by avoiding co-location placement of critical components. We present an approach for service owners to influence placement of their service components by explicitly specifying service structure, component relationships, and placement constraints between components. We show how the structure and constraints can be expressed and subsequently formulated as constraints that can be used in placement of virtual machines in the cloud. We use an integer linear programming scheduling approach to illustrate the approach, show the corresponding mathematical formulation of the model, and evaluate it using a large set of simulated input. Our experimental evaluation confirms the feasibility of the model and shows how varying amounts of placement constraints and data center background load affects the possibility for a solver to find a solution satisfying all constraints within a certain time-frame. Our experiments indicate that the number of constraints affects the ability of finding a solution to a higher degree than background load, and that for a high number of hosts with low capacity, component affinity is the dominating factor affecting the possibility to find a solution.

  • 319.
    Espling, Daniel
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Östberg, Per-Olov
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Integration and Evaluation of Decentralized Fairshare Prioritization (Aequus)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Fairshare is commonly one of the factors used by cluster resource management systems to prioritize jobs during scheduling. Despite the grid vision of a transparent and unified infrastructure, fairshare is normally calculated and enforced at the local cluster level rather than at a grid-wide scale. Aequus is a self-contained decentralized system for grid-wide fairshare job prioritization. Using Aequus, detailed global share policies can be combined with local cluster policies to offer a unified grid fairshare prioritization system where local administrations retain control over their clusters. This work shows how Aequus can be integrated with local resource management systems such as SLURM and Maui with minimal intrusion. Early results from production use are presented, and the system is further tested and evaluated for use at a nation-wide scale. Statistical models are created based on historical national grid usage data, and synthetic traces based on these models are used to create a diverse input set used to exemplify system behavior. The system is shown to behave consistently despite great variations in job arrival patterns and partial participation of some of the collaborating installations.

  • 320.
    Espling, Daniel
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Östberg, Per-Olov
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Integration and evaluation of decentralized fairshare prioritization (Aequus)2014Inngår i: Proceedings of the IEEE 28th International Parallel & Distributed Processing Symposium Workshops IPDPSW 2014, IEEE Computer Society, 2014, s. 1198-1207Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fairshare is commonly one of the factors used by cluster resource management systems to prioritize jobs during scheduling. Despite the grid vision of a transparent and unified infrastructure, fairshare is normally calculated and enforced at the local cluster level rather than at a grid-wide scale. Aequus is a self-contained decentralized system for grid-wide fairshare job prioritization. Using Aequus, detailed global share policies can be combined with local cluster policies to offer a unified grid fairshare prioritization system where local administrations retain control over their clusters. This work shows how Aequus can be integrated with local resource management systems such as SLURM and Maui with minimal intrusion. Early results from production help assess the maturity of the system, and the system is further tested and evaluated for use at a nation-wide scale using workload modeling techniques. Statistical models are created based on historical national grid usage data, and synthetic traces based on these models are used to create a diverse input set used to exemplify system behavior. The system is shown to behave consistently despite great variations in job arrival patterns and partial participation of some of the collaborating installations.

  • 321.
    Falgas-Ravry, Victor
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    O'Connell, Kelly
    Uzzell, Andrew
    Multicolor containers, extremal entropy, and counting2019Inngår i: Random structures & algorithms (Print), ISSN 1042-9832, E-ISSN 1098-2418, Vol. 54, nr 4, s. 676-720Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In breakthrough results, Saxton-Thomason and Balogh-Morris-Samotij developed powerful theories of hypergraph containers. In this paper, we explore some consequences of these theories. We use a simple container theorem of Saxton-Thomason and an entropy-based framework to deduce container and counting theorems for hereditary properties of k-colorings of very general objects, which include both vertex- and edge-colorings of general hypergraph sequences as special cases. In the case of sequences of complete graphs, we further derive characterization and transference results for hereditary properties in terms of their stability families and extremal entropy. This covers within a unified framework a great variety of combinatorial structures, some of which had not previously been studied via containers: directed graphs, oriented graphs, tournaments, multigraphs with bounded multiplicity, and multicolored graphs among others. Similar results were recently and independently obtained by Terry.

  • 322.
    Farnes, Karen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    The genetic algorithm vs alpha-beta algorithm when applied to othello2013Inngår i: Proceedings of Umeå's 16th student conference in computing science: USCCS 2013 / [ed] Suna Bensch & Frank Drewes, Umeå: Umeå universitet , 2013, s. 13-25Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The Alpha-beta algorithm is a commonly used algorithmin two-player zero-sum games, such as Othello, for making AI-players.This article presents the application of the Alpha-beta algorithm and thegenetic algorihtm for Othello with a set of commonly used strategies.The genetic algorithm is in many ways a contrast to the more struc-tured Alpha-beta algorihtm, where the results often appear more as ifby magic. The work presented herein has implemented and run teo AI-players for Othello using both algorithms. The result indicates that thegenetic player outshines the Alpha-beta player when they play againsteach other.

  • 323. Farokhi, Soodeh
    et al.
    Jamshidi, Pooyan
    Lakew, Ewnetu Bayuh
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Brandic, Ivona
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A hybrid cloud controller for vertical memory elasticity: a control-theoretic approach2016Inngår i: Future generations computer systems, ISSN 0167-739X, E-ISSN 1872-7115, Vol. 65, s. 57-72Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Web-facing applications are expected to provide certain performance guarantees despite dynamic and continuous workload changes. As a result, application owners are using cloud computing as it offers the ability to dynamically provision computing resources (e.g., memory, CPU) in response to changes in workload demands to meet performance targets and eliminates upfront costs. Horizontal, vertical, and the combination of the two are the possible dimensions that cloud application can be scaled in terms of the allocated resources. In vertical elasticity as the focus of this work, the size of virtual machines (VMs) can be adjusted in terms of allocated computing resources according to the runtime workload. A commonly used vertical resource elasticity approach is realized by deciding based on resource utilization, named capacity-based. While a new trend is to use the application performance as a decision making criterion, and such an approach is named performance-based. This paper discusses these two approaches and proposes a novel hybrid elasticity approach that takes into account both the application performance and the resource utilization to leverage the benefits of both approaches. The proposed approach is used in realizing vertical elasticity of memory (named as vertical memory elasticity), where the allocated memory of the VM is auto-scaled at runtime. To this aim, we use control theory to synthesize a feedback controller that meets the application performance constraints by auto-scaling the allocated memory, i.e., applying vertical memory elasticity. Different from the existing vertical resource elasticity approaches, the novelty of our work lies in utilizing both the memory utilization and application response time as decision making criteria. To verify the resource efficiency and the ability of the controller in handling unexpected workloads, we have implemented the controller on top of the Xen hypervisor and performed a series of experiments using the RUBBoS interactive benchmark application, under synthetic and real workloads including Wikipedia and FIFA. The results reveal that the hybrid controller meets the application performance target with better performance stability (i.e., lower standard deviation of response time), while achieving a high memory utilization (close to 83%), and allocating less memory compared to all other baseline controllers.

  • 324. Ferrando, Angelo
    et al.
    Winikoff, Michael
    Cranefield, Stephen
    Dignum, Frank
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Mascardi, Viviana
    On Enactability of Agent Interaction Protocols: Towards a Unified Approach2019Inngår i: AAMAS '19: Proceedings of the International Joint Conference on Autonomous Agents and Multiagent Systems, ACM Digital Library, 2019, s. 1955-1957Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Interactions between agents are usually designed from a global viewpoint. However, the implementation of a multi-agent interaction is distributed. This difference can introduce problems. For instance, it is possible to specify protocols from a global viewpoint that cannot be implemented as a collection of individual agents. This leads naturally to the question of whether a given (global) protocol is enactable. We consider this question in a powerful setting (trace expressions), considering a range of message ordering interpretations (specifying what it means to say that an interaction step occurs before another), and a range of possible constraints on the semantics of message delivery, corresponding to different properties of the underlying communication middleware.

  • 325. Ferrer, Ana Juan
    et al.
    Hernandez, Francisco
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Tordsson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Aley-Eldin, Ahmed
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Zsigri, Csilla
    Sirvent, Rauel
    Guitart, Jordi
    Badia, Rosa M.
    Djemame, Karim
    Ziegler, Wolfgang
    Dimitrakos, Theo
    Nair, Srijith K.
    Kousiouris, George
    Konstanteli, Kleopatra
    Varvarigou, Theodora
    Hudzia, Benoit
    Kipp, Alexander
    Wesner, Stefan
    Corrales, Marcelo
    Forgo, Nikolaus
    Sharif, Tabassum
    Sheridan, Craig
    OPTIMIS: A holistic approach to cloud service provisioning2012Inngår i: Future generations computer systems, ISSN 0167-739X, E-ISSN 1872-7115, Vol. 28, nr 1, s. 66-77Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present fundamental challenges for scalable and dependable service platforms and architectures that enable flexible and dynamic provisioning of cloud services. Our findings are incorporated in a toolkit targeting the cloud service and infrastructure providers. The innovations behind the toolkit are aimed at optimizing the whole service life cycle, including service construction, deployment, and operation, on a basis of aspects such as trust, risk, eco-efficiency and cost. Notably, adaptive self-preservation is crucial to meet predicted and unforeseen changes in resource requirements. By addressing the whole service life cycle, taking into account several cloud architectures, and by taking a holistic approach to sustainable service provisioning, the toolkit aims to provide a foundation for a reliable, sustainable, and trustful cloud computing industry.

  • 326. Floridi, Luciano
    et al.
    Cowls, Josh
    Beltrametti, Monica
    Chatila, Raja
    Chazerand, Patrice
    Dignum, Virginia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Delft Design for Values Institute, Delft University of Technology, Delft, The Netherlands.
    Luetge, Christoph
    Madelin, Robert
    Pagallo, Ugo
    Rossi, Francesca
    Schafer, Burkhard
    Valcke, Peggy
    Vayena, Effy
    AI4People - An Ethical Framework for a Good AI Society: Opportunities, Risks, Principles, and Recommendations2018Inngår i: Minds and Machines, ISSN 0924-6495, E-ISSN 1572-8641, Vol. 28, nr 4, s. 689-707Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article reports the findings of AI4People, an Atomium—EISMD initiative designed to lay the foundations for a "Good AI Society". We introduce the core opportunities and risks of AI for society; present a synthesis of five ethical principles that should undergird its development and adoption; and offer 20 concrete recommendations—to assess, to develop, to incentivise, and to support good AI—which in some cases may be undertaken directly by national or supranational policy makers, while in others may be led by other stakeholders. If adopted, these recommendations would serve as a firm foundation for the establishment of a Good AI Society.

  • 327.
    Forsström, J. J.
    et al.
    Department of Medicine, University of Turku, Turku, Finland.
    Irjala, K.
    Central Laboratory, Turku University Central Hospital, Turku, Finland.
    Selén, Gustaf
    Åbo Akademi University, Department of Computer Science, Åbo, Finland.
    Nyström, Mats
    Åbo Akademi University, Department of Computer Science, Åbo, Finland.
    Eklund, Patrik
    Åbo Akademi University, Department of Computer Science, Åbo, Finland.
    Using data preprocessing and single layer perceptron to analyze laboratory data1995Inngår i: Scandinavian Journal of Clinical and Laboratory Investigation, ISSN 0036-5513, E-ISSN 1502-7686, Vol. 55, nr s222, s. 75-81Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During daily work in hospitals a large amount of clinical data is produced each day. Totally computerized patient records are not yet widely used but a large part of essential information is already stored on computer files. These include laboratory test results, diagnoses, codes for operations, codes of histopathological diagnoses and maybe even the patient's medication. Accordingly, these databases include much clinical knowledge that would be useful for clinicians.

    Laboratories try to support clinicians by producing reference values for laboratory tests. It is, of course, necessary information but, however, it does not give very much information about the weight of evidence that an abnormal laboratory test will give in special clinical settings.

    We have developed a software package - DiagaiD - in order to build a smart link between patient databases and clinicians. It utilizes neural network-based machine learning techniques and can produce decision support which meets the special needs of clinicians. From example cases it can learn clinically relevant transformations from original numeric values to logical values. By using data transformation together with a single layer perceptron it is possible to build nonlinear models from a set of preclassified example cases.

    In this paper, we use two small datasets to show how this scheme works in the diagnosis of acute appendicitis and in the diagnosis of myocardial infarction. Results are compared with those obtained using logistic regression or backpropagation neural networks. The performance of our neuro-fuzzy tool seemed to be slightly better in these two materials but the differences did not reach statistical significance.

  • 328.
    Forsström, Jari
    et al.
    University of Turku, Department of Clinical Chemistry, Central Laboratory, Turku University Central Hospital, Turku, Finland.
    Eklund, Patrik
    Department of Computer Science, Åbo Akademi, Åbo, Finland.
    Virtanen, Harry
    Department of Computer Science, Åbo Akademi, Åbo, Finland.
    Waxlax, Joakim
    Department of Computer Science, Åbo Akademi, Åbo, Finland.
    Lähdevirta, Juhani
    Aurora Hospital, Helsinki, Finland.
    DIAGAID: a connectionists approach to determine the information value of clinical data1991Inngår i: Artificial Intelligence in Medicine, ISSN 0933-3657, E-ISSN 1873-2860, Vol. 3, nr 4, s. 193-201Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In clinical medicine the diagnosis is usually based on several signs and symptoms and some laboratory test results. It would be of great benefit if we could learn the diagnostic criteria from example cases and represent systematically the most important findings supporting or rejecting the diagnosis. In rare diseases where the physician may not be familiar with the ailment the scoring of symptoms would be very useful. In this paper we describe a connectionist approach based on Minsky-Papert's perceptrons for evaluation of the information value of clinical data in diagnosing the Nephropathia epidemica. The scores are compared with those from the Bayesian approach and from the evaluation by an experienced clinician.

  • 329.
    Fox, William
    et al.
    Lawrence Berkeley National Laboratory.
    Ghoshal, Devarshi
    Souza, Abel
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Lawrence Berkeley National Laboratory.
    P. Rodrigo, Gonzalo
    Ramakrishnan, Lavanya
    E-HPC: A Library for Elastic Resource Management in HPC Environments2017Inngår i: 12th Workshop on Workflows in Support of Large-Scale Science (WORKS), New York, NY, USA: Association for Computing Machinery (ACM), 2017, artikkel-id 1Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Next-generation data-intensive scientific workflows need to support streaming and real-time applications with dynamic resource needs on high performance computing (HPC) platforms. The static resource allocation model on current HPC systems that was designed for monolithic MPI applications is insufficient to support the elastic resource needs of current and future workflows. In this paper, we discuss the design, implementation and evaluation of Elastic-HPC (E-HPC), an elastic framework for managing resources for scientific workflows on current HPC systems. E-HPC considers a resource slot for a workflow as an elastic window that might map to different physical resources over the duration of a workflow. Our framework uses checkpoint-restart as the underlying mechanism to migrate workflow execution across the dynamic window of resources. E-HPC provides the foundation necessary to enable dynamic resource allocation of HPC resources that are needed for streaming and real-time workflows. E-HPC has negligible overhead beyond the cost of checkpointing. Additionally, E-HPC results in decreased turnaround time of workflows compared to traditional model of resource allocation for workflows, where resources are allocated per stage of the workflow. Our evaluation shows that E-HPC improves core hour utilization for common workflow resource use patterns and provides an effective framework for elastic expansion of resources for applications with dynamic resource needs.

  • 330. Friedland, S.
    et al.
    Lundow, P. H.
    Markström, Klas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    The 1-vertex transfer matrix and accurate estimation of channel capacity2010Inngår i: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 57, nr 8, s. 3692-3699Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The notion of a 1-vertex transfer matrix for multidimensional codes is introduced. It is shown that the capacity of such codes, or the topological entropy, can be expressed as the limit of the logarithm of spectral radii of 1-vertex transfer matrices. Storage and computations using the 1-vertex transfer matrix are much smaller than storage and computations needed for the standard transfer matrix. The method is applied to estimate the first 15 digits of the entropy of the 2-D (0, 1) run length limited channel. A large-scale computation of eigenvalues for the (0, 1) run length limited channel in 2-D and 3-D have been carried out. This was done in order to be able to compare the computational cost of the new method with the standard transfer matrix and have rigorous bounds to compare the estimates with. This in turn leads to improvements on the best previous lower and upper bounds for these channels.

  • 331.
    Frilund, Marianne
    et al.
    Åbo Akademi University, Vaasa, Finland and Novia University of Applied Sciences, Vaasa, Finland.
    Fagerström, Lisbeth
    Åbo Akademi University, Vaasa, Finland and Buskerud University College, Drammen, Norway.
    Eriksson, Katie
    Department of Caring Science, Åbo Akademi University, Vaasa, Finland and Helsinki Hospital District of Helsinki and Uusimaa, Finland.
    Eklund, Patrik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Assessment of ethical ideals and ethical manners in care of older people2013Inngår i: Nursing Research and Practice, ISSN 2090-1429, E-ISSN 2090-1437, s. Article ID 374132-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this study is to establish structured clusters and well-defined ontological entities (nodes) describing ethical values as both ideal and opportunity for ethical manner as perceived by the caregiver. In this study, we use Bayesian Belief Networks (BBNs) to analyse ethical values (ethos) and ethical manners in daily work with older people. Material is based on questionnaire data collected by the instrument for the self-assessment of individual ethos in the care of older people (ISAEC) in spring 2007 in a municipality in Western Finland. This study is unique in its kind, both concerning the selected approach and methodological questions. BBNs have not been used significantly in nursing research, nor are there any studies that examine the ethical possibilities with focus on the probable effects upon changing conditions.

  • 332.
    Funck, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Distributed Database Storage Solution in Java2010Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Car sales companies have in the last couple of years discovered that there is a big market in storing their customer's summer and winter tires for a small fee. For the customers it is very convenient to get rid of the all known storage problem with season tires. Burlin Motor Umeå is one of these companies and they are offering seasonal storage and change of tires in autumn and spring as well as washing of tires.The main problem for this kind of storage is how to make the storage easy to overview and how to keep track of all tires. This paper is a report on a distributed storage solution in Java for summer and winter tires based on criteria from Burlin Motor Umeå.

  • 333.
    Galán García, María Ángeles
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Datavetenskap.
    Categorical Unification2004Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis deals with different aspects towards many-valued unification which have been studied in the scope of category theory. The main motivation of this investigation comes from the fact that in logic programming, classical unification has been identified as the provision of coequalizers in Kleisli categories of term monads. Continuing in that direction, we have used categorical instrumentations to generalise the classical concept of a term. It is expected that this approach will provide an appropriate formal framework for useful developments of generalised terms as a basis for many-valued logic programming involving an extended notion of terms.

    As a first step a concept for generalised terms has been studied. A generalised term is given by a composition of monads that again yields a monad, i.e. compositions of powerset monads with the term monad provide definitions for generalised terms. A composition of monads does, however, not always produce a monad. In this sense, techniques for monads composition provide a helpful tool for our concerns and therefore the study of these techniques has been a focus of this research.

    The composition of monads make use of a lot of equations. Proofs become complicated, not to mention the challenge of understanding different steps of the equations. In this respect, we have studied visual techniques and show how a graphical approach can provide the support we need.

    For the purpose of many-valued unification, similarity relations, generalised substitutions and unifiers have been defined for generalised terms.

  • 334.
    Gardfjäll, Peter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Capacity allocation mechanisms for grid environments2006Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    During the past decade, Grid computing has gained popularity as a means to build powerful computing infrastructures by aggregating distributed computing capacity. Grid technology allows computing resources that belong to different organizations to be integrated into a single unified system image – a Grid. As such, Grid technology constitutes a key enabler of large-scale, crossorganizational sharing of computing resources. An important objective for the Virtual Organizations (VOs) that result from such sharing is to tame the distributed capacity of the Grid in order to manage it and make fair and efficient use of the pooled computing resources.

    Most Grids to date have, however, been completely unregulated, essentially serving as a “source of free CPU cycles” for authorized Grid users. Whenever unrestricted access is admitted to a shared resource there is a risk of overexploitation and degradation of the common resource, a phenomenon often referred to as “the tragedy of the commons”. This thesis addresses this problem by presenting two complementary Grid capacity allocation systems that allow the aggregate computing capacity of a Grid to be divided between users in order to protect the Grid from overuse while delivering fair service that satisfies the individual computational needs of different user groups.

    These two Grid capacity allocation mechanisms constitute the core contribution of this thesis. The first mechanism, the SweGrid Accounting System (SGAS), addresses the need for coordinated soft, real-time quota enforcement across Grid sites. The SGAS project was an early adopter of the serviceoriented principles that are now common practice in the Grid community, and the system has been tested in the Swegrid production environment. Furthermore, SGAS has been included in the Globus Toolkit, the de-facto standard Grid middleware toolkit. SGAS employs a credit-based allocation model where research projects are granted quota allowances that can be spent across the Grid resources, which charge users for their resource consumption. This enforcement of usage limits thus produces real-time overuse protection.

    The second approach, employed by the Fair Share Grid (FSGrid) system, uses a share-based allocation model where project entitlements are expressed in terms of hierarchical share policies that logically divide the Grid capacity between user groups. By coordinating local job scheduling to maintain these global capacity shares, the Grid resources collectively strive to schedule users for a “share of the Grid”. We refer to this cooperative scheduling model as decentralized Grid-wide fairshare scheduling.

  • 335.
    Gardfjäll, Peter
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Johnsson, Lennart
    Mulmo, Olle
    Sandholm, Thomas
    Scalable grid-wide capacity allocation with the SweGrid accounting system (SGAS)2008Inngår i: Concurrency and Computation, ISSN 1532-0626, E-ISSN 1532-0634, Vol. 20, nr 18, s. 2089-2122Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The SweGrid Accounting System (SGAS) allocates capacity in collaborative Grid environments by coordinating enforcement of Grid-wide usage limits as a means to offer usage guarantees and prevent overuse. SGAS employs a credit-based allocation model where Grid capacity is granted to projects via Grid-wide quota allowances that can be spent across the Grid resources. The resources collectively enforce these allowances in a soft, real-time manner. SGAS is built on service-oriented principles with a strong focus on interoperability and Web services standards. This article covers the SGAS design and implementation, which, besides addressing inherent Grid challenges (scale, security, heterogeneity, decentralization), emphasizes generality and flexibility to produce a customizable system with lightweight integration into different middleware and scheduling system combinations. We focus the discussion around the system design, a flexible allocation model, middleware integration experiences and scalability improvements via a distributed virtual banking system, and finally, an extensive set of testbed experiments. The experiments evaluate the performance of SGAS in terms of response times, request throughput, overall system scalability, and its performance impact on the Globus Toolkit 4 job submission software. We conclude that, for all practical purposes, the quota enforcement overhead incurred by SGAS on job submissions is not a limiting factor for the job-handling capacity of the job submission software.

  • 336.
    Georgakis, Apostolos
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Part-of-speech tagging for client-side link prefetching2007Inngår i: Proceedings of the IASTED European Conference on Internet and Multimedia Systems and Applications / [ed] Marco Roccetti, Anaheim: ACTA Press, 2007, s. 272-277Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper a client-side algorithm that learns and predicts user requests is presented. The proposed approach is based on a user behavior profile. The profile is based on textual information extracted from visited web pages. The novelty of the paper is in the use of a part-of-speech tagger to filter the useful user-keywords. The keywords comprising the profile are employed by a transparent and speculative link weighting mechanism. The generated weights are used in estimating future web traversing. Afterwards some linked web pages are prefetched and stored locally in the browser's cache. A comparison between the proposed algorithms and four other client-side algorithms yield improved cache-hit rates given a moderate bandwidth overhead.

  • 337.
    Georgakis, Apostolos
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Osadebey, Michael E.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Spread spectrum wavelet watermarking system2005Rapport (Annet vitenskapelig)
    Abstract [en]

    Lately attention has been focused on wavelet-based watermarking because of its compatibility with the newly developed JPEG 2000 image compression scheme. The major setback associated with wavelet-based watermarking is its vulnerability to geometric distortion caused by the lack of invariance property of wavelet transform. The domain of digital watermarking focused on spread spectrum based technique because of its excellent antijamming feature in wireless communication. However existing digital watermarking systems based on spread spectrum technique are yet to replay the anti-jamming feature in wireless communication, hence have not yielded the desired fully robust characteristics. Existing geometric invariant spread spectrum watermarking systems are complex, difficult to implement and unreliable. In our view this is due to inability of researchers to faithfully implement spread spectrum principle. Our investigation showed that most spread spectrum based watermarking faithfully implement the embedding process but fail to despread the signal before detection as required in a typical wireless spread spectrum communication. In this project we propose a simple spread spectrum wavelet watermarking system that is secure, tuneable and fully robust to all known forms and severities of attacks. The novel feature of our watermarking system design is its model as a communication system with the original (host) image representing the communication channel, the watermark represent the message (base band) signal and the legal and malicious attacks represent the noise, interference or jamming of the message signal. Experimental results from our system showed a replay of the excellent anti-jamming feature of spread spectrum communication

    technique and confirm the superior performance of our system over existing correlation-based spread spectrum wavelet watermarking system.

  • 338.
    Georgiev, Nikolay
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Visualization of FunctionalDependencies in a Web Environment2010Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    As the core of a previous thesis, a Web-based tool, called LDBN(Learn DataBase Normalization), was developed. The purpose of this tool is to provide an interactive learning environment for the normalization of relational database schemata whose constraints are defined by functional dependencies (FDs). During the fall terms of 2008 and 2009, LDBN was used in conjunction with the course Principles of Database Systems at the Umeå University Department of Computing Science, and some important observations were made.As a part of this thesis, some crucial extensions to LDBN, based upon these observations, are developed. The most signifcant extension is a tool for the visualization of FDs, based upon templates found in popular textbooks. Often, such visual representations are much easier for humans to grasp than purely text-based representations. However, this extension does not compromise the existing capabilities of LDBN. In addition, we present some other shortcomings of the previous version of LDBN and our approach to deal with those, in particular issues surrounding user privileges.

  • 339.
    Georgsson, Anna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Agila metoder – en kartläggning av teori och praktik2010Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    In recent years, agile software development methods have become increasingly popular throughout the world. Today there are a number of different agile methods and they all rest on the Agile Manifesto that was formulated in 2001 as a reaction to the traditional software processes.The aim of this thesis is to make a survey of some of the agile methods used today and to see how they are being used in practice. It consists of two parts: a literature study and an interview study with people working in the software business. First, a definition of agile methods is proposed and a number of different agile methods are described. Second, the interviews are being analysed with special focus on communication, collaboration, expectations and results. Third, the theory and practice are compared and the results are being analysed.Only three of the agile methods were used by the companies, and Scrum was the most common one. The respondents had all adopted the agile methods to their needs and they all seemed very pleased with this way of working. Their expectations on the agile methods were mainly satisfied. They stressed that documentation is still needed but is now done differently. Communication, both within the team and with the customer is also very important.

  • 340.
    Georgsson, Anna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Introducing Story Points and User Stories to Perform Estimations in a Software Development Organisation. A case study at Swedbank IT2011Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    Today, software can be found almost everywhere. The software development industry is a large industry, but unfortunately the process of developing software is associated with exceeded budgets and delays. Many companies now use one of the agile processes to meet the changing requirements that often cause the problems. One of these companies is Swedbank IT, a company that has used the agile process Scrum for some time but now wants to see how they can make further progress in their agile work. The aim of the work presented in this thesis is to investigate if the introduction of story points for estimation and further developing the utilisation of user stories when gathering requirements can be used to achieve this progress.

    The first part of this thesis is a literature study where the agile process Scrum is described. The concepts user stories and story points are also explained. The second part is an interview study with seven people working at Swedbank, all involved in software development projects. Finally the interviews are analysed and some conclusions are drawn.

    The conclusion is that the introduction of story points and further encouragement of the usage of user stories can actually help Swedbank IT make further progress in their agile work. It can also increase the efficiency of the team and facilitate the collaboration between Swedbank IT and the business side at Swedbank.

  • 341.
    Georgsson, Fredrik
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Christina, Olsén
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Stefan, Jansson
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Fractal Analysis of Mammograms2007Inngår i: SCIA 2007 / [ed] B. K. Ersboll, K. S. Pedersen, Berlin: Springer , 2007, s. 92-101Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper it is shown that there is a difference in local fractal dimension between imaged glandular tissue, supporting tissue and muscle tissue based on an assessment from a mammogram. By estimating the density difference at four different local dimensions (2.06, 2.33, 2.48, 2.70) from 142 mammograms we can define a measure and by using this measure we are able to distinguish between the tissue types. A ROC-analysis gives us an area under the curve-value of 0.9998 for separating glandular tissue from muscular tissue and 0.9405 for separating glandular tissue from supporting tissue. To some extent we can say that the measured difference in fractal properties is due to different fractal properties of the unprojected tissue. For example, to a large extent muscle tissue seems to have different fractal properties than glandular or supportive tissue. However, a large variance in the local dimension densities makes it difficult to make proper use of the proposed measure for segmentation purposes.

  • 342.
    Georgsson, Fredrik
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Eklund, Patrik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    An identication of handling uncertaintieswithin medical screening: a case study within screening for breast cancer1999Inngår i: Fuzzy & Neuro-Fuzzy Systems in Medicine / [ed] Horia-Nicolai L Teodorescu, Abraham Kandel, Lakhmi C. Jain, CRC Press, 1999, s. 173-193Kapittel i bok, del av antologi (Fagfellevurdert)
  • 343.
    Georgsson, Fredrik
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Hellström, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Johansson, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Prorok, Kalle
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Ringdahl, Ola
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Sandström, Urban
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Development of an Autonomous Path Tracking Forest Machine: a status report2005Rapport (Annet vitenskapelig)
    Abstract [en]

    In many respects traditional automation in the forest-machine industry has reached an up- per limit, since the driver already has to deal with an excess of information and take too many decisions at a very high pace. To further automation still, introduction of semi-autonomous and autonomous functions are expected and considered necessary. This paper describes an ongoing project along these ideas. We describe the development of the hardware and software of an unmanned shuttle that shifts timber from the area of felling to the main roads for fur- ther transportation. A new path-tracking algorithm is introduced, and demonstrated as being superior to standard techniques, such as Follow-the-Carrot and Pure-Pursuit. To facilitate the research and development, a comprehensive software architecture for sensor and actuator interfacing is developed. Obstacle avoidance is accomplished by a new kind of radar, developed for and by the automotive industry. Localization is accomplished by a Kalman filter combining data from a Real-Time Kinematic Differential GPS/GLONASS and a gyro/compass. Tests conducted on a simulator and a small-scale robot show promising results. Tests on the real forest machine are ongoing, and will be completed before the end of 2005.

  • 344.
    Ghorbanzadeh, Mehdi
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Zhang, Jin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Andersson, Patrik L.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Binary classification model to predict developmental toxicity of industrial chemicals in zebrafish2016Inngår i: Journal of Chemometrics, ISSN 0886-9383, E-ISSN 1099-128X, Vol. 30, nr 6, s. 298-307Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The identification of industrial chemicals, which may cause developmental effects, is of great importance for an early detection of hazardous chemicals. Accordingly, categorical quantitative structure-activity relationship (QSAR) models were developed, based on developmental toxicity profile data for zebrafish from the ToxCast Phase I testing, to predict the toxicity of a large set of high and low production volume chemicals (H/LPVCs). QSARs were created using linear (LDA), quadratic, and partial least squares-discriminant analysis with different chemical descriptors. The predictions of the best model (LDA) were compared with those obtained by the freely available QSAR model VEGA, created based on a dataset with a different chemical domain. The results showed that despite similar accuracy (AC) of both models, the LDA model is more specific than VEGA and shows a better agreement between sensitivity (SE) and specificity (SP). Applying a 90% confidence level on the Lou model led to even better predictions showing SE of 0.92, AC of 0.95, and geometric mean of SE and SP (G) of 0.96 for the prediction set. The LDA model predicted 608 H/LPVCs as toxicants among which 123 chemicals fall inside the AD of the VEGA model, which predicted 112 of those as toxicants. Among the 112 chemicals predicted as toxic H/LPVCs, 23 have been previously reported as developmental toxicants. The here presented LDA model could be used to identify and prioritize H/LPVCs for subsequent developmental toxicity assessment, as a screening tool of potential developmental effects of new chemicals, and to guide synthesis of safer alternative chemicals.

  • 345. Gonzalez, Roberto
    et al.
    Jiang, Lili
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ahmed, Mohamed
    Marciel, Miriam
    Cuevas, Ruben
    Metwalley, Hassan
    Niccolini, Saverio
    The cookie recipe: Untangling the use of cookies in the wild2017Inngår i: TMA Conference 2017: Proceedings of the 1st Network Traffic Measurement and Analysis Conference, IEEE, 2017, nr C 2014. Proceedings: LNCS 8783InformationSecurity 17th International Confe= nce, ISC 2014, 12-14 Oct. 2014, Hong Kong, China, P309 osh A., 2015, ACM Transactions on Economics and Computation, V3,=20 vakorn Suphannee, 2016, 2016 IEEE SYMPOSIUM ON SECURITY AND PRIVACY (SP)I=Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Users online are commonly tracked using HTTP cookies when browsing on the web. To protect their privacy, users tend to use simple tools to block the activity of HTTP cookies. However, the "block all" design of tools breaks critical web services or severely limits the online advertising ecosystem. Therefore, to ease this tension, a more nuanced strategy that discerns better the intended functionality of the HTTP cookies users encounter is required. We present the first large-scale study of the use of HTTP cookies in the wild using network traces containing more than 5.6 billion HTTP requests from real users for a period of two and a half months. We first present a statistical analysis of how cookies are used. We then analyze the structure of cookies and observe that; HTTP cookies are significantly more sophisticated than the name=3Dvalue defined by the standard and assumed by researchers and developers. Based on our findings we present an algorithm that is able to extract the information included in 86% of the cookies in our dataset with an accuracy of 91.7%. Finally, we discuss the implications of our findings and provide solutions that can be used to improve the most promising privacy preserving tools.

  • 346.
    Gonzalo P., Rodrigo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    HPC scheduling in a brave new world2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Many breakthroughs in scientific and industrial research are supported by simulations and calculations performed on high performance computing (HPC) systems. These systems typically consist of uniform, largely parallel compute resources and high bandwidth concurrent file systems interconnected by low latency synchronous networks. HPC systems are managed by batch schedulers that order the execution of application jobs to maximize utilization while steering turnaround time. In the past, demands for greater capacity were met by building more powerful systems with more compute nodes, greater transistor densities, and higher processor operating frequencies. Unfortunately, the scope for further increases in processor frequency is restricted by the limitations of semiconductor technology. Instead, parallelism within processors and in numbers of compute nodes is increasing, while the capacity of single processing units remains unchanged. In addition, HPC systems’ memory and I/O hierarchies are becoming deeper and more complex to keep up with the systems’ processing power. HPC applications are also changing: the need to analyze large data sets and simulation results is increasing the importance of data processing and data-intensive applications. Moreover, composition of applications through workflows within HPC centers is becoming increasingly important. This thesis addresses the HPC scheduling challenges created by such new systems and applications. It begins with a detailed analysis of the evolution of the workloads of three reference HPC systems at the National Energy Research Supercomputing Center (NERSC), with a focus on job heterogeneity and scheduler performance. This is followed by an analysis and improvement of a fairshare prioritization mechanism for HPC schedulers. The thesis then surveys the current state of the art and expected near-future developments in HPC hardware and applications, and identifies unaddressed scheduling challenges that they will introduce. These challenges include application diversity and issues with workflow scheduling or the scheduling of I/O resources to support applications. Next, a cloud-inspired HPC scheduling model is presented that can accommodate application diversity, takes advantage of malleable applications, and enables short wait times for applications. Finally, to support ongoing scheduling research, an open source scheduling simulation framework is proposed that allows new scheduling algorithms to be implemented and evaluated in a production scheduler using workloads modeled on those of a real system. The thesis concludes with the presentation of a workflow scheduling algorithm to minimize workflows’ turnaround time without over-allocating resources.

  • 347.
    Gonzalo P., Rodrigo
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Östberg, Per-Olov
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ramakrishnan, Lavanya
    Lawrence Berkeley National Lab, Berkeley, California, USA.
    ScSF: a scheduling simulation framework2018Inngår i: Proceedings of the 21th Workshop on Job Scheduling Strategies for Parallel Processing, Springer, 2018, Vol. 10773, s. 152-173Konferansepaper (Fagfellevurdert)
    Abstract [en]

    High-throughput and data-intensive applications are increasingly present, often composed as workflows, in the workloads of current HPC systems. At the same time, trends for future HPC systems point towards more heterogeneous systems with deeper I/O and memory hierarchies. However, current HPC schedulers are designed to support classical large tightly coupled parallel jobs over homogeneous systems. Therefore, There is an urgent need to investigate new scheduling algorithms that can manage the future workloads on HPC systems. However, there is a lack of appropriate models and frameworks to enable development, testing, and validation of new scheduling ideas.

    In this paper, we present an open-source scheduler simulation framework (ScSF) that covers all the steps of scheduling research through simulation. ScSF provides capabilities for workload modeling, workload generation, system simulation, comparative workload analysis, and experiment orchestration. The simulator is designed to be run over a distributed computing infrastructure enabling to test at scale. We describe in detail a use case of ScSF to develop new techniques to manage scientific workflows in a batch scheduler. In the use case, such technique was implemented in the framework scheduler. For evaluation purposes, 1728 experiments, equivalent to 33 years of simulated time, were run in a deployment of ScSF over a distributed infrastructure of 17 compute nodes during two months. Finally, the experimental results were analyzed in the framework to judge that the technique minimizes workflows’ turnaround time without over-allocating resources. Finally, we discuss lessons learned from our experiences that will help future researchers.

  • 348.
    Gonzalo P., Rodrigo
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Östberg, P-O
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ramakrishnan, Lavanya
    Lawrence Berkeley National Lab, USA.
    Enabling workflow aware scheduling on HPC systemsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Workƒows from diverse scienti€c domains are increasingly present in the workloads of current HPC systems. However, HPC scheduling systems do not incorporate workƒow speci€c mechanisms beyond the capacity to declare dependencies between jobs. Œus, when users run workƒows as sets of batch jobs with completion dependencies, the workƒows experience long turn around times. Alternatively, when they are submiŠed as single jobs, allocating the maximum requirementof resources for the whole runtime, they resources, reducing the HPC system utilization. In this paper, we present a workƒow aware scheduling (WoAS) system that enables pre-existing scheduling algorithms to take advantage of the €ne grained workƒow resource requirements and structure, without any modi€cation to the original algorithms. Œe current implementation of WoAS is integrated in Slurm, a widely used HPC batch scheduler. We evaluate the system in simulation using real and synthetic workƒows and a synthetic baseline workload that captures the job paŠerns observed over three years of the real workload data of Edison, a large supercomputer hosted at the National Energy Research Scienti€c Computing Center. Finally, our results show that WoAS e‚ectively reduces workƒow turnaround time and improves system utilization without a signi€cant impact on the slowdown of traditional jobs.

  • 349.
    Granat, Robert
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Algorithms and Library Software for Periodic and Parallel Eigenvalue Reordering and Sylvester-Type Matrix Equations with Condition Estimation2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This Thesis contains contributions in two different but closely related subfields of Scientific and Parallel Computing which arise in the context of various eigenvalue problems: periodic and parallel eigenvalue reordering and parallel algorithms for Sylvestertype matrix equations with applications in condition estimation.

    Many real world phenomena behave periodically, e.g., helicopter rotors, revolving satellites and dynamic systems corresponding to natural processes, like the water flow in a system of connected lakes, and can be described in terms of periodic eigenvalue problems. Typically, eigenvalues and invariant subspaces (or, specifically, eigenvectors) to certain periodic matrix products are of interest and have direct physical interpretations. The eigenvalues of a matrix product can be computed without forming the product explicitly via variants of the periodic Schur decomposition. In the first part of the Thesis, we propose direct methods for eigenvalue reordering in the periodic standard and generalized real Schur forms which extend earlier work on the standard and generalized eigenvalue problems. The core step of the methods consists of solving periodic Sylvester-type equations to high accuracy. Periodic eigenvalue reordering is vital in the computation of periodic eigenspaces corresponding to specified spectra. The proposed direct reordering methods rely on orthogonal transformations and can be generalized to more general periodic matrix products where the factors have varying dimensions and ±1 exponents of arbitrary order.

    In the second part, we consider Sylvester-type matrix equations, like the continuoustime Sylvester equation AX −XB =C, where A of size m×m, B of size n×n, and C of size m×n are general matrices with real entries, which have applications in many areas. Examples include eigenvalue problems and condition estimation, and several problems in control system design and analysis. The parallel algorithms presented are based on the well-known Bartels–Stewart’s method and extend earlier work on triangular Sylvester-type matrix equations resulting in a novel software library SCASY. The parallel library provides robust and scalable software for solving 44 sign and transpose variants of eight common Sylvester-type matrix equations. SCASY also includes a parallel condition estimator associated with each matrix equation.

    In the last part of the Thesis, we propose parallel variants of the direct eigenvalue reordering method for the standard and generalized real Schur forms. Together with the existing and future parallel implementations of the non-symmetric QR/QZ algorithms and the parallel Sylvester solvers presented in the Thesis, the developed software can be used for parallel computation of invariant and deflating subspaces corresponding to specified spectra and associated reciprocal condition number estimates.

  • 350.
    Granat, Robert
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Högpresterande beräkningscentrum norr (HPC2N).
    Jonsson, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Högpresterande beräkningscentrum norr (HPC2N).
    Kågström, Bo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Högpresterande beräkningscentrum norr (HPC2N).
    RECSY and SCASY library software: recursive blocked and parallel algorithms for Sylvester-type matrix equations with some applications2009Inngår i: Parallel scientific computing and optimization: advances and applications / [ed] Raimondas Čiegis, David Henty, Bo Kågström, Julius Žilinskas, Springer-Verlag New York, 2009, s. 3-24Kapittel i bok, del av antologi (Annet vitenskapelig)
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