umu.sePublications
Change search
Refine search result
31323334353637 1651 - 1700 of 1860
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1651.
    Svärd, Petter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hudzia, Benoit
    Stratoscale, Belfast, UK.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hecatonchire: Towards Multi-Host Virtual Machines by Server Disaggregation2014In: EuroPar 2014: 20:th International Conference on Parallell Processing / [ed] Luis Lopes, Springer, 2014, p. 519-529Conference paper (Refereed)
    Abstract [en]

    Horizontal elasticity through scale-out is the current dogma for scaling cloud applications but requires a particular application architecture. Vertical elasticity is transparent to applications but less used as scale-up is limited by the size of a single physical server. In this paper, we propose a novel approach, server disaggregation, that aggregates memory, compute and I/O resources from multiple physical machines in resource pools. From these pools, virtual machines can be seamlessly provisioned with the right amount of resources for each application and more resources can be added to vertically scale a virtual machine as needed, regardless of the bound of any single physical machine. We present our proposed architecture and implement key functionality such as transparent memory scale-out and cloud management integration. Our approach is validated by a demonstration using benchmarks and a real-world big-data application and results indicate a low overhead in using memory scale-out in both test cases.

  • 1652.
    Svärd, Petter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hudzia, Benoit
    SAP Research CEC Belfast.
    Walsh, Steve
    SAP Research CEC Belfast.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Principles and performance characteristics of algorithms for live VM migration2015In: ACM SIGOPS Operating Systems Review, Vol. 49, no 1, p. 142-155Article in journal (Refereed)
    Abstract [en]

    Since first demonstrated by Clark et al. in 2005, live migration of virtual machines has both become a standard feature of hypervisors and created an active field of research. However, the rich ongoing research in live migration focusmainly on performance improvements to well-known techniques, most of them being variations of the Clark approach. In order to advance live migration beyond incremental performance improvements, it is important to gain a deeper understanding of the live migration problem itself and its underlying principles.

    To address this issue, this contribution takes a step back and investigates the essential characteristics of live migration. The paper identifies five fundamental properties of live migration and uses these to investigate, categorize, and compare three approaches to live migration: precopy, postcopy and hybrid. The evaluated algorithms include well-known techniques derived from that of Clark as well as novel RDMA in-kernel approaches. Our analysis of the fundamental properties of the algorithms is validated by a set of experiments. In these, we migrate virtual machines with large memory sizes hosting workloads with high page dirtying rates to expose differences and limitations of the different approaches. Finally, we provide guidelines for which approach to use in different scenarios.

  • 1653.
    Svärd, Petter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Li, Wubin
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Wadbro, Eddie
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Continuous Datacenter Consolidation2014Report (Refereed)
    Abstract [en]

    Efficient mapping of Virtual Machines (VMs) onto physical servers is a key problem for cloud infrastructure providers as hardware utilization directly im- pacts revenue. Today, this mapping is commonly only performed when new VMs are created, but as VM workloads fluctuate and server availability varies, any ini- tial mapping is bound to become suboptimal over time. We introduce a set of heuristic methods for continuous optimization of the VM-to-server mapping based on combina- tions of fundamental management actions, namely suspending and resuming physical machines, migrating VMs, and suspending and resuming VMs. Using these methods cloud infrastructure providers can continuously optimize their server resources regard- less of the predictability of the workload. To verify that our approach is applicable in real-world scenarios, we build a proof-of-concept datacenter management system that implements the proposed algorithms. The feasibility of our approach is evaluated through a combination of simulations and real experiments where our system provi- sions a workload of benchmark applications. Our results indicate that the proposed algorithms are feasible, that the combined management approach achieves the best results, and that the VM suspend and resume mechanism has the largest impact. 

  • 1654.
    Svärd, Petter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Li, Wubin
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Wadbro, Eddie
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Continuous Datacenter Consolidation2015In: 2015 IEEE 7TH INTERNATIONAL CONFERENCE ON CLOUD COMPUTING TECHNOLOGY AND SCIENCE (CLOUDCOM), 2015, p. 387-396Conference paper (Refereed)
    Abstract [en]

    Efficient mapping of Virtual Machines (VMs) onto physical servers is a key problem for cloud infrastructure providers as hardware utilization directly impacts profit. Today, this mapping is commonly only performed when new VMs are created, but as VM workloads fluctuate and server availability varies, any initial mapping is bound to become suboptimal over time. We introduce a set of heuristic methods for continuous optimization of the VM-to-server mapping based on combinations of fundamental management actions, namely suspending and resuming physical machines, migrating VMs, and suspending and resuming VMs. By using these methods, cloud infrastructure providers can continuously optimize their server resources regardless of the predictability of the workload. To verify that our approach is applicable in real-world scenarios, we build a proof-of-concept datacenter management system that implements the proposed algorithms. The feasibility of our approach is evaluated through a combination of simulations and real experiments where our system provisions a workload of benchmark applications. Our results indicate that the proposed algorithms are feasible, that the combined management approach achieves the best results, and that the VM suspend and resume mechanism has the largest impact on provider profit.

  • 1655.
    Svärd, Petter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    The Noble art of Live MigrationManuscript (preprint) (Other academic)
    Abstract [en]

    Although a mature technique and an important feature of virtualization, live VM migration still suffers from performance and robustness issues, limiting its usefulness. This is particularly true if the migration technique is not appropriately selected for the usage scenario. In this contribution, we define requirements for live migration and discuss some of the challenges that arise in meeting these. We investigate, categorize, and compare current approaches to live migration as well as provide guidelines for which to use in different scenarios. Our investigation is validated by a set of experiments that highlights different characteristics of these approaches. We also propose methods for hybrid live migration and an improved memory page reordering algorithm. Finally we outline the future research landscape in the area. 

  • 1656.
    Svärd, Petter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hudzia, Benoit
    SAP Research CEC Belfast, UK.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    High Performance Live Migration through Dynamic Page Transfer Reordering and Compression2011In: 2011 IEEE Third International Conference on Cloud Computing Technology and Science, IEEE Computer Society, 2011, p. 542-548Conference paper (Refereed)
    Abstract [en]

    Although supported by many contemporary Virtual Machine (VM) hyper visors, live migration is impossible for certain applications. When migrating CPU and/or memory intensive VMs two problems occur, extended migration downtime that may cause service interruption or even failure, and prolonged total migration time that is harmful for the overall system performance as significant network resources must be allocated to migration. These problems become more severe for migration over slower networks, such as long distance migration between clouds. We approach this two-fold problem through a combination of techniques. A novel algorithm that dynamically adapts the transfer order of VM memory pages during live migration reduces the risk of re-transfers for frequently dirtied pages. As the amount of transferred data is thereby reduced, the total migration time is shortened. By combining this technique with a compression scheme that increases the migration bandwidth the migration downtime is also reduced. An evaluation by means of synthetic migration benchmarks shows that our combined approach reduces migration downtime by a factor 10 to 20, shortens total migration time by around 35%, as well as consumes between 26% and 39% less network bandwidth. The feasibility of our approach for real-life applications is demonstrated by migrating a streaming video server 31% faster while transferring 51% less data.

  • 1657.
    Söderberg, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    High frequency Verlet integration physics on iPhone2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    When Apple first introduced the iPhone it was thought by many to be groundbraking. The main visible difference was that the phone had no keypad, just a touch screen. Another interesting feature in this phone was the addition of accelerometers. With this the device knows the forces applied to it and therefore knows how it is tilted. In april 2010 Steve Jobs announced 85 million iPhone OS devices sold. This makes it a very interesting OS from a developers point of view.This project aims to explore those two new key features and the iPhone OS by implementing a simplified version of the game Mad Skills Motocross by Turborilla. This is a fast paced sideways scrolling motocross game with demanding physics simulation. The physics is modeled via high frequency (1000 Hz) Verlet integration. Important aspects of the project are therefore also if the iPhone can handle the game and if it still will be a fun game considering the changes going from desktop to iPhone.The results were a game playable on one track with accurate physics, running with a visible frame rate of 30 frames per second and some interesting insights in what you need to think about when developing for iPhone OS.

  • 1658.
    Söderkvist, Inge
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Wedin, Per-Åke
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Determining the movements of the skeleton using well-configured markers1993In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 26, no 12, p. 1473-1477Article in journal (Refereed)
    Abstract [en]

    The problem of determining skeletal movements in three dimensions by using a number of landmarks is treated. We present a method that determines the motion of a rigid body by using the positions of the landmarks in least-squares sense. The method uses the singular value decomposition of a matrix derived from the positions of the landmarks. We show how one can use this method to express movement of skeleton segments relative to each other. As many others have pointed out, the movement can be very ill determined if the landmarks are badly configured. We present a condition number for the problem with good geometrical properties. The condition number depends on the configuration of the landmarks and indicates how to distribute the landmarks in a suitable way.

  • 1659.
    Söderlind, Simon
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Evaluation of a Novel Technique for Determining Near Optimal Task Granularity in Parallel Programs2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The evolution of computers is moving more and more towards multi-core processors and parallel programs. For parallel programs to perform effciently the task granularity has to be near optimal for that specific problem. The aim of this thesis is to evaluate a novel technique, called Control of the Critical Path Delay (CCPD), for determining a near optimal granularity for parallel programs, and determine when the technique succeeds, why it performs as it does and if there is a way to improve the technique. The CCPD-technique showed promising on problems where non-optimal scheduling did not play any part. Where the non-optimal scheduling affected the problem the CCPD-technique did not perform well. To deal with potentially poor scheduling a method to improve the technique by incorporating more information from the critical path curve is proposed. Experimental results on a shared memory system as well as theoretical analysis are presented.

  • 1660.
    Söderlund, Magnus
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    An Advertisement Framework Implementation and Scalable Database Architecture Evaluation2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis report provides a detailed description of an iOS framework implementation for the product developed at Dohi Sweden, used to target advertisement. Targeting properties are stored in a relational database and the customer estimates the amount of requests performed against the database to reach several hundred million requests per month when fully integrated. Possible system architectures are therefore evaluated using denitions of scalability, elasticity and availability made in this report. With the possibility of a cloud based deployment three large cloud service providers are also evaluated using the definitions made. Testing of the back-end, coupled with the theory for the evaluation show that the back-end should be able to handle the amount of requests required. The framework is designed to provide easy integration, high modularity and only necessary exposure of possibilities.

  • 1661.
    Söderlund, Per
    et al.
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Orthopaedics.
    Börlin, Niclas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Nivbrant, Bo
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Orthopaedics.
    Röhrl, Stephan
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Orthopaedics.
    Accuracy of RSA using Manual or Digital methods2001In: 4th Combined meeting of the Orthopaedic Research Societies of The USA, Canada, Europe, and Japan, 2001, p. 79-79Conference paper (Other academic)
  • 1662.
    Söderström, Jonny
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    INCREASING OBSERVABILITY OF PERFORMANCE IN DISTRIBUTED SYSTEMS2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The technical evolution is increasing rapidly and with that, the systems available today grow more complex. The need for being able to understand and monitor system performance, such as data throughput and timing, is almost as important as the functionality itself. So is there a way of increasing the way we look at performance near real time in an already existing system without compromising performance? Distributed tracing is an example of such a technology that lets the developers track transactions through a distributed system. A distributed tracing solution will be compared to a way of visualizing log les using ElasticStack for increase in observability of performance. Both the distributed tracing and ElasticStack solutions increases the observability of performance, but in different ways. While a distributed tracing solution will visualize on method level how transactions flow through the system, the message overhead will be noticeable and decrease performance. The Elasticstack method however will not impact the performance, but the information visualized are all depending on the existing log file. There is not a best method that is applicable to all systems, so the methods for each systems has to be carefully decided depending on the information that needs to be visualized.

  • 1663.
    Söderström, Tor
    et al.
    Umeå University, Faculty of Social Sciences, Department of Education. Umea School of Sport Science.
    Brusvik, Peter
    Umeå University, Faculty of Social Sciences, Department of Education. Umea School of Sport Science.
    Sandlund, Stefan
    Umea School of Sport Science.
    Guerrero, Esteban
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umea School of Sport Science.
    The meaning and significance of physiological tests from the perspective of elite athletes2018In: World Congress of Sociology of Sport, Lausanne, Switzerland, June 5 - 8, 2018: ISSA 2018 Book of Abstracts, Lausanne, 2018, p. 105-105Conference paper (Refereed)
    Abstract [en]

    The use of physiological tests has received a lot of attention within high performance sport. One major motive for using physiological tests is to help the athlete enhance their performance (Tanner and Gore, 2013). However, to date, research undertaken in the field has not acknowledged or taken into consideration those that actually use the tests. What do they think about tests and how useful do they find them? Thus, in this paper we aim to explore the meaning and significance of physiological tests from the athletes’ perspective by scrutinizing their experiences of physiological tests and their importance for enhancing performance.

    The material in this study is based on interviews with eight elite athletes between 20-30 years of age in three different individual sports. They were all dual career athlete-university students. The results show that their experiences of using physiological test vary according to which training group they belonged to prior to entering university. The athletes believed that their pre-University coaches generally used tests as a checkpoint or single indicator of fitness. As a consequence, for most athletes, the tests had little or no importance with respect to how they evaluated and planned their training. In other words, physiological tests are not automatically useful for enhancing performance. Drawing on Bourdieu (1990), we argue that the use of tests in high performance sport can be considered as part of a practical logic that counteracts reflexive attention and processing necessary for enhancing the athletes performance (cf. Dewey, 1910).

  • 1664. Talyansky, Roman
    et al.
    Lakew, Ewnetu Bayuh
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Klein, Cristian
    Hernandez-Rodriguez, Francisco
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Levy, Eliezer
    Towards Optimized Self-Management of Distributed Object Storage Systems2015Report (Other academic)
    Abstract [en]

    Cloud storage is increasingly adopted by users due to simplified storage systems compared to on-premise storage. These systems are mostly presented as Object Storage Systems (OSSs), hiding issues, such as redundancy, from users. As new industries are considering adopting clouds for storage, OSSs have to evolve to support new needs. Among the most challenging is assuring guaranteed performance.

    In this paper, we present Controllable Trade-offs (CTO), an OSS-agnostic solution to add performance guarantees. CTO presents itself as a thin layer that mediates requests between the user and the OSS. For generic support, performance is controlled by tuning the rejection probability, and implemented as a user-side queue. Results show that CTO may reduce penalties 3.23 times on average and up to 68 times when the load is high.

  • 1665.
    Tarnvik, E.
    Umeå University, Faculty of Science and Technology, Departement of Computing Science.
    DYNAMO - A PORTABLE TOOL FOR DYNAMIC LOAD BALANCING ON DISTRIBUTED MEMORY MULTICOMPUTERS1992In: Lecture Notes in Computer Science, Vol. 634, p. 485-490Article in journal (Refereed)
    Abstract [en]

    Dynamic load balancing is an important technique when developing applications with unpredictable load distribution on distributed memory multicomputers. A tool, Dynamo, that can be used to utilize dynamic load balancing is presented. This tool separates the application from the load balancer and thus makes it possible to easily exchange the load balancer of a given application and experiment with different load balancing strategies.

  • 1666.
    Tengroth, Wiktor
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Cross-Platform Development: Bringing a desktop web application to the mobile platform2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cross-platform development frameworks make it possible to develop web applications for multiple platforms with just one code-base.

    The aim of this thesis is to determine which kind of framework is best suited to bring a web application targeting desktop browsers to the mobile platform. This includes being able to use already developed web components.

    The evalutation was done by first selecting six frameworks from two different choices of cross-platform technologies. Then a literature study was done to select one framework from each technique for which a prototype for Trimmas application INSIKT was developed

    .Performance tests of the prototypes together with the literature study is then used to determine which kind of frameworks are to prefer when bringing a web application targeting desktops to the mobile platform. This is done with, in particular, INSIKT but as well for general applicationsin mind. From this we have successfully determined the bes tchoice for INSIKT as well as key points when selecting a framework to use for other applications.

  • 1667.
    Tesfatsion Kostentinos, Selome
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    A Combined Frequency Scaling and Application Elasticity Approach for Energy-Efficient Virtualized Data Centers2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    At present, large-scale data centers are typically over-provisioned in order to handle peak

    load requirements. The resulting low utilization of resources contribute to a huge amounts

    of power consumption in data centers. The effects of high power consumption manifest in a

    high operational cost in data centers and carbon footprints to the environment. Therefore,

    the management solutions for large-scale data centers must be designed to effectively take

    power consumption into account. In this work, we combine three management techniques

    that can be used to control systems in an energy-efficient manner: changing the number of

    virtual machines, changing the number of cores, and scaling the CPU frequencies. The proposed

    system consists of a controller that combines feedback and feedforward information

    to determine a configuration that minimizes power consumption while meeting the performance

    target. The controller can also be configured to accomplish power minimization in

    a stable manner, without causing large oscillations in the resource allocations. Our experimental

    evaluation based on the Sysbench benchmark combined with workload traces from

    production systems shows that our approach achieves the lowest energy consumption among

    the compared three approaches while meeting the performance target.

  • 1668.
    Tesfatsion, Selome Kostentinos
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Energy-efficient cloud computing: autonomic resource provisioning for datacenters2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Energy efficiency has become an increasingly important concern in data centers because of issues associated with energy consumption, such as capital costs, operating expenses, and environmental impact. While energy loss due to suboptimal use of facilities and non-IT equipment has largely been reduced through the use of best-practice technologies, addressing energy wastage in IT equipment still requires the design and implementation of energy-aware resource management systems. This thesis focuses on the development of resource allocation methods to improve energy efficiency in data centers. The thesis employs three approaches to improve efficiency for optimized power and performance: scaling virtual machine (VM) and server processing capabilities to reduce energy consumption; improving resource usage through workload consolidation; and exploiting resource heterogeneity.

    To achieve these goals, the first part of the thesis proposes models, algorithms, and techniques that reduce energy usage through the use of VM scaling, VM sizing for CPU and memory, CPU frequency adaptation, as well as hardware power capping for server-level resource allocation. The proposed online performance and power models capture system behavior while adapting to changes in the underlying infrastructure. Based on these models, the thesis proposes controllers that dynamically determine power-efficient resource allocations while minimizing performance penalty.

    These methods are then extended to support resource overbooking and workload consolidation to improve resource utilization and energy efficiency across the cluster or data center. In order to cater for different performance requirements among collocated applications, such as latency-sensitive services and batch jobs, the controllers apply service differentiation among prioritized VMs and performance isolation techniques, including CPU pinning, quota enforcement, and online resource tuning.

    This thesis also considers resource heterogeneity and proposes heterogeneousaware scheduling techniques to improve energy efficiency by integrating hardware accelerators (in this case FPGAs) and exploiting differences in energy footprint of different servers. In addition, the thesis provides a comprehensive study of the overheads associated with a number of virtualization platforms in order to understand the trade-offs provided by the latest technological advances and to make the best resource allocation decisions accordingly. The proposed methods in this thesis are evaluated by implementing prototypes on real testbeds and conducting experiments using real workload data taken from production systems and synthetic workload data that we generated. Our evaluation results demonstrate that the proposed approaches provide improved energy management of resources in virtualized data centers.

  • 1669.
    Tesfatsion, Selome Kostentinos
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Klein, Cristian
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Virtualization Techniques Compared: Performance, Resource, and Power Usage Overheads in Clouds2018Manuscript (preprint) (Other academic)
    Abstract [en]

    Virtualization solutions based on hypervisors or containers are enabling technologies

    for scalable, flexible, and cost-effective resource sharing. As the fundamental

    limitations of each technology are yet to be understood, they need to be regularly

    reevaluated to better understand the trade-off provided by latest technological advances.

    This paper presents an in-depth quantitative analysis of virtualization

    overheads in these two groups of systems and their gaps relative to native environments

    based on a diverse set of workloads that stress CPU, memory, storage,

    and networking resources. KVM and XEN are used to represent hypervisor-based

    virtualization, and LXC and Docker for container-based platforms. The systems

    were evaluated with respect to several cloud resource management dimensions including

    performance, isolation, resource usage, energy efficiency, start-up time,

    and density. Our study is useful both to practitioners to understand the current

    state of the technology in order to make the right decision in the selection, operation

    and/or design of platforms and to scholars to illustrate how these technologies

    evolved over time.

  • 1670.
    Tesfatsion, Selome Kostentinos
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tomás, Luis
    Red Hat, Madrid, Spain.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    OptiBook: Optimal Resource Booking for Energy-efficient Datacenters2017In: 2017 IEEE/ACM 25th International Symposium on Quality of Service (IWQoS), IEEE Communications Society, 2017Conference paper (Refereed)
    Abstract [en]

    A lack of energy proportionality, low resource utilization, and interference in virtualized infrastructure make the cloud a challenging target environment for improving energy efficiency. In this paper we present OptiBook, a system that improves energy proportionality and/or resource utilization to optimize performance and energy efficiency. OptiBook shares servers between latency-sensitive services and batch jobs, over- books the system in a controllable manner, uses vertical (CPU and DVFS) scaling for prioritized virtual machines, and applies performance isolation techniques such as CPU pinning and quota enforcement as well as online resource tuning to effectively improve energy efficiency. Our evaluations show that on average, OptiBook improves performance per watt by 20% and reduces energy consumption by 9% while minimizing SLO violations. 

  • 1671.
    Tesfatsion, Selome Kostentinos
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Wadbro, Eddie
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    PerfGreen: Performance and Energy Aware Resource Provisioning for Heterogeneous Clouds2018In: 2018 IEEE International Conference on Autonomic Computing (ICAC), 2018, p. 81-90Conference paper (Refereed)
    Abstract [en]

    Improving energy efficiency in a cloud environment is challenging because of poor energy proportionality, low resource utilization, interference as well as workload, application, and hardware dynamism. In this paper we present PerfGreen, a dynamic auto-tuning resource management system for improving energy efficiency with minimal performance impact in heterogeneous clouds. PerfGreen achieves this through a combination of admission control, scheduling, and online resource allocation methods with performance isolation and application priority techniques. Scheduling in PerfGreen is energy aware and power management capabilities such as CPU frequency adaptation and hard CPU power limiting are exploited. CPU scaling is combined with performance isolation techniques, including CPU pinning and quota enforcement, for prioritized virtual machines to improve energy efficiency. An evaluation based on our prototype implementation shows that PerfGreen with its energy-aware scheduler and resource allocator on average reduces energy usage by 53%, improves performance per watt by 64%, and server density by 25% while keeping performance deviations to a minimum.

  • 1672.
    Tesfatsion, Selome
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Wadbro, Eddie
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    A combined frequency scaling and application elasticity approach for energy-efficient cloud computing2014In: Sustainable Computing: Informatics and Systems, ISSN 2210-5379, E-ISSN 2210-5387, Vol. 4, no 4, p. 205-214Article in journal (Refereed)
    Abstract [en]

    Energy management has become increasingly necessary in large-scale cloud data centers to address high operational costs and carbon footprints to the environment. In this work, we combine three management techniques that can be used to control cloud data centers in an energy-efficient manner: changing the number of virtual machines, the number of cores, and scaling the CPU frequencies. We present a feedback controller that determines an optimal configuration to minimize energy consumption while meeting performance objectives. The controller can be configured to accomplish these goals in a stable manner, without causing large oscillations in the resource allocations. To meet the needs of individual applications under different workload conditions, the controller parameters are automatically adjusted at runtime based on a system model that is learned online. The potential of the proposed approach is evaluated in a video encoding scenario. The results show that our combined approach achieves up to 34% energy savings compared to the constituent approaches—core change, virtual machine change, and CPU frequency change policies, while meeting the performance target.

  • 1673.
    Tewari, Maitreyee
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Bensch, Suna
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Natural Language Communication with Social Robots for Assisted Living2018Conference paper (Refereed)
    Abstract [en]

    We explore a new dialogue modelling approach for assistive social robots that enables us to formalize flexible conversation flows between a robot and a human. We achieve this by introducing an expectation mechanism to handle, for example, topic change, clarification questions or misunderstandings during a dialogue. The model gave us insight into the dialogue structure and how it is shaped by several linguistic and pragmatic features. This is work in progress and in the future we will explore learning algorithms that mine the features, implement and validate the model with real conversations. 

  • 1674.
    Thelin, Robert
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Interactive Video in Online Education: Evaluation of Current Video Delivery Systems for Interactive Features Defined in Literature2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Increasingly lectures are being offered online in the form of online lecture videos. Although more and more lectures are now being offered online in the form of videos, they tend to be mostly non-interactive and linear. This thesis examines current approaches to online learning and evaluate current video delivery services to determine if they can support the kind of interactive features that are defined in the literature. The thesis shows that the video delivery services can be used to integrate interactive elements, but will do so by being used together with other technologies, such as HTML5.

  • 1675.
    Theodorou, Andreas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Why is AI a matter of design2020In: Artificial Intelligence: Reflections in Philosophy, Theology, and the Social Sciences / [ed] Benedikt Paul Goecke and Astrid Marieke Rosenthal-von der Pütten, Leiden, Netherlands: Brill Academic Publishers, 2020Chapter in book (Refereed)
  • 1676.
    Theodorou, Andreas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Bandt-Law, Bryn
    Bryson, Joanna J.
    University of Bath.
    The Sustainability Game: AI Technology as an Intervention for Public Understanding of Cooperative Investment2019In: 2019 IEEE Conference on Games (CoG), Institute of Electrical and Electronics Engineers (IEEE), 2019Conference paper (Other academic)
    Abstract [en]

    Cooperative behaviour is a fundamental strategy for survival; it positively affects economies, social relationships, and makes larger societal structures possible. People vary, however, in their willingness to engage in cooperative behaviour in a particular context. Here we examine whether AI can be effectively used to to alter individuals' implicit understanding of cooperative dynamics, and hence increase cooperation and participation in public goods projects. We developed an intervention-the Sustainability Game (SG)-to allow players to experience the consequences of individual investment strategies on a sustainable society. Results show that the intervention significantly increases individuals' cooperative behaviour in partially anonymised public goods contexts, but enhances competition one-on-one. This indicates our intervention does improve transparency of the systemic consequences of individual cooperative behaviour.

  • 1677.
    Theodorou, Andreas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Dignum, Virginia
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Towards ethical and socio-legal governance in AI2020In: Nature Machine Intelligence, ISSN 2522-5839Article in journal (Refereed)
  • 1678.
    Thrash, Tyler
    et al.
    University of Zürich, Switzerland.
    Lanini-Maggi, Sara
    University of Zürich, Switzerland.
    Fabrikant, Sara I.
    University of Zürich, Switzerland.
    Bertel, Sven
    Hochschule Flensburg, Germany.
    Brügger, Annina
    University of Zürich, Switzerland.
    Credé, Sascha
    University of Zürich, Switzerland.
    Do, Cao Tri
    University of Zürich / ETH Zürich, Switzerland.
    Gartner, Georg
    TU Wien, Austria.
    Huang, Haosheng
    University of Zürich, Switzerland.
    Münzer, Stefan
    Universität Mannheim, Germany.
    Richter, Kai-Florian
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    The Future of Geographic Information Displays from GIScience, Cartographic, and Cognitive Science Perspectives2019In: 14th International Conference on Spatial Information Theory / [ed] Sabine Timpf, Christoph Schlieder, Markus Kattenbeck, Bernd Ludwig and Kathleen Stewart, Dagstuhl, Germany, 2019, Vol. 142, p. 19:1-19:11Conference paper (Refereed)
    Abstract [en]

    With the development of modern geovisual analytics tools, several researchers have emphasized the importance of understanding users' cognitive, perceptual, and affective tendencies for supporting spatial decisions with geographic information displays (GIDs). However, most recent technological developments have focused on support for navigation in terms of efficiency and effectiveness while neglecting the importance of spatial learning. In the present paper, we will envision the future of GIDs that also support spatial learning in the context of large-scale navigation. Specifically, we will illustrate the manner in which GIDs have been (in the past) and might be (in the future) designed to be context-responsive, personalized, and supportive for active spatial learning from three different perspectives (i.e., GIScience, cartography, and cognitive science). We will also explain why this approach is essential for preventing the technological infantilizing of society (i.e., the reduction of our capacity to make decisions without technological assistance). Although these issues are common to nearly all emerging digital technologies, we argue that these issues become especially relevant in consideration of a person's current and future locations.

  • 1679. Tomas, L
    et al.
    Östberg, Per-Olov
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Caminero, B.
    Carrion, C.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    An adaptable in-advance and fairshare meta-scheduling architecture to improve grid QoS2011In: Grid Computing (GRID), 2011 12th IEEE/ACM International Conference on, 2011, p. 220-221Conference paper (Refereed)
    Abstract [en]

    Grids are highly variable heterogeneous systems where resources may span multiple administrative domains and utilize heterogeneous schedulers, which complicates enforcement of end-user resource utilization quotas. This work focuses on enhancement of resource utilization quality of service through combination of two systems. A predictive meta-scheduling framework and a distributed fairs hare job prioritization system. The first, SA-Layer, is a system designed to provide scheduling of jobs in advance by ensuring resource availability for future job executions. The second, FS Grid, provides an efficient mechanism for fairs hare-based job prioritization. The integrated architecture presented in this work combines the strengths of both systems and improves perceived end-user quality of service by providing reliable resource allocations adhering to usage allocation policies.

  • 1680.
    Tomas, Luis
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Bayuh Lakew, Ewnetu
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Service Level and Performance Aware Dynamic Resource Allocation in Overbooked Data Centers2016In: 2016 16TH IEEE/ACM INTERNATIONAL SYMPOSIUM ON CLUSTER, CLOUD AND GRID COMPUTING (CCGRID), 2016, p. 42-51Conference paper (Refereed)
    Abstract [en]

    Many cloud computing providers use overbooking to increase their low utilization ratios. This however increases the risk of performance degradation due to interference among co-located VMs. To address this problem we present a service level and performance aware controller that: (1) provides performance isolation for high QoS VMs; and (2) reduces the VM interference between low QoS VMs by dynamically mapping virtual cores to physical cores, thus limiting the amount of resources that each VM can access depending on their performance. Our evaluation based on real cloud applications and both stress, synthetic and realistic workloads demonstrates that a more efficient use of the resources is achieved, dynamically allocating the available capacity to the applications that need it more, which in turn lead to a more stable and predictable performance over time.

  • 1681.
    Tomas, Luis
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Caminero, Blanca
    University of Castilla-La Mancha.
    Carrión, Carmen
    University of Castilla-La Mancha.
    Opportunistic Energy-Aware Rescheduling in Desktop Grid Environments2013In: 2013 International Conference on High Performance Computing & Simulation (HPCS2013), 2013, p. 178-185Conference paper (Refereed)
    Abstract [en]

    Nowadays either maximizing energy efficiency andimproving resource utilization is a challenge among the differentexisting distributed systems, specially in large scale distributedenvironments such as Grids or Clouds. With this objective, wepropose a rescheduling technique that tries to improve resourceusage, whilst at the same time tries to minimize the energy neededfor the executions of the already accepted jobs by using first/morethe resources that are more energy efficient and without reducingthe QoS provided. The information obtained from a devicecapable of measuring the energy that each desktop resourceneeds is used by the algorithm at the resource selection process,resulting in a noticeable reduction in the energy used as it hasbeen demonstrated in a real desktop Grid environment.

  • 1682.
    Tomas, Luis
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Masoumzadeh, Seyed Saeid
    Hlavacs, Helmut
    Self-Adaptive Capacity Controller: A Reinforcement Learning Approach2016In: 2016 IEEE INTERNATIONAL CONFERENCE ON AUTONOMIC COMPUTING (ICAC), LOS ALAMITOS: IEEE Computer Society, 2016, p. 233-234Conference paper (Refereed)
    Abstract [en]

    Interference between co-located VMs may lead to performance fluctuations and degradation. To limit this problem, VMs access to physical resources needs to be controlled to ensure certain degree of isolation among them. This mapping between virtual and physical resources must be performed in a dynamic way so that it can be adaptive to the changing applications requirements, as well as to the different set of co-located VMs. To address this problem we propose a self-adaptive fuzzy Q-learning capacity controller that proactively readjusts the isolation degree based on applications performance. Our evaluation demonstrates a reduction into VMs interference and an increment on the overall utilization, while still ensuring critical applications performance, and providing more resources to non-critical applications.

  • 1683.
    Tomas, Luis
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Saeid Masoumzadeh, Seyed
    Hlavacs, Helmut
    Self-Adaptive Capacity Controller: A Reinforcement Learning Approach2016In: 2016 IEEE International Conference on Autonomic Computing (ICAC), IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    Interference between co-located VMs may lead to performance fluctuations and degradation. To limit this problem, VMs access to physical resources needs to be controlled to ensure certain degree of isolation among them. This mapping between virtual and physical resources must be performed in a dynamic way so that it can be adaptive to the changing applications requirements, as well as to the different set of co-located VMs. To address this problem we propose a self-adaptive fuzzy Q-learning capacity controller that proactively readjusts the isolation degree based on applications performance. Our evaluation demonstrates a reduction into VMs interference and an increment on the overall utilization, while still ensuring critical applications performance, and providing more resources to non-critical applications.

  • 1684.
    Tomas, Luis
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    An autonomic approach to risk-aware data center overbooking2014In: IEEE Transactions on Cloud Computing, ISSN 2168-7161, Vol. 2, no 3, p. 292-305Article in journal (Refereed)
    Abstract [en]

    Elasticity is a key characteristic of cloud computing that increases the flexibility for cloud consumers, allowing them to adapt the amount of physical resources associated to their services over time in an on-demand basis. However, elasticity creates problems for cloud providers as it may lead to poor resource utilization, specially in combination with other factors, such as user overestimations and pre-defined VM sizes. Admission control mechanisms are thus needed to increase the number of services accepted, raising the utilization without affecting services performance. This work focuses on implementing an autonomic risk-aware overbooking architecture capable of increasing the resource utilization of cloud data centers by accepting more virtual machines than physical available resources. Fuzzy logic functions are used to estimate the associated risk to each overbooking decision. By using a distributed PID controller approach, the system is capable of self-adapting over time – changing the acceptable level of risk – depending on the current status of the cloud data center. The suggested approach is extensively evaluated using a combination of simulations and experiments executing real cloud applications with real-life available workloads. Our results show a 50% increment at both resource utilization and capacity allocated with acceptable performance degradation and more stable resource utilization over time.

  • 1685.
    Tomas, Luis
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Cloudy with a Chance of Load Spikes: Admission Control with Fuzzy Risk Assessments2013In: 6th IEEE International Conference on Utility and Cloud Computing, 2013, p. 155-162Conference paper (Refereed)
    Abstract [en]

    Elasticity is key for the cloud paradigm, wherethe pay-per use nature provides great flexibility for end-users.However, elasticity complicates long-term capacity planning forcloud providers as the exact amount of resources requiredover time becomes uncertain. Admission control techniques arethus needed to handle the trade-off between resource utilizationand potential overload. We define a set of admission controlalgorithms that combine risk assessment methods with a fuzzyaggregation framework. An experimental evaluation using amixture of bursty and steady applications demonstrate that ouralgorithms can increase resource utilization by a factor of twowhile limiting overload problems to a few percent.

  • 1686.
    Tomas, Luis
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Improving Cloud Infrastructure Utilization through Overbooking2013In: Proceedings of the 2013 ACM Cloud and Autonomic Computing Conference, 2013Conference paper (Refereed)
    Abstract [en]

    Despite the potential given by the combination of multitenancyand virtualization, resource utilization in today’sdata centers is still low. We identify three key characteristicsof cloud services and infrastructure as-a-service managementpractices: burstiness in service workloads, fluctuationsin virtual machine resource usage over time, and virtual machinesbeing limited to pre-defined sizes only. Based on thesecharacteristics, we propose scheduling and admission controlalgorithms that incorporate resource overbooking to improveutilization. A combination of modeling, monitoring, andprediction techniques is used to avoid overpassing the totalinfrastructure capacity. A performance evaluation using amixture of workload traces demonstrates the potential forsignificant improvements in resource utilization while stillavoiding overpassing the total capacity.

  • 1687.
    Tomas, Luis
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Vazquez, Carlos
    University of Castilla-La Mancha.
    Moreno, Gines
    Reducing Noisy-Neighbor Impact with a Fuzzy Affinity-Aware Scheduler2015In: 2015 INTERNATIONAL CONFERENCE ON CLOUD AND AUTONOMIC COMPUTING (ICCAC), New York: IEEE Computer Society, 2015, p. 33-44Conference paper (Refereed)
    Abstract [en]

    Overbooking techniques have been proven efficientto increase overall utilization of cloud datacenters. However,overbooking may also degrade applications performance as (atleast) some applications need to share physical resources suchas CPU or memory. Consequently, interference may increaseamong the virtual machines that share resources, the so callednoisy neighbors effect. We present an affinity-aware schedulerto reduce the impact of such interference. A fuzzy logic engineaccounts for the uncertainty in these environments and estimateswhich CPU cores are currently more suitable for each incomingapplication. This helps the scheduler make virtual machine tophysical resource mapping decisions, also known as vcpu pinning.An experimental evaluation based on a combination of interactiveservices and batch applications confirms that our affinity-awarefuzzy scheduler reduces the interference among applications,enabling more predictable performance and consequently saferoverbooking.

  • 1688. Tomás, L.
    et al.
    Östberg, Per-Olov
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Caminero, B.
    Carrión, C.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Addressing QoS in grids through a fairshare meta-scheduling in-advance architecture2012Conference paper (Refereed)
    Abstract [en]

    Federated Grid resources typically span multiple administrative domains and utilize heterogeneous schedulers. This complexity complicates not only provisioning of quality of service but also management and enforcement of end-user resource utilization allocations. to overcome these problems, we propose to combine high-level meta-scheduling techniques with lower-level fairs hare prioritization mechanisms to create a framework that improves end-user quality of service in heterogeneous distributed computing environments. to illustrate the approach we present a prototype architecture based on two existing systems, the meta-scheduling framework SA-Layer and the distributed fairs hare prioritization system Aequus. the proposed architecture constitutes a predictive meta-scheduling architecture that performs fair user-level scheduling prioritization and enacts resource utilization quotas, whilst also providing synergetic effects that improve the performance of the individual system components. to characterize the contribution, the proposed system is evaluated on a test bed consisting of geographically dispersed, heterogeneous computing resources spanning multiple administration domains.

  • 1689.
    Tomás, Luis
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Klein, Cristian
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hernández, Francisco
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    The straw that broke the camel’s back: safe cloud overbooking with application brownout2014In: 2014 International Conference on Cloud and Autonomic Computing (ICCAC 2014), IEEE Press, 2014, p. 151-160Conference paper (Refereed)
    Abstract [en]

    Resource overbooking is an admission control technique to increase utilization in cloud environments. However, due to uncertainty about future application workloads, overbooking may result in overload situations and deteriorated performance. We mitigate this using brownout, a feedback approach to application performance steering, that ensures graceful degradation during load spikes and thus avoids overload. Additionally, brownout management information is included into the overbooking system, enabling the development of improved reactive methods to overload situations. Our combined brownout-overbooking approach is evaluated based on real-life interactive workloads and non-interactive batch applications. The results show that our approach achieves an improvement of resource utilization of 11 to 37 percentage points, while keeping response times lower than the set target of 1 second, with negligible application degradation.

  • 1690.
    Tomás, Luis
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Cloud Service Differentiation in Overbooked Data Centers2014In: 2014 IEEE/ACM 7th International Conference on Utility and Cloud Computing (UCC), IEEE, 2014, p. 541-546Conference paper (Refereed)
    Abstract [en]

    Low resource utilization in cloud data centers can be mitigated by overbooking but this increases the risk of performance degradation. We propose a three level Quality of Service (QoS) scheme for overbooked cloud data centers to assure high performance QoS for applications that need it. We design a controller that dynamically maps virtual cores to physical cores and whenever feasible shares physical cores among applications. Our evaluation based on real cloud applications and workloads demonstrates that performance isolation can be achieved for critical applications while overall utilization is increased thanks to overbooking.

  • 1691.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Decentralized resource brokering for heterogeneous grid environments2006Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The emergence of Grid computing infrastructures enables researchers to share resources and collaborate in more efficient ways than before, despite belonging to different organizations and being distanced geographically. While the Grid computing paradigm offers new opportunities, it also gives rise to new difficulties. One such problem is the selection of resources for user applications. Given the large and disparate set of Grid resources, manual resource selection becomes impractical, even for experienced users. This thesis investigates methods, algorithms and software for a Grid resource broker, i.e., a scheduling agent that automates the resource selection process for the user. The development of such a component is a non-trivial task as Grid resources are heterogeneous in hardware, software, availability, ownership and usage policies. A wide range of algorithmically difficult issues must also be solved, including characterization of jobs, prediction of resource performance, data placement considerations, and, how to provide Quality of Service guarantees. One contribution of this thesis is the development of resource brokering algorithms that enable resource selection based on Grid job performance predictions and use advance reservations to provide Quality of Service guarantees. The thesis also includes an algorithm for coallocation of sets of jobs. This algorithm guarantees a simultaneous start of each subjob, as required e.g., when running larger-than-supercomputer simulations that involve multiple resources.

    We today have the somewhat paradoxal situation where Grids, originally aimed to overcome interoperability problems between different computing platforms, themselves struggle with interoperability problems caused by the wide range of interfaces, protocols and data formats that are used in different environments. The reasons for this situation are obvious, expected and almost impossible to avoid, as the task of defining appropriate standards, models and best-practices must be preceded by basic research, proof-of-concept implementations and real-world testing. We address the interoperability problem with a generic Grid resource brokering architecture and job submission service.

    By using (proposed) standard formats and protocols, the service acts as an interoperability-bridge that translates job requests between clients and resources running different Grid middlewares. This concept is demonstrated by the integration of the service with three different Grid middlewares. The service also enables users to both fine-tune the existing resource selection algorithms and plug in custom brokering algorithms tailored to their requirements.

  • 1692.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Departement of Computing Science.
    Portable Tools for Interoperable Grids: Modular Architectures and Software for Job and Workflow Management2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The emergence of Grid computing infrastructures enables researchers to shareresources and collaborate in more efficient ways than before, despite belongingto different organizations and being geographically distributed. While the Gridcomputing paradigm offers new opportunities, it also gives rise to newdifficulties. This thesis investigates methods, architectures, and algorithmsfor a range of topics in the area of Grid resource management. One studiedtopic is how to automate and improve resource selection, despite heterogeneityin Grid hardware, software, availability, ownership, and usage policies.Algorithmical difficulties for this are, e.g., characterization of jobs andresources, prediction of resource performance, and data placementconsiderations. Investigated Quality of Service aspects of resource selectioninclude how to guarantee job start and/or completion times as well as how tosynchronize multiple resources for coordinated use through coallocation.Another explored research topic is architectural considerations for frameworksthat simplify and automate submission, monitoring, and fault handling for largeamounts of jobs. This thesis also investigates suitable Grid interactionpatterns for scientific workflows, studies programming models that enable dataparallelism for such workflows, as well as analyzes how workflow compositiontools should be designed to increase flexibility and expressiveness. We today have the somewhat paradoxical situation where Grids, originally aimed tofederate resources and overcome interoperability problems between differentcomputing platforms, themselves struggle with interoperability problems causedby the wide range of interfaces, protocols, and data formats that are used indifferent environments. This thesis demonstrates how proof-of-concept softwaretools for Grid resource management can, by using (proposed) standard formatsand protocols as well as leveraging state-of-the-art principles fromservice-oriented architectures, be made independent of current Gridinfrastructures. Further interoperability contributions include an in-depthstudy that surveys issues related to the use of Grid resources in scientificworkflows. This study improves our understanding of interoperability amongscientific workflow systems by viewing this topic from three differentperspectives: model of computation, workflow language, and executionenvironment. A final contribution in this thesis is the investigation of how the design ofGrid middleware tools can adopt principles and concepts from softwareengineering in order to improve, e.g., adaptability and interoperability.

  • 1693.
    Tordsson, Johan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Montero, Ruben S.
    Universidad Complutense de Madrid.
    Moreno-Vozmediano, Rafael
    Universidad Complutense de Madrid.
    Llorente, Ignacio M.
    Universidad Complutense de Madrid.
    Cloud brokering mechanisms for optimized placement of virtual machines across multiple providers2012In: Future generations computer systems, ISSN 0167-739X, E-ISSN 1872-7115, Vol. 28, no 2, p. 358-367Article in journal (Refereed)
    Abstract [en]

    In the past few years, we have witnessed the proliferation of a heterogeneous ecosystem of cloud providers, each one with a different infrastructure offer and pricing policy. We explore this heterogeneity in a novel cloud brokering approach that optimizes placement of virtual infrastructures across multiple clouds and also abstracts the deployment and management of infrastructure components in these clouds. The feasibility of our approach is evaluated in a high throughput computing cluster case study. Experimental results confirm that multi-cloud deployment provides better performance and lower costs compared to the usage of a single cloud only. 

  • 1694.
    Tornblad, Rickard
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Carlsson, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    En riktig jul i iPhoneIndependent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    iPhone belongs to the group smartphones. It is a type of mobile phones that has a richer interface and allows more advanced preformences, i.e surfing the Internet and handling e-mails. This report outlines the work to develop an iPhoneapplication from idea to released product. The project is a thesis which was commissioned by ICA AB (a major Swedish grocery chain). The report includes how the work has been carried out in practice and theory. The finished application is part of ICA’s Christmas campaign at Christmas 2009. The report can be viewed as a case study on how to proceed in developing a mobileapplication for marketing purposes.

  • 1695.
    Torstensson, Jonas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Android Security: An evaluation of applications in Google Play2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis examines security issues that might occur in the applications from Google Play. It examines vulnerabilities by an evaluation of how well the policies and guidelines of the store transfers to the applications.

    After a short literature study about android and security. The polices and guidelines of Google Play is examined. Experiments with 10 of Google Plays top listed applications are conducted. Then a simple pen test explores how this may affect the security in the user’s phones. Lastly the result is discussed in respect to guide lines and policies and Google Play.

  • 1696. Tran, Son N.
    et al.
    Nguyen, Dung
    Ngo, Tung-Son
    Vu, Xuan-Son
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hoang, Long
    Zhang, Qing
    Karunanithi, Mohan
    On multi-resident activity recognition in ambient smart-homes2019In: Artificial Intelligence Review, ISSN 0269-2821, E-ISSN 1573-7462Article in journal (Refereed)
    Abstract [en]

    Increasing attention to the research on activity monitoring in smart homes has motivated the employment of ambient intelligence to reduce the deployment cost and solve the privacy issue. Several approaches have been proposed for multi-resident activity recognition, however, there still lacks a comprehensive benchmark for future research and practical selection of models. In this paper, we study different methods for multi-resident activity recognition and evaluate them on the same sets of data. In particular, we explore the effectiveness and efficiency of temporal learning algorithms using sequential data and non-temporal learning algorithms using temporally-manipulated features. In the experiments we compare and analyse the results of the studied methods using datasets from three smart homes.

  • 1697.
    Tran, Son N.
    et al.
    The Australian E-Health Research Centre, CSIRO, Brisbane, QLD 4026, Australia.
    Zhang, Qing
    Nguyen, Anthony
    Vu, Xuan-Son
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Ngo, Son
    Improving Recurrent Neural Networks with Predictive Propagation for Sequence Labelling2018In: Neural Information Processing: 25th International Conference, ICONIP 2018, Siem Reap, Cambodia, December 13-16, 2018, Proceedings, Part I, Springer, 2018, p. 452-462Conference paper (Refereed)
    Abstract [en]

    Recurrent neural networks (RNNs) is a useful tool for sequence labelling tasks in natural language processing. Although in practice RNNs suffer a problem of vanishing/exploding gradient, their compactness still offers efficiency and make them less prone to overfitting. In this paper we show that by propagating the prediction of previous labels we can improve the performance of RNNs while keeping the number of parameters in RNNs unchanged and adding only one more step for inference. As a result, the models are still more compact and efficient than other models with complex memory gates. In the experiment, we evaluate the idea on optical character recognition and Chunking which achieve promising results.

  • 1698. Tärneberg, William
    et al.
    Mehta, Amardeep
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Wadbro, Eddie
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Eker, Johan
    Kihl, Maria
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Dynamic application placement in the Mobile Cloud Network2017In: Future generations computer systems, ISSN 0167-739X, E-ISSN 1872-7115, Vol. 70, p. 163-177Article in journal (Refereed)
    Abstract [en]

    To meet the challenges of consistent performance, low communication latency, and a high degree of user mobility, cloud and Telecom infrastructure vendors and operators foresee a Mobile Cloud Network that incorporates public cloud infrastructures with cloud augmented Telecom nodes in forthcoming mobile access networks. A Mobile Cloud Network is composed of distributed cost- and capacityheterogeneous resources that host applications that in turn are subject to a spatially and quantitatively rapidly changing demand. Such an infrastructure requires a holistic management approach that ensures that the resident applications’ performance requirements are met while sustainably supported by the underlying infrastructure. The contribution of this paper is three-fold. Firstly, this paper contributes with a model that captures the cost- and capacity-heterogeneity of a Mobile Cloud Network infrastructure. The model bridges the Mobile Edge Computing and Distributed Cloud paradigms by modelling multiple tiers of resources across the network and serves not just mobile devices but any client beyond and within the network. A set of resource management challenges is presented based on this model. Secondly, an algorithm that holistically and optimally solves these challenges is proposed. The algorithm is formulated as an application placement method that incorporates aspects of network link capacity, desired user latency and user mobility, as well as data centre resource utilisation and server provisioning costs. Thirdly, to address scalability, a tractable locally optimal algorithm is presented. The evaluation demonstrates that the placement algorithm significantly improves latency, resource utilisation skewness while minimising the operational cost of the system. Additionally, the proposed model and evaluation method demonstrate the viability of dynamic resource management of the Mobile Cloud Network and the need for accommodating rapidly mobile demand in a holistic manner.

  • 1699. Tärneberg, William
    et al.
    Papadopoulos, Alessandro V.
    Mehta, Amardeep
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kihl, Maria
    Distributed Approach to the Holistic Resource Management of a Mobile Cloud Network2017In: 2017 IEEE 1st International Conference on Fog and Edge Computing (ICFEC), 2017, p. 51-60Conference paper (Refereed)
    Abstract [en]

    The Mobile Cloud Network is an emerging cost and capacity heterogeneous distributed cloud topological paradigm that aims to remedy the application performance constraints imposed by centralised cloud infrastructures. A centralised cloud infrastructure and the adjoining Telecom network will struggle to accommodate the exploding amount of traffic generated by forthcoming highly interactive applications. Cost effectively managing a Mobile Cloud Network computing infrastructure while meeting individual application's performance goals is non-trivial and is at the core of our contribution. Due to the scale of a Mobile Cloud Network, a centralised approach is infeasible. Therefore, in this paper a distributed algorithm that addresses these challenges is presented. The presented approach works towards meeting individual application's performance objectives, constricting system-wide operational cost, and mitigating resource usage skewness. The presented distributed algorithm does so by iteratively and independently acting on the objectives of each component with a common heuristic objective function. Systematic evaluations reveal that the presented algorithm quickly converges and performs near optimal in terms of system-wide operational cost and application performance, and significantly outperforms similar naïve and random methods.

  • 1700.
    Tångrot, Jeanette
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Structural Information and Hidden Markov Models for Biological Sequence Analysis2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Bioinformatics is a fast-developing field, which makes use of computational methods to analyse and structure biological data. An important branch of bioinformatics is structure and function prediction of proteins, which is often based on finding relationships to already characterized proteins. It is known that two proteins with very similar sequences also share the same 3D structure. However, there are many proteins with similar structures that have no clear sequence similarity, which make it difficult to find these relationships.

    In this thesis, two methods for annotating protein domains are presented, one aiming at assigning the correct domain family or families to a protein sequence, and the other aiming at fold recognition. Both methods use hidden Markov models (HMMs) to find related proteins, and they both exploit the fact that structure is more conserved than sequence, but in two different ways.

    Most of the research presented in the thesis focuses on the structure-anchored HMMs, saHMMs. For each domain family, an saHMM is constructed from a multiple structure alignment of carefully selected representative domains, the saHMM-members. These saHMM-members are collected in the so called "midnight ASTRAL set", and are chosen so that all saHMM-members within the same family have mutual sequence identities below a threshold of about 20%.

    In order to construct the midnight ASTRAL set and the saHMMs, a pipe-line of software tools are developed. The saHMMs are shown to be able to detect the correct family relationships at very high accuracy,

    and perform better than the standard tool Pfam in assigning the correct domain families to new domain sequences. We also introduce the FI-score, which is used to measure the performance of the saHMMs, in order to select the optimal model for each domain family.

    The saHMMs are made available for searching through the FISH server, and can be used for assigning family relationships to protein sequences.

    The other approach presented in the thesis is secondary structure HMMs (ssHMMs).

    These HMMs are designed to use both the sequence and the predicted secondary structure of a query protein when scoring it against the model.

    A rigorous benchmark is used, which shows that HMMs made from multiple sequences result in better fold recognition than those based on single sequences. Adding secondary structure information to the HMMs improves the ability of fold recognition further, both when using true and predicted secondary structures for the query sequence.

31323334353637 1651 - 1700 of 1860
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf