kth.sePublications
Change search
Refine search result
1234567 1 - 50 of 1220
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.
  • 1.
    Abbas, Zainab
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Software and Computer systems, SCS.
    Scalable Streaming Graph and Time Series Analysis Using Partitioning and Machine Learning2021Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Recent years have witnessed a massive increase in the amount of data generated by the Internet of Things (IoT) and social media. Processing huge amounts of this data poses non-trivial challenges in terms of the hardware and performance requirements of modern-day applications. The data we are dealing with today is of massive scale, high intensity and comes in various forms. MapReduce was a popular and clever choice of handling big data using a distributed programming model, which made the processing of huge volumes of data possible using clusters of commodity machines. However, MapReduce was not a good fit for performing complex tasks, such as graph processing, iterative programs and machine learning. Modern data processing frameworks, that are being popularly used to process complex data and perform complex analysis tasks, overcome the shortcomings of MapReduce. Some of these popular frameworks include Apache Spark for batch and stream processing, Apache Flink for stream processing and Tensor Flow for machine learning.

    In this thesis, we deal with complex analytics on data modeled as time series, graphs and streams. Time series are commonly used to represent temporal data generated by IoT sensors. Analysing and forecasting time series, i.e. extracting useful characteristics and statistics of data and predicting data, is useful for many fields that include, neuro-physiology, economics, environmental studies, transportation, etc. Another useful data representation we work with, are graphs. Graphs are complex data structures used to represent relational data in the form of vertices and edges. Graphs are present in various application domains, such as recommendation systems, road traffic analytics, web analysis, social media analysis. Due to the increasing size of graph data, a single machine is often not sufficient to process the complete graph. Therefore, the computation, as well as the data, must be distributed. Graph partitioning, the process of dividing graphs into subgraphs, is an essential step in distributed graph processing of large scale graphs because it enables parallel and distributed processing.

    The majority of data generated from IoT and social media originates as a continuous stream, such as series of events from a social media network, time series generated from sensors, financial transactions, etc. The stream processing paradigm refers to the processing of data streaming that is continuous and possibly unbounded. Combining both graphs and streams leads to an interesting and rather challenging domain of streaming graph analytics. Graph streams refer to data that is modelled as a stream of edges or vertices with adjacency lists representing relations between entities of continuously evolving data generated by a single or multiple data sources. Streaming graph analytics is an emerging research field with great potential due to its capabilities of processing large graph streams with limited amounts of memory and low latency. 

    In this dissertation, we present graph partitioning techniques for scalable streaming graph and time series analysis. First, we present and evaluate the use of data partitioning to enable data parallelism in order to address the challenge of scale in large spatial time series forecasting. We propose a graph partitioning technique for large scale spatial time series forecasting of road traffic as a use-case. Our experimental results on traffic density prediction for real-world sensor dataset using Long Short-Term Memory Neural Networks show that the partitioning-based models take 12x lower training time when run in parallel compared to the unpartitioned model of the entire road infrastructure. Furthermore, the partitioning-based models have 2x lower prediction error (RMSE) compared to the entire road model. Second, we showcase the practical usefulness of streaming graph analytics for large spatial time series analysis with the real-world task of traffic jam detection and reduction. We propose to apply streaming graph analytics by performing useful analytics on traffic data stream at scale with high throughput and low latency. Third, we study, evaluate, and compare the existing state-of-the-art streaming graph partitioning algorithms. We propose a uniform analysis framework built using Apache Flink to evaluate and compare partitioning features and characteristics of streaming graph partitioning methods. Finally, we present GCNSplit, a novel ML-driven streaming graph partitioning solution, that uses a small and constant in-memory state (bounded state) to partition (possibly unbounded) graph streams. Our results demonstrate that \ours provides high-throughput partitioning and can leverage data parallelism to sustain input rates of 100K edges/s. GCNSplit exhibits a partitioning quality, in terms of graph cuts and load balance, that matches that of the state-of-the-art HDRF (High Degree Replicated First) algorithm while storing three orders of magnitude smaller partitioning state.

    Download full text (pdf)
    fulltext
  • 2.
    Abdullah, Nazri
    et al.
    Universiti Tun Hussien Onn Malaysia, Malaysia .
    Kounelis, Ioannis
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Muftic, Sead
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Security Extensions for Mobile Commerce Objects2014In: SECURWARE 2014, The Eighth International Conference on Emerging Security Information, Systems and Technologies, 2014Conference paper (Refereed)
    Abstract [en]

    Electronic commerce and its variance mobile commerce have tremendously increased their popularity in the last several years. As mobile devices have become the most popular mean to access and use the Internet, mobile commerce and its security are timely and very hot topics. Yet, today there is still no consistent model of various m–commerce applications and transactions, even less clear specification of their security. In order to address and solve those issues, in this paper, we first establish the concept of mobile commerce objects, an equivalent of virtual currencies, used for m–commerce transactions. We describe functionalities and unique characteristics of these objects; we follow with security requirements, and then offer some solutions – security extensions of these objects. All solutions are treated within the complete lifecycle of creation and use of the m–commerce objects.

  • 3. Abouelhoda, Mohamed
    et al.
    Issa, Shady
    Center for Informatics Sciences, Nile University, Giza, Egypt.
    Ghanem, Moustafa
    Tavaxy: integrating Taverna and Galaxy workflows with cloud computing support.2012In: BMC Bioinformatics, E-ISSN 1471-2105, Vol. 13Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Over the past decade the workflow system paradigm has evolved as an efficient and user-friendly approach for developing complex bioinformatics applications. Two popular workflow systems that have gained acceptance by the bioinformatics community are Taverna and Galaxy. Each system has a large user-base and supports an ever-growing repository of application workflows. However, workflows developed for one system cannot be imported and executed easily on the other. The lack of interoperability is due to differences in the models of computation, workflow languages, and architectures of both systems. This lack of interoperability limits sharing of workflows between the user communities and leads to duplication of development efforts.

    RESULTS: In this paper, we present Tavaxy, a stand-alone system for creating and executing workflows based on using an extensible set of re-usable workflow patterns. Tavaxy offers a set of new features that simplify and enhance the development of sequence analysis applications: It allows the integration of existing Taverna and Galaxy workflows in a single environment, and supports the use of cloud computing capabilities. The integration of existing Taverna and Galaxy workflows is supported seamlessly at both run-time and design-time levels, based on the concepts of hierarchical workflows and workflow patterns. The use of cloud computing in Tavaxy is flexible, where the users can either instantiate the whole system on the cloud, or delegate the execution of certain sub-workflows to the cloud infrastructure.

    CONCLUSIONS: Tavaxy reduces the workflow development cycle by introducing the use of workflow patterns to simplify workflow creation. It enables the re-use and integration of existing (sub-) workflows from Taverna and Galaxy, and allows the creation of hybrid workflows. Its additional features exploit recent advances in high performance cloud computing to cope with the increasing data size and complexity of analysis.The system can be accessed either through a cloud-enabled web-interface or downloaded and installed to run within the user's local environment. All resources related to Tavaxy are available at http://www.tavaxy.org.

  • 4.
    Abourraja, Mohamed Nezar
    KTH.
    Gestion multi-agents d’un terminal à conteneurs2018Other (Other academic)
  • 5.
    Abourraja, Mohamed Nezar
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Health Informatics and Logistics.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Meijer, Sebastiaan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Health Informatics and Logistics.
    Exploiting simulation model potential in investigating handling capacity of Ro-Ro terminals: The case study of Norvik seaport2022In: Simulation Modelling Practice and Theory, ISSN 1569-190X, Vol. 117, p. 102513-102513, article id 102513Article in journal (Refereed)
    Abstract [en]

    In this paper, the spotlight is directed towards studying the handling capacity of pure Ro-Ro terminals, especially the new terminal of Norvik port. To this end, a simulation model based on a distributed architecture is built to assess the handling capacity under different flow scenarios with a particular focus on the trailer flow and export-lorry flow the terminal can handle in terms of resource availability, trailer-dwell times and management rules. This helped to determine the number of resources required to evacuate smoothly the incoming flows and to identify where potential bottlenecks happen the most inside the terminal. The established model is verified then validated by experts to conduct properly the experiment study where the model is fed with empirical data provided by terminal authorities. This experiment showed that the terminal can handle flows of which trailers do not exceed 17% and the export fraction of lorries is at most 42%.

  • 6. Abourraja, Mohamed Nezar
    et al.
    Oudani, Mustapha
    Samiri, Mohamed Yassine
    Boudebous, Dalila
    El Fazziki, Abdelaziz
    Najib, Mehdi
    Bouain, Abdelhadi
    Rouky, Naoufal
    A multi-agent based simulation model for rail–rail transshipment: An engineering approach for gantry crane scheduling2017In: IEEE Access, E-ISSN 2169-3536, Vol. 5, p. 13142-13156Article in journal (Refereed)
    Abstract [en]

    Le Havre Port Authority is putting into service a multimodal hub terminal with massified hinterland links (trains and barges) in order to restrict the intensive use of roads, to achieve a more attractive massification share of hinterland transportation and to provide a river connection to its maritime terminals that do not currently have one. This paper focuses on the rail-rail transshipment yard of this new terminal. In the current organizational policy, this yard is divided into two equal operating areas, and, in each one, a crane is placed, and it is equipped with reach stackers to enable container moves across both operating areas. However, this policy causes poor scheduling of crane moves, because it gives rise to many crane interference situations. For the sake of minimizing the occurrence of these undesirable situations, this paper proposes a multi-agent simulation model including an improved strategy for crane scheduling. This strategy is inspired by the ant colony approach and it is governed by a new configuration for the rail yard's working area that eliminates the use of reach stackers. The proposed simulation model is based on two planner agents, to each of which a time-horizon planning is assigned. The simulation results show that the model developed here is very successful in significantly reducing unproductive times and moves (undesirable situations), and it outperforms other existing simulation models based on the current organizational policy.

  • 7.
    Abourraja, Mohamed Nezar
    et al.
    Normandie University, UNIHAVRE, 76600 Le Havre, France; Cadi Ayyad University of Marrakech, Morocco.
    Oudani, Mustapha
    International University of Rabat, Morocco.
    Samiri, Mohamed Yassine
    Normandie University, UNIHAVRE, 76600 Le Havre, France; Cadi Ayyad University of Marrakech, Morocco.
    Boukachour, Jaouad
    Normandie University, UNIHAVRE, 76600 Le Havre, France.
    Elfazziki, Abdelaziz
    Cadi Ayyad University of Marrakech, Morocco.
    Bouain, Abdelhadi
    Cadi Ayyad University of Marrakech, Morocco.
    Najib, Mehdi
    Private University of Marrakech, Morocco.
    An improving agent-based engineering strategy for minimizing unproductive situations of cranes in a rail–rail transshipment yard2018In: Simulation, ISSN 0037-5497, Vol. 94, no 8, p. 681-705Article in journal (Refereed)
    Abstract [en]

    Nowadays, seaports seek to achieve a better massification (massive transportation of containers) share of their hinterland transport by promoting rail and river connections in order to more rapidly evacuate increasing container traffic shipped by sea and to avoid landside congestion. The attractiveness of a seaport to shipping enterprises depends not only on its reliability and nautical qualities but also on its massified hinterland connection capacity. Contrary to what has been observed in Europe, the massification share of Le Havre seaport has stagnated in recent years. To overcome this situation, Le Havre Port Authority is putting into service a multimodal hub terminal linked only with massified modes. In this study, we focus on rail–rail transshipment of this new terminal, specifically on minimizing unproductive situations of cranes to improve crane productivity and to speed up freight train processing. To this end, an improving agent-based engineering strategy called the “crane anti-collision strategy” is proposed and tested using multi-method simulation software (Anylogic). In a numerical study, the simulation results reveal that our developed model is very satisfactory and outperforms other existing simulation models.

  • 8.
    Abtahi, Farhad
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Berndtsson, Andreas
    Abtahi, Shirin
    Seoane, Fernando
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical Engineering, Medical sensors, signals and systems.
    Development and preliminary evaluation of an Android based heart rate variability biofeedback system2014In: Engineering in Medicine and Biology Society (EMBC), 2014 36th Annual International Conference of the IEEE, IEEE conference proceedings, 2014, p. 3382-3385Conference paper (Refereed)
    Abstract [en]

    The reduced Heart Rate Variability (HRV) is believed to be associated with several diseases such as congestive heart failure, diabetes and chronic kidney diseases (CKD). In these cases, HRV biofeedback may be a potential intervention method to increase HRV which in turn is beneficial to these patients. In this work, a real-time Android biofeedback application based on a Bluetooth enabled ECG and thoracic electrical bioimpedance (respiration) measurement device has been developed. The system performance and usability have been evaluated in a brief study with eight healthy volunteers. The result demonstrates real-time performance of system and positive effects of biofeedback training session by increased HRV and reduced heart rate. Further development of the application and training protocol is ongoing to investigate duration of training session to find an optimum length and interval of biofeedback sessions to use in potential interventions.

  • 9. Adams, Sophie
    et al.
    Kuch, Declan
    Diamond, Lisa
    Fröhlich, Peter
    Henriksen, Ida-Marie
    Katzeff, Cecilia
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Strategic Sustainability Studies.
    Ryghaug, Marianne
    Yilmaz, Selin
    Social license to automate: A critical review of emerging approaches to electricity demand management2021In: Energy Research & Social Science, ISSN 2214-6296, E-ISSN 2214-6326, Vol. 80, no October, p. 102210-12, article id https://doi.org/10.1016/j.erss.20102210Article in journal (Refereed)
    Abstract [en]

     Electricity demand-side management (DSM) programs are becoming increasingly important to energy system managers in advanced industrialized countries, especially those with high renewable energy penetration. As energy user participation is paramount for their success but has proven to be difficult to obtain, we explore the usefulness of the ‘social license’ concept, originally developed in the mining sector, to refer to the process of creating acceptance in DSM programs aimed at managing or controlling household energy resources such EVs, batteries, and heating and cooling devices. We argue that analyzing the attainment or lack of ‘social license’ may be useful to energy policy-makers and researchers for understanding public concerns with not only supply-side energy resources, but also DSM. We do so by (1) drawing attention to potential frictions between demands for flexibility on the one hand and social practices and habits on the other; (2) attending to the ways that users’ engagement in DSM programs is influenced by their sense of control and agency, and their trust in program providers; and (3) exploring the ways that users may understand their stake in the energy system and may participate in programs as collectives rather than simply as individuals. We argue that a ‘social license to automate’ could not only describe a set of tools to manage participation in DSM projects, but rather assess the ways users effectively feel part of new energy systems designed to serve them. 

  • 10.
    Adriaens, Florian
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Theoretical Computer Science, TCS. HIIT, University of Helsinki Helsinki, Finland.
    Apers, Simon
    Université de Paris, CNRS, IRIF Paris, France.
    Testing Cluster Properties of Signed Graphs2023In: ACM Web Conference 2023: Proceedings of the World Wide Web Conference, WWW 2023, Association for Computing Machinery (ACM) , 2023, p. 49-59Conference paper (Refereed)
    Abstract [en]

    This work initiates the study of property testing in signed graphs, where every edge has either a positive or a negative sign. We show that there exist sublinear query and time algorithms for testing three key properties of signed graphs: balance (or 2-clusterability), clusterability and signed triangle freeness. We consider both the dense graph model, where one queries the adjacency matrix entries of a signed graph, and the bounded-degree model, where one queries for the neighbors of a node and the sign of the connecting edge. Our algorithms use a variety of tools from unsigned graph property testing, as well as reductions from one setting to the other. Our main technical contribution is a sublinear algorithm for testing clusterability in the bounded-degree model. This contrasts with the property of k-clusterability in unsigned graphs, which is not testable with a sublinear number of queries in the bounded-degree model. We experimentally evaluate the complexity and usefulness of several of our testers on real-life and synthetic datasets.

  • 11.
    Agelfors, Eva
    et al.
    KTH, Superseded Departments (pre-2005), Speech Transmission and Music Acoustics.
    Beskow, Jonas
    Dahlquist, M
    Granström, Björn
    Lundeberg, M
    Salvi, Giampiero
    Spens, K-E
    Öhman, Tobias
    Two methods for Visual Parameter Extraction in the Teleface Project1999In: Proceedings of Fonetik, Gothenburg, Sweden, 1999Conference paper (Other academic)
  • 12.
    Aguilar, Xavier
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Computational Science and Technology (CST). KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for High Performance Computing, PDC.
    Performance Monitoring, Analysis, and Real-Time Introspection on Large-Scale Parallel Systems2020Doctoral thesis, monograph (Other academic)
    Abstract [en]

    High-Performance Computing (HPC) has become an important scientific driver. A wide variety of research ranging for example from drug design to climate modelling is nowadays performed in HPC systems. Furthermore, the tremendous computer power of such HPC systems allows scientists to simulate problems that were unimaginable a few years ago. However, the continuous increase in size and complexity of HPC systems is turning the development of efficient parallel software into a difficult task. Therefore, the use of per- formance monitoring and analysis is a must in order to unveil inefficiencies in parallel software. Nevertheless, performance tools also face challenges as a result of the size of HPC systems, for example, coping with huge amounts of performance data generated.

    In this thesis, we propose a new model for performance characterisation of MPI applications that tackles the challenge of big performance data sets. Our approach uses Event Flow Graphs to balance the scalability of profiling techniques (generating performance reports with aggregated metrics) with the richness of information of tracing methods (generating files with sequences of time-stamped events). In other words, graphs allow to encode ordered se- quences of events without storing the whole sequence of such events, and therefore, they need much less memory and disk space, and are more scal- able. We demonstrate in this thesis how our Event Flow Graph model can be used as a trace compression method. Furthermore, we propose a method to automatically detect the structure of MPI applications using our Event Flow Graphs. This knowledge can afterwards be used to collect performance data in a smarter way, reducing for example the amount of redundant data collected. Finally, we demonstrate that our graphs can be used beyond trace compression and automatic analysis of performance data. We propose a new methodology to use Event Flow Graphs in the task of visual performance data exploration.

    In addition to the Event Flow Graph model, we also explore in this thesis the design and use of performance data introspection frameworks. Future HPC systems will be very dynamic environments providing extreme levels of parallelism, but with energy constraints, considerable resource sharing, and heterogeneous hardware. Thus, the use of real-time performance data to or- chestrate program execution in such a complex and dynamic environment will be a necessity. This thesis presents two different performance data introspec- tion frameworks that we have implemented. These introspection frameworks are easy to use, and provide performance data in real time with very low overhead. We demonstrate, among other things, how our approach can be used to reduce in real time the energy consumed by the system.

    The approaches proposed in this thesis have been validated in different HPC systems using multiple scientific kernels as well as real scientific applica- tions. The experiments show that our approaches in performance character- isation and performance data introspection are not intrusive at all, and can be a valuable contribution to help in the performance monitoring of future HPC systems.

    Download full text (pdf)
    fulltext
  • 13.
    Aguilar, Xavier
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Towards Scalable Performance Analysis of MPI Parallel Applications2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

      A considerably fraction of science discovery is nowadays relying on computer simulations. High Performance Computing  (HPC) provides scientists with the means to simulate processes ranging from climate modeling to protein folding. However, achieving good application performance and making an optimal use of HPC resources is a heroic task due to the complexity of parallel software. Therefore, performance tools  and runtime systems that help users to execute  applications in the most optimal way are of utmost importance in the landscape of HPC.  In this thesis, we explore different techniques to tackle the challenges of collecting, storing, and using  fine-grained performance data. First, we investigate the automatic use of real-time performance data in order to run applications in an optimal way. To that end, we present a prototype of an adaptive task-based runtime system that uses real-time performance data for task scheduling. This runtime system has a performance monitoring component that provides real-time access to the performance behavior of anapplication while it runs. The implementation of this monitoring component is presented and evaluated within this thesis. Secondly, we explore lossless compression approaches  for MPI monitoring. One of the main problems that  performance tools face is the huge amount of fine-grained data that can be generated from an instrumented application. Collecting fine-grained data from a program is the best method to uncover the root causes of performance bottlenecks, however, it is unfeasible with extremely parallel applications  or applications with long execution times. On the other hand, collecting coarse-grained data is scalable but  sometimes not enough to discern the root cause of a performance problem. Thus, we propose a new method for performance monitoring of MPI programs using event flow graphs. Event flow graphs  provide very low overhead in terms of execution time and  storage size, and can be used to reconstruct fine-grained trace files of application events ordered in time.

    Download full text (pdf)
    Licentiate Thesis
  • 14.
    Aguilar, Xavier
    et al.
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Fürlinger, Karl
    Ludwig-Maximilians-Universitat (LMU).
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    MPI Trace Compression Using Event Flow Graphs2014Conference paper (Refereed)
    Abstract [en]

    Understanding how parallel applications behave is crucial for using high-performance computing (HPC) resources efficiently. However, the task of performance analysis is becoming increasingly difficult due to the growing complexity of scientific codes and the size of machines. Even though many tools have been developed over the past years to help in this task, current approaches either only offer an overview of the application discarding temporal information, or they generate huge trace files that are often difficult to handle.

    In this paper we propose the use of event flow graphs for monitoring MPI applications, a new and different approach that balances the low overhead of profiling tools with the abundance of information available from tracers. Event flow graphs are captured with very low overhead, require orders of magnitude less storage than standard trace files, and can still recover the full sequence of events in the application. We test this new approach with the NERSC-8/Trinity Benchmark suite and achieve compression ratios up to 119x.

  • 15.
    Aguilar, Xavier
    et al.
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Fürlinger, Karl
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Visual MPI Performance Analysis using Event Flow Graphs2015In: Procedia Computer Science, E-ISSN 1877-0509, Vol. 51, p. 1353-1362Article in journal (Refereed)
    Abstract [en]

    Event flow graphs used in the context of performance monitoring combine the scalability and low overhead of profiling methods with lossless information recording of tracing tools. In other words, they capture statistics on the performance behavior of parallel applications while pre- serving the temporal ordering of events. Event flow graphs require significantly less storage than regular event traces and can still be used to recover the full ordered sequence of events performed by the application.  In this paper we explore the usage of event flow graphs in the context of visual performance analysis. We show that graphs can be used to quickly spot performance problems, helping to better understand the behavior of an application. We demonstrate our performance analysis approach with MiniFE, a mini-application that mimics the key performance aspects of finite- element applications in High Performance Computing (HPC).

    Download full text (pdf)
    xaguilar_iccs2015
  • 16.
    Aguilar, Xavier
    et al.
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Fürlinger, Karl
    Ludwig-Maximilians-Universität München.
    Online Performance Data Introspection with IPM2014In: Proceedings of the 15th IEEE International Conference on High Performance Computing and Communications (HPCC 2013), IEEE Computer Society, 2014, p. 728-734Conference paper (Refereed)
    Abstract [en]

    Exascale systems will be heterogeneous architectures with multiple levels of concurrency and energy constraints. In such a complex scenario, performance monitoring and runtime systems play a major role to obtain good application performance and scalability. Furthermore, online access to performance data becomes a necessity to decide how to schedule resources and orchestrate computational elements: processes, threads, tasks, etc. We present the Performance Introspection API, an extension of the IPM tool that provides online runtime access to performance data from an application while it runs. We describe its design and implementation and show its overhead on several test benchmarks. We also present a real test case using the Performance Introspection API in conjunction with processor frequency scaling to reduce power consumption.

    Download full text (pdf)
    fulltext
  • 17.
    Aguilar, Xavier
    et al.
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz). KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Schliephake, Michael
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz). KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Vahtras, Olav
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Gimenez, Judit
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz). KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Scalability analysis of Dalton, a molecular structure program2013In: Future generations computer systems, ISSN 0167-739X, E-ISSN 1872-7115, Vol. 29, no 8, p. 2197-2204Article in journal (Refereed)
    Abstract [en]

    Dalton is a molecular electronic structure program featuring common methods of computational chemistry that are based on pure quantum mechanics (QM) as well as hybrid quantum mechanics/molecular mechanics (QM/MM). It is specialized and has a leading position in calculation of molecular properties with a large world-wide user community (over 2000 licenses issued). In this paper, we present a performance characterization and optimization of Dalton. We also propose a solution to avoid the master/worker design of Dalton to become a performance bottleneck for larger process numbers. With these improvements we obtain speedups of 4x, increasing the parallel efficiency of the code and being able to run in it in a much bigger number of cores.

  • 18.
    Ahmadian, Amir M.
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Theoretical Computer Science, TCS.
    Balliu, Musard
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Theoretical Computer Science, TCS.
    Dynamic Policies Revisited2022In: Proceedings - 7th IEEE European Symposium on Security and Privacy, Euro S and P 2022, Institute of Electrical and Electronics Engineers (IEEE), 2022, p. 448-466Conference paper (Refereed)
    Abstract [en]

    Information flow control and dynamic policies is a difficult relationship yet to be fully understood. While dynamic policies are a natural choice in many real-world applications that downgrade and upgrade the sensitivity of information, understanding the meaning of security in this setting is challenging. In this paper we revisit the knowledge-based security conditions to reinstate a simple and intuitive security condition for dynamic policies: A program is secure if at any point during the execution the attacker's knowledge is in accordance with the active security policy at that execution point. Our key observation is the new notion of policy consistency to prevent policy changes whenever an attacker is already in possession of the information that the new policy intends to protect. We use this notion to study a range of realistic attackers including the perfect recall attacker, bounded attackers, and forgetful attackers, and their relationship. Importantly, our new security condition provides a clean connection between the dynamic policy and the underlying attacker model independently of the specific use case. We illustrate this by considering the different facets of dynamic policies in our framework. On the verification side, we design and implement DynCoVer, a tool for checking dynamic information-flow policies for Java programs via symbolic execution and SMT solving. Our verification operates by first extracting a graph of program dependencies and then visiting the graph to check dynamic policies for a range of attackers. We evaluate the effectiveness and efficiency of DyncoVeron a benchmark of use cases from the literature and designed by ourselves, as well as the case study of a social network. The results show that DynCoVer can analyze small but intricate programs indicating that it can help verify security-critical parts of Java applications. We release Dyncover publicly to support open science and encourage researchers to explore the topic further.

    Download full text (pdf)
    fulltext
  • 19.
    Ahmadpanah, Mohammad M.
    et al.
    Chalmers Univ Technol, Gothenburg, Sweden..
    Hedin, Daniel
    Chalmers Univ Technol, Gothenburg, Sweden.;Mälardalen Univ, Västerås, Sweden..
    Balliu, Musard
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Theoretical Computer Science, TCS.
    Olsson, Lars Eric
    Chalmers Univ Technol, Gothenburg, Sweden..
    Sabelfeld, Andrei
    Chalmers Univ Technol, Gothenburg, Sweden..
    SandTrap: Securing JavaScript-driven Trigger-Action Platforms2021In: Proceedings Of The 30Th USENIX Security Symposium, USENIX ASSOC , 2021, p. 2899-2916Conference paper (Refereed)
    Abstract [en]

    Trigger-Action Platforms (TAPs) seamlessly connect a wide variety of otherwise unconnected devices and services, ranging from IoT devices to cloud services and social networks. TAPs raise critical security and privacy concerns because a TAP is effectively a "person-in-the-middle" between trigger and action services. Third-party code, routinely deployed as "apps" on TAPs, further exacerbates these concerns. This paper focuses on JavaScript-driven TAPs. We show that the popular IFTTT and Zapier platforms and an open-source alternative Node-RED are susceptible to attacks ranging from exfiltrating data from unsuspecting users to taking over the entire platform. We report on the changes by the platforms in response to our findings and present an empirical study to assess the implications for Node-RED. Motivated by the need for a secure yet flexible way to integrate third-party JavaScript apps, we propose SandTrap, a novel JavaScript monitor that securely combines the Node.js vm module with fully structural proxy-based two-sided membranes to enforce fine-grained access control policies. To aid developers, SandTrap includes a policy generation mechanism. We instantiate SandTrap to IFTTT, Zapier, and Node-RED and illustrate on a set of benchmarks how SandTrap enforces a variety of policies while incurring a tolerable runtime overhead.

  • 20. Ahmed, J.
    et al.
    Johnsson, A.
    Yanggratoke, Rerngvit
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Networks.
    Ardelius, J.
    Flinta, C.
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Predicting SLA conformance for cluster-based services using distributed analytics2016In: Proceedings of the NOMS 2016 - 2016 IEEE/IFIP Network Operations and Management Symposium, IEEE conference proceedings, 2016, p. 848-852Conference paper (Refereed)
    Abstract [en]

    Service assurance for the telecom cloud is a challenging task and is continuously being addressed by academics and industry. One promising approach is to utilize machine learning to predict service quality in order to take early mitigation actions. In previous work we have shown how to predict service-level metrics, such as frame rate for a video application on the client side, from operational data gathered at the server side. This gives the service provider early indications on whether the platform can support the current load demand. This paper extends previous work by addressing scalability issues for cluster-based services. Operational data being generated in large volumes, from several sources, and at high velocity puts strain on computational and communication resources. We propose and evaluate a distributed machine learning system based on the Winnow algorithm to tackle scalability issues, and then compare the new distributed solution with the previously proposed centralized solution. We show that network overhead and computational execution time is substantially reduced while maintaining high prediction accuracy making it possible to achieve real-time service quality predictions in large systems.

  • 21.
    Ahmed, Tanvir Saif
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Computer and Electronic Engineering.
    Markovic, Bratislav
    KTH, School of Technology and Health (STH), Medical Engineering, Computer and Electronic Engineering.
    Distribuerade datalagringssystem för tjänsteleverantörer: Undersökning av olika användningsfall för distribuerade datalagringssystem2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this thesis, a study of three different uses cases has been made within the field of data storage, which are as following: Cold Storage, High Performance Storage and Virtual Machine Storage. The purpose of the survey is to give an overview of commercial distributed file systems and a deeper study of open source codes distributed file systems in order to find the most optimal solution for these use cases. Within the study, previous works concerning performance, data protection and costs were an-alyzed and compared in means to find different functionalities (snapshotting, multi-tenancy, data duplication and data replication) which distinguish modern distributed file systems. Both commercial and open distributed file systems were examined. A cost estimation for commercial and open distrib-uted file systems were made in means to find out the profitability for these two types of distributed file systems.After comparing and analyzing previous works, it was clear that the open source distributed file sys-tem Ceph was proper as a solution in accordance to the objectives that were set for High Performance Storage and Virtual Machine Storage. The cost estimation showed that it was more profitable to im-plement an open distributed file system. This study can be used as guidance to choose between different distributed file systems.

    Download full text (pdf)
    FULLTEXT99
  • 22.
    Aidi, Laili
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Markendahl, Jan
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS, Radio Systems Laboratory (RS Lab). KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Tollmar, Konrad
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Selvakumar, Ekambar
    KTH, School of Information and Communication Technology (ICT).
    Huang, Jin
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Blennerud, Greger
    Ericsson, Torshamnsgatan 48, S-16440, Sweden., Torshamnsgatan 48.
    Mobile music business models in Asia’s emerging markets2013In: 12th International Conference on Mobile Business, ICMB 2013, Association for Information Systems , 2013Conference paper (Refereed)
    Abstract [en]

    In the telecom business, there has been a heavy competition from Internet, media and handset vendors companies. These over-the-top (OTT) players offer compiling telecom services, cause a transformation in the telecom business ecosystem, and the most challenging services posed here are media services. China, India and Indonesia, as world’s emerging markets in Asia, are predicted to take the largest share in the global mobile traffic explosion by 2015. It is critical for mobile network operators (MNOs) in this region to explore strategy for mobile media services, as mobile broadband is likely preferred compared to fixed broadband. In this paper, we analyze and compare mobile music business models used in these markets and structure the relation models between the key actors, using Actors, Relations and Business Activities (ARA) model. We present the economic models that are emerging, and an insight of why and how these multitudes actors are betting on currently. We found that the MNOs generally have a much stronger position compared to their counterparts in the developed markets, and the personalization services, like ring-back tone, are still a huge success. The actors tend to deliver the services by their own, rather than to collaborate in a horizontal business setting.

  • 23. Akhmetova, D.
    et al.
    Kestor, G.
    Gioiosa, R.
    Markidis, Stefano
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    On the application task granularity and the interplay with the scheduling overhead in many-core shared memory systems2015In: Proceedings - IEEE International Conference on Cluster Computing, ICCC, IEEE , 2015, p. 428-437Conference paper (Refereed)
    Abstract [en]

    Task-based programming models are considered one of the most promising programming model approaches for exascale supercomputers because of their ability to dynamically react to changing conditions and reassign work to processing elements. One question, however, remains unsolved: what should the task granularity of task-based applications be? Fine-grained tasks offer more opportunities to balance the system and generally result in higher system utilization. However, they also induce in large scheduling overhead. The impact of scheduling overhead on coarse-grained tasks is lower, but large systems may result imbalanced and underutilized. In this work we propose a methodology to analyze the interplay between application task granularity and scheduling overhead. Our methodology is based on three main points: 1) a novel task algorithm that analyzes an application directed acyclic graph (DAG) and aggregates tasks, 2) a fast and precise emulator to analyze the application behavior on systems with up to 1,024 cores, 3) a comprehensive sensitivity analysis of application performance and scheduling overhead breakdown. Our results show that there is an optimal task granularity between 1.2x10^4 and 10x10^4 cycles for the representative schedulers. Moreover, our analysis indicates that a suitable scheduler for exascale task-based applications should employ a best-effort local scheduler and a sophisticated remote scheduler to move tasks across worker threads.

  • 24.
    Akhmetova, Dana
    et al.
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Iakymchuk, Roman
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Ekeberg, Örjan
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), Computational Science and Technology (CST).
    Performance study of multithreaded MPI and Openmp tasking in a large scientific code2017In: Proceedings - 2017 IEEE 31st International Parallel and Distributed Processing Symposium Workshops, IPDPSW 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 756-765, article id 7965119Conference paper (Refereed)
    Abstract [en]

    With a large variety and complexity of existing HPC machines and uncertainty regarding exact future Exascale hardware, it is not clear whether existing parallel scientific codes will perform well on future Exascale systems: they can be largely modified or even completely rewritten from scratch. Therefore, now it is important to ensure that software is ready for Exascale computing and will utilize all Exascale resources well. Many parallel programming models try to take into account all possible hardware features and nuances. However, the HPC community does not yet have a precise answer whether, for Exascale computing, there should be a natural evolution of existing models interoperable with each other or it should be a disruptive approach. Here, we focus on the first option, particularly on a practical assessment of how some parallel programming models can coexist with each other. This work describes two API combination scenarios on the example of iPIC3D [26], an implicit Particle-in-Cell code for space weather applications written in C++ and MPI plus OpenMP. The first scenario is to enable multiple OpenMP threads call MPI functions simultaneously, with no restrictions, using an MPI THREAD MULTIPLE thread safety level. The second scenario is to utilize the OpenMP tasking model on top of the first scenario. The paper reports a step-by-step methodology and experience with these API combinations in iPIC3D; provides the scaling tests for these implementations with up to 2048 physical cores; discusses occurred interoperability issues; and provides suggestions to programmers and scientists who may adopt these API combinations in their own codes.

    Download full text (pdf)
    fulltext
  • 25.
    Al-Atat, Ghina
    et al.
    IMDEA Networks Institute, Madrid, Spain.
    Fresa, Andrea
    IMDEA Networks Institute, Madrid, Spain.
    Behera, Adarsh Prasad
    IMDEA Networks Institute, Madrid, Spain.
    Moothedath, Vishnu Narayanan
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Gross, James
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Champati, Jaya Prakash
    IMDEA Networks Institute, Madrid, Spain.
    The Case for Hierarchical Deep Learning Inference at the Network Edge2023In: NetAISys 2023 - Proceedings of the 1st International Workshop on Networked AI Systems, Part of MobiSys 2023, Association for Computing Machinery (ACM) , 2023, p. 13-18Conference paper (Refereed)
    Abstract [en]

    Resource-constrained Edge Devices (EDs), e.g., IoT sensors and microcontroller units, are expected to make intelligent decisions using Deep Learning (DL) inference at the edge of the network. Toward this end, developing tinyML models is an area of active research - DL models with reduced computation and memory storage requirements - that can be embedded on these devices. However, tinyML models have lower inference accuracy. On a different front, DNN partitioning and inference offloading techniques were studied for distributed DL inference between EDs and Edge Servers (ESs). In this paper, we explore Hierarchical Inference (HI), a novel approach proposed in [19] for performing distributed DL inference at the edge. Under HI, for each data sample, an ED first uses a local algorithm (e.g., a tinyML model) for inference. Depending on the application, if the inference provided by the local algorithm is incorrect or further assistance is required from large DL models on edge or cloud, only then the ED offloads the data sample. At the outset, HI seems infeasible as the ED, in general, cannot know if the local inference is sufficient or not. Nevertheless, we present the feasibility of implementing HI for image classification applications. We demonstrate its benefits using quantitative analysis and show that HI provides a better trade-off between offloading cost, throughput, and inference accuracy compared to alternate approaches.

  • 26.
    Alexandru, Iordan
    et al.
    Norwegian University of Science and Technology Trondheim.
    Podobas, Artur
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Software and Computer Systems, SCS.
    Natvig, Lasse
    Norwegian University of Science and Technology Trondheim.
    Brorsson, Mats
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Software and Computer Systems, SCS.
    Investigating the Potential of Energy-savings Using a Fine-grained Task Based Programming Model on Multi-cores2011Conference paper (Refereed)
    Abstract [en]

    In this paper we study the relation between energy-efficiencyand parallel executions when implemented with a fine-grained task-centricprogramming model. Using a simulation framework comprised of an ar-chitectural simulator and a power and area estimation tool, we haveinvestigated the potential energy-savings when employing parallelism onmulti-cores system. In our experiments with 2 - 8 multi-cores systems,we employed frequency and voltage scaling in order to keep the relativeperformance of the systems constant and measured the energy-efficiencyusing the Energy-delay-product. Also, we compared the energy consump-tion of the parallel execution against the serial one. Our results showthat through judicious choice of load balancing parameters, significantimprovements of around 200 % in energy consumption can be acheived.

    Download full text (pdf)
    iordan-podobas-a4mmc-2011.pdf
  • 27.
    Alibakhshikenari, Mohammad
    et al.
    Univ Carlos III Madrid, Dept Signal Theory & Commun, Madrid 28911, Spain..
    Virdee, Bal S.
    London Metropolitan Univ, Ctr Commun Technol, Sch Comp & Digital Media, London N7 8DB, England..
    Benetatos, Harry
    London Metropolitan Univ, Ctr Commun Technol, Sch Comp & Digital Media, London N7 8DB, England..
    Ali, Esraa Mousa
    Amman Arab Univ, Fac Aviat Sci, Amman 11953, Jordan..
    Soruri, Mohammad
    Univ Birjand, Tech Fac Ferdows, Birjand 9717434765, Iran..
    Dalarsson, Mariana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Naser-Moghadasi, Mohammad
    Islamic Azad Univ, Dept Elect & Comp Engn, Sci & Res Branch, Tehran 1477893855, Iran..
    See, Chan Hwang
    Edinburgh Napier Univ, Sch Engn & Built Environm, 10 Colinton Rd, Edinburgh EH10 5DT, Midlothian, Scotland..
    Pietrenko-Dabrowska, Anna
    Gdansk Univ Technol, Fac Elect Telecommun & Informat, PL-80233 Gdansk, Poland..
    Koziel, Slawomir
    Gdansk Univ Technol, Fac Elect Telecommun & Informat, PL-80233 Gdansk, Poland.;Reykjavik Univ, Engn Optimizat & Modeling Ctr, IS-101 Reykjavik, Iceland..
    Szczepanski, Stanislaw
    Gdansk Univ Technol, Fac Elect Telecommun & Informat, PL-80233 Gdansk, Poland..
    Limiti, Ernesto
    Univ Roma Tor Vergata, Elect Engn Dept, Via Politecn 1, I-00133 Rome, Italy..
    An innovative antenna array with high inter element isolation for sub-6 GHz 5G MIMO communication systems2022In: Scientific Reports, E-ISSN 2045-2322, Vol. 12, no 1, article id 7907Article in journal (Refereed)
    Abstract [en]

    A novel technique is shown to improve the isolation between radiators in antenna arrays. The proposed technique suppresses the surface-wave propagation and reduces substrate loss thereby enhancing the overall performance of the array. This is achieved without affecting the antenna's footprint. The proposed approach is demonstrated on a four-element array for 5G MIMO applications. Each radiating element in the array is constituted from a 3 x 3 matrix of interconnected resonant elements. The technique involves (1) incorporating matching stubs within the resonant elements, (2) framing each of the four-radiating elements inside a dot-wall, and (3) defecting the ground plane with dielectric slots that are aligned under the dot-walls. Results show that with the proposed approach the impedance bandwidth of the array is increased by 58.82% and the improvement in the average isolation between antennas #1&2, #1&3, #1&4 are 8 dB, 14 dB, 16 dB, and 13 dB, respectively. Moreover, improvement in the antenna gain is 4.2% and the total radiation efficiency is 23.53%. These results confirm the efficacy of the technique. The agreement between the simulated and measured results is excellent. Furthermore, the manufacture of the antenna array using the proposed approach is relatively straightforward and cost effective.

  • 28. Almgren, M.
    et al.
    Andersson, P.
    Björkman, Gunnar
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Ekstedt, Mathias
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Hallberg, J.
    Nadjm-Tehrani, S.
    Westring, E.
    RICS-el: Building a national testbed for research and training on SCADA security (short paper)2019In: Lect. Notes Comput. Sci., Springer Nature , 2019, p. 219-225Conference paper (Refereed)
    Abstract [en]

    Trends show that cyber attacks targeting critical infrastructures are increasing, but security research for protecting such systems are challenging. There is a gap between the somewhat simplified models researchers at universities can sustain contra the complex systems at infrastructure owners that seldom can be used for direct research. There is also a lack of common datasets for research benchmarking. This paper presents a national experimental testbed for security research within supervisory control and data acquisition systems (SCADA), accessible for both research training and experiments. The virtualized testbed has been designed and implemented with both vendor experts and security researchers to balance the goals of realism with specific research needs. It includes a real SCADA product for energy management, a number of network zones, substation nodes, and a simulated power system. This environment enables creation of scenarios similar to real world utility scenarios, attack generation, development of defence mechanisms, and perhaps just as important: generating open datasets for comparative research evaluation.

  • 29.
    Al-Mousa, Mohammad
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport planning.
    Kordnejad, Behzad
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport planning.
    Capacity Allocation of Unmonitored Railway Yards2023In: TRA Lisbon 2022 Conference Proceedings Transport Research Arena (TRA Lisbon 2022),14th-17th November 2022, Lisboa, Portugal, Elsevier B.V. , 2023, p. 4041-4048Conference paper (Refereed)
    Abstract [en]

    The demand for railway service facilities in Europe has been rapidly increasing, prompting for more conflicts in capacity requests by railway undertakings. In Sweden, many of these facilities do not have any automatic monitoring possibilities and the infrastructure manager does not have accurate or real-time information about vehicles occupying the tracks. This introduces challenges in having efficient capacity utilization in such facilities. This paper proposes a framework for capacity allocation for facilities which are currently unmonitored in general and for railway yards in specific. The framework is proposed upon abessment of the feasibility of emerging technologies in monitoring railway service facilities, as well as evaluating the current capacity allocation process and the suitability of different pricing principles as a basis for a charging scheme for capacity reservation.

  • 30.
    Al-Shishtawy, Ahmad
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Self-Management for Large-Scale Distributed Systems2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Autonomic computing aims at making computing systems self-managing by using autonomic managers in order to reduce obstacles caused by management complexity. This thesis presents results of research on self-management for large-scale distributed systems. This research was motivated by the increasing complexity of computing systems and their management.

    In the first part, we present our platform, called Niche, for programming self-managing component-based distributed applications. In our work on Niche, we have faced and addressed the following four challenges in achieving self-management in a dynamic environment characterized by volatile resources and high churn: resource discovery, robust and efficient sensing and actuation, management bottleneck, and scale. We present results of our research on addressing the above challenges. Niche implements the autonomic computing architecture, proposed by IBM, in a fully decentralized way. Niche supports a network-transparent view of the system architecture simplifying the design of distributed self-management. Niche provides a concise and expressive API for self-management. The implementation of the platform relies on the scalability and robustness of structured overlay networks. We proceed by presenting a methodology for designing the management part of a distributed self-managing application. We define design steps that include partitioning of management functions and orchestration of multiple autonomic managers.

    In the second part, we discuss robustness of management and data consistency, which are necessary in a distributed system. Dealing with the effect of churn on management increases the complexity of the management logic and thus makes its development time consuming and error prone. We propose the abstraction of Robust Management Elements, which are able to heal themselves under continuous churn. Our approach is based on replicating a management element using finite state machine replication with a reconfigurable replica set. Our algorithm automates the reconfiguration (migration) of the replica set in order to tolerate continuous churn. For data consistency, we propose a majority-based distributed key-value store supporting multiple consistency levels that is based on a peer-to-peer network. The store enables the tradeoff between high availability and data consistency. Using majority allows avoiding potential drawbacks of a master-based consistency control, namely, a single-point of failure and a potential performance bottleneck.

    In the third part, we investigate self-management for Cloud-based storage systems with the focus on elasticity control using elements of control theory and machine learning. We have conducted research on a number of different designs of an elasticity controller, including a State-Space feedback controller and a controller that combines feedback and feedforward control. We describe our experience in designing an elasticity controller for a Cloud-based key-value store using state-space model that enables to trade-off performance for cost. We describe the steps in designing an elasticity controller. We continue by presenting the design and evaluation of ElastMan, an elasticity controller for Cloud-based elastic key-value stores that combines feedforward and feedback control.

    Download full text (pdf)
    AhmadAlShishtawy_PhDThesis
  • 31.
    Al-Shishtawy, Ahmad
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Software and Computer Systems, SCS.
    Fayyaz, Muhammad Asif
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Software and Computer Systems, SCS.
    Popov, Konstantin
    Swedish Institute of Computer Science (SICS), Kista, Sweden.
    Vlassov, Vladimir
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Software and Computer Systems, SCS.
    Achieving Robust Self-Management for Large-Scale Distributed Applications2010In: Self-Adaptive and Self-Organizing Systems (SASO), 2010 4th IEEE International Conference on: SASO 2010, IEEE Computer Society, 2010, p. 31-40Conference paper (Refereed)
    Abstract [sv]

    Achieving self-management can be challenging, particularly in dynamic environments with resource churn (joins/leaves/failures). Dealing with the effect of churn on management increases the complexity of the management logic and thus makes its development time consuming and error prone. We propose the abstraction of robust management elements (RMEs), which are able to heal themselves under continuous churn. Using RMEs allows the developer to separate the issue of dealing with the effect of churn on management from the management logic. This facilitates the development of robust management by making the developer focus on managing the application while relying on the platform to provide the robustness of management. RMEs can be implemented as fault-tolerant long-living services. We present a generic approach and an associated algorithm to achieve fault-tolerant long-living services. Our approach is based on replicating a service using finite state machine replication with a reconfigurable replica set. Our algorithm automates the reconfiguration (migration) of the replica set in order to tolerate continuous churn. The algorithm uses P2P replica placement schemes to place replicas and uses the P2P overlay to monitor them. The replicated state machine is extended to analyze monitoring data in order to decide on when and where to migrate. We describe how to use our approach to achieve robust management elements. We present a simulation-based evaluation of our approach which shows its feasibility.

  • 32.
    Al-Shishtawy, Ahmad
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Vlassov, Vladimir
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    ElastMan: Autonomic elasticity manager for cloud-based key-value stores2013In: HPDC 2013 - Proceedings of the 22nd ACM International Symposium on High-Performance Parallel and Distributed Computing, 2013, p. 115-116Conference paper (Refereed)
    Abstract [en]

    The increasing spread of elastic Cloud services, together with the pay-as-you-go pricing model of Cloud computing, has led to the need of an elasticity controller. The controller automatically resizes an elastic service in response to changes in workload, in order to meet Service Level Objectives (SLOs) at a reduced cost. However, variable performance of Cloud virtual machines and nonlinearities in Cloud services complicates the controller design. We present the design and evaluation of ElastMan, an elasticity controller for Cloud-based elastic key-value stores. ElastMan combines feedforward and feedback control. Feedforward control is used to respond to spikes in the workload by quickly resizing the service to meet SLOs at a minimal cost. Feedback control is used to correct modeling errors and to handle diurnal workload. We have implemented and evaluated ElastMan using the Voldemort key-value store running in a Cloud environment based on OpenStack. Our evaluation shows the feasibility and effectiveness of our approach to automation of Cloud service elasticity.

  • 33.
    Al-Shishtawy, Ahmad
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Vlassov, Vladimir
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    ElastMan: Autonomic Elasticity Manager for Cloud-Based Key-Value Stores2012Report (Other academic)
    Abstract [en]

    The increasing spread of elastic Cloud services, together with the pay-asyou-go pricing model of Cloud computing, has led to the need of an elasticity controller. The controller automatically resizes an elastic service, in response to changes in workload, in order to meet Service Level Objectives (SLOs) at a reduced cost. However, variable performance of Cloud virtual machines and nonlinearities in Cloud services, such as the diminishing reward of adding a service instance with increasing the scale, complicates the controller design. We present the design and evaluation of ElastMan, an elasticity controller for Cloud-based elastic key-value stores. ElastMan combines feedforward and feedback control. Feedforward control is used to respond to spikes in the workload by quickly resizing the service to meet SLOs at a minimal cost. Feedback control is used to correct modeling errors and to handle diurnal workload. To address nonlinearities, our design of ElastMan leverages the near-linear scalability of elastic Cloud services in order to build a scale-independent model of the service. Our design based on combining feedforward and feedback control allows to efficiently handle both diurnal and rapid changes in workload in order to meet SLOs at a minimal cost. Our evaluation shows the feasibility of our approach to automation of Cloud service elasticity.

    Download full text (pdf)
    fulltext
  • 34.
    Al-Shishtawy, Ahmad
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Vlassov, Vladimir
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    ElastMan: Elasticity manager for elastic key-value stores in the cloud2013In: Proceedings of the 2013 ACM Cloud and Autonomic Computing Conference, New York, NY, USA: Association for Computing Machinery (ACM), 2013, p. 7:1-7:10Conference paper (Refereed)
    Abstract [en]

    The increasing spread of elastic Cloud services, together with the pay-as-you-go pricing model of Cloud computing, has led to the need of an elasticity controller. The controller automatically resizes an elastic service in response to changes in workload, in order to meet Service Level Objectives (SLOs) at a reduced cost. However, variable performance of Cloud Virtual Machines and nonlinearities in Cloud services, such as the diminishing reward of adding a service instance with increasing the scale, complicates the controller design. We present the design and evaluation of ElastMan, an elasticity controller for Cloud-based elastic key-value stores. ElastMan combines feedforward and feedback control. Feedforward control is used to respond to spikes in the workload by quickly resizing the service to meet SLOs at a minimal cost. Feedback control is used to correct modeling errors and to handle diurnal workload. To address nonlinearities, our design of ElastMan leverages the near-linear scalability of elastic Cloud services in order to build a scale-independent model of the service. We have implemented and evaluated ElastMan using the Voldemort key-value store running in an OpenStack Cloud environment. Our evaluation shows the feasibility and effectiveness of our approach to automation of Cloud service elasticity.

  • 35.
    Altayo Gonzalez, u1dr0yqp
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Stathis, Dimitrios
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Hemani, Ahmed
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems.
    Synthesis of Predictable Global NoC by Abutment in Synchoros VLSI Design2021In: Proceedings - 2021 15th IEEE/ACM International Symposium on Networks-on-Chip, NOCS 2021, Association for Computing Machinery (ACM), 2021, p. 61-66Conference paper (Refereed)
    Abstract [en]

    Synchoros VLSI design style has been proposed as an alternative to the standard cell-based design style; the word synchoros is derived from the Greek word choros for space. Synchoricity discretises space with a virtual grid, the way synchronicity discretises time with clock ticks. SiLago (Silicon Lego) blocks are atomic synchoros building blocks like Lego bricks. SiLago blocks absorb all metal layer details, i.e., all wires, to enable composition by abutment of valid; valid in the sense of being technology design rules compliant, timing clean and OCV ruggedized. Effectively, composition by abutment eliminates logic and physical synthesis for the end user. Like Lego system, synchoricity does need a finite number of SiLago block types to cater to different types of designs. Global NoCs are important system level design components. In this paper, we show, how with a small library of SiLago blocks for global NoCs, it is possible to automatically synthesize arbitrary global NoCs of different types, dimensions, and topology. The synthesized global NoCs are not only valid VLSI designs, but their cost metrics (area, latency, and energy) are known with post-layout accuracy in linear time. We argue that this is essential to be able to do chip-level design space exploration. We show how the abstract timing model of such global NoC SiLago blocks can be built and used to analyse the timing of global NoC links with post layout accuracy and in linear time. We validate this claim by subjecting the same VLSI designs of global NoC to commercial EDA's static timing analysis and show that the abstract timing analysis enabled by synchoros VLSI design gives the same results as the commercial EDA tools.

  • 36.
    Alyoussef, Elyas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Health Informatics and Logistics.
    Kategorisering på uppfattningar om digitala hot på webbapplikationer: Med en studie som visar de ekonomiska konsekvenserna av cyberattacker2022Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis presents a categorization of conceptions about digital threats on web applications with a study showing the economic consequences of cyber-attacks. The aim of this thesis is to contribute to a scientific article, which can be valuable to the public, as well as for future work and employment.

    Constant comparison method was used to analyse aggregate perceptions. The results reveal several exciting findings for theory and practice, where perceptions of the cyber world were presented in order to understand more how others see cybersecurity today. It also shows significant variations among the participants' perceptions. This shows that information security, even if it is gradually developed, has a long way to go until it becomes an unbroken part of the business. 

    This study can also serve as a guide for the different perceptions of cyber-attacks as it provides an overview of the most relevant cyber-attacks today. This thesis was supplemented with a study that highlights the economic consequences of cyberattacks. In addition to this, the cyber-attack on Coop during the summer of 2021 was also studied. 

    Download full text (pdf)
    Elyas_Examensarbete
  • 37.
    Amighi, Afshin
    et al.
    University of Twente.
    de Carvalho Gomes, Pedro
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Gurov, Dilian
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Huisman, Marieke
    University of Twente.
    Provably Correct Control-Flow Graphs from Java Programs with Exceptions2012Report (Other academic)
    Abstract [en]

    We present an algorithm to extract flow graphs from Java bytecode, including exceptional control flows. We prove its correctness, meaning that the behavior of the extracted control-flow graph is a sound over-approximation of the behavior of the original program. Thus any safety property that holds for the extracted control-flow graph also holds for the original program. This makes control-flow graphs suitable for performing various static analyses, such as model checking.The extraction is performed in two phases. In the first phase the program is transformed into a BIR program, a stack-less intermediate representation of Java bytecode, from which the control-flow graph is extracted in the second phase. We use this intermediate format because it results in compact flow graphs, with provably correct exceptional control flow. To prove the correctness of the two-phase extraction, we also define an idealized extraction algorithm, whose correctness can be proven directly. Then we show that the behavior of the control-flow graph extracted via the intermediate representation is an over-approximation of the behavior of the directly extracted graphs, and thus of the original program. We implemented the indirect extraction as the CFGEx tool and performed several test-cases to show the efficiency of the algorithm.

    Download full text (pdf)
    fulltext
  • 38.
    Amighi, Afshin
    et al.
    University of Twente.
    de Carvalho Gomes, Pedro
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Gurov, Dilian
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Huisman, Marieke
    University of Twente.
    Sound Control-Flow Graph Extraction for Java Programs with Exceptions2012In: Software Engineering and Formal Methods: 10th International Conference, SEFM 2012, Thessaloniki, Greece, October 1-5, 2012. Proceedings, Springer Berlin/Heidelberg, 2012, p. 33-47Conference paper (Refereed)
    Abstract [en]

    We present an algorithm to extract control-flow graphs from Java bytecode, considering exceptional flows. We then establish its correctness: the behavior of the extracted graphs is shown to be a sound over-approximation of the behavior of the original programs. Thus, any temporal safety property that holds for the extracted control-flow graph also holds for the original program. This makes the extracted graphs suitable for performing various static analyses, in particular model checking. The extraction proceeds in two phases. First, we translate Java bytecode into BIR, a stack-less intermediate representation. The BIR transformation is developed as a module of Sawja, a novel static analysis framework for Java bytecode. Besides Sawja’s efficiency, the resulting intermediate representation is more compact than the original bytecode and provides an explicit representation of exceptions. These features make BIR a natural starting point for sound control-flow graph extraction. Next, we formally define the transformation from BIR to control-flow graphs, which (among other features) considers the propagation of uncaught exceptions within method calls. We prove the correctness of the two-phase extraction by suitably combining the properties of the two transformations with those of an idealized control-flow graph extraction algorithm, whose correctness has been proved directly. The control-flow graph extraction algorithm is implemented in the ConFlEx tool. A number of test-cases show the efficiency and the utility of the implementation.

  • 39.
    Amor, Christian
    et al.
    Univ Politecn Madrid, Sch Aerosp Engn, E-28040 Madrid, Spain..
    Perez, Jose M.
    Univ Politecn Madrid, Sch Aerosp Engn, E-28040 Madrid, Spain..
    Schlatter, Philipp
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Vinuesa, Ricardo
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Le Clainche, Soledad
    Univ Politecn Madrid, Sch Aerosp Engn, E-28040 Madrid, Spain..
    Soft Computing Techniques to Analyze the Turbulent Wake of a Wall-Mounted Square Cylinder2020In: 14th International Conference on Soft Computing Models in Industrial and Environmental Applications, SOCO 2019 / [ed] Alvarez, FM Lora, AT Munoz, JAS Quintian, H Corchado, E, Springer, 2020, Vol. 950, p. 577-586Conference paper (Refereed)
    Abstract [en]

    This paper introduces several methods, generally used in fluid dynamics, to provide low-rank approximations. The algorithm describing these methods are mainly based on singular value decomposition (SVD) and dynamic mode decomposition (DMD) techniques, and are suitable to analyze turbulent flows. The application of these methods will be illustrated in the analysis of the turbulent wake of a wall-mounted cylinder, a geometry modeling a skyscraper. A brief discussion about the large and small size structures of the flow will provide the key ideas to represent the general dynamics of the flow using low-rank approximations. If the flow physics is understood, then it is possible to adapt these techniques, or some other strategies, to solve general complex problems with reduced computational cost. The main goal is to introduce these methods as machine learning strategies that could be potentially used in the field of fluid dynamics, and that can be extended to any other research field.

  • 40.
    Amorebieta, Josu
    et al.
    Univ Basque Country, UPV EHU, Dept Commun Engn, Bilbao 48013, Spain..
    Pereira, Joao
    RISE Res Inst Sweden, Fiber Opt, S-16440 Stockholm, Sweden..
    Durana, Gaizka
    Univ Basque Country, UPV EHU, Dept Commun Engn, Bilbao 48013, Spain..
    Franciscangelis, Carolina
    RISE Res Inst Sweden, Fiber Opt, S-16440 Stockholm, Sweden..
    Ortega-Gomez, Angel
    Univ Basque Country, UPV EHU, Dept Commun Engn, Bilbao 48013, Spain..
    Zubia, Joseba
    Univ Basque Country, UPV EHU, Dept Commun Engn, Bilbao 48013, Spain..
    Villatoro, Joel
    Univ Basque Country, UPV EHU, Dept Commun Engn, Bilbao 48013, Spain.;Basque Fdn Sci, Ikerbasque, Bilbao 48011, Spain..
    Margulis, Walter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics. RISE Res Inst Sweden, Fiber Opt, S-16440 Stockholm.
    Twin-core fiber sensor integrated in laser cavity2022In: Scientific Reports, E-ISSN 2045-2322, Vol. 12, no 1, article id 11797Article in journal (Refereed)
    Abstract [en]

    In this work, we report on a twin-core fiber sensor system that provides improved spectral efficiency, allows for multiplexing and gives low level of crosstalk. Pieces of the referred strongly coupled multicore fiber are used as sensors in a laser cavity incorporating a pulsed semiconductor optical amplifier (SOA). Each sensor has its unique cavity length and can be addressed individually by electrically matching the periodic gating of the SOA to the sensor's cavity roundtrip time. The interrogator acts as a laser and provides a narrow spectrum with high signal-to-noise ratio. Furthermore, it allows distinguishing the response of individual sensors even in the case of overlapping spectra. Potentially, the number of interrogated sensors can be increased significantly, which is an appealing feature for multipoint sensing.

  • 41.
    Anderson, Thomas
    et al.
    University of Washington.
    Canini, Marco
    KAUST.
    Kim, Jongyul
    KAIST.
    Kostic, Dejan
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Kwon, Youngjin
    KAIST.
    Peter, Simon
    The University of Texas at Austin.
    Reda, Waleed
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Schuh, Henry
    University of Washington.
    Witchel, Emmett
    The University of Texas at Austin.
    Assise: Performance and Availability via Client-local NVM in a Distributed File System2020In: / [ed] USENIX Association, USENIX - The Advanced Computing Systems Association, 2020, p. 1011--1027Conference paper (Refereed)
    Abstract [en]

    The adoption of low latency persistent memory modules (PMMs) upends the long-established model of remote storage for distributed file systems. Instead, by colocating computation with PMM storage, we can provide applications with much higher IO performance, sub-second application failover, and strong consistency. To demonstrate this, we built the Assise distributed file system, based on a persistent, replicated coherence protocol that manages client-local PMM as a linearizable and crash-recoverable cache between applications and slower (and possibly remote) storage. Assise maximizes locality for all file IO by carrying out IO on process-local, socket-local, and client-local PMM whenever possible. Assise minimizes coherence overhead by maintaining consistency at IO operation granularity, rather than at fixed block sizes.

    We compare Assise to Ceph/BlueStore, NFS, and Octopus on a cluster with Intel Optane DC PMMs and SSDs for common cloud applications and benchmarks, such as LevelDB, Postfix, and FileBench. We find that Assise improves write latency up to 22x, throughput up to 56x, fail-over time up to 103x, and scales up to 6x better than its counterparts, while providing stronger consistency semantics.

    Download full text (pdf)
    assise.pdf
  • 42.
    Andersson, Birger
    et al.
    KTH, School of Information and Communication Technology (ICT), Computer and Systems Sciences, DSV.
    Bergholtz, Maria
    KTH, School of Information and Communication Technology (ICT), Computer and Systems Sciences, DSV.
    Edirisuriya, A.
    Ilayperuma, T.
    Jayaweera, P.
    Johannesson, Paul
    KTH, School of Information and Communication Technology (ICT), Computer and Systems Sciences, DSV.
    Zdravkovic, Jelena
    KTH, School of Information and Communication Technology (ICT), Computer and Systems Sciences, DSV.
    Enterprise sustainability through the alignment of goal models and business models2008In: CEUR Workshop Proc., 2008, p. 73-87Conference paper (Refereed)
    Abstract [en]

    Business modelling can be used as a starting point for business analysis. The core of a business model is information about resources, events, agents, and their relations. The motivation of a business model can be found in the goals of an enterprise and those are made explicit in a goal model. This paper discusses the alignment of business models with goal models and proposes a method for constructing business models based on goal models. The method assists in the design of business models that conform to the explicit goals of an enterprise. Main benefits are clear and uniform goal formulations, well founded business model designs, and increased traceability between models.

  • 43.
    Andersson, Dan
    KTH, School of Technology and Health (STH), Data- och elektroteknik.
    Implementation av prototyp för inomhuspositionering2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Development of technology constantly creates new opportunities but it can also mean major chang-es for companies and organizations. Today phones, tablets, laptops, mobile communications and cloud technology make it possible to be no longer bound by the time, location or device in order to work. The change means that a new office type that is more flexible and space efficient due to no fixed workplaces, is becoming more common. A problem with this type of offices that are known as flex-offices is that it is not obvious where or when a colleague is in the office, especially if it is large office with multiple floors.

    The aim of this work is to develop and implement a Location-Based Service for the company Connecta AB. The service will enable users to use their mobile phone to share their current workplace location in an office environment.

    The result of this work is a Location-Based Service that enables a user to use an Android phone with support for Near Field Communcication to share their current workplace position. The cloud-based server solution, Windows Azure is used to store indexed workplace positions.

    Download full text (pdf)
    fulltext
  • 44. Antaris, Stefanos
    Link injection for boosting information spread in social networks2014In: Social Network Analysis and Mining, ISSN 1869-5450, E-ISSN 1869-5469, Vol. 4, no 1, article id 236Article in journal (Refereed)
    Download full text (pdf)
    fulltext
  • 45.
    Antaris, Stefanos
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Software and Computer systems, SCS. Hive Streaming AB, Stockholm, Sweden..
    Rafailidis, Dimitrios
    Univ Thessaly, Volos, Greece..
    Girdzijauskas, Sarunas
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Software and Computer systems, SCS.
    A Deep Graph Reinforcement Learning Model for Improving User Experience in Live Video Streaming2021In: 2021 IEEE INTERNATIONAL CONFERENCE ON BIG DATA (BIG DATA) / [ed] Chen, Y Ludwig, H Tu, Y Fayyad, U Zhu, X Hu, X Byna, S Liu, X Zhang, J Pan, S Papalexakis, V Wang, J Cuzzocrea, A Ordonez, C, Institute of Electrical and Electronics Engineers (IEEE) , 2021, p. 1787-1796Conference paper (Refereed)
    Abstract [en]

    In this paper we present a deep graph reinforcement learning model to predict and improve the user experience during a live video streaming event, orchestrated by an agent/tracker. We first formulate the user experience prediction problem as a classification task, accounting for the fact that most of the viewers at the beginning of an event have poor quality of experience due to low-bandwidth connections and limited interactions with the tracker. In our model we consider different factors that influence the quality of user experience and train the proposed model on diverse state-action transitions when viewers interact with the tracker. In addition, provided that past events have various user experience characteristics we follow a gradient boosting strategy to compute a global model that learns from different events. Our experiments with three real-world datasets of live video streaming events demonstrate the superiority of the proposed model against several baseline strategies. Moreover, as the majority of the viewers at the beginning of an event has poor experience, we show that our model can significantly increase the number of viewers with high quality experience by at least 75% over the first streaming minutes. Our evaluation datasets and implementation are publicly available at https://publicresearch.z13.web.core.windows.net

  • 46.
    Antonova, Rika
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for Autonomous Systems, CAS. KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Robotics, Perception and Learning, RPL.
    Kokic, Mia
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for Autonomous Systems, CAS. KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Robotics, Perception and Learning, RPL.
    Stork, Johannes A.
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for Autonomous Systems, CAS. KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Robotics, Perception and Learning, RPL.
    Kragic, Danica
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for Autonomous Systems, CAS. KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Robotics, Perception and Learning, RPL.
    Global Search with Bernoulli Alternation Kernel for Task-oriented Grasping Informed by Simulation2018In: Proceedings of The 2nd Conference on Robot Learning, PMLR 87, 2018, p. 641-650Conference paper (Refereed)
    Abstract [en]

    We develop an approach that benefits from large simulated datasets and takes full advantage of the limited online data that is most relevant. We propose a variant of Bayesian optimization that alternates between using informed and uninformed kernels. With this Bernoulli Alternation Kernel we ensure that discrepancies between simulation and reality do not hinder adapting robot control policies online. The proposed approach is applied to a challenging real-world problem of task-oriented grasping with novel objects. Our further contribution is a neural network architecture and training pipeline that use experience from grasping objects in simulation to learn grasp stability scores. We learn task scores from a labeled dataset with a convolutional network, which is used to construct an informed kernel for our variant of Bayesian optimization. Experiments on an ABB Yumi robot with real sensor data demonstrate success of our approach, despite the challenge of fulfilling task requirements and high uncertainty over physical properties of objects.

    Download full text (pdf)
    fulltext
  • 47. Anzanpour, A.
    et al.
    Rahmani, Amir-Mohammad
    KTH, School of Information and Communication Technology (ICT), Industrial and Medical Electronics. University of Turku, Finland.
    Liljeberg, P.
    Tenhunen, Hannu
    KTH, School of Information and Communication Technology (ICT), Industrial and Medical Electronics. University of Turku, Finland.
    Context-aware early warning system for in-home healthcare using internet-of-things2016In: 2nd International Summit on Internet of Things, IoT 360° 2015, Springer, 2016, p. 517-522Conference paper (Refereed)
    Abstract [en]

    Early warning score (EWS) is a prediction method to notify caregivers at a hospital about the deterioration of a patient. Deterioration can be identified by detecting abnormalities in patient’s vital signs several hours prior the condition of the patient gets life-threatening. In the existing EWS systems, monitoring of patient’s vital signs and the determining the score is mostly performed in a paper and pen based way. Furthermore, currently it is done solely in a hospital environment. In this paper, we propose to import this system to patients’ home to provide an automated platform which not only monitors patents’ vital signs but also looks over his/her activities and the surrounding environment. Thanks to the Internet-of-Things technology, we present an intelligent early warning method to remotely monitor in-home patients and generate alerts in case of different medical emergencies or radical changes in condition of the patient. We also demonstrate an early warning score analysis system which continuously performs sensing, transferring, and recording vital signs, activity-related data, and environmental parameters.

  • 48.
    Apelkrans, Mats
    et al.
    Dept of Informatics, Jönköping International Business School.
    Håkansson, Anne
    Uppsala University, Sweden.
    Information Coordination Using Meta-agents in Information Logistics Processes2008In: Proceedings of Knowledge-Based and Intelligent Information & Engineering Systems: KES2008 / [ed] Ignac Lovrek, Robert J. Howlett, Lakhmi C. Jain, Berlin Heidelberg: Springer Berlin/Heidelberg, 2008, p. 788-798Conference paper (Refereed)
    Abstract [en]

    In order to coordinate and deliver information in the right time and to the right place, theories from multi-agent systems and information logistics are combined. We use agents to support supply chain by searching for company specific information. Hence, there are a vast number of agents working at the Internet, simultaneously, which requires supervising agents. In this paper, we suggest using meta-agents to control the behaviour of a number of intelligent agents, where the meta-agents are working with coordination of the communication that takes place in a supply chain system. As an example, we look at a manufacturing company receiving orders on items from customers, which need to be produced. The handling of this distributed information flow can be thought of as an Information Logistics Processes and the similarities of the functioning of processes and intelligent agents’ behaviour are illuminated.

  • 49.
    Arad, Cosmin
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Haridi, Seif
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Message-Passing Concurrency for Scalable, Stateful, Reconfigurable Middleware2012In: Middleware 2012: ACM/IFIP/USENIX 13th International Middleware Conference, Montreal, QC, Canada, December 3-7, 2012. Proceedings / [ed] Priya Narasimhan and Peter Triantafillou, Springer Berlin/Heidelberg, 2012, p. 208-228Conference paper (Refereed)
    Abstract [en]

    Message-passing concurrency (MPC) is increasingly being used to build systems software that scales well on multi-core hardware. Functional programming implementations of MPC, such as Erlang, have also leveraged their stateless nature to build middleware that is not just scalable, but also dynamically reconfigurable. However, many middleware platforms lend themselves more naturally to a stateful programming model, supporting session and application state. A limitation of existing programming models and frameworks that support dynamic reconfiguration for stateful middleware, such as component frameworks, is that they are not designed for MPC.

    In this paper, we present Kompics, a component model and programming framework, that supports the construction and composition of dynamically reconfigurable middleware using stateful, concurrent, message-passing components. An added benefit of our approach is that by decoupling our component execution model, we can run the same code in both simulation and production environments. We present the architectural patterns and abstractions that Kompics facilitates and we evaluate them using a case study of a non-trivial key-value store that we built using Kompics. We show how our model enables the systematic development and testing of scalable, dynamically reconfigurable middleware.

    Download full text (pdf)
    fulltext
  • 50.
    Arad, Cosmin Ionel
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Programming Model and Protocols for Reconfigurable Distributed Systems2013Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Distributed systems are everywhere. From large datacenters to mobile devices, an ever richer assortment of applications and services relies on distributed systems, infrastructure, and protocols. Despite their ubiquity, testing and debugging distributed systems remains notoriously hard. Moreover, aside from inherent design challenges posed by partial failure, concurrency, or asynchrony, there remain significant challenges in the implementation of distributed systems. These programming challenges stem from the increasing complexity of the concurrent activities and reactive behaviors in a distributed system on the one hand, and the need to effectively leverage the parallelism offered by modern multi-core hardware, on the other hand.

    This thesis contributes Kompics, a programming model designed to alleviate some of these challenges. Kompics is a component model and programming framework for building distributed systems by composing message-passing concurrent components. Systems built with Kompics leverage multi-core machines out of the box, and they can be dynamically reconfigured to support hot software upgrades. A simulation framework enables deterministic execution replay for debugging, testing, and reproducible behavior evaluation for largescale Kompics distributed systems. The same system code is used for both simulation and production deployment, greatly simplifying the system development, testing, and debugging cycle.

    We highlight the architectural patterns and abstractions facilitated by Kompics through a case study of a non-trivial distributed key-value storage system. CATS is a scalable, fault-tolerant, elastic, and self-managing key-value store which trades off service availability for guarantees of atomic data consistency and tolerance to network partitions. We present the composition architecture for the numerous protocols employed by the CATS system, as well as our methodology for testing the correctness of key CATS algorithms using the Kompics simulation framework.

    Results from a comprehensive performance evaluation attest that CATS achieves its claimed properties and delivers a level of performance competitive with similar systems which provide only weaker consistency guarantees. More importantly, this testifies that Kompics admits efficient system implementations. Its use as a teaching framework as well as its use for rapid prototyping, development, and evaluation of a myriad of scalable distributed systems, both within and outside our research group, confirm the practicality of Kompics.

    Download full text (pdf)
    fulltext
1234567 1 - 50 of 1220
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