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  • 1.
    Abdullah, Nazri
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Håkansson, Anne
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Moradian, E.
    Blockchain based approach to enhance big data authentication in distributed environment2017Inngår i: 2017 Ninth International Conference on Ubiquitous and Future Networks (ICUFN), IEEE Computer Society, 2017, s. 887-892Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Existing authentication protocols for Big Data system such as Apache Hadoop is based on Kerberos. In the Kerberos protocol, there are numerous security issues that have remained unsolved; replay attacks, DDoS and single point of failure are some examples. These indicate potential security vulnerabilities and Big Data risks in using Hadoop. This paper presents drawbacks of Kerberos implementations and identifies authentication requirements that can enhance the security of Big Data in distributed environments. The enhancement proposed is based on the rising technology of blockchain that overcomes shortcomings of Kerberos.

  • 2. Aldinucci, Marco
    et al.
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    D'Agostino, Daniele
    Daneshtalab, Masoud
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Elektronik och inbyggda system.
    Kilpatrick, Peter
    Leppanen, Ville
    Preface2017Inngår i: The international journal of high performance computing applications, ISSN 1094-3420, E-ISSN 1741-2846, Vol. 31, nr 3, s. 179-180Artikkel i tidsskrift (Fagfellevurdert)
  • 3.
    Al-Shishtawy, Ahmad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Self-Management for Large-Scale Distributed Systems2012Doktoravhandling, med artikler (Annet vitenskapelig)
    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.

  • 4.
    Al-Shishtawy, Ahmad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    ElastMan: Autonomic elasticity manager for cloud-based key-value stores2013Inngår i: HPDC 2013 - Proceedings of the 22nd ACM International Symposium on High-Performance Parallel and Distributed Computing, 2013, s. 115-116Konferansepaper (Fagfellevurdert)
    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.

  • 5.
    Al-Shishtawy, Ahmad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    ElastMan: Autonomic Elasticity Manager for Cloud-Based Key-Value Stores2012Rapport (Annet vitenskapelig)
    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.

  • 6.
    Al-Shishtawy, Ahmad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    ElastMan: Elasticity manager for elastic key-value stores in the cloud2013Inngår i: Proceedings of the 2013 ACM Cloud and Autonomic Computing Conference, New York, NY, USA: Association for Computing Machinery (ACM), 2013, s. 7:1-7:10Konferansepaper (Fagfellevurdert)
    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.

  • 7. Apolonia, N.
    et al.
    Freitag, F.
    Navarro, L.
    Girdzijauskas, Sarunas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Gossip-based service monitoring platform for wireless edge cloud computing2017Inngår i: Proceedings of the 2017 IEEE 14th International Conference on Networking, Sensing and Control, ICNSC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 789-794, artikkel-id 8000191Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Edge cloud computing proposes to support shared services, by using the infrastructure at the network's edge. An important problem is the monitoring and management of services across the edge environment. Therefore, dissemination and gathering of data is not straightforward, differing from the classic cloud infrastructure. In this paper, we consider the environment of community networks for edge cloud computing, in which the monitoring of cloud services is required. We propose a monitoring platform to collect near real-time data about the services offered in the community network using a gossip-enabled network. We analyze and apply this gossip-enabled network to perform service discovery and information sharing, enabling data dissemination among the community. We implemented our solution as a prototype and used it for collecting service monitoring data from the real operational community network cloud, as a feasible deployment of our solution. By means of emulation and simulation we analyze in different scenarios, the behavior of the gossip overlay solution, and obtain average results regarding information propagation and consistency needs, i.e. in high latency situations, data convergence occurs within minutes.

  • 8.
    Arad, Cosmin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Dowling, Jim
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Haridi, Seif
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Message-Passing Concurrency for Scalable, Stateful, Reconfigurable Middleware2012Inngår i: 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, s. 208-228Konferansepaper (Fagfellevurdert)
    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.

  • 9.
    Arad, Cosmin Ionel
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Programming Model and Protocols for Reconfigurable Distributed Systems2013Doktoravhandling, monografi (Annet vitenskapelig)
    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.

  • 10.
    Arad, Cosmin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Shafaat, Tallat Mahmood
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Haridi, Seif
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Brief announcement: Atomic consistency and partition tolerance in scalable key-value stores2012Inngår i: Distributed Computing: 26th International Symposium, DISC 2012, Salvador, Brazil, October 16-18, 2012. Proceedings / [ed] Marcos K. Aguilera, Springer, 2012, s. 445-446Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose consistent quorums to achieve linearizability in scalable and self-organizing key-value stores based on consistent hashing.

  • 11.
    Ardelius, John
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    On the Performance Analysis of Large Scale, Dynamic, Distributed and Parallel Systems.2013Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Evaluating the performance of large distributed applications is an important and non-trivial task. With the onset of Internet wide applications there is an increasing need to quantify reliability, dependability and performance of these systems, both as a guide in system design as well as a means to understand the fundamental properties of large-scale distributed systems. Previous research has mainly focused on either formalised models where system properties can be deduced and verified using rigorous mathematics or on measurements and experiments on deployed applications. Our aim in this thesis is to study models on an abstraction level lying between the two ends of this spectrum. We adopt a model of distributed systems inspired by methods used in the study of large scale system of particles in physics and model the application nodes as a set of interacting particles each with an internal state whose actions are specified by the application program. We apply our modeling and performance evaluation methodology to four different distributed and parallel systems. The first system is the distributed hash table (DHT) Chord running in a dynamic environment.  We study the system under two scenarios. First we study how performance (in terms of lookup latency) is affectedon a network with finite communication latency. We show that an average delay in conjunction with other parameters describing changes in the network (such as timescales for network repair and join and leave processes)induces fundamentally different system performance. We also verify our analytical predictions via simulations.In the second scenario we introduce network address translators (NATs) to the network model. This makes the overlay topology non-transitive and we explore the implications of this fact to various performance metrics such as lookup latency, consistency and load balance. The latter analysis is mainly simulation based.Even though these two studies focus on a specific DHT, many of our results can easily be translated to other similar ring-based DHTs with long-range links, and the same methodology can be applied evento DHT's based on other geometries.The second type of system studied is an unstructured gossip protocol running a distributed version of the famous Belman-Ford algorithm. The algorithm, called GAP, generates a spanning tree over the participating nodes and the question we set out to study is how reliable this structure is(in terms of generating accurate aggregate values at the root)  in the presence of node churn. All our analytical results are also verified  using simulations.The third system studied is a content distribution network (CDN) of interconnected caches in an aggregation access network. In this model, content which sits at the leaves of the cache hierarchy tree, is requested by end users. Requests can then either be served by the first cache level or sent further up the tree. We study the performance of the whole system under two cache eviction policies namely LRU and LFU. We compare our analytical results with traces from related caching systems.The last system is a work stealing heuristic for task distribution in the TileraPro64 chip. This system has access to a shared memory and is therefore classified as a parallel system. We create a model for the dynamic generation of tasks as well as how they are executed and distributed among the participating nodes. We study how the heuristic scales when the number of nodes exceeds the number of processors on the chip as well as how different work stealing policies compare with each other. The work on this model is mainly simulation-based.

  • 12.
    Arman, Ala
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Al-Shishtawy, Ahmad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Elasticity controller for Cloud-based key-value stores2012Inngår i: Parallel and Distributed Systems (ICPADS), 2012 IEEE 18th International Conference on, IEEE , 2012, s. 268-275Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Clouds provide an illusion of an infinite amount of resources and enable elastic services and applications that are capable to scale up and down (grow and shrink by requesting and releasing resources) in response to changes in its environment, workload, and Quality of Service (QoS) requirements. Elasticity allows to achieve required QoS at a minimal cost in a Cloud environment with its pay-as-you-go pricing model. In this paper, we present our experience in designing a feedback elastically controller for a key-value store. The goal of our research is to investigate the feasibility of the control theoretic approach to the automation of elasticity of Cloud-based key-value stores. We describe design steps necessary to build a feedback controller for a real system, namely Voldemort, which we use as a case study in this work. The design steps include defining touchpoints (sensors and actuators), system identification, and controller design. We have designed, developed, and implemented a prototype of the feedback elasticity controller for Voldemort. Our initial evaluation results show the feasibility of using feedback control to automate elasticity of distributed keyvalue stores.

  • 13.
    Awan, Ahsan Javed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Accelerating Apache Spark with Fixed Function Hardware Accelerators Near DRAM and NVRAM2016Annet (Fagfellevurdert)
  • 14.
    Awan, Ahsan Javed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Performance Characterization and Optimization of In-Memory Data Analytics on a Scale-up Server2017Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    The sheer increase in the volume of data over the last decade has triggered research in cluster computing frameworks that enable web enterprises to extract big insights from big data. While Apache Spark defines the state of the art in big data analytics platforms for (i) exploiting data-flow and in-memory computing and (ii) for exhibiting superior scale-out performance on the commodity machines, little effort has been devoted to understanding the performance of in-memory data analytics with Spark on modern scale-up servers. This thesis characterizes the performance of in-memory data analytics with Spark on scale-up servers.Through empirical evaluation of representative benchmark workloads on a dual socket server, we have found that in-memory data analytics with Spark exhibit poor multi-core scalability beyond 12 cores due to thread level load imbalance and work-time inflation (the additional CPU time spent by threads in a multi-threaded computation beyond the CPU time required to perform the same work in a sequential computation). We have also found that workloads are bound by the latency of frequent data accesses to the memory. By enlarging input data size, application performance degrades significantly due to the substantial increase in wait time during I/O operations and garbage collection, despite 10% better instruction retirement rate (due to lower L1cache misses and higher core utilization).For data accesses, we have found that simultaneous multi-threading is effective in hiding the data latencies. We have also observed that (i) data locality on NUMA nodes can improve the performance by 10% on average,(ii) disabling next-line L1-D prefetchers can reduce the execution time by upto14%. For garbage collection impact, we match memory behavior with the garbage collector to improve the performance of applications between 1.6xto 3x and recommend using multiple small Spark executors that can provide up to 36% reduction in execution time over single large executor. Based on the characteristics of workloads, the thesis envisions near-memory and near storage hardware acceleration to improve the single-node performance of scale-out frameworks like Apache Spark. Using modeling techniques, it estimates the speed-up of 4x for Apache Spark on scale-up servers augmented with near-data accelerators.

  • 15.
    Awan, Ahsan Javed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS. KTH Royal Institute of Technology.
    Performance Characterization of In-Memory Data Analytics on a Scale-up Server2016Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The sheer increase in volume of data over the last decade has triggered research in cluster computing frameworks that enable web enterprises to extract big insights from big data. While Apache Spark defines the state of the art in big data analytics platforms for (i) exploiting data-flow and in-memory computing and (ii) for exhibiting superior scale-out performance on the commodity machines, little effort has been devoted at understanding the performance of in-memory data analytics with Spark on modern scale-up servers. This thesis characterizes the performance of in-memory data analytics with Spark on scale-up servers.

    Through empirical evaluation of representative benchmark workloads on a dual socket server, we have found that in-memory data analytics with Spark exhibit poor multi-core scalability beyond 12 cores due to thread level load imbalance and work-time inflation. We have also found that workloads are bound by the latency of frequent data accesses to DRAM. By enlarging input data size, application performance degrades significantly due to substantial increase in wait time during I/O operations and garbage collection, despite 10% better instruction retirement rate (due to lower L1 cache misses and higher core utilization).

    For data accesses we have found that simultaneous multi-threading is effective in hiding the data latencies. We have also observed that (i) data locality on NUMA nodes can improve the performance by 10% on average, (ii) disabling next-line L1-D prefetchers can reduce the execution time by up-to 14%. For GC impact, we match memory behaviour with the garbage collector to improve performance of applications between 1.6x to 3x. and recommend to use multiple small executors that can provide up-to 36% speedup over single large executor.

  • 16.
    Awan, Ahsan Javed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Project Night-King: Improving the performance of big data analytics using Near Data Computing Architectures2017Annet (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    The goal of Project Night-King is to improve the single-node performance of scale-out big data processing frameworks like Apache Spark using programmable accelerators near DRAM and NVRAM. Using modeling techniques, we estimate the lower bound of 5x performance improvement for Spark MLlib workloads.

  • 17.
    Awan, Ahsan Javed
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Ayguade, Eduard
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Ohara, Moriyoshi
    Ishizaki, Kazauki
    Identifying the potential of Near Data Processing for Apache Spark2017Inngår i: ACM International Conference Proceeding Series, Association for Computing Machinery (ACM), 2017, s. 60-67, artikkel-id F131197Konferansepaper (Fagfellevurdert)
    Abstract [en]

    While cluster computing frameworks are continuously evolving to provide real-time data analysis capabilities, Apache Spark has managed to be at the forefront of big data analytics for being a unified framework for both, batch and stream data processing. There is also a renewed interest in Near Data Processing (NDP) due to technological advancement in the last decade. However, it is not known if NDP architectures can improve the performance of big data processing frameworks such as Apache Spark. In this paper, we build the case of NDP architecture comprising programmable logic based hybrid 2D integrated processing-in-memory and instorage processing for Apache Spark, by extensive profiling of Apache Spark based workloads on Ivy Bridge Server.

  • 18.
    Awan, Ahsan Javed
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Ayguade, Eduard
    Barcelona Super Computing Center and Technical University of Catalunya.
    Architectural Impact on Performance of In-memoryData Analytics: Apache Spark Case StudyManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    While cluster computing frameworks are contin-uously evolving to provide real-time data analysis capabilities,Apache Spark has managed to be at the forefront of big data an-alytics for being a unified framework for both, batch and streamdata processing. However, recent studies on micro-architecturalcharacterization of in-memory data analytics are limited to onlybatch processing workloads. We compare micro-architectural per-formance of batch processing and stream processing workloadsin Apache Spark using hardware performance counters on a dualsocket server. In our evaluation experiments, we have found thatbatch processing are stream processing workloads have similarmicro-architectural characteristics are bounded by the latency offrequent data access to DRAM. For data accesses we have foundthat simultaneous multi-threading is effective in hiding the datalatencies. We have also observed that (i) data locality on NUMAnodes can improve the performance by 10% on average and(ii)disabling next-line L1-D prefetchers can reduce the executiontime by up-to 14% and (iii) multiple small executors can provideup-to 36% speedup over single large executor

  • 19.
    Awan, Ahsan Javed
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Ayguade, Eduard
    Technical University of Catalunya, Barcelona Super Computing Center.
    How Data Volume Affects Spark Based Data Analytics on a Scale-up Server2015Inngår i: Big Data Benchmarks, Performance Optimization, and Emerging Hardware: 6th Workshop, BPOE 2015, Kohala, HI, USA, August 31 - September 4, 2015. Revised Selected Papers, Springer, 2015, Vol. 9495, s. 81-92Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Sheer increase in volume of data over the last decade has triggered research in cluster computing frameworks that enable web enterprises to extract big insights from big data. While Apache Spark is gaining popularity for exhibiting superior scale-out performance on the commodity machines, the impact of data volume on the performance of Spark based data analytics in scale-up configuration is not well understood. We present a deep-dive analysis of Spark based applications on a large scale-up server machine. Our analysis reveals that Spark based data analytics are DRAM bound and do not benefit by using more than 12 cores for an executor. By enlarging input data size, application performance degrades significantly due to substantial increase in wait time during I/O operations and garbage collection, despite 10 % better instruction retirement rate (due to lower L1 cache misses and higher core utilization). We match memory behaviour with the garbage collector to improve performance of applications between 1.6x to 3x.

  • 20.
    Awan, Ahsan Javed
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Ayguade, Eduard
    Barcelona Super Computing Center and Technical University of Catalunya.
    Micro-architectural Characterization of Apache Spark on Batch and Stream Processing Workloads2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    While cluster computing frameworks are continuously evolving to provide real-time data analysis capabilities, Apache Spark has managed to be at the forefront of big data analytics for being a unified framework for both, batch and stream data processing. However, recent studies on micro-architectural characterization of in-memory data analytics are limited to only batch processing workloads. We compare the micro-architectural performance of batch processing and stream processing workloads in Apache Spark using hardware performance counters on a dual socket server. In our evaluation experiments, we have found that batch processing and stream processing has same micro-architectural behavior in Spark if the difference between two implementations is of micro-batching only. If the input data rates are small, stream processing workloads are front-end bound. However, the front end bound stalls are reduced at larger input data rates and instruction retirement is improved. Moreover, Spark workloads using DataFrames have improved instruction retirement over workloads using RDDs.

  • 21.
    Awan, Ahsan Javed
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Ayguade, Eduard
    Barcelona Super Computing Center and Technical University of Catalunya.
    Node architecture implications for in-memory data analytics on scale-in clusters2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    While cluster computing frameworks are continuously evolving to provide real-time data analysis capabilities, Apache Spark has managed to be at the forefront of big data analytics. Recent studies propose scale-in clusters with in-storage processing devices to process big data analytics with Spark However the proposal is based solely on the memory bandwidth characterization of in-memory data analytics and also does not shed light on the specification of host CPU and memory. Through empirical evaluation of in-memory data analytics with Apache Spark on an Ivy Bridge dual socket server, we have found that (i) simultaneous multi-threading is effective up to 6 cores (ii) data locality on NUMA nodes can improve the performance by 10% on average, (iii) disabling next-line L1-D prefetchers can reduce the execution time by up to 14%, (iv) DDR3 operating at 1333 MT/s is sufficient and (v) multiple small executors can provide up to 36% speedup over single large executor.

  • 22. Aydt, H.
    et al.
    Turner, S. J.
    Cai, W.
    Yoke Hean Low, M.
    Lendermann, P.
    Gan, B. P.
    Ayani, Russel
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Preventive what-if analysis in symbiotic simulation2008Inngår i: Proc. Winter Simul. Conf., 2008, s. 750-758Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The what-if analysis process is essential in symbiotic simulation systems. It is responsible for creating a number of alternative what-if scenarios and evaluating their performance by means of simulation. Most applications use a reactive approach for triggering the what-if analysis process. In this paper we describe a preventive triggering approach which is based on the detection of a future critical condition in the forecast of a physical system. With decreasing probability of a critical condition, using preventive what-if analysis becomes undesirable. We introduce the notion of a Gvalue and explain how this metric can be used to decide whether or not to use preventive what-if analysis. In addition, we give an example for a possible application in semiconductor manufacturing.

  • 23. Azizyan, G.
    et al.
    Magarian, M. K.
    Kajko-Mattson, Mira
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Survey of agile tool usage and needs2011Inngår i: Proceedings - 2011 Agile Conference, 2011, s. 29-38Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Today little is known about what tools software companies are using to support their Agile methods and whether they are satisfied or dissatisfied with them. This is due to lack of objective surveys on the subject. The surveys that have been conducted so far are of a subjective nature and have mostly been performed by tool vendors. They are very limited in number and focus mainly on company structure and adherence to a specific Agile method rather than on tool usage and needs. For this reason many companies have difficulties to choose appropriate tools to support their Agile process. One such company is the Swedish telecommunications giant Ericsson. To account for this lack of data Ericsson commissioned us to conduct an independent survey focusing on the tool usage and needs as experienced by the Agile software community today. In this paper we report on the results of our survey. The survey covers 121 responses from 120 different companies coming from 35 different countries. Our results show that the most satisfactory tool aspect is ease of use whereas the least satisfactory one is lack of integration with other systems. Finally our results provide a list of features that are most desired by the software companies today.

  • 24.
    Bahri, Leila
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Identity related threats, vulnerabilities and risk mitigation in online social networks: A tutorial2017Inngår i: CCS '17 Proceedings of the 2017 ACM SIGSAC Conference on Computer and Communications Security, Association for Computing Machinery (ACM), 2017, Vol. Part F131467, s. 2603-2605Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This tutorial provides a thorough review of the main research directions in the field of identity management and identity related security threats in Online Social Networks (OSNs). The continuous increase in the numbers and sophistication levels of fake accounts constitutes a big threat to the privacy and to the security of honest OSN users. Uninformed OSN users could be easily fooled into accepting friendship links with fake accounts, giving them by that access to personal information they intend to exclusively share with their real friends. Moreover, these fake accounts subvert the security of the system by spreading malware, connecting with honest users for nefarious goals such as sexual harassment or child abuse, and make the social computing environment mostly untrustworthy. The tutorial introduces the main available research results available in this area, and presents our work on collaborative identity validation techniques to estimate OSN profiles trustworthiness.

  • 25. Bahri, Leila
    et al.
    Soliman, Amira
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Squillaci, Jacopo
    Carminati, Barbara
    Ferrari, Elena
    Girdzijauskas, Sarunas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Beat the DIVa: Decentralized Identity Validation for Online Social Networks2016Inngår i: 2016 32ND IEEE INTERNATIONAL CONFERENCE ON DATA ENGINEERING (ICDE), 2016, s. 1330-1333Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fake accounts in online social networks (OSNs) have known considerable sophistication and are now attempting to gain network trust by infiltrating within honest communities. Honest users have limited perspective on the truthfulness of new online identities requesting their friendship. This facilitates the task of fake accounts in deceiving honest users to befriend them. To address this, we have proposed a model that learns hidden correlations between profile attributes within OSN communities, and exploits them to assist users in estimating the trustworthiness of new profiles. To demonstrate our method, we suggest, in this demo, a game application through which players try to cheat the system and convince nodes in a simulated OSN to befriend them. The game deploys different strategies to challenge the players and to reach the objectives of the demo. These objectives are to make participants aware of how fake accounts can infiltrate within their OSN communities, to demonstrate how our suggested method could aid in mitigating this threat, and to eventually strengthen our model based on the data collected from the moves of the players.

  • 26.
    Baig, Roger
    et al.
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Carbajales, Rodrigo
    The Abdus Salam International Centre for Theoretical Physics (ICTP). Trieste, Italy.
    Escrich, Pau
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Florit, Jorge
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain.
    Freitag, Felix
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain .
    Moll, Agusti
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Navarro, Leandro
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain.
    Pietrosemoli, Ermanno
    The Abdus Salam International Centre for Theoretical Physics (ICTP). Trieste, Italy.
    Pueyo, Roger
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Selimi, Mennan
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain .
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Zennaro, Marco
    The Abdus Salam International Centre for Theoretical Physics (ICTP). Trieste, Italy.
    The Cloudy Distribution in Community Network Clouds in Guifi.net2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This demo paper presents Cloudy, a Debian-based distribution to build and deploy clouds incommunity networks. The demonstration covers the following aspects: Installation of Cloudy, theCloudy GUI for usage and administration by end users, demonstration of Cloudy nodes and services deployed in the Guifi community network.

  • 27.
    Baig, Roger
    et al.
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Dowling, Jim
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Escrich, Pau
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Freitag, Felix
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain .
    Meseguer, Roc
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain.
    Moll, Agusti
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Navarro, Leandro
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain.
    Pietrosemoli, Ermanno
    The Abdus Salam International Centre for Theoretical Physics (ICTP). Trieste, Italy.
    Pueyo, Roger
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Zennaro, Marco
    The Abdus Salam International Centre for Theoretical Physics (ICTP). Trieste, Italy.
    Deploying Clouds in the Guifi Community Network2015Inngår i: Proceedings of the 2015 IFIP/IEEE International Symposium on Integrated Network Management, IM 2015, IEEE , 2015, s. 1020-1025Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper describes an operational geographically distributed and heterogeneous cloudinfrastructure with services and applications deployed in the Guifi community network. The presentedcloud is a particular case of a community cloud, developed according to the specific needs and conditions of community networks. We describe the concept of this community cloud, explain our technical choices for building it, and our experience with the deployment of this cloud. We review our solutions and experience on offering the different service models of cloud computing (IaaS, PaaS and SaaS) in community networks. The deployed cloud infrastructure aims to provide stable and attractive cloud services in order to encourage community network user to use, keep and extend it with new services and applications.

  • 28.
    Baig, Roger
    et al.
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Freitag, Felix
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain .
    Khan, Amin M.
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain.
    Moll, Agusti
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Navarro, Leandro
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain.
    Pueyo, Roger
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Community clouds at the edge deployed in Guifi.net2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Community clouds are a cloud deployment model in which the cloud infrastructure is built with specific features for a community of users with shared concerns, goals, and interests. Commercialcommunity clouds already operate in several application areas such as in the finance, government and health, fulfilling community-specific requirements. In this demo, a community cloud for citizens is presented. It is formed by devices at the edge of the network, contributed by the members of acommunity network and brought together into a distributed community cloud system through the Cloudy distribution. The demonstration shows to the audience in a live access the deployedcommunity cloud from the perspective of the user, by accessing a Cloudy node, inspecting the services available in the community cloud, and showing the usage of some of its services.

  • 29.
    Baig, Roger
    et al.
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Freitag, Felix
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain .
    Moll, Agusti
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Navarro, Leandro
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain.
    Pueyo, Roger
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Cloud-based community services in community networks2016Inngår i: 2016 International Conference on Computing, Networking and Communications, ICNC 2016, IEEE conference proceedings, 2016, s. 1-5, artikkel-id 7440621Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Wireless networks have shown to be a cost effective solution for an IP-based communication infrastructure in under-served areas. Services and application, if deployed within these wireless networks, add value for the users. This paper shows how cloud infrastructures have been made operational in a community wireless network, as a particular case of a community cloud, developed according to the specific requirements and conditions of the community. We describe the conditions and requirements of such a community cloud and explain our technical choices and experience in its deployment in the community network. The user take-up has started, and our case supports the tendency of cloud computing moving towards the network edge.

  • 30.
    Baig, Roger
    et al.
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Freitag, Felix
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain .
    Moll, Agusti
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Navarro, Leandro
    Department of Computer Architecture. Universitat Politecnica de Catalunya. Barcelona, Spain.
    Pueyo, Roger
    Fundacio Privada per la Xarxa Lliure, Oberta i Neural Guifi.net. Mas l’Esperanca, 08503 Gurb, Catalonia.
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Community network clouds as a case for the IEEE Intercloud standardization2015Inngår i: 2015 IEEE Conference on Standards for Communications and Networking, CSCN 2015, 2015, s. 269-274, artikkel-id 7390456Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The IEEE P2302 Intercloud WG conducts work since 2011 on the project Standard for Intercloud Interoperability and Federation with the goal to define a standard architecture and building components for large-scale interoperability of independent cloud providers. While the standardization process has achieved fine-grained definitions of several Intercloud components, a deployment of the Intercloud to demonstrate the architectural feasibility is not yet operational. In this paper, we describe a deployed community network cloud and we show how it matches in several aspects the vision of the Intercloud. Similar to the Intercloud, the community network cloud consists of many small cloud providers, which for interoperability use a set of common services. In this sense, the community network cloud is a real use case for elements that the Intercloud standardization WG envisions, and can feed back to and even become part of the Intercloud. In fact, a study on Small or Medium Enterprise (SME) provided commercial services in the community network cloud indicates the importance of the success of the Intercloud standardization initiative for SMEs.

  • 31. Baig, Roger
    et al.
    Freitag, Felix
    Moll, Agusti
    Navarro, Leandro
    Pueyo, Roger
    Vlassov, Vladimir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Experiences in Building Micro-Cloud Provider Federation in the Guifi Community Network2015Inngår i: 2015 IEEE/ACM 8TH INTERNATIONAL CONFERENCE ON UTILITY AND CLOUD COMPUTING (UCC), 2015, s. 516-521Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Cloud federation is foreseen to happen among large cloud providers. The resulting interoperability of cloud services among these providers will then increase even more the elasticity of cloud services. The cloud provisioned that is targeted by this scenario is mainly one which combines the cloud services offered by large enterprises. Cloud computing, however, has started moving to the edge. We now increasingly see the tendency to fullfil cloud computing requirements by multiple levels and different kind of infrastructures, where the Fog Computing paradigm has started playing its role. For this scenario of edge computing, we show in this paper the case of the federation of multiple independent micro-cloud providers within a community network, where providers pool their resources and services into a community cloud. Federation happens here primarily at the service level and the domain of trust is the community of practice. While we can today already report this case in the context of community networks, IPv6 deployment in the Internet will principally allow micro-cloud providers to appear everywhere, needing cloud federation mechanisms. We describe for a real case how this micro-cloud provider federation has been built and argue why micro-cloud provider should be considered for the integration in cloud federations.

  • 32. Bailis, P.
    et al.
    Fekete, A.
    Ghodsi, Ali
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Hellerstein, J. M.
    Stoica, I.
    The potential dangers of causal consistency and an explicit solution2012Inngår i: Proceedings of the 3rd ACM Symposium on Cloud Computing, SoCC 2012, ACM , 2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Causal consistency is the strongest consistency model that is available in the presence of partitions and provides useful semantics for human-facing distributed services. Here, we expose its serious and inherent scalability limitations due to write propagation requirements and traditional dependency tracking mechanisms. As an alternative to classic potential causality, we advocate the use of explicit causality, or application-defined happens-before relations. Explicit causality, a subset of potential causality, tracks only relevant dependencies and reduces several of the potential dangers of causal consistency.

  • 33. Bailis, P.
    et al.
    Ghodsi, Ali
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Hellerstein, J. M.
    Stoica, I.
    Bolt-on causal consistency2013Inngår i: SIGMOD '13 Proceedings of the 2013 ACM SIGMOD International Conference on Management of Data, Association for Computing Machinery (ACM), 2013, s. 761-772Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider the problem of separating consistency-related safety properties from availability and durability in distributed data stores via the application of a "bolt-on" shim layer that upgrades the safety of an underlying general-purpose data store. This shim provides the same consistency guarantees atop a wide range of widely deployed but often inflexible stores. As causal consistency is one of the strongest consistency models that remain available during system partitions, we develop a shim layer that upgrades eventually consistent stores to provide convergent causal consistency. Accordingly, we leverage widely deployed eventually consistent infrastructure as a common substrate for providing causal guarantees. We describe algorithms and shim implementations that are suitable for a large class of application-level causality relationships and evaluate our techniques using an existing, production-ready data store and with real-world explicit causality relationships.

  • 34. Bailis, Peter
    et al.
    Ghodsi, Ali
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Eventual Consistency Today: Limitations, Extensions, and Beyond2013Inngår i: Communications of the ACM, ISSN 0001-0782, E-ISSN 1557-7317, Vol. 56, nr 5, s. 55-63Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Brewer's conjecture'based on his experiences building infrastructure for some of the first Internet search engines at Inktomi'states that distributed systems requiring always on, highly available operation cannot guarantee the illusion of coherent, consistent single-system operation in the presence of network partitions, which cut communication between active servers. Moreover, even without partitions, a system that chooses availability over consistency enjoys benefits of low latency. If a server can safely respond to a user's request when it is partitioned from all other servers, then it can also respond to a user's request without contacting other servers even when it is able to do so. Eventual consistency as an available alternative. Given the CAP impossibility result, distributed-database designers sought weaker consistency models that would enable both availability and high performance.

  • 35.
    Bazhko, Dzianis
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Distributed system for evaluation of strategies in the stock market and the soccer betting industry2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Development of software and strategies for prices, odds calculation, and risk management in the stock market and the soccer betting industry involves testing functionality using recorded real-world data. This process is called backtesting. If a system for backtesting is represented by software that is run on a single workstation then due to the complexity of mathematical computations, amount of recorded data and variety of strategies — backtesting can require significant amount of wall time. This is a problem because the development cycle increases in time. This paper proposes a design of a distributed system for backtesting that distributes the workload among available workstations considering limitations on the network usage.

  • 36. Bessani, A.
    et al.
    Brandt, J.
    Bux, M.
    Cogo, V.
    Dimitrova, L.
    Dowling, Jim
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Gholami, Ali
    KTH.
    Hakimzadeh, Kamal
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Hummel, M.
    Ismail, Mahmoud
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Laure, Erwin
    KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Parallelldatorcentrum, PDC. KTH, Skolan för datavetenskap och kommunikation (CSC), High Performance Computing and Visualization (HPCViz).
    Leser, U.
    Litton, J. -E
    Martinez, R.
    Niazi, Salman
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Reichel, J.
    Zimmermann, K.
    BiobankCloud: A platform for the secure storage, sharing, and processing of large biomedical data sets2016Inngår i: 1st International Workshop on Data Management and Analytics for Medicine and Healthcare, DMAH 2015 and Workshop on Big-Graphs Online Querying, Big-O(Q) 2015 held in conjunction with 41st International Conference on Very Large Data Bases, VLDB 2015, Springer, 2016, s. 89-105Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Biobanks store and catalog human biological material that is increasingly being digitized using next-generation sequencing (NGS). There is, however, a computational bottleneck, as existing software systems are not scalable and secure enough to store and process the incoming wave of genomic data from NGS machines. In the BiobankCloud project, we are building a Hadoop-based platform for the secure storage, sharing, and parallel processing of genomic data. We extended Hadoop to include support for multi-tenant studies, reduced storage requirements with erasure coding, and added support for extensible and consistent metadata. On top of Hadoop, we built a scalable scientific workflow engine featuring a proper workflow definition language focusing on simple integration and chaining of existing tools, adaptive scheduling on Apache Yarn, and support for iterative dataflows. Our platform also supports the secure sharing of data across different, distributed Hadoop clusters. The software is easily installed and comes with a user-friendly web interface for running, managing, and accessing data sets behind a secure 2-factor authentication. Initial tests have shown that the engine scales well to dozens of nodes. The entire system is open-source and includes pre-defined workflows for popular tasks in biomedical data analysis, such as variant identification, differential transcriptome analysis using RNA-Seq, and analysis of miRNA-Seq and ChIP-Seq data.

  • 37. Bhatti, Muhammad Khurram
    et al.
    Oz, Isil
    Popov, Konstantin
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Farooq, Umer
    Scheduling of Parallel Tasks with Proportionate Priorities2016Inngår i: ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING, ISSN 2193-567X, Vol. 41, nr 8, s. 3279-3295Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Parallel computing systems promise higher performance for computationally intensive applications. Since programmes for parallel systems consist of tasks that can be executed simultaneously, task scheduling becomes crucial for the performance of these applications. Given dependence constraints between tasks, their arbitrary sizes, and bounded resources available for execution, optimal task scheduling is considered as an NP-hard problem. Therefore, proposed scheduling algorithms are based on heuristics. This paper presents a novel list scheduling heuristic, called the Noodle heuristic. Noodle is a simple yet effective scheduling heuristic that differs from the existing list scheduling techniques in the way it assigns task priorities. The priority mechanism of Noodle maintains a proportionate fairness among all ready tasks belonging to all paths within a task graph. We conduct an extensive experimental evaluation of Noodle heuristic with task graphs taken from Standard Task Graph. Our experimental study includes results for task graphs comprising of 50, 100, and 300 tasks per graph and execution scenarios with 2-, 4-, 8-, and 16-core systems. We report results for average Schedule Length Ratio (SLR) obtained by producing variations in Communication to Computation cost Ratio. We also analyse results for different degree of parallelism and number of edges in the task graphs. Our results demonstrate that Noodle produces schedules that are within a maximum of 12 % (in worst-case) of the optimal schedule for 2-, 4-, and 8-core systems. We also compare Noodle with existing scheduling heuristics and perform comparative analysis of its performance. Noodle outperforms existing heuristics for average SLR values.

  • 38. Bhatti, Muhammad Khurram
    et al.
    Oz, Isil
    Popov, Konstantin
    Muddukrishna, Ananya
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS. SICS Swedish ICT, Sweden.
    Noodle: A Heuristic Algorithm for Task Scheduling in MPSoC Architectures2014Inngår i: Proceedings - 2014 17th Euromicro Conference on Digital System Design, DSD 2014, 2014, s. 667-670Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Task scheduling is crucial for the performance of parallel applications. Given dependence constraints between tasks, their arbitrary sizes, and bounded resources available for execution, optimal task scheduling is considered as an NP-hard problem. Therefore, proposed scheduling algorithms are based on heuristics. This paper(1) presents a novel heuristic algorithm, called the Noodle heuristic, which differs from the existing list scheduling techniques in the way it assigns task priorities. We conduct an extensive experimental to validate Noodle for task graphs taken from Standard Task Graph (STG). Results show that Noodle produces schedules that are within a maximum of 12% (in worst-case) of the optimal schedule for 2, 4, and 8 core systems. We also compare Noodle with existing scheduling heuristics and perform comparative analysis of its performance.

  • 39.
    Boman, Magnus
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Digital Cities: Strategic White Paper2013Rapport (Annet (populærvitenskap, debatt, mm))
  • 40.
    Boman, Magnus
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Speedwriting in Networked Foresight2014Inngår i: Innovation for Sustainable Economy & Society: The Proceedings of The XXV ISPIM Conference 2014 / [ed] Huizingh, K.R.E., Conn, S., Torkkeli, M. and Bitran, I., ISPIM Society , 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Networked foresight is an established means to achieve an understanding of trends, changes, disruptives, and ideas with high innovation potential. When managed successfully, it allows for the elicitation of knowledge from competent professionals, with complementary resources, assets, and capabilities, providing benefit both to partners and to the network as a whole. The Innovation Radar business catalyst of EIT ICT Labs (a virtual organisation of multi-nationals, research institutes, and academic institutions) has used speedwriting as an integral part of its structured brainstorming, with the aim of efficiently producing networked foresight with adequate depth and width. Speedwriting aids width in particular, as it prompts the inclusion of disruptives and speculative developments. Eight Innovation Radar workshops involving more than 100 experts in total have employed the speedwriting element to maximise value for the organisation. Since speedwriting is a largely undocumented method, its merits to strategic and corporate foresight are here scrutinised in detail.

  • 41.
    Boman, Magnus
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Technical Foresight Report: Future Media Distribution2013Rapport (Annet (populærvitenskap, debatt, mm))
  • 42.
    Boman, Magnus
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Who Were Where When?: On the Use of Social Collective Intelligence in Computational Epidemiology2014Inngår i: Social Collective Intelligence / [ed] Daniele Miorandi, Vincenzo Maltese, Michael Rovatsos, Anton Nijholt and James Stewart, Switzerland: Springer , 2014, s. 203-225Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    A triangular (case, theoretical, and literature) study approach is used to investigate if and how social collective intelligence is useful to computational epidemiology. The hypothesis is that the former can be employed for assisting in converting data into useful information through intelligent analyses by deploying new methods from data analytics that render previously unintelligible data intelligible. A conceptual bridge is built between the two concepts of crowd signals and syndromic surveillance. A concise list of empirical observations supporting the hypothesis is presented. The key observation is that new social collective intelligence methods and algorithms allow for massive data analytics to stay with the individual, in micro. It is thus possible to provide the analyst with advice tailored to the individual and with relevant policies, without resorting to macro (statistical) analyses of homogeneous populations.

  • 43.
    Boman, Magnus
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Cakici, Baki
    Stockholm University.
    Guttmann, Christian
    EBTIC.
    Al Hosani, Farida
    HAAD.
    Al Mannaei, Asma
    HAAD.
    Syndromic Surveillance in the United Arab Emirates2012Inngår i: International Conference on Innovations in Information Technology (IIT), 2012, IEEE conference proceedings, 2012, s. 31-35Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Opportunities for innovation in view of three complex problems faced by the UAE health care providers are described. The information dissemination problem faced could be approached by creating new channels for providing the population with public health information. These channels are precisely the ones typically used in so-called syndromic surveillance, including care-related data from communicable disease spread indicators, but also tweets and blog posts, for example. Syndromic surveillance could likewise assist the health authorities in addressing the knowledge elicitation problem: how to get more information on the life style, self care, and prevention among individual citizens. To some extent the prediction problem—how to predict the spread of infectious disease in the future and how to mathematically model social behaviour in the case of various health-threatening scenarios—would also be addressed by syndromic surveillance. Fully employed, the solutions proposed would provide new ICT services enabling preparedness for many forms of communicable disease outbreaks, as well as for natural disasters.

  • 44.
    Boman, Magnus
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS. SICS.
    Gillblad, Daniel
    SICS.
    Learning Machines for Computational Epidemiology2014Inngår i: Proceedings - 2014 IEEE International Conference on Big Data, Washington DC: IEEE conference proceedings, 2014, s. 1-5Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Resting on our experience of computational epidemiologyin practice and of industrial projects on analytics ofcomplex networks, we point to an innovation opportunity forimproving the digital services to epidemiologists for monitoring,modeling, and mitigating the effects of communicable disease.Artificial intelligence and intelligent analytics of syndromicsurveillance data promise new insights to epidemiologists, butthe real value can only be realized if human assessments arepaired with assessments made by machines. Neither massivedata itself, nor careful analytics will necessarily lead to betterinformed decisions. The process producing feedback to humanson decision making informed by machines can be reversed toconsider feedback to machines on decision making informed byhumans, enabling learning machines. We predict and argue forthe fact that the sensemaking that such machines can perform intandem with humans can be of immense value to epidemiologistsin the future.

  • 45.
    Boman, Magnus
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Gullström, Charlie
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Arkitektur.
    Mediated Futures: Technical Foresight report. European Institute of Innovation and Technology, EIT ICT Labs2015Rapport (Annet vitenskapelig)
    Abstract [en]

    This report outlines trends, challenges, and opportunities relating to the future of

    Smart Spaces and ICT-mediated human communication, as observed from within

    one of the EIT ICT Labs focus areas: Mediating Presence, during 2012-2013. The

    study should be seen as an initial and open-ended exploration that seeks to

    contribute a productive point of departure for more ambitious work, which will be

    undertaken across the Smart Spaces Action Line and using the Innovation Radar

    platform in future years. In particular, the business potential of mediating presence is

    the focus of a forthcoming 2014 Foresight Technical Report.

    As a foresight, Mediated Futures identifies and exposes future themes with high

    innovation potential relating to presence technologies, using a time frame roughly six

    months to five years ahead. Its purpose is to create a common outlook on the future

    of ICT and to establish a shared vocabulary and fruitful methodologies for future

    strategy thinking across the EIT ICT Labs nodes and partner organisations.

    A series of workshops and other collaborative activities have been organised within

    the Mediating Presence activity over the last 15 months. The pivotal output is a

    series of one-pagers, short fictional texts, three of which can be encountered on the

    following pages. Tentative and possibly provocative, these are slogan-based

    descriptions of future scenarios that serve to trigger new perspectives. A total of six

    clusters of topics were covered by one-pagers:

     Data doubles

     New magic

     Luddites

     Socialites

     Future of WorkA working future

     Spaces and things

  • 46.
    Boman, Magnus
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS. RISE SICS AB, Sweden.
    Kruse, E.
    Supporting global health goals with information and communications technology2017Inngår i: Global Health Action, ISSN 1654-9716, E-ISSN 1654-9880, Vol. 10, artikkel-id 1321904Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this study is to critically assess the possible roles of information and communications technology (ICT) in supporting global health goals. This is done by considering privilege and connectibility. In short, ICT can contribute by providing health information via four different kinds of access, each with its own history and prospective future. All four are analyzed here, in two perspectives: business-as-usual and disruptive. Health data analytics is difficult since the digital representation of past, current, and future health information is lacking. The flow of analytics that may prove beneficial to the individual and not just meet abstract population-level goals or ambitions is analyzed in detail. Sensemaking is also needed, to meet the minimum requirement of making prospective future services understandable to policymakers. Drivers as well as barriers for areas in which policy decisions have the potential to drive positive developments for meeting the Sustainable Development Goals are identified.

  • 47.
    Boman, Magnus
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Sanches, Pedro
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Sensemaking in Intelligent Data Analytics2015Inngår i: Künstliche Intelligenz, ISSN 0933-1875, E-ISSN 1610-1987Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A systemic model for making sense of health data is presented, in which networked foresight complements intelligent data analytics. Data here serves the goal of a future systems medicine approach by explaining the past and the current, while foresight can serve by explaining the future. Anecdotal evidence from a case study is presented, in which the complex decisions faced by the traditional stakeholder of results—the policymaker—are replaced by the often mundane problems faced by an individual trying to make sense of sensor input and output when self-tracking wellness. The conclusion is that the employment of our systemic model for successful sensemaking integrates not only data with networked foresight, but also unpacks such problems and the user practices associated with their solutions.

  • 48. Bonnichsen, L.
    et al.
    Podobas, Artur
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Using transactional memory to avoid blocking in OpenMP synchronization directives: Don’t wait, speculate!2015Inngår i: 11th International Workshop on OpenMP, IWOMP 2015, Springer, 2015, s. 149-161Konferansepaper (Fagfellevurdert)
    Abstract [en]

    OpenMP applications with abundant parallelism are often characterized by their high-performance. Unfortunately, OpenMP applications with a lot of synchronization or serialization-points perform poorly because of blocking, i.e. the threads have to wait for each other. In this paper, we present methods based on hardware transactional memory (HTM) for executing OpenMP barrier, critical, and taskwait directives without blocking. Although HTM is still relatively new in the Intel and IBM architectures, we experimentally show a 73% performance improvement over traditional locking approaches, and 23% better than other HTM approaches on critical sections. Speculation over barriers can decrease execution time by up-to 41 %. We expect that future systems with HTM support and more cores will have a greater benefit from our approach as they are more likely to block.

  • 49. Bordencea, D.
    et al.
    Shafaat, Tallat Mahmood
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Arad, Cosmin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Haridi, Seif
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Valean, H.
    Efficient linearizable write operations using bounded global time uncertainty2013Inngår i: Proceedings - 2013 IEEE 12th International Symposium on Parallel and Distributed Computing, ISPDC 2013, IEEE , 2013, s. 59-66Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Distributed key-value stores employed in data centers treat each key-value pair as a shared memory register. For fault-tolerance and performance, each key-value pair is replicated. Various models exist for the consistency of data amongst the replicas. While atomic consistency, also known as linearizability, provides the strongest form of consistency for read and write operations, various key-value stores, such as Cassandra, and Dynamo, offer only eventual consistency instead. One main motivation for such a decision is performance degradation when guaranteeing atomic consistency. In this paper, we use time with known bounded uncertainty to improve the performance of write operations, while maintaining atomic consistency. We show how to use the concept of commit wait in a shared memory register to perform a write operation in one phase (message round trip), instead of two. We evaluate the solution experimentally by comparing it to ABD, a well-known algorithm for achieving atomic consistency in an asynchronous network, which uses two phases for write operations. We also compare our protocol to an eventually consistent register. Our experiments show an improved throughput, and lower write latency, compared to the ABD algorithm.

  • 50.
    Bradley, Gunilla
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Social informatics: From theory to actions for the good ICT society2006Inngår i: IFIP International Federation for Information Processing, 2006, s. 383-394Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents ongoing social changes related to the use of ICT. They are analyzed under the headings: workforce, organizational design and structure, psychosocial communication, and work content. A theoretical model entitled 'The Convergence theory on ICT and Psychosocial Life Environment' is described, which reflects main ongoing processes in the Network society encompassing various spheres of life, environments, and human roles. A special section analyzes the ongoing changes in the home and home environment. Social Informatics is discussed related to the model and special attention is devoted to the individual level and humans. Concluding remarks deal with visions and actions. Figures with circles and converging circles are used to illustrate and summarize.

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