| 1. |
- Asplund, Mikael, et al.
(författare)
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Middleware extensions that trade consistency for availability
- 2009
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Ingår i: CONCURRENCY AND COMPUTATION-PRACTICE and EXPERIENCE. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 21:9, s. 1181-1203
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Tidskriftsartikel (refereegranskat)abstract
- Replicated distributed object systems are deployed to provide timely and reliable services to actors at distributed locations. This paper treats applications in which data updates are dependent on satisfaction of integrity constraints over multiple objects. Network partitions, caused by occasional link failures, overload or attacks create problems in keeping both consistency and availability in such networks. We propose a means of achieving higher availability by providing partition-awareness in middleware. The general approach has been illustrated by implementing a number of CORBA extensions that trade consistency for availability during network partitions. This paper contains a thorough experimental evaluation that presents the gains and costs of our approach. The experiments clearly illustrate the benefit of our protocols in terms of significantly higher availability and the number of performed operations.
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| 2. |
- Bergman, Sara, et al.
(författare)
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Permissioned Blockchains and Distributed Databases : A Performance Study
- 2020
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Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 32:12
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Tidskriftsartikel (refereegranskat)abstract
- Blockchains are increasingly studied in the context of new applications. Permissioned blockchains promise to deal with the issue of complete removal of trust, a notion that is currently the hallmark of the developed society. Before the idea is adopted in contexts where resource efficiency and fast operation is a requirement, one could legitimately ask the question: can permissioned blockchains match the performance of traditional large‐scale databases? This paper compares two popular frameworks, Hyperledger Fabric and Apache Cassandra, as representatives of permissioned blockchains and distributed databases, respectively. We compare their latency for varying workloads and network sizes. The results show that, for small systems, blockchains can start to compete with traditional databases, but also that the difference in consistency models and differences in setup can have a large impact on the resulting performance.
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| 3. |
- Brandic, Ivona, et al.
(författare)
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Specification, Planning, and Execution of QoS-awareGrid Workflows within the Amadeus Environment
- 2008
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Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 20:4, s. 331-345
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Tidskriftsartikel (refereegranskat)abstract
- Commonly, at a high level of abstraction Grid applications are specified based on the workflow paradigm. However, majority of Grid workflow systems either do not support Quality of Service (QoS), or provide only partial QoS support for certain phases of the workflow lifecycle. In this paper we present Amadeus, which is a holistic service-oriented environment for QoS-aware Grid workflows. Amadeus considers user requirements, in terms of QoS constraints, during workflow specification, planning, and execution. Within the Amadeus environment workflows and the associated QoS constraints are specified at a high level using an intuitive graphical notation. A distinguishing feature of our system is the support of a comprehensive set of QoS requirements, which considers in addition to performance and economical aspects also legal and security aspects. A set of QoS-aware service-oriented components is provided for workflow planning to support automatic constraint-based service negotiation and workflow optimization. For improving the efficiency of workflow planning we introduce a QoS-aware workflow reduction technique. Furthermore, we present our static and dynamic planning strategies for workflow execution in accordance with user-specified requirements. For each phase of the workflow lifecycle we experimentally evaluate the corresponding Amadeus components.
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| 4. |
- Casalicchio, Emiliano, et al.
(författare)
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The state-of-the-art in container technologies : Application, orchestration and security
- 2020
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Ingår i: Concurrency and Computation. - : John Wiley and Sons Ltd. - 1532-0626 .- 1532-0634. ; 32:17
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Tidskriftsartikel (refereegranskat)abstract
- Containerization is a lightweight virtualization technology enabling the deployment and execution of distributed applications on cloud, edge/fog, and Internet-of-Things platforms. Container technologies are evolving at the speed of light, and there are many open research challenges. In this paper, an extensive literature review is presented that identifies the challenges related to the adoption of container technologies in High Performance Computing, Big Data analytics, and geo-distributed (Edge, Fog, Internet-of-Things) applications. From our study, it emerges that performance, orchestration, and cyber-security are the main issues. For each challenge, the state-of-the-art solutions are then analyzed. Performance is related to the assessment of the performance footprint of containers and comparison with the footprint of virtual machines and bare metal deployments, the monitoring, the performance prediction, the I/O throughput improvement. Orchestration is related to the selection, the deployment, and the dynamic control of the configuration of multi-container packaged applications on distributed platforms. The focus of this work is on run-time adaptation. Cyber-security is about container isolation, confidentiality of containerized data, and network security. From the analysis of 97 papers, it came out that the state-of-the-art is more mature in the area of performance evaluation and run-time adaptation rather than in security solutions. However, the main unsolved challenges are I/O throughput optimization, performance prediction, multilayer monitoring, isolation, and data confidentiality (at rest and in transit). © 2020 John Wiley & Sons, Ltd.
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| 5. |
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| 6. |
- Edmundsson, Niklas, et al.
(författare)
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Design and Evaluation of a TOP100 Linux Super Cluster System
- 2004
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Ingår i: Concurrency and Computation: Practice & Experiences. - : John Wiley & Sons, Inc.. - 1532-0634 .- 1532-0626. ; 16:8, s. 735-750
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Tidskriftsartikel (refereegranskat)abstract
- The High Performance Computing Center North (HPC2N) Super Cluster is a truly self-made high-performance Linux cluster with 240 AMD processors in 120 dual nodes, interconnected with a high-bandwidth, low-latency SCI network. This contribution describes the hardware selected for the system, the work needed to build it, important software issues and an extensive performance analysis. The performance is evaluated using a number of state-of-the-art benchmarks and software, including STREAM, Pallas MPI, the Atlas DGEMM, High-Performance Linpack and NAS Parallel benchmarks. Using these benchmarks we first determine the raw memory bandwidth and network characteristics; the practical peak performance of a single CPU, a single dual-node and the complete 240-processor system; and investigate the parallel performance for non-optimized dusty-deck Fortran applications. In summary, this $500 000 system is extremely cost-effective and shows the performance one would expect of a large-scale supercomputing system with distributed memory architecture. According to the TOP500 list of June 2002, this cluster was the 94th fastest computer in the world. It is now fully operational and stable as the main computing facility at HPC2N. The system’s utilization figures exceed 90%, i.e. all 240 processors are on average utilized over 90% of the time, 24 hours a day, seven days a week.
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| 7. |
- Elmroth, Erik, 1964-, et al.
(författare)
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A standards-based Grid resource brokering service supporting advance reservations, coallocation and cross-Grid interoperability
- 2009
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 21:18, s. 2298-2335
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Tidskriftsartikel (refereegranskat)abstract
- The problem of Grid-middleware interoperability is addressed by the design and analysis of a feature-rich, standards-based framework for all-to-all cross-middleware job submission.The architecture is designed with focus on generality and flexibility and builds on extensive use, internally and externally, of (proposed) Web and Grid services standards such asWSRF, JSDL, GLUE, and WS-Agreement. The external use providesthe foundation for easy integration into specific middlewares,which is performed by the design of a small set of plugins for each middleware. Currently, plugins are provided for integrationinto Globus Toolkit 4 and NorduGrid/ARC. The internal use of standard formats facilitates customizationof the job submission service by replacement of custom components for performing specific well-defined tasks.Most importantly, this enables the easy replacement of resource selection algorithms by algorithms that addresses the specific needs of a particular Grid environment and job submission scenario.By default, the service implements a decentralized brokering policy, strivingto optimize the performance for the individual user by minimizing the response time for each job submitted. The algorithms in our implementation perform resource selectionbased on performance predictions, and provide support for advance reservations as well as coallocation of multiple resources for coordinated use.The performance of the system is analyzed with focuson overall service throughput (up to over 250 jobs per minute)and individual job submission response time (down to under one second).
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| 8. |
- Ernstsson, August, et al.
(författare)
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Extending smart containers for data locality-aware skeleton programming
- 2019
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Ingår i: Concurrency and Computation. - : WILEY. - 1532-0626 .- 1532-0634. ; 31:5
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Tidskriftsartikel (refereegranskat)abstract
- We present an extension for the SkePU skeleton programming framework to improve the performance of sequences of transformations on smart containers. By using lazy evaluation, SkePU records skeleton invocations and dependencies as directed by smart container operands. When a partial result is required by a different part of the program, the run-time system will process the entire lineage of skeleton invocations; tiling is applied to keep chunks of container data in the working set for the whole sequence of transformations. The approach is inspired by big data frameworks operating on large clusters where good data locality is crucial. We also consider benefits other than data locality with the increased run-time information given by the lineage structures, such as backend selection for heterogeneous systems. Experimental evaluation of example applications shows potential for performance improvements due to better cache utilization, as long as the overhead of lineage construction and management is kept low.
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| 9. |
- Fahringer, Thomas, et al.
(författare)
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ASKALON : a tool set for clusterand Grid computing
- 2005
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 17:2-4, s. 143-169
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Tidskriftsartikel (refereegranskat)abstract
- Performance engineering of parallel and distributed applications is a complex task that iterates through various phases, ranging from modeling and prediction, to performance measurement, experiment management, data collection, and bottleneck analysis. There is no evidence so far that all of these phases should/can be integrated into a single monolithic tool. Moreover, the emergence of computational Grids as a common single wide-area platform for high-performance computing raises the idea to provide tools as interacting Grid services that share resources, support interoperability among different users and tools, and, most importantly, provide omnipresent services over the Grid. We have developed the ASKALON tool set to support performance-oriented development of parallel and distributed (Grid) applications. ASKALON comprises four tools, coherently integrated into a service-oriented architecture. SCALEA is a performance instrumentation, measurement, and analysis tool of parallel and distributed applications. ZENTURIO is a general purpose experiment management tool with advanced support for multi-experiment performance analysis and parameter studies. AKSUM provides semi-automatic high-level performance bottleneck detection through a special-purpose performance property specification language. The PerformanceProphet enables the user to model and predict the performance of parallel applications at the early stages of development. In this paper we describe the overall architecture of the ASKALON tool set and outline the basic functionality of the four constituent tools. The structure of each tool is based on the composition and sharing of remote Grid services, thus enabling tool interoperability. In addition, a data repository allows the tools to share the common application performance and output data that have been derived by the individual tools. A service repository is used to store common portable Grid service implementations. A general-purpose Factory service is employed to create service instances on arbitrary remote Grid sites. Discovering and dynamically binding to existing remote services is achieved through registry services. The ASKALON visualization diagrams support both online and post-mortem visualization of performance and output data. We demonstrate the usefulness and effectiveness of ASKALON by applying the tools to real-world applications.
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| 10. |
- Gardfjäll, Peter, 1979-, et al.
(författare)
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Scalable Grid-wide capacity allocation with the SweGrid Accounting System (SGAS)
- 2008
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 20:18, s. 2089-2122
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Tidskriftsartikel (refereegranskat)abstract
- The SweGrid Accounting System (SGAS) allocates capacity in collaborative Grid environments by coordinating enforcement of Grid-wide usage limits as a means to offer usage guarantees and prevent overuse. SGAS employs a credit-based allocation model where Grid capacity is granted to projects via Grid-wide quota allowances that can be spent across the Grid resources. The resources Collectively enforce these allowances in a soft, real-time manner. SGAS is built on service-oriented principles with a strong focus on interoperability, and Web services standards. This article covers the SGAS design and implementation, which, besides addressing inherent Grid challenges (scale, security, heterogeneity, decentralization), emphasizes generality and flexibility to produce a customizable system with lightweight integration into different middleware and scheduling system combinations. We focus the discussion around the system design, a flexible allocation model, middleware integration experiences and scalability improvements via a distributed virtual banking system, and finally, an extensive set of testhed experiments. The experiments evaluate the performance of SGAS in terms of response times, request throughput, overall system scalability, and its performance impact on the Globus Toolkit 4 job submission software. We conclude that, for all practical purposes, the quota enforcement overhead incurred by SGAS on job submissions is not a limiting factor for the job-handling capacity of the job submission software.
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| 11. |
- Gidenstam, Anders, et al.
(författare)
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Scalable group communication supporting configurable levels of consistency
- 2013
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Ingår i: Concurrency Computation Practice and Experience. - : Wiley. - 1532-0634 .- 1532-0626. ; 25:5, s. 649-671
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Tidskriftsartikel (refereegranskat)abstract
- Group communication is deployed in many evolving Internet-scale cooperative applications such as multiplayer online games and virtual worlds to efficiently support interaction on information relevant to a potentially very large number of users or objects. Especially peer-to-peer based group communication protocols have evolved as a promising approach to allow intercommunication between many distributed peers. Yet, the delivery semantics of robust and scalable protocols such as gossiping is not sufficient to support consistency semantics beyond eventual consistency because no relationship on the order of events is enforced. On the other hand, traditional consistency models provided by reliable group communication providing causal or even total order are restricted to support only small groups.This article proposes the cluster consistency model which bridges the gap between traditional and current approaches in supporting both scalability and ordered event delivery. We introduce a dynamic and fault tolerant cluster management method that can coordinate concurrent access to resources in a peer-to-peer system and can be used to establish fault-tolerant configurable cluster consistency with predictable reliability, running on top of decentralised probabilistic protocols supporting scalable group communication. This is achieved by a general two-layered architecture that can be applied on top of the standard Internet communication layers and offers a modular, layered set of services to the applications that need them. Further, we present a fault-tolerant method implementing causal cluster consistency with predictable reliability, running on top of decentralised probabilistic protocols supporting group communication.This paper provides analytical and experimental evaluation of the properties regarding the fault tolerance of the approach. Furthermore, our experimental study, conducted by implementing and evaluating the two-layered architecture on top of standard Internet transport services, shows that the approach scales well, imposes an even load on the system, and provides high-probability reliability guarantees.
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| 12. |
- Granat, Robert, et al.
(författare)
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Parallel Eigenvalue Reordering in Real Schur Forms
- 2009
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 21:9, s. 1225-1250
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Tidskriftsartikel (refereegranskat)abstract
- A parallel algorithm for reordering the eigenvalues in the real Schur form of a matrix is presented and discussed. Our novel approach adopts computational windows and delays multiple outside-window updates until each window has been completely reordered locally. By using multiple concurrent windows the parallel algorithm has a high level of concurrency, and most work is level 3 BLAS operations. The presented algorithm is also extended to the generalized real Schur form. Experimental results for ScaLAPACK-style Fortran 77 implementations on a Linux cluster confirm the efficiency and scalability of our algorithms in terms of more than 16 times of parallel speedup using 64 processors for large-scale problems. Even on a single processor our implementation is demonstrated to perform significantly better compared with the state-of-the-art serial implementation.
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| 13. |
- Hashemian, Raoufehsadat, et al.
(författare)
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Characterizing the Scalability of a Web Application on a Multi-core Server
- 2014
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Ingår i: Concurrency and Computation: Practice and Experience. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 26:12, s. 2027-2052
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Tidskriftsartikel (refereegranskat)abstract
- The advent of multi‒core technology motivates new studies to understand how efficiently Web servers utilize such hardware. This paper presents a detailed performance study of a Web server application deployed on a modern eight‒core server. Our study shows that default Web server configurations result in poor scalability with increasing core counts. We study two different types of workloads, namely, a workload with intense TCP/IP related OS activity and the SPECweb2009 Support workload with more application‒level processing. We observe that the scaling behaviour is markedly different for these workloads, mainly because of the difference in the performance of static and dynamic requests. While static requests perform poorly when moving from using one socket to both sockets in the system, the converse is true for dynamic requests. We show that, contrary to what was suggested by previous work, Web server scalability improvement policies need to be adapted based on the type of workload experienced by the server. The results of our experiments reveal that with workload‒specific Web server configuration strategies, a multi‒core server can be utilized up to 80% while still serving requests without significant queuing delays; utilizations beyond 90% are also possible, while still serving requests with ‘acceptable’ response times.
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| 14. |
- Herskind, Lasse, et al.
(författare)
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BitFlow : Enabling Real‐time Cash‐flow Evaluations through Blockchain
- 2020
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Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 32:12
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Tidskriftsartikel (refereegranskat)abstract
- Disbursement registration has always been a cumbersome, opaque, and inefficient process, up to the point that most businesses perform cash-flow evaluations only on a quarterly basis. We believe that automatic cash-flow evaluations can actively mitigate these issues. In this paper, we presentBitFlow, ablockchain-based architecture thatprovides complete cash-flow transparency and diminishes the probability of undetected frauds through the BitKrone, a non-volatile cryptocurrency that maps to the Danish Krone (DKK). We show that confidentiality can be effectively achieved on a permissionless blockchain using Zero-Knowledge proofs, ensuring verifiable transfers and automatic evaluations. Furthermore, we discuss several experiments to evaluate our proposal, in particular, the impact that confidential transactions have on the whole system, in terms of responsiveness and from an economical expenditure perspective.
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| 15. |
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| 16. |
- HoseinyFarahabady, MohammadReza, et al.
(författare)
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Energy efficient resource controller for Apache Storm
- 2023
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Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 35:17
-
Tidskriftsartikel (refereegranskat)abstract
- Apache Storm is a distributed processing engine that can reliably process unbounded streams of data for real-time applications. While recent research activities mostly focused on devising a resource allocation and task scheduling algorithm to satisfy high performance or low latency requirements of Storm applications across a distributed and multi-core system, finding a solution that can optimize the energy consumption of running applications remains an important research question to be further explored. In this article, we present a controlling strategy for CPU throttling that continuously optimize the level of consumed energy of a Storm platform by adjusting the voltage and frequency of the CPU cores while running the assigned tasks under latency constraints defined by the end-users. The experimental results running over a Storm cluster with 4 physical nodes (total 24 cores) validates the effectiveness of proposed solution when running multiple compute-intensive operations. In particular, the proposed controller can keep the latency of analytic tasks, in terms of 99th latency percentile, within the quality of service requirement specified by the end-user while reducing the total energy consumption by 18% on average across the entire Storm platform.
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| 17. |
- HoseinyFarahabady, MohammadReza, et al.
(författare)
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Enhancing disk input output performance in consolidated virtualized cloud platforms using a randomized approximation scheme
- 2022
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Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 34:2
-
Tidskriftsartikel (refereegranskat)abstract
- In a virtualized computer system with shared resources, consolidated virtual services (VSs) fiercely compete with each other to obtain the required capacity of resources, and this causes significant system's performance degradation. The performance of input output (I/O)-bound applications running inside their own VS is mainly determined by the total time required to schedule every read/write request, plus the actual time needed by the device driver to complete the request. To achieve a right performance isolation of shared resources (e.g., the last level cache, memory bandwidth, and the disk buffer), it is essential to limit the performance degradation level among collocated applications, as simultaneously several I/O operations are requested by VSs, perhaps with different priorities. This article proposes a resource allocation controller that uses a fully polynomial-time randomized approximation scheme to enable performance isolation of concurrent I/O requests in a shared system with multiple consolidated VSs. This controller uses a Monte Carlo sampling approach to measure and estimate the unknown attributes of operational requests originating from each VS. This is formalized as an optimization problem with the aim to minimize the degree of total quality of service (QoS) violation incidents in the entire platform. We associated a reward function to every working machine that represents the fulfillment degree of quality of service metric among all running VSs. The conducted comprehensive set of experiments showed that the proposed algorithm can reduce the QoS violation incidents by 32%, compared with the result which is obtained by employing the default resource allocation policy embedded in the existing Linux container layer.
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| 18. |
- Hughes, Danny, et al.
(författare)
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An experiment with reflective middleware to support grid-based flood monitoring
- 2008
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 20:11, s. 1303-1316
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Flooding is a growing problem, which affects more than 10% of the U.K. population. The cost of damage caused by flooding correlates closely with the warning time given before a flood event, making flood monitoring and prediction critical to minimizing the cost of flood damage. This paper describes a wireless sensor network (WSN) for flood warning, which is capable of not only integrating with remote fixed-network grids for computationally intensive flood modelling purposes but also performing on-site grid computation. This functionality is supported by the reflective and component-based GridKit middleware, which provides support for both WSN and grid application domains. Copyright (c) 2007 John Wiley & Sons, Ltd.
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| 19. |
- Kessler, Christoph, 1966-, et al.
(författare)
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Classification and generation of schedules for VLIW processors
- 2007
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Ingår i: Concurrency. - : Wiley. - 1040-3108 .- 1096-9128. ; 19, s. 2369-2389
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Tidskriftsartikel (refereegranskat)abstract
- We identify and analyze different classes of schedules for instruction-level parallel processor architectures. The classes are induced by various common techniques for generating or enumerating them, such as integer linear programming or list scheduling with backtracking. In particular, we study the relationship between VLIW schedules and their equivalent linearized forms (which may be used, e.g., with superscalar processors), and we identify classes of VLIW schedules that can be created from a linearized form using an in-order VLIW compaction heuristic, which is just the static equivalent of the dynamic instruction dispatch algorithm of in-order issue superscalar processors. We formulate and give a proof of the dominance of greedy schedules for instruction-level parallel architectures where all instructions have multiblock reservation tables, and we show how scheduling anomalies can occur in the presence of instructions with non-multiblock reservation tables. We also show that, in certain situations, certain schedules generally cannot be constructed by incremental scheduling algorithms that are based on topological sorting of the data dependence graph. We also discuss properties of strongly linearizable schedules, out-of-order schedules and non-dawdling schedules, and show their relationships to greedy schedules and to general schedules. We summarize our findings as a hierarchy of classes of VLIW schedules. Finally we provide an experimental evaluation showing the sizes of schedule classes in the above hierarchy, for different benchmarks and example VLIW architectures, including a single-cluster version of the TI C62x DSP processor and variants of that. Our results can sharpen the interpretation of the term optimality used with various methods for optimal VLIW scheduling, and help to identify sets of schedules that can be safely ignored when searching for a time-optimal schedule.
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| 20. |
- Kessler, Christoph
(författare)
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Managing distributed shared arrays in a bulk-synchronous parallel programming environment
- 2004
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 16:02-Mar, s. 133-153
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Tidskriftsartikel (refereegranskat)abstract
- NestStep is a parallel programming language for the BSP (bulk-hronous parallel) programming model. In this article we describe the concept of distributed shared arrays in NestStep and its implementation on top of MPI. In particular, we present a novel method for runtime scheduling of irregular, direct remote accesses to sections of distributed shared arrays. Our method, which is fully parallelized, uses conventional two-sided message passing and thus avoids the overhead of a standard implementation of direct remote memory access based on one-sided communication. The main prerequisite is that the given program is structured in a BSP-compliant way. Copyright (C) 2004 John Wiley Sons, Ltd.
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| 21. |
- Kessler, Christoph, et al.
(författare)
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Optimal integrated code generation for VLIW architectures
- 2006
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 18:11, s. 1353-1390
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Tidskriftsartikel (refereegranskat)abstract
- We present a dynamic programming method for optimal integrated code generation for basic blocks that minimizes execution time. It can be applied to single-issue pipelined processors, in-order-issue superscalar processors, VLIW architectures with a single homogeneous register set, and clustered VLIW architectures with multiple register sets. For the case of a single register set, our method simultaneously copes with instruction selection, instruction scheduling, and register allocation. For clustered VLIW architectures, we also integrate the optimal partitioning of instructions, allocation of registers for temporary variables, and scheduling of data transfer operations between clusters. Our method is implemented in the prototype of a retargetable code generation framework for digital signal processors (DSPs), called OPTIMIST. We present results for the processors ARM9E, TI C62x, and a single-cluster variant of C62x. Our results show that the method can produce optimal solutions for small and (in the case of a single register set) medium-sized problem instances with a reasonable amount of time and space. For larger problem instances, our method can be seamlessly changed into a heuristic. Copyright (c) 2006 John Wiley & Sons, Ltd.
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| 22. |
- Kessler, Christoph, et al.
(författare)
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Optimized composition of performance-aware parallel components
- 2012
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Ingår i: Concurrency and Computation. - : John Wiley and Sons. - 1532-0626 .- 1532-0634. ; 24:5, s. 481-498
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Tidskriftsartikel (refereegranskat)abstract
- We describe the principles of a novel framework for performance-aware composition of sequential and explicitly parallel software components with implementation variants. Automatic composition results in a table-driven implementation that, for each parallel call of a performance-aware component, looks up the expected best implementation variant, processor allocation and schedule given the current problem, and processor group sizes. The dispatch tables are computed off-line at component deployment time by an interleaved dynamic programming algorithm from time-prediction meta-code provided by the component supplier.
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| 23. |
- Khan, Zaheer, et al.
(författare)
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Blockchain and edge computing–based architecture for participatory smart city applications
- 2019
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Ingår i: Concurrency and Computation. - : John Wiley and Sons Ltd. - 1532-0626 .- 1532-0634.
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Tidskriftsartikel (refereegranskat)abstract
- Smart cities aim to provide smart governance with the emphasis on gaining high transparency and trust in public services and enabling citizen participation in decision making processes. This means on the one hand data generated from urban transactions need to be open and trustworthy. On the other hand, security and privacy of public data needs to be handled at different administrative and geographical levels. In this paper, we investigate the pivotal role of blockchain in providing privacy, self-verification, authentication, and authorization of participatory transactions in open governance. We also investigate up to what extent edge computing can contribute toward management of permissioned sharing at specific administrative levels and enhance privacy and provide an economic approach for resource utilization in a distributed environment. We introduce a novel architecture that is based on distributed hybrid ledger and edge computing model. The architecture provides refined and secure management of data generated and processed in different geographical and administrative units of a city. We implemented a proof of concept of the architecture and applied it on a carefully designed use case, ie, citizen participation in administrative decisions through consensus. This use case highlights the need to keep and process citizen participation data at local level by deploying district chaincodes and only share consensus results through permissioned chaincodes. The results reveal that proposed architecture is scalable and provide secure and privacy protected environment for citizen participatory applications. Our performance test results are promising and show that under control conditions, the average registration time for a citizen transaction is about 42 ms, whilst the validation and result compilation of 100 concurrent citizens' transactions took about 2.4 seconds.
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| 24. |
- Kjelgaard Mikkelsen, Carl Christian, 1976-, et al.
(författare)
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Newton's method revisited : how accurate do we have to be?
- 2024
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Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 36:10
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the convergence of quasi-Newton methods in exact and finite precision arithmetic using three different techniques. We derive an upper bound for the stagnation level and we show that any sufficiently exact quasi-Newton method will converge quadratically until stagnation. In the absence of sufficient accuracy, we are likely to retain rapid linear convergence. We confirm our analysis by computing square roots and solving bond constraint equations in the context of molecular dynamics. In particular, we apply both a symmetric variant and Forsgren's variant of the simplified Newton method. This work has implications for the implementation of quasi-Newton methods regardless of the scale of the calculation or the machine.
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| 25. |
- Kjelgaard Mikkelsen, Carl Christian, 1976-, et al.
(författare)
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Parallel robust solution of triangular linear systems
- 2019
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Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 31:19
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Tidskriftsartikel (refereegranskat)abstract
- Triangular linear systems are central to the solution of general linear systems and the computation of eigenvectors. In the absence of floating‐point exceptions, substitution runs to completion and solves a system which is a small perturbation of the original system. If the matrix is well‐conditioned, then the normwise relative error is small. However, there are well‐conditioned systems for which substitution fails due to overflow. The robust solvers xLATRS from LAPACK extend the set of linear systems which can be solved by dynamically scaling the solution and the right‐hand side to avoid overflow. These solvers are sequential and apply to systems with a single right‐hand side. This paper presents algorithms which are blocked and parallel. A new task‐based parallel robust solver (Kiya) is presented and compared against both DLATRS and the non‐robust solvers DTRSV and DTRSM. When there are many right‐hand sides, Kiya performs significantly better than the robust solver DLATRS and is not significantly slower than the non‐robust solver DTRSM.
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| 26. |
- Kostentinos Tesfatsion, Selome, et al.
(författare)
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Power and Performance Optimization in FPGA-accelerated Clouds
- 2018
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Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 30:18
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Energy management has become increasingly necessary in data centers to address all energy-related costs, including capital costs, operating expenses, and environmental impacts. Heterogeneous systems with mixed hardware architectures provide both throughput and processing efficiency for different specialized application types and thus have a potential for significant energy savings. However, the presence of multiple and different processing elements increases the complexity of resource assignment. In this paper, we propose a system for efficient resource management in heterogeneous clouds. The proposed approach maps applications' requirement to different resources reducing power usage with minimum impact on performance. A technique that combines the scheduling of custom hardware accelerators, in our case, Field-Programmable Gate Arrays (FPGAs) and optimized resource allocation technique for commodity servers, is proposed. We consider an energy-aware scheduling technique that uses both the applications' performance and their deadlines to control the assignment of FPGAs to applications that would consume the most energy. Once the scheduler has performed the mapping between a VM and an FPGA, an optimizer handles the remaining VMs in the server, using vertical scaling and CPU frequency adaptation to reduce energy consumption while maintaining the required performance. Our evaluation using interactive and data-intensive applications compare the effectiveness of the proposed solution in energy savings as well as maintaining applications performance, obtaining up to a 32% improvement in the performance-energy ratio on a mix of multimedia and e-commerce applications.
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| 27. |
- Laure, Erwin, et al.
(författare)
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Performance Engineering in Data Grids
- 2005
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 17:2-4, s. 171-191
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Tidskriftsartikel (refereegranskat)abstract
- The vision of Grid computing is to facilitate worldwide resource sharing among distributed collaborations. With the help of numerous national and international Grid projects, this vision is becoming reality and Grid systems are attracting an ever increasing user base. However, Grids are still quite complex software systems whose efficient use is a difficult and error-prone task. In this paper we present performance engineering techniques that aim to facilitate an efficient use of Grid systems, in particular systems that deal with the management of large-scale data sets in the tera- and petabyte range (also referred to as data Grids). These techniques are applicable at different layers of a Grid architecture and we discuss the tools required at each of these layers to implement them. Having discussed important performance engineering techniques, we investigate how major Grid projects deal with performance issues particularly related to data Grids and how they implement the techniques presented.
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| 28. |
- Luan, Siyu, et al.
(författare)
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LRP-based network pruning and policy distillation of robust and non-robust DRL agents for embedded systems
- 2023
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Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 35:19
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Tidskriftsartikel (refereegranskat)abstract
- Reinforcement learning (RL) is an effective approach to developing control policies by maximizing the agent's reward. Deep reinforcement learning uses deep neural networks (DNNs) for function approximation in RL, and has achieved tremendous success in recent years. Large DNNs often incur significant memory size and computational overheads, which may impede their deployment into resource-constrained embedded systems. For deployment of a trained RL agent on embedded systems, it is necessary to compress the policy network of the RL agent to improve its memory and computation efficiency. In this article, we perform model compression of the policy network of an RL agent by leveraging the relevance scores computed by layer-wise relevance propagation (LRP), a technique for Explainable AI (XAI), to rank and prune the convolutional filters in the policy network, combined with fine-tuning with policy distillation. Performance evaluation based on several Atari games indicates that our proposed approach is effective in reducing model size and inference time of RL agents. We also consider robust RL agents trained with RADIAL-RL versus standard RL agents, and show that a robust RL agent can achieve better performance (higher average reward) after pruning than a standard RL agent for different attack strengths and pruning rates.
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| 29. |
- Majd, Amin, et al.
(författare)
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Parallel imperialist competitive algorithms
- 2018
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Ingår i: Concurrency and Computation. - : WILEY. - 1532-0626 .- 1532-0634. ; 30:7
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Tidskriftsartikel (refereegranskat)abstract
- The importance of optimization and NP-problem solving cannot be overemphasized. The usefulness and popularity of evolutionary computing methods are also well established. There are various types of evolutionary methods; they are mostly sequential but some of them have parallel implementations as well. We propose a multi-population method to parallelize the Imperialist Competitive Algorithm. The algorithm has been implemented with the Message Passing Interface on 2 computer platforms, and we have tested our method based on shared memory and message passing architectural models. An outstanding performance is obtained, demonstrating that the proposed method is very efficient concerning both speed and accuracy. In addition, compared with a set of existing well-known parallel algorithms, our approach obtains more accurate results within a shorter time period.
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| 30. |
- Martinsen, Jan Kasper, et al.
(författare)
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Combining thread-level speculation and just-in-time compilation in Google’s V8 JavaScript engine
- 2017
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Ingår i: Concurrency and Computation. - : Wiley Online Library. - 1532-0626 .- 1532-0634. ; 29:1
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Tidskriftsartikel (refereegranskat)abstract
- Summary: Thread-level speculation can be used to take advantage of multicore architectures for JavaScript in web applications. We extend previous studies with these main contributions; we implement thread-level speculation in the state-of-the art just-in-time-enabled JavaScript engine V8 and make the measurements in the Chromium web browser both from Google instead of using an interpreted JavaScript engine. We evaluate the thread-level speculation and just-in-time compilation combination on 15 very popular web applications, 20 HTML5 demos from the JS1K competition, and 4 Google Maps use cases. The performance is evaluated on two, four, and eight cores. The results clearly show that it is possible to successfully combine thread-level speculation and just-in-time compilation. This makes it possible to take advantage of multicore architectures for web applications while hiding the details of parallel programming from the programmer. Further, our results show an average speedup for the thread-level speculation and just-in-time compilation combination by a factor of almost 3 on four cores and over 4 on eight cores, without changing any of the JavaScript source code.
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| 31. |
- Memeti, Suejb, et al.
(författare)
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Combinatorial optimization of DNA sequence analysis on heterogeneous systems
- 2017
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Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 29:7
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Tidskriftsartikel (refereegranskat)abstract
- Analysis of DNA sequences is a data and computational intensive problem, and therefore, it requires suitable parallel computing resources and algorithms. In this paper, we describe our parallel algorithm for DNA sequence analysis that determines how many times a pattern appears in the DNA sequence. The algorithm is engineered for heterogeneous platforms that comprise a host with multi-core processors and one or more many-core devices. For combinatorial optimization, we use the simulated annealing algorithm. The optimization goal is to determine the number of threads, thread affinities, and DNA sequence fractions for host and device, such that the overall execution time of DNA sequence analysis is minimized. We evaluate our approach experimentally using real-world DNA sequences of various organisms on a heterogeneous platform that comprises two Intel Xeon E5 processors and an Intel Xeon Phi 7120P co-processing device. By running only about 5% of possible experiments, our optimization method finds a near-optimal system configuration for DNA sequence analysis that yields with average speedup of 1.6 × and 2 × compared with the host-only and device-only execution.
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| 32. |
- Myllykoski, Mirko, 1988-, et al.
(författare)
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Task‐based, GPU‐accelerated and robust library for solving dense nonsymmetric eigenvalue problems
- 2021
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Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 33:11
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present the StarNEig library for solving dense nonsymmetric standard and generalized eigenvalue problems. The library is built on top of the StarPU runtime system and targets both shared and distributed memory machines. Some components of the library have support for GPU acceleration. The library currently applies to real matrices with real and complex eigenvalues and all calculations are done using real arithmetic. Support for complex matrices is planned for a future release. This paper is aimed at potential users of the library. We describe the design choices and capabilities of the library, and contrast them to existing software such as LAPACK and ScaLAPACK. StarNEig implements a ScaLAPACK compatibility layer which should assist new users in the transition to StarNEig. We demonstrate the performance of the library with a sample of computational experiments.
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| 33. |
- Podobas, Artur, 1982-, et al.
(författare)
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A comparative performance study of common and popular task-centric programming frameworks
- 2013
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634.
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Tidskriftsartikel (refereegranskat)abstract
- SUMMARY: Programmers today face a bewildering array of parallel programming models and tools, making it difficult to choose an appropriate one for each application. An increasingly popular programming model supporting structured parallel programming patterns in a portable and composable manner is the task-centric programming model. In this study, we compare several popular task-centric programming frameworks, including Cilk Plus, Threading Building Blocks, and various implementations of OpenMP 3.0. We have analyzed their performance on the Barcelona OpenMP Tasking Suite benchmark suite both on a 48-core AMD Opteron 6172 server and a 64-core TILEPro64 embedded many-core processor. Our results show that the OpenMP offers the highest flexibility for programmers, and this flexibility comes to a cost. Frameworks supporting only a specific and more restrictive model, such as Cilk Plus and Threading Building Blocks, are generally more efficient both in terms of performance and energy consumption. However, Intel's implementation of OpenMP tasks performs the best and closest to the specialized run-time systems.
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| 34. |
- Riedel, M., et al.
(författare)
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Interoperation of World-Wide Production e-Science Infrastructures
- 2009
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 21:8, s. 961-990
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Tidskriftsartikel (refereegranskat)abstract
- Many production Grid and e-Science infrastructures have begun to offer services to end-users during the past several years with an increasing number of scientific applications that require access to a wide variety of resources and services in multiple Grids. Therefore, the Grid Interoperation Now-Community Group of the Open Grid Forum-organizes and manages interoperation efforts among those production Grid infrastructures to reach the goal of a world-wide Grid vision on a technical level in the near future. This contribution highlights fundamental approaches of the group and discusses open standards in the context of production e-Science infrastructures.
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| 35. |
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| 36. |
- Shirinbab, Sogand, et al.
(författare)
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Performance evaluation of containers and virtual machines when running Cassandra workload concurrently
- 2020
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Ingår i: Concurrency and Computation. - : Wiley-Blackwell. - 1532-0626 .- 1532-0634. ; 32:17
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Tidskriftsartikel (refereegranskat)abstract
- NoSQL distributed databases are often used as Big Data platforms. To provide efficient resource sharing and cost effectiveness, such distributed databases typically run concurrently on a virtualized infrastructure that could be implemented using hypervisor-based virtualization or container-based virtualization. Hypervisor-based virtualization is a mature technology but imposes overhead on CPU, networking, and disk. Recently, by sharing the operating system resources and simplifying the deployment of applications, container-based virtualization is getting more popular. This article presents a performance comparison between multiple instances of VMware VMs and Docker containers running concurrently. Our workload models a real-world Big Data Apache Cassandra application from Ericsson. As a baseline, we evaluated the performance of Cassandra when running on the nonvirtualized physical infrastructure. Our study shows that Docker has lower overhead compared with VMware; the performance on the container-based infrastructure was as good as on the nonvirtualized. Our performance evaluations also show that running multiple instances of a Cassandra database concurrently affected the performance of read and write operations differently; for both VMware and Docker, the maximum number of read operations was reduced when we ran several instances concurrently, whereas the maximum number of write operations increased when we ran instances concurrently.
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| 37. |
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| 38. |
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| 39. |
- Valero-Lara, P., et al.
(författare)
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Heterogeneous CPU+GPU approaches for mesh refinement over Lattice-Boltzmann simulations
- 2016
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Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634.
-
Tidskriftsartikel (refereegranskat)abstract
- The use of mesh refinement in CFD is an efficient and widely used methodology to minimize the computational cost by solving those regions of high geometrical complexity with a finer grid. In this work, the author focuses on studying two methods, one based on Multi-Domain and one based on Irregular meshing, to deal with mesh refinement over LBM simulations. The numerical formulation is presented in detail. It is proposed two approaches, homogeneous GPU and heterogeneous CPU+GPU, on each of the refinement methods. Obviously, the use of the two architectures, CPU and GPU, to compute the same problem involves more important challenges with respect to the homogeneous counterpart. These challenges and the strategies to deal with them are described in detail into the present work. We pay a particular attention to the differences among both methodologies/implementations in terms of programmability, memory management, and performance. The size of the refined sub-domain has important consequences over both methodologies; however, the influence on Multi-Domain approach is much higher. For instance, when dealing with a big refined sub-domain, the Multi-Domain approach achieves an important fall in performance with respect to other cases, where the size of the refined sub-domain is smaller. Otherwise, using the Irregular approach, there is no such a dramatic fall in performance when increasing the size of the refined sub-domain.
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| 40. |
- Vapirev, A., et al.
(författare)
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Initial results on computational performance of Intel many integrated core, sandy bridge, and graphical processing unit architectures : implementation of a 1D c++/OpenMP electrostatic particle-in-cell code
- 2015
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 27:3, s. 581-593
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Tidskriftsartikel (refereegranskat)abstract
- We present initial comparison performance results for Intel many integrated core (MIC), Sandy Bridge (SB), and graphical processing unit (GPU). A 1D explicit electrostatic particle-in-cell code is used to simulate a two-stream instability in plasma. We compare the computation times for various number of cores/threads and compiler options. The parallelization is implemented via OpenMP with a maximum thread number of 128. Parallelization and vectorization on the GPU is achieved with modifying the code syntax for compatibility with CUDA. We assess the speedup due to various auto-vectorization and optimization level compiler options. Our results show that the MIC is several times slower than SB for a single thread, and it becomes faster than SB when the number of cores increases with vectorization switched on. The compute times for the GPU are consistently about six to seven times faster than the ones for MIC. Compared with SB, the GPU is about two times faster for a single thread and about an order of magnitude faster for 128 threads. The net speedup, however, for MIC and GPU are almost the same. An initial attempt to offload parts of the code to the MIC coprocessor shows that there is an optimal number of threads where the speedup reaches a maximum.
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| 41. |
- Varisteas, Georgios, 1982-, et al.
(författare)
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Palirria : accurate on-line parallelism estimation for adaptive work-stealing
- 2016
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Ingår i: Concurrency and Computation. - : John Wiley and Sons Ltd. - 1532-0626 .- 1532-0634. ; 28:2, s. 472-491
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Tidskriftsartikel (refereegranskat)abstract
- Summary We present Palirria, a self-adapting work-stealing scheduling method for nested fork/join parallelism that can be used to estimate the number of utilizable workers and self-adapt accordingly. The estimation mechanism is optimized for accuracy, minimizing the requested resources without degrading performance. We implemented Palirria for both the Linux and Barrelfish operating systems and evaluated it on two platforms: a 48-core Non-Uniform Memory Access (NUMA) multiprocessor and a simulated 32-core system. Compared with state-of-the-art, we observed higher accuracy in estimating resource requirements. This leads to improved resource utilization and performance on par or better to executing with fixed resource allotments.
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| 42. |
- Waliullah, Mridha Mohammad, 1979, et al.
(författare)
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Schemes for avoiding starvation in transactional memory systems
- 2009
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Ingår i: Concurrency Computation Practice and Experience. - : Wiley. - 1532-0634 .- 1532-0626. ; 21:7, s. 859-873
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Tidskriftsartikel (refereegranskat)abstract
- Transactional memory systems trade ease of programming with run-time performance losses in handling transactions. This paper focuses on starvation effects that show up in systems where unordered transactions are committed on a demand-driven basis. Such simple commit arbitration policies are prone to starvation. The design issues for commit arbitration policies are analyzed and novel policies that reduce the amount of wasted computation due to roll-back and, most important, that avoid starvation are proposed. We analyze in detail how to incorporate them in the transactional coherence and consistency protocol as well as a scalable version of it. The proposed schemes are shown to have no impact on the common-case performance and add quite modest complexity to the baseline protocol. Copyright (C) 2008 John Wiley & Sons, Ltd.
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| 43. |
- Wang, Jiechen, et al.
(författare)
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A parallel algorithm for constructing Voronoi diagrams based on point-set adaptive grouping
- 2014
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 26:2, s. 434-446
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a parallel algorithm for constructing Voronoi diagrams based on point-set adaptive grouping. The binary tree splitting method is used to adaptively group the point set in the plane and construct sub-Voronoi diagrams for each group. Given that the construction of Voronoi diagrams in each group consumes the majority of time and that construction within one group does not affect that in other groups, the use of a parallel algorithm is suitable.After constructing the sub-Voronoi diagrams, we extracted the boundary points of the four sides of each sub-group and used to construct boundary site Voronoi diagrams. Finally, the sub-Voronoi diagrams containing each boundary point are merged with the corresponding boundary site Voronoi diagrams. This produces the desired Voronoi diagram. Experiments demonstrate the efficiency of this parallel algorithm, and its time complexity is calculated as a function of the size of the point set, the number of processors, the average number of points in each block, and the number of boundary points.
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| 44. |
- Xhafa, Fatos, et al.
(författare)
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Grid and P2P middleware for wide-area parallel processing
- 2011
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Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 23:5, s. 458-476
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Tidskriftsartikel (refereegranskat)abstract
- Grid computing emerged as a paradigm for high-performance computing and massive parallel processing. Currently, Grid systems have become an important paradigm for efficiently solving large-scale complex problems from many fields. On the other hand, P2P paradigm originated from file-sharing, but each time more is being used for the development of large-scale distributed platforms. Grid and P2P systems have thus followed different trajectories pushed by different motivations, needs and research communities. In fact, both paradigms are evolving in a way that each time they are sharing more common characteristics and are mutually benefiting from their best features. Among these characteristics, we could distinguish the cooperative model for solving complex problems by exploiting their large computing capacity. As such, Grid and P2P systems have achieved notable success, in particular, for e-Science applications, a family of complex applications arising in science and engineering that need considerable computation power. Despite important advances in the design and use of Grid and P2P systems, they remain still difficult to implement and apply to real-life problems. The main difficulties reside in the lack of easy-to-use middleware for Grid and P2P, in the complexities of setting up and in the tedious task of deploying real-world Grid/P2P platforms as well as in experimental studies which are often complex and not easy to repeat. In this paper we survey and analyze the advances in communication libraries and middleware for both Grid and P2P systems as well as their limitations when used in real Grid and P2P infrastructures. We also bring examples of real-life applications of massive data processing that can be efficiently handled through Grid and P2P approaches.
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