19,307 research outputs found

    GoFFish: A Sub-Graph Centric Framework for Large-Scale Graph Analytics

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    Large scale graph processing is a major research area for Big Data exploration. Vertex centric programming models like Pregel are gaining traction due to their simple abstraction that allows for scalable execution on distributed systems naturally. However, there are limitations to this approach which cause vertex centric algorithms to under-perform due to poor compute to communication overhead ratio and slow convergence of iterative superstep. In this paper we introduce GoFFish a scalable sub-graph centric framework co-designed with a distributed persistent graph storage for large scale graph analytics on commodity clusters. We introduce a sub-graph centric programming abstraction that combines the scalability of a vertex centric approach with the flexibility of shared memory sub-graph computation. We map Connected Components, SSSP and PageRank algorithms to this model to illustrate its flexibility. Further, we empirically analyze GoFFish using several real world graphs and demonstrate its significant performance improvement, orders of magnitude in some cases, compared to Apache Giraph, the leading open source vertex centric implementation.Comment: Under review by a conference, 201

    Ubiquitous Cell-Free Massive MIMO Communications

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    Since the first cellular networks were trialled in the 1970s, we have witnessed an incredible wireless revolution. From 1G to 4G, the massive traffic growth has been managed by a combination of wider bandwidths, refined radio interfaces, and network densification, namely increasing the number of antennas per site. Due its cost-efficiency, the latter has contributed the most. Massive MIMO (multiple-input multiple-output) is a key 5G technology that uses massive antenna arrays to provide a very high beamforming gain and spatially multiplexing of users, and hence, increases the spectral and energy efficiency. It constitutes a centralized solution to densify a network, and its performance is limited by the inter-cell interference inherent in its cell-centric design. Conversely, ubiquitous cell-free Massive MIMO refers to a distributed Massive MIMO system implementing coherent user-centric transmission to overcome the inter-cell interference limitation in cellular networks and provide additional macro-diversity. These features, combined with the system scalability inherent in the Massive MIMO design, distinguishes ubiquitous cell-free Massive MIMO from prior coordinated distributed wireless systems. In this article, we investigate the enormous potential of this promising technology while addressing practical deployment issues to deal with the increased back/front-hauling overhead deriving from the signal co-processing.Comment: Published in EURASIP Journal on Wireless Communications and Networking on August 5, 201

    A data-flow language for business process models

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    On the basis of the artifact-centric approach to business process modeling, this paper proposes a notation named ACTA that provides two equivalent forms of representation: in one, all the life cycles of the artifacts involved in the business under consideration are shown in a single model, while in the other they are defined in separate models. The latter may be easier to understand when the model is large but requires synchronization points between life cycles: two kinds of mechanisms, i.e., driven transitions and driven tasks are analyzed in this paper. The major feature of ACTA is its nature of data flow language: the activation of tasks depends on the presence of suitable input entities rather than on the precedence relationships between tasks as it takes place in the conventional activity-centric approach. The advantage is the ease with which a number of situations that are difficult to handle with the activity-centric approach can be managed. Such situations encompass the selection of homogeneous entities to be processed in batches and the many-to-many mapping between entities of different types, such as requisition orders and procurement orders
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