bluuebunny/crossref_metadata_2025 huggingface dataset:
A Mobility and Traffic Generation Framework for Modeling and Simulating Ad Hoc Communication Networks
Authors: Barrett Chris , Drozda Martin , Marathe Madhav V. , Ravi S.S. , Smith James P.
Published: January 2015

We present a generic mobility and traffic generation framework that can be incorporated into a tool for modeling and simulating large scale ad~hoc networks. Three components of this framework, namely a mobility data generator (MDG), a graph structure generator (GSG) and an occlusion modification tool (OMT) allow a variety of mobility models to be incorporated into the tool. The MDG module generates positions of transceivers at specified time instants. The GSG module constructs the graph corresponding to the ad hoc network from the mobility data provided by MDG. The OMT module modifies the connectivity of the graph produced by GSG to allow for occlusion effects. With two other modules, namely an activity data generator (ADG) which generates packet transmission activities for transceivers and a packet activity simulator (PAS) which simulates the movement and interaction of packets among the transceivers, the framework allows the modeling and simulation of ad hoc communication networks. The design of the framework allows a user to incorporate various realistic parameters crucial in the simulation. We illustrate the utility of our framework through a comparative study of three mobility models. Two of these are synthetic models (random waypoint and exponentially correlated mobility) proposed in the literature. The third model is based on an urban population mobility modeling tool (TRANSIMS) developed at the Los Alamos National Laboratory. This tool is capable of providing comprehensive information about the demographics, mobility and interactions of members of a large urban population. A comparison of these models is carried out by computing a variety of parameters associated with the graph structures generated by the models. There has recently been interest in the structural properties of graphs that arise in real world systems. We examine two aspects of this for the graphs created by the mobility models: change associated with power control (range of transceivers) and variation in time as transceivers move in space.
Remote Memory Access: A Case for Portable, Efficient and Library Independent Parallel Programming
Authors: Gerbessiotis Alexandros V. , Lee Seung-Yeop
Published: January 2015

In this work we make a strong case for remote memory access (RMA) as the effective way to program a parallel computer by proposing a framework that supports RMA in a library independent, simple and intuitive way. If one uses our approach the parallel code one writes will run transparently under MPI‐2 enabled libraries but also bulk‐synchronous parallel libraries. The advantage of using RMA is code simplicity, reduced programming complexity, and increased efficiency. We support the latter claims by implementing under this framework a collection of benchmark programs consisting of a communication and synchronization performance assessment program, a dense matrix multiplication algorithm, and two variants of a parallel radix‐sort algorithm and examine their performance on a LINUX‐based PC cluster under three different RMA enabled libraries: LAM MPI, BSPlib, and PUB. We conclude that implementations of such parallel algorithms using RMA communication primitives lead to code that is as efficient as the message‐passing equivalent code and in the case of radix‐sort substantially more efficient. In addition our work can be used as a comparative study of the relevant capabilities of the three libraries.
Collaborating Components in Mesh‐Based Electronic Packaging
Authors: Chow P. , Lai C.-H.
Published: January 2015

From the model geometry creation to the model analysis, the stages in between such as mesh generation are the most manpower intensive phase in a mesh‐based computational mechanics simulation process. On the other hand the model analysis is the most computing intensive phase. Advanced computational hardware and software have significantly reduced the computing time – and more importantly the trend is downward. With the kind of models envisaged coming, which are larger, more complex in geometry and modelling, and multiphysics, there is no clear trend that the manpower intensive phase is to decrease significantly in time – in the present way of operation it is more likely to increase with model complexity. In this paper we address this dilemma in collaborating components for models in electronic packaging application.
Pegasus: A Framework for Mapping Complex Scientific Workflows onto Distributed Systems
Authors: Deelman Ewa , Singh Gurmeet , Su Mei-Hui , Blythe James , Gil Yolanda , Kesselman Carl , Mehta Gaurang , Vahi Karan , Berriman G. Bruce , Good John , Laity Anastasia , Jacob Joseph C. , Katz Daniel S.
Published: January 2015

This paper describes the Pegasus framework that can be used to map complex scientific workflows onto distributed resources. Pegasus enables users to represent the workflows at an abstract level without needing to worry about the particulars of the target execution systems. The paper describes general issues in mapping applications and the functionality of Pegasus. We present the results of improving application performance through workflow restructuring which clusters multiple tasks in a workflow into single entities. A real‐life astronomy application is used as the basis for the study.
Managing Data Persistence in Network Enabled Servers
Authors: Caron Eddy , DelFabbro Bruno , Desprez Frédéric , Jeannot Emmanuel , Nicod Jean-Marc
Published: January 2015

The GridRPC model [17] is an emerging standard promoted by the Global Grid Forum (GGF) that defines how to perform remote client‐server computations on a distributed architecture. In this model data are sent back to the client at the end of every computation. This implies unnecessary communications when computed data are needed by an other server in further computations. Since, communication time is sometimes the dominant cost of remote computations, this cost has to be lowered. Several tools instantiate the GridRPC model such as NetSolve developed at the University of Tennessee, Knoxville, USA, and DIET developed at LIP laboratory, ENS Lyon, France. They are usually called Network Enabled Servers (NES). In this paper, we present a discussion of the data management solutions chosen for these two NES (NetSolve and DIET) as well as experimental results.
The CanonicalProducer: An Instrument Monitoring Component of the Relational Grid Monitoring Architecture (R‐GMA)
Authors: Kenny Stuart , Coghlan Brian , O′Callaghan David , Ryan John , Byrom Rob , Field Laurence , Hicks Steve , Soni Manish , Wilson Antony , Zhu Xiaomei , Cordenonsi Roney , Datta Ari , Cornwall Linda , Djaoui Abdeslem , Podhorszki Norbert
Published: January 2015

We describe how the R‐GMA (Relational Grid Monitoring Architecture) can be used to allow for instrument monitoring in a Grid environment. The R‐GMA has been developed within the European DataGrid Project (EDG) as a Grid Information and Monitoring System. It is based on the Grid Monitoring Architecture (GMA) from the Global Grid Forum (GGF), which is a simple Consumer‐Producer model. The special strength of this implementation comes from the power of the relational model. It offers a global view of the information as if each Virtual Organisation had one large relational database. It provides a number of different Producer types with different characteristics; for example some support streaming of information. We describe the R‐GMA component that allows for instrument monitoring, the CanonicalProducer. We also describe an example use of this approach in the European CrossGrid project, SANTA‐G, a network monitoring tool.
Similarity‐Based Clustering Strategy for Mobile Ad Hoc Multimedia Databases
Authors: Yang Bo , Hurson Ali R.
Published: January 2015

Multimedia data are becoming popular in wireless ad hoc environments. However, the traditional content‐based retrieval techniques are inefficient in ad hoc networks due to the multiple limitations such as node mobility, computation capability, memory space, network bandwidth, and data heterogeneity. To provide an efficient platform for multimedia retrieval, we propose to cluster ad hoc multimedia databases based on their semantic contents, and construct a virtual hierarchical indexing infrastructure overlaid on the mobile databases. This content‐aware clustering scheme uses a semantic‐aware framework as the theoretical foundation for data organization. Several novel techniques are presented to facilitate the representation and manipulation of multimedia data in ad hoc networks: 1) using concise distribution expressions to represent the semantic similarity of multimedia data, 2) constructing clusters based on the semantic relationships between multimedia entities, 3) reducing the cost of content‐based multimedia retrieval through the restriction of semantic distances, and 4) employing a self‐adaptive mechanism that dynamically adjusts to the content and topology changes of the ad hoc networks. The proposed scheme is scalable, fault‐tolerant, and efficient in performing content‐based multimedia retrieval as demonstrated in our combination of theoretical analysis and extensive experimental studies.
Development and Execution of an Impact Cratering Application on a Computational Grid
Authors: Huedo E. , Lepinette A. , Montero R.S. , Llorente I.M. , Vázquez L.
Published: January 2015

Impact cratering is an important geological process of special interest in Astrobiology. Its numerical simulation comprises the execution of a high number of tasks, since the search space of input parameter values includes the projectile diameter, the water depth and the impactor velocity. Furthermore, the execution time of each task is not uniform because of the different numerical properties of each experimental configuration. Grid technology is a promising platform to execute this kind of applications, since it provides the end user with a performance much higher than that achievable on any single organization. However, the scheduling of each task on a Grid involves challenging issues due to the unpredictable and heterogeneous behavior of both the Grid and the numerical code. This paper evaluates the performance of a Grid infrastructure based on the Globus toolkit and the GridWay framework, which provides the adaptive and fault tolerance functionality required to harness Grid resources, in the simulation of the impact cratering process. The experiments have been performed on a testbed composed of resources shared by five sites interconnected by RedIRIS, the Spanish Research and Education Network.
The TeraGyroid Experiment – Supercomputing 2003
Authors: Blake R.J. , Coveney P.V. , Clarke P. , Pickles S.M.
Published: January 2015

Amphiphiles are molecules with hydrophobic tails and hydrophilic heads. When dispersed in solvents, they self assemble into complex mesophases including the beautiful cubic gyroid phase. The goal of the TeraGyroid experiment was to study defect pathways and dynamics in these gyroids. The UK′s supercomputing and USA′s TeraGrid facilities were coupled together, through a dedicated high‐speed network, into a single computational Grid for research work that peaked around the Supercomputing 2003 conference. The gyroids were modeled using lattice Boltzmann methods with parameter spaces explored using many 1283 and 3grid point simulations, this data being used to inform the world′s largest three‐dimensional time dependent simulation with 10243‐grid points. The experiment generated some 2 TBytes of useful data. In terms of Grid technology the project demonstrated the migration of simulations (using Globus middleware) to and fro across the Atlantic exploiting the availability of resources. Integration of the systems accelerated the time to insight. Distributed visualisation of the output datasets enabled the parameter space of the interactions within the complex fluid to be explored from a number of sites, informed by discourse over the Access Grid. The project was sponsored by EPSRC (UK) and NSF (USA) with trans‐Atlantic optical bandwidth provided by British Telecommunications.
Parallel Preconditioned Conjugate Gradient Square Method Based on Normalized Approximate Inverses
Authors: Gravvanis George A. , Giannoutakis Konstantinos M.
Published: January 2015

A new class of normalized explicit approximate inverse matrix techniques, based on normalized approximate factorization procedures, for solving sparse linear systems resulting from the finite difference discretization of partial differential equations in three space variables are introduced. A new parallel normalized explicit preconditioned conjugate gradient square method in conjunction with normalized approximate inverse matrix techniques for solving efficiently sparse linear systems on distributed memory systems, using Message Passing Interface (MPI) communication library, is also presented along with theoretical estimates on speedups and efficiency. The implementation and performance on a distributed memory MIMD machine, using Message Passing Interface (MPI) is also investigated. Applications on characteristic initial/boundary value problems in three dimensions are discussed and numerical results are given.
Supporting User Mobility through Cache Relocation
Authors: Lai Kwong Yuen , Tari Zahir , Bertok Peter
Published: January 2015

Traffic and access delay can be reduced in a mobile network by caching data objects at network nodes near the clients. Traditional caching techniques, however, are unsuitable in this environment because they do not account for the changing location of the users. To deal with this problem, cache relocation techniques can be applied to dynamically relocate data objects so they remain close to the moving clients. Existing relocation techniques rely heavily on path prediction. Unfortunately, the inaccuracy of path prediction can lead to high relocation overhead and poor response time. This paper presents an analytical study of the effects of client mobility on network cache performance. Two new cache relocation techniques are proposed to deal with the issue of poor path prediction and reduce the overhead of existing cache relocation schemes. The first technique, 2PR, compensates for poor path prediction by temporarily moving data objects to a common parent node prior to a handover. Objects are moved to the correct destination once the client′s new location has been confirmed. The second technique, ROLP, reduces the traffic overhead associated with cache relocation by ensuring duplicate objects are not relocated and relocation of objects are performed only from the nearest node to the destination. Test results show that 2PR reduces the query delay experienced by mobile clients by 60 to 83% after handovers, while ROLP reduces the overhead of cache relocation by between 33 to 65% compared to existing schemes.
On the Performance of the Python Programming Language for Serial and Parallel Scientific Computations
Authors: Cai Xing , Langtangen Hans Petter , Moe Halvard
Published: January 2015

This article addresses the performance of scientific applications that use the Python programming language. First, we investigate several techniques for improving the computational efficiency of serial Python codes. Then, we discuss the basic programming techniques in Python for parallelizing serial scientific applications. It is shown that an efficient implementation of the array‐related operations is essential for achieving good parallel performance, as for the serial case. Once the array‐related operations are efficiently implemented, probably using a mixed‐language implementation, good serial and parallel performance become achievable. This is confirmed by a set of numerical experiments. Python is also shown to be well suited for writing high‐level parallel programs.
Design and Implementation of a Grid Extension for Maple
Authors: Petcu Dana , Paprzycki Marcin , Dubu Diana
Published: January 2015

One of the important issues facing the development of the grid as a computational framework of the future is availability of grid‐enabled software. In this context, we discuss possible approaches to constructing a grid‐enabled version of a computer algebra system. Our case study involves Maple: the proposed Maple2g package allows the connection between Maple and the computational grids based on the Globus Toolkit. We present the design of the Maple2g package and follow with a detailed discussion of its implementation. Finally, we illustrate performance of Maple2g in a number of experiments.
K Nearest Neighbor Search in Navigation Systems
Authors: Safar Maytham
Published: January 2015

A frequent type of query in a car navigation system is to find the k nearest neighbors (kNN) of a given query object (e.g., car) using the actual road network maps. With road networks (spatial networks), the distances between objects depend on their network connectivity and it is computationally expensive to compute the distances (e.g., shortest paths) between objects. In this paper, we propose a novel approach to efficiently and accurately evaluate kNN queries in a mobile information system that uses spatial network databases. The approach uses first order Voronoi diagram and Dijkstra′s algorithm. This approach is based on partitioning a large network to small Voronoi regions, and then pre‐computing distances across the regions. By performing across the network computation for only the border points of the neighboring regions, we avoid global pre‐computation between every object‐pair. Our empirical experiments with real‐world data sets show that our proposed solution outperforms approaches that are based on on‐line distance computation by up to one order of magnitude. In addition, our approach has better response times than approaches that are based on pre‐computation.
Mobile Join Operators for Restricted Sources
Authors: Ozakar Belgin , Morvan Franck , Hameurlain Abdelkader
Published: January 2015

We consider the problem of query execution when there is limited access to the relations, i.e. when binding patterns require values to be specified in order to get data from the relation. This problem is common in virtual data integration systems where there are heterogeneous sources with various restricted access patterns and query capabilities. Another problem is the lack of the statistical information about the sources and occurrence of unpredictable events. We introduce two mobile join operators, MDJoin and SMDJoin which are designed for restricted sources and implemented using ′mobile agents′ in order to benefit from their autonomous and reactive characteristics. Mobile operators of restricted sources are capable to deal with restricted sources and react to the variations between the compile‐time estimations and run‐time computations of data during query execution. The difference between the two new query operators lies in their level of adaptation ability to the execution environment. Performance results show that mobile agent‐based approach at operator level can lead to a significant reduction in response time with restricted sources.
Secure Route Structures for Parallel Mobile Agents Based Systems Using Fast Binary Dispatch
Authors: Wang Yan , Varadharajan Vijay
Published: January 2015

In a distributed environment, where a large number of computers are connected together to enable the large‐scale sharing of data and computing resources, agents, especially mobile agents, are the tools for autonomously completing tasks on behalf of their owners. For applications of large‐scale mobile agents, security and efficiency are of great concern. In this paper, we present a fast binary dispatch model and corresponding secure route structures for mobile agents dispatched in parallel to protect the dispatch routes of agents while ensuring the dispatch efficiency. The fast binary dispatch model is simple but efficient with a dispatch complexity of O(log2
n. The secure route structures adopt the combination of public‐key encryption and digital signature schemes and expose minimal route information to hosts. The nested structure can help detect attacks as early as possible. We evaluated the various models both analytically and empirically.
Execution Model of Three Parallel Languages: OpenMP, UPC and CAF
Authors: Marowka Ami
Published: January 2015

The aim of this paper is to present a qualitative evaluation of three state‐of‐the‐art parallel languages: OpenMP, Unified Parallel C (UPC) and Co‐Array Fortran (CAF). OpenMP and UPC are explicit parallel programming languages based on the ANSI standard. CAF is an implicit programming language. On the one hand, OpenMP designs for shared‐memory architectures and extends the base‐language by using compiler directives that annotate the original source‐code. On the other hand, UPC and CAF designs for distribute‐shared memory architectures and extends the base‐language by new parallel constructs. We deconstruct each language into its basic components, show examples, make a detailed analysis, compare them, and finally draw some conclusions.
Data Retrieval for Location‐Dependent Queries in a Multi‐Cell Wireless Environment
Authors: Jayaputera James , Taniar David
Published: January 2015

The advances of mobile computing technologies in recent years contributes to the growing of mobile information services. Consequently, we need to give special attentions to producing correct answers of those requests, considering the scope of queries and user locations. In this paper, we propose an approach of mobile query processing when the users location moves from one Base Station to another and the queries cross multi‐cells. The efficiency of our proposed approach is presented by giving some examples and performance evaluations.
Interpreting the Data: Parallel Analysis with Sawzall
Authors: Pike Rob , Dorward Sean , Griesemer Robert , Quinlan Sean
Published: January 2015

Very large data sets often have a flat but regular structure and span multiple disks and machines. Examples include telephone call records, network logs, and web document repositories. These large data sets are not amenable to study using traditional database techniques, if only because they can be too large to fit in a single relational database. On the other hand, many of the analyses done on them can be expressed using simple, easily distributed computations: filtering, aggregation, extraction of statistics, and so on. We present a system for automating such analyses. A filtering phase, in which a query is expressed using a new procedural programming language, emits data to an aggregation phase. Both phases are distributed over hundreds or even thousands of computers. The results are then collated and saved to a file. The design – including the separation into two phases, the form of the programming language, and the properties of the aggregators – exploits the parallelism inherent in having data and computation distributed across many machines.
Data Partitioning for Multiprocessors with Memory Heterogeneity and Memory Constraints
Authors: Lastovetsky Alexey , Reddy Ravi
Published: January 2015

The paper presents a performance model that can be used to optimally distribute computations over heterogeneous computers. This model is application‐centric representing the speed of each computer by a function of the problem size. This way it takes into account the processor heterogeneity, the heterogeneity of memory structure, and the memory limitations at each level of memory hierarchy. A problem of optimal partitioning of an n‐element set over p heterogeneous processors using this performance model is formulated, and its efficient solution of the complexity O(p3× log2n) is given.
Personalized Avatars for Mobile Entertainment
Authors: Kosutic Tomislav , Mosmondor Miran , Andrisek Ivan , Weber Mario , Matijasevic Maja , Pandzic Igor
Published: January 2015

With evolution in computer and mobile networking technologies comes the challenge of offering novel and complex multimedia applications and end‐user services in heterogeneous environments for both developers and service providers. This paper describes one novel service, called LiveMail that explores the potential of existing face animation technologies for innovative and attractive services intended for the mobile market. This prototype service allows mobile subscribers to communicate using personalized 3D face models created from images taken by their phone cameras. The user can take a snapshot of someone′s face – a friend, famous person, themselves, even a pet – using the mobile phone′s camera. After a quick manipulation on the phone, a 3D model of that face is created and can be animated simply by typing in some text. Speech and appropriate animation of the face are created automatically by speech synthesis. Furthermore, these highly personalized animations can be sent to others as real 3D animated messages or as short videos in MMS. The clients were implemented on different platforms, and different network and face animation techniques, and connected into one complex system. This paper presents the architecture and experience gained in building such a system.
A Domain Specific Embedded Language in C++ for Automatic Differentiation, Projection, Integration and Variational Formulations
Authors: Prud′homme Christophe
Published: January 2015

In this article, we present a domain specific embedded language in C++ that can be used in various contexts such as numerical projection onto a functional space, numerical integration, variational formulations and automatic differentiation. Albeit these tools operate in different ways, the language overcomes this difficulty by decoupling expression constructions from evaluation. The language is implemented using expression templates and meta‐programming techniques and uses various Boost libraries. The language is exercised on a number of non‐trivial examples and a benchmark presents the performance behavior on a few test problems.
Modelling and Quantitative Analysis of LTRACK–A Novel Mobility Management Algorithm
Authors: Kovács Benedek , Szalay M. , Imre S.
Published: January 2015

This paper discusses the improvements and parameter optimization issues of LTRACK, a recently proposed mobility management algorithm. Mathematical modelling of the algorithm and the behavior of the Mobile Node (MN) are used to optimize the parameters of LTRACK. A numerical method is given to determine the optimal values of the parameters. Markov chains are used to model both the base algorithm and the so‐called loop removal effect. An extended qualitative and quantitative analysis is carried out to compare LTRACK to existing handover mechanisms such as MIP, Hierarchical Mobile IP (HMIP), Dynamic Hierarchical Mobility Management Strategy (DHMIP), Telecommunication Enhanced Mobile IP (TeleMIP), Cellular IP (CIP) and HAWAII. LTRACK is sensitive to network topology and MN behavior so MN movement modelling is also introduced and discussed with different topologies. The techniques presented here can not only be used to model the LTRACK algorithm, but other algorithms too. There are many discussions and calculations to support our mathematical model to prove that it is adequate in many cases. The model is valid on various network levels, scalable vertically in the ISO‐OSI layers and also scales well with the number of network elements.
Supporting the Construction of Workflows for Biodiversity Problem‐Solving Accessing Secure, Distributed Resources
Authors: Pahwa J.S. , Jones A.C. , White R.J. , Burgess M. , Gray W.A. , Fiddian N.J. , Smith R.O. , Hardisty A.R. , Sutton T. , Brewer P. , Yesson C. , Caithness N. , Culham A. , Bisby F.A. , Scoble M. , Williams P. , Bhagwat S.
Published: January 2015

In the Biodiversity World (BDW) project we have created a flexible and extensible Web Services‐based Grid environment for biodiversity researchers to solve problems in biodiversity and analyse biodiversity patterns. In this environment, heterogeneous and globally distributed biodiversity‐related resources such as data sets and analytical tools are made available to be accessed and assembled by users into workflows to perform complex scientific experiments. One such experiment is bioclimatic modelling of the geographical distribution of individual species using climate variables in order to explain past and future climate‐related changes in species distribution. Data sources and analytical tools required for such analysis of species distribution are widely dispersed, available on heterogeneous platforms, present data in different formats and lack inherent interoperability. The present BDW system brings all these disparate units together so that the user can combine tools with little thought as to their original availability, data formats and interoperability. The new prototype BDW system architecture not only brings together heterogeneous resources but also enables utilisation of computational resources and provides a secure access to BDW resources via a federated security model. We describe features of the new BDW system and its security model which enable user authentication from a workflow application as part of workflow execution.
Scheduling Scientific Workflow Applications with Deadline and Budget Constraints Using Genetic Algorithms
Authors: Yu Jia , Buyya Rajkumar
Published: January 2015

Grid technologies have progressed towards a service‐oriented paradigm that enables a new way of service provisioning based on utility computing models, which are capable of supporting diverse computing services. It facilitates scientific applications to take advantage of computing resources distributed world wide to enhance the capability and performance. Many scientific applications in areas such as bioinformatics and astronomy require workflow processing in which tasks are executed based on their control or data dependencies. Scheduling such interdependent tasks on utility Grid environments need to consider users′ QoS requirements. In this paper, we present a genetic algorithm approach to address scheduling optimization problems in workflow applications, based on two QoS constraints, deadline and budget.
A Three Tier Architecture Applied to LiDAR Processing and Monitoring
Authors: Jaeger-Frank Efrat , Crosby Christopher J. , Memon Ashraf , Nandigam Viswanath , Conner Jeffery , Arrowsmith J. Ramon , Altintas Ilkay , Baru Chaitan
Published: January 2015

Emerging Grid technologies enable solving scientific problems that involve large datasets and complex analyses, which in the past were often considered difficult to solve. Coordinating distributed Grid resources and computational processes requires adaptable interfaces and tools that provide modularized and configurable environments for accessing Grid clusters and executing high performance computational tasks. Computationally intensive processes are also subject to a high risk of component failures and thus require close monitoring. In this paper we describe a scientific workflow approach to coordinate various resources via data analysis pipelines. We present a three tier architecture for LiDAR interpolation and analysis, a high performance processing of point intensive datasets, utilizing a portal, a scientific workflow engine and Grid technologies. Our proposed solution is available to the community in a unified framework through a shared cyberinfrastructure, the GEON portal, enabling scientists to focus on their scientific work and not be concerned with the implementation of the underlying infrastructure.
Replica Dissemination and Update Strategies in Cluster‐Based Mobile Ad Hoc Networks
Authors: Denko Mieso K. , Lu Hua
Published: January 2015

A mobile ad hoc network (MANET) is a collection of wireless mobile nodes that forms a temporary network without the aid of a fixed communication infrastructure. Since every node can be mobile and network topology changes can occur frequently, node disconnection is a common mode of operation in MANETs. Providing reliable data access and message delivery is a challenge in this dynamic network environment. Caching and replica allocation within the network can improve data accessibility by storing the data and accessing them locally. However, maintaining data consistency among replicas becomes a challenging problem. Hence, balancing data accessibility and consistency is an important step toward data management in MANETs. In this paper, we propose a replica‐based data‐storage mechanism and undelivered‐message queue schemes to provide reliable data storage and dissemination. We also propose replica update strategies to maintain data consistency while improving data accessibility. These solutions are based on a clustered MANET where nodes in the network are divided into small groups that are suitable for localized data management. The goal is to reduce communication overhead, support localized computation, and enhance scalability. A simulation environment was built using an NS‐2 network simulator to evaluate the performance of the proposed schemes. The results show that our schemes distribute replicas effectively, provide high data accessibility rates and maintain consistency.
A Generic Framework for Location‐Based Services (LBS) Provisioning
Authors: Priggouris Ioannis , Spanoudakis Dimitrios , Spanoudakis Manos , Hadjiefthymiades Stathes
Published: January 2015

Location Based Services can be considered as one of the most rapidly expanding fields of the mobile communications sector, with an impressively large application range. The proliferation of mobile/wireless Internet and mobile computing, and the constantly increasing use of handheld, mobile devices and position tracking technologies prepared the grounds for the introduction of this new type of services. The combination of position fixing mechanisms with location‐dependent, geographical information, can offer truly customized personal communication services through the mobile phone or other type of devices. Prompted by the avalanche of technology advances in the aforementioned areas in this paper we present an integrated platform for delivering Location Based Services (LBS). The platform covers the full life cycle of a LBS starting from the specification of the service, covering issues like the deployment and maintenance of services, the service invocation and the final delivery of the produced results to the invoking user. A prototype implementation of the discussed platform was developed and used to perform a series of trial services, with the purpose of demonstrating the pursued functionality.
An Approach for the High‐Level Specification of QoS‐Aware Grid Workflows Considering Location Affinity
Authors: Brandic Ivona , Pllana Sabri , Benkner Siegfried
Published: January 2015

Many important scientific and engineering problems may be solved by combining multiple applications in the form of a Grid workflow. We consider that for the wide acceptance of Grid technology it is important that the user has the possibility to express requirements on Quality of Service (QoS) at workflow specification time. However, most of the existing workflow languages lack constructs for QoS specification. In this paper we present an approach for high level workflow specification that considers a comprehensive set of QoS requirements. Besides performance related QoS, it includes economical, legal and security aspects. For instance, for security or legal reasons the user may express the location affinity regarding Grid resources on which certain workflow tasks may be executed. Our QoS‐aware workflow system provides support for the whole workflow life cycle from specification to execution. Workflow is specified graphically, in an intuitive manner, based on a standard visual modeling language. A set of QoS‐aware service‐oriented components is provided for workflow planning to support automatic constraint‐based service negotiation and workflow optimization. For reducing the complexity of workflow planning, we introduce a QoS‐aware workflow reduction technique. We illustrate our approach with a real‐world workflow for maxillo facial surgery simulation.
SPLAI: Computational Finite Element Model for Sensor Networks
Authors: Ishak Ruzana , Salleh Shaharuddin , Olariu Stephan , Abdul Aziz Mohd.Ismail
Published: January 2015

Wireless sensor network refers to a group of sensors, linked by a wireless medium to perform distributed sensing task. The primary interest is their capability in monitoring the physical environment through the deployment of numerous tiny, intelligent, wireless networked sensor nodes. Our interest consists of a sensor network, which includes a few specialized nodes called processing elements that can perform some limited computational capabilities. In this paper, we propose a model called SPLAI that allows the network to compute a finite element problem where the processing elements are modeled as the nodes in the linear triangular approximation problem. Our model also considers the case of some failures of the sensors. A simulation model to visualize this network has been developed using C++ on the Windows environment.
Federated Database Services for Wind Tunnel Experiment Workflows
Authors: Paventhan A. , Takeda Kenji , Cox Simon J. , Nicole Denis A.
Published: January 2015

Enabling the full life cycle of scientific and engineering workflows requires robust middleware and services that support effective data management, near‐realtime data movement and custom data processing. Many existing solutions exploit the database as a passive metadata catalog. In this paper, we present an approach that makes use of federation of databases to host data‐centric wind tunnel application workflows. The user is able to compose customized application workflows based on database services. We provide a reference implementation that leverages typical business tools and technologies: Microsoft SQL Server for database services and Windows Workflow Foundation for workflow services. The application data and user′s code are both hosted in federated databases. With the growing interest in XML Web Services in scientific Grids, and with databases beginning to support native XML types and XML Web services, we can expect the role of databases in scientific computation to grow in importance.
On‐the‐fly XMM‐Newton Spacecraft Data Reduction on the Grid
Authors: Ibarra A. , Tapiador D. , Huedo E. , Montero R.S. , Gabriel C. , Arviset C. , Llorente I.M.
Published: January 2015

We present the results of the first prototype of a XMM‐Newton pipeline processing task, parallelized at a CCD level, which can be run in a Grid system. By using the Grid Way application and the XMM‐Newton Science Archive system, the processing of the XMM‐Newton data is distributed across the Virtual Organization (VO) constituted by three different research centres: ESAC (European Space Astronomy Centre), ESTEC (the European Space research and TEchnology Centre) and UCM (Complutense University of Madrid). The proposed application workflow adjusts well to the Grid environment, making use of the massive parallel resources in a flexible and adaptive fashion.
Designing for Geometrical Symmetry Exploitation
Authors: Yamba Yamba André , Ålander Krister , Ljungberg Malin
Published: January 2015

Symmetry‐exploiting software based on the generalized Fourier transform (GFT) is presented from a practical design point of view. The algorithms and data structures map closely to the relevant mathematical abstractions, which primarily are based upon representation theory for groups. Particular care has been taken in the design of the data layout of the performance‐sensitive numerical data structures. The use of a vanilla strategy is advocated for the design of flexible mathematical software libraries: An efficient general‐purpose routine should be supplied, to obtain a practical and useful system, while the possibility to extend the library and replace the default routine with a special‐purpose – even more optimized – routine should be supported. Compared with a direct approach, the performance results show the superiority of the GFT‐based approach for so‐called dense equivariant systems. The GFT application is found to be well suited for parallelism.
RSCS: A Parallel Simplex Algorithm for the Nimrod/O Optimization Toolset
Authors: Lewis Andrew , Abramson David , Peachey Tom
Published: January 2015

This paper describes a method of parallelisation of the popular Nelder‐Mead simplex optimization algorithms that can lead to enhanced performance on parallel and distributed computing resources. A reducing set of simplex vertices are used to derive search directions generally closely aligned with the local gradient. When tested on a range of problems drawn from real‐world applications in science and engineering, this reducing set concurrent simplex (RSCS) variant of the Nelder‐Mead algorithm compared favourably with the original algorithm, and also with the inherently parallel multidirectional search algorithm (MDS). All algorithms were implemented and tested in a general‐purpose, grid‐enabled optimization toolset.
Performance Evaluation of Wireless Sensor Networks for Event‐Detection with Shadowing‐Induced Radio Irregularities
Authors: De Marco Giuseppe , Yang Tao , Ikeda Makoto , Barolli Leonard
Published: January 2015

In this paper, we study a particular application of wireless sensor networks for event‐detection and tracking. In this kind of application, the transport of data is simplified, and guaranteeing a minimum number of packets at the monitoring node is the only constraint on the performance of the sensor network. This minimum number of packets is called event‐reliability. Contrary to other studies on the subject, here we consider the behavior of such a network in presence of a realistic radio model, such as the shadowing of the radio signal. With this setting, we extend our previous analysis of the event‐reliability approach for the transport of data. In particular, both regular and random networks are considered. The contribute of this work is to show via simulations that, in the presence of randomness or irregularities in the radio channel, the event‐reliability can be jeopardized, that is the constraint on the minimum number of packets at the sink node could not be satisfied.
Distributing Workflows over a Ubiquitous P2P Network
Authors: Al-Shakarchi Eddie , Cozza Pasquale , Harrison Andrew , Mastroianni Carlo , Shields Matthew , Talia Domenico , Taylor Ian
Published: January 2015

This paper discusses issues in the distribution of bundled workflows across ubiquitous peer‐to‐peer networks for the application of music information retrieval. The underlying motivation for this work is provided by the DART project, which aims to develop a novel music recommendation system by gathering statistical data using collaborative filtering techniques and the analysis of the audio itsel, in order to create a reliable and comprehensive database of the music that people own and which they listen to. To achieve this, the DART scientists creating the algorithms need the ability to distribute the Triana workflows they create, representing the analysis to be performed, across the network on a regular basis (perhaps even daily) in order to update the network as a whole with new workflows to be executed for the analysis. DART uses a similar approach to BOINC but differs in that the workers receive input data in the form of a bundled Triana workflow, which is executed in order to process any MP3 files that they own on their machine. Once analysed, the results are returned to DART′s distributed database that collects and aggregates the resulting information. DART employs the use of package repositories to decentralise the distribution of such workflow bundles and this approach is validated in this paper through simulations that show that suitable scalability is maintained through the system as the number of participants increases. The results clearly illustrate the effectiveness of the approach.
From FORTRAN 77 to Locality‐Aware High Productivity Languages for Peta‐Scale Computing
Authors: Zima Hans P.
Published: January 2015

When the first specification of the FORTRAN language was released in 1956, the goal was to provide an "automatic programming system" that would enhance the economy of programming by replacing assembly language with a notation closer to the domain of scientific programming. A key issue in this context, explicitly recognized by the authors of the language, was the requirement to produce efficient object programs that could compete with their hand‐coded counterparts. More than 50 years later, a similar situation exists with respect to finding the right programming paradigm for high performance
computing systems. FORTRAN, as the traditional language for scientific programming, has played a major role in the quest
for high‐productivity programming languages that satisfy very strict performance constraints. This paper focuses on high‐level
support for locality awareness, one of the most important requirements in this context. The discussion centers on the High
Performance Fortran (HPF) family of languages, and their influence on current language developments for peta‐scale computing.
HPF is a data‐parallel language that was designed to provide the user with a high‐level interface for programming scientific
applications, while delegating to the compiler the task of generating an explicitly parallel message‐passing program. We outline
developments that led to HPF, explain its major features, identify a set of weaknesses, and discuss subsequent languages that
address these problems. The final part of the paper deals with Chapel, a modern object‐oriented language developed in the High
Productivity Computing Systems (HPCS) program sponsored by DARPA. A salient property of Chapel is its general framework
for the support of user‐defined distributions, which is related in many ways to ideas first described in Vienna Fortran. This
framework is general enough to allow a concise specification of sparse data distributions. The paper concludes with an outlook
to future research in this area.
Electric Propulsion Plume Simulations Using Parallel Computer
Authors: Wang Joseph , Cao Yong , Kafafy Raed , Decyk Viktor
Published: January 2015

A parallel, three‐dimensional electrostatic PIC code is developed for large‐scale electric propulsion simulations using parallel supercomputers. This code uses a newly developed immersed‐finite‐element particle‐in‐cell (IFE‐PIC) algorithm designed to handle complex boundary conditions accurately while maintaining the computational speed of the standard PIC code. Domain decomposition is used in both field solve and particle push to divide the computation among processors. Two simulations studies are presented to demonstrate the capability of the code. The first is a full particle simulation of near‐thruster plume using real ion to electron mass ratio. The second is a high‐resolution simulation of multiple ion thruster plume interactions for a realistic spacecraft using a domain enclosing the entire solar array panel. Performance benchmarks show that the IFE‐PIC achieves a high parallel efficiency of ≥ 90%
The Application of Fluid Mobility Modelling in Wireless Cellular Networks
Authors: Skehill Ronan J. , McGrath Sean
Published: January 2015

Mobility models, synthetic or trace, try to accurately model the movement of a single user or a group of users. Models can be used in simulators and emulators to investigate the consequences of mobility on new protocols or network management techniques. A limitation with current trace mobility models is they are based on empirical data which are limited to specific network types and environments. Limitations with synthetic models are that they are complex, computationally heavy, and lack realism. To address these issue a new approach needs to be taken. One such approach is the use of fluid mechanics and transport theory to represent user mobility. A model based on viscous free irrotational fluid mechanics with empirical data from pedestrian and vehicular studies provide a means of creating realistic group movement characteristics with smooth non random trajectories and smooth continuous velocity. The model is used in an example to provide boundary crossing rates for users in a cellular network and optimising the size of cellular location areas.