LBG-SQUARE - Fault Tolerant, Locality-Aware Co-allocation in P2P Grids

in Huang, Zhiyi; Xu, Zhiwei; Rountree, Nathan (Eds.) et al Ninth International Conference On Parallel And Distributed Computing, Applications And Technologies : PDCAT 2008 (2008, December)

In this paper, the deployment and execution of Iterative Stencil applications on a P2P Grid middleware are investigated. So-called Iterative Stencil applications are composed of sets of heavily ... [more ▼]

In this paper, the deployment and execution of Iterative Stencil applications on a P2P Grid middleware are investigated. So-called Iterative Stencil applications are composed of sets of heavily-communicating, long-running Tasks. They thus require co-allocation of multiple reliable resources for extended periods of time. P2P Grids are totally decentralized and provide on-demand, transparent access to edge resources, e.g. Internet-connected, non-dedicated desktop computers. A P2P Grid has the potential to provide access to a large number of resources at the fraction of the cost of a dedicated cluster. However, edge resources are heterogeneous in performance and intrinsically unreliable: Task execution failures are common due to resource preemption or resource failure. Furthermore, P2P Grid schedulers usually target sets of independent computational Tasks, i.e. so-called Bags of Tasks applications. It is therefore not trivial to deploy and run an Iterative Stencil application on a P2P Grid. Checkpointing is a common fault-tolerance mechanism in High Performance Distributed Computing, often based on a centralized architecture. Locality-aware co-allocation in P2P Grids has been recently investigated. Checkpointing and locality-aware co-allocation yet have to be integrated in P2P Grids. We propose to provide co-allocation through an existing middleware-level Bag of Tasks scheduling mechanism. We also introduce a layer of fault-tolerance for the Iterative Stencils that relies on a scalable, application-level, P2P checkpointing mechanism. Finally, LBG-SQUARE is described. This software results from the combination of a specific Iterative Stencil application (a Computational Fluid Dynamics simulation software called LaBoGrid) with a P2P Grid middleware (Lightweight Bartering Grid). [less ▲]

Faire escale de dix ans

Article for general public (2008)

Pour envisager différemment les analyses de situation

in Education Santé (2008), (240), 13-17

Towards an Improved Single-Frequency Ionospheric Correction: Focus on Mid-Latitudes

in 4th ESA Workshop on Satellite Navigation User Equipment Technologies NAVITEC (2008, December)

The modelling of the Total Electron Content (TEC) plays an important role in global satellite navigation systems (GNSS) accuracy, especially for single frequency receivers, the most common ones ... [more ▼]

The modelling of the Total Electron Content (TEC) plays an important role in global satellite navigation systems (GNSS) accuracy, especially for single frequency receivers, the most common ones constituting the mass market. For the latter and in the framework of Galileo, the NeQuick model has been chosen for correcting the ionospheric error contribution. It has been designed to calculate the electron density at a given point of the ionosphere according to the time conditions and the solar activity. This electron density can be integrated along the path from the receiver to the considered satellite to provide the TEC. For Galileo, a parameter Az (“effective ionisation level”) will be provided to the model as solar activity information and will be daily updated by the ground stations. In order to reach the ionosphere error correction level objective (70% or 20 TECu whichever is larger), the model itself as well as its use for Galileo are investigated. Different situations have to be considered: different latitude regions (space conditions), different hours, seasons and years (time conditions) and specific phenomena appearance (magnetic storms, Travelling Ionospheric Disturbances – TIDs). In addition the results can be compared to different data sets among which GPS slant or vertical TEC (sTEC or vTEC) measurements, Global Ionospheric Maps, ionosonde profiles, topside soundings but also other ionosphere models results such as IRI. In our comparison process, we take benefit of various ionosphere data from several European stations (Chilton in UK, Dourbes in Belgium, El Arenosillo and Roquetes in Spain, Pruhonice in Czech Republic) where ionosonde and GPS TEC data are available for different solar activity levels. These data allow us to study NeQuick representation of the ionosphere at mid-latitudes. We investigate the difference between GPS-derived vTEC and corresponding values from NeQuick for the latest years (between solar maximum in 2000 and minimum in 2007) in order to observe the temporal dependencies towards Universal Time, season and solar activity. On the one hand, we use ionosonde data to constrain the model so that we can concentrate on its formulation of the profile only. We especially highlight the improvements from the latest (second) version of NeQuick and show the critical importance of the topside formulation. On the other hand, we analyse the model residual errors for the same situations computing vTEC through the Galileo algorithm. [less ▲]

5 ans d’expérience monocentrique de transplantation hépatique avec des donneurs à cœur arrêté de catégorie 3 de Maastricht

in Journal de Chirurgie (2008, December), 145

Development of products for GNSS users at the Belgian Solar-Terrestrial Centre of Excellence

Conference (2008, December)

Etude de dépôts en alliage Nickel - Diamants fabriqués par Laser Cladding

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Séparation de fait - Commentaire pratique. La sécurité sociale

in Michiels, Olivier (Ed.) Séparation de fait - Commentaire pratique (2008)

L'auteur analyse les conséquences de la séparation de fait des époux sur les prestations de sécurité sociale

Large N(c) QCD versus quark model

in Few-Body Systems (2008), 44

Francophones et plurilingues : le rapport au français des Belges issus de l’immigration

in Français et Société (2008), 19