Médecins, chirurgiens et apothicaires du Roi : l’hôpital militaire de Strasbourg et ses praticiens au XVIIIe siècle

Dans l’histoire d’une ville, monuments et toponymes sont toujours les relais de la mémoire. À Strasbourg, en ce début de XXIe siècle, les termes d’Esplanade, de Citadelle, voire de Glacis, ne renvoient qu’à de rares vestiges de l’imposante emprise militaire qu’a pu connaître la cité au cours des âges, et plus particulièrement à l’époque moderne, ne connaissant pas forcément de réelle mise en valeur. Ainsi, le passant ou l’utilisateur peut à juste titre s’interroger sur l’origine de ces bâtime..

Résolution numérique de l'équation des ondes par une méthode d'éléments finis d'ordre élevé sur calculateur parallèle

Nous présentons une méthode d'éléments finis d'ordre élevé permettant de résoudre l'équation des ondes acoustiques dans le domaine espace--temps par un schéma explicite. Nous construisons un nouvel élément fini permettant la condensation de masse, sans perte de précision. Cette construction est basée sur la recherche d'une formule de quadrature symétrique, dont les noeuds forment un élément fini. Après discrétisation en temps par une méthode explicite, nous obtenons une méthode de résolution parallèle, basée sur une décomposition en sous-domaines. Les sous-domaines peuvent être non-structurés. Nous décrivons la mise en oeuvre de la méthode dans un logiciel en , utilisant la bibliothèque de communications pour la portabilité. La méthode est validée sur des exemples simples, et également dans des cas de géométrie complexe. Nous donnons enfin des résultats de performance parallèl

Accelerating Cosmic Microwave Background map-making procedure through preconditioning

Estimation of the sky signal from sequences of time ordered data is one of the key steps in Cosmic Microwave Background (CMB) data analysis, commonly referred to as the map-making problem. Some of the most popular and general methods proposed for this problem involve solving generalised least squares (GLS) equations with non-diagonal noise weights given by a block-diagonal matrix with Toeplitz blocks. In this work we study new map-making solvers potentially suitable for applications to the largest anticipated data sets. They are based on iterative conjugate gradient (CG) approaches enhanced with novel, parallel, two-level preconditioners. We apply the proposed solvers to examples of simulated non-polarised and polarised CMB observations, and a set of idealised scanning strategies with sky coverage ranging from nearly a full sky down to small sky patches. We discuss in detail their implementation for massively parallel computational platforms and their performance for a broad range of parameters characterising the simulated data sets. We find that our best new solver can outperform carefully-optimised standard solvers used today by a factor of as much as 5 in terms of the convergence rate and a factor of up to $4$ in terms of the time to solution, and to do so without significantly increasing the memory consumption and the volume of inter-processor communication. The performance of the new algorithms is also found to be more stable and robust, and less dependent on specific characteristics of the analysed data set. We therefore conclude that the proposed approaches are well suited to address successfully challenges posed by new and forthcoming CMB data sets.Comment: 19 pages // Final version submitted to A&

PetFMM--A dynamically load-balancing parallel fast multipole library

Fast algorithms for the computation of $N$-body problems can be broadly classified into mesh-based interpolation methods, and hierarchical or multiresolution methods. To this last class belongs the well-known fast multipole method (FMM), which offers O(N) complexity. This paper presents an extensible parallel library for $N$-body interactions utilizing the FMM algorithm, built on the framework of PETSc. A prominent feature of this library is that it is designed to be extensible, with a view to unifying efforts involving many algorithms based on the same principles as the FMM and enabling easy development of scientific application codes. The paper also details an exhaustive model for the computation of tree-based $N$-body algorithms in parallel, including both work estimates and communications estimates. With this model, we are able to implement a method to provide automatic, a priori load balancing of the parallel execution, achieving optimal distribution of the computational work among processors and minimal inter-processor communications. Using a client application that performs the calculation of velocity induced by $N$ vortex particles, ample verification and testing of the library was performed. Strong scaling results are presented with close to a million particles in up to 64 processors, including both speedup and parallel efficiency. The library is currently able to achieve over 85% parallel efficiency for 64 processors. The software library is open source under the PETSc license; this guarantees the maximum impact to the scientific community and encourages peer-based collaboration for the extensions and applications.Comment: 28 pages, 9 figure

Last Men Standing: Chlamydatus Portraits and Public Life in Late Antique Corinth

Notable among the marble sculptures excavated at Corinth are seven portraits of men wearing the long chlamys of Late Antique imperial office. This unusual costume, contemporary portrait heads, and inscribed statue bases all help confirm that new public statuary was created and erected at Corinth during the 4th and 5th centuries. These chlamydatus portraits, published together here for the first time, are likely to represent the Governor of Achaia in his capital city, in the company of local benefactors. Among the last works of the ancient sculptural tradition, they form a valuable source of information on public life in Late Antique Corinth

Méthodes Multipôles Rapides pour l'électromagnétisme : Parallélisme et Basses Fréquences

Jury: L.Greengard (Courant Institut, NYU), P.Joly (Inria, Rocquencourt), B.Desprès (UPMC), P.Frey (UPMC), P.Soudais (Dassault Aviation)The dense system resolution issued of interaction modeling is an heavy problem that multipole methods help to optimize through hierarchical approximations based on the regularity of underlying potentials. This PhD thesis gives developments on a new multipole method for electromagnetism problem as well on unified treatment of the full range of frequencies as on parallel computer developments for data dependency partitioning based on graphs and communications overlapped by computations.Le traitement des systèmes pleins issus de modélisation d'interactions de type particulaires est un problème lourd que les méthodes multipôles proposent d'optimiser grâce à des approximations hiérarchiques basées sur la régularité des potentiels sous-jacents. Cette thèse offre des développements sur une nouvelle méthode multipôle pour l'électromagnétisme à la fois en terme d'un traitement unifié de l'ensemble des fréquences et informatique dans le cadre du paralléélisme et d'optimisations algorithmiques telles que le partitionnement par graphes et le recouvrement des communications par des calculs

Typology-technology , Function and Evolution of Early Dynastic Mesopotamian Stemmed Dishes

International audienceThe « offering stands » of the middle-third of IIIrd millenium BC Mesopotamia are a hallmark of Early Dynastic to Akkadian Periods. These ceramic shapes are amongst the most sophisticated pottery types for these periods, and as such are often at the center of chronology discussions.I first show how some statistical analyses of contexts help to refine previously proposed functional interpretations for this mysterious class of objects.The presentation then compares typology and techniques of production of pottery stemmed dishes and offering stands from Mari, the Diyala (Khafaja, Tell Agrab, Asmar), Kish, Nippur and Ur. The existence of regional repartitions and specificities is extrapolated from comparisons with other sites, and from sherds coming from survey data. A chronological synthesis is proposed. This presentation also explores the interpretation of techniques evolution in relation with other studies