Scheduling multiple divisible loads on a linear processor network

Min, Veeravalli, and Barlas have recently proposed strategies to minimize the overall execution time of one or several divisible loads on a heterogeneous linear network, using one or more installments. We show on a very simple example that their approach does not always produce a solution and that, when it does, the solution is often suboptimal. We also show how to find an optimal schedule for any instance, once the number of installments per load is given. Then, we formally state that any optimal schedule has an infinite number of installments under a linear cost model as the one assumed in the original papers. Therefore, such a cost model cannot be used to design practical multi-installment strategies. Finally, through extensive simulations we confirmed that the best solution is always produced by the linear programming approach, while solutions of the original papers can be far away from the optimal

L’architecture gothique en Normandie, xiie-xive siècles. Recherches récentes

Alors qu’elle avait été inexplicablement négligée jusqu’à ces dernières années, la Normandie gothique des xiie-xive siècles fait un retour en force dans l’actualité scientifique. Coup sur coup, deux thèses importantes sont consacrées à la cathédrale de Rouen, tandis qu’est enfin publiée la synthèse régionale méditée depuis de longues années par Lindy Grant. Avec quelques études antérieures, avec surtout les monographies rassemblées dans le volume 2003 du Congrès de la Société Française d’Arch..

The dawn of archeomagnetic dating

The use of secular variation in Earth’s magnetic field for dating purposes in archeology and volcanology began with the first developments in paleomagnetism. This paper traces the key contributions of Paul-Louis Mercanton, Pierre David, Bernard Brunhes, and Raymond Chevallier in the early 20th century, between the seminal works of Giuseppe Folgheraiter in the 1890s and Emile Thellier in the 1930s, all of whom expressed a strong interest in these applications. These researchers raised issues that are still at the forefront of present-day research, though archeomagnetists are now able to address them with modern tools and much larger sets of data. Surprisingly, in 1901, a first and long plea for the use of archeomagnetism as a dating tool came not from a paleomagnetist but from the limnologist François-Alphonse Forel

Comments on "Design and performance evaluation of load distribution strategies for multiple loads on heterogeneous linear daisy chain networks''

Min, Veeravalli, and Barlas proposed strategies to minimize the overall execution time of one or several divisible loads on a heterogeneous linear network, using one or more installments. We show on a very simple example that the proposed approach does not always produce a solution and that, when it does, the solution is often suboptimal. We also show how to find an optimal scheduling for any instance, once the number of installments per load is given. Finally, we formally prove that under a linear cost model, as in the original paper, an optimal schedule has an infinite number of installments. Such a cost model can therefore not be sed to design practical multi-installment strategies.Min, Veeravalli, and Barlas ont proposé [8,9] des stratégies pour minimiser le temps d’exécution d’une ou de plusieurs tâches divisibles sur un réseau linéaire de processeurs hétérogènes, en distribuant le travail en une ou plusieurs tournées. Sur un exemple très simple nous montrons que l’approche proposée dans [9] ne produit pas toujours une solution et que, quand elle le fait, la solution est souvent sous-optimale. Nous montrons également comment trouver un ordonnancement optimal pour toute instance, quand le nombre de tournées par tâches est spécifié. Finalement, nous montrons formellement que lorsque les fonctions de coûts sont linéaires, comme c’est le cas dans [8,9], un ordonnancement optimal au n nombre infini de tournées. Un tel modèle de coût ne peut donc pas être utilisé pour définir des stratégies en multi-tournées utilisables en pratiqu

Comments on "Design and performance evaluation of load distribution strategies for multiple loads on heterogeneous linear daisy chain networks''

Min, Veeravalli, and Barlas proposed strategies to minimize the overall execution time of one or several divisible loads on a heterogeneous linear network, using one or more installments. We show on a very simple example that the proposed approach does not always produce a solution and that, when it does, the solution is often suboptimal. We also show how to find an optimal scheduling for any instance, once the number of installments per load is given. Finally, we formally prove that under a linear cost model, as in the original paper, an optimal schedule has an infinite number of installments. Such a cost model can therefore not be sed to design practical multi-installment strategies

L’activité métallurgique à l’abbaye de Morimond (Haute-Marne) : nouvel éclairage de la fouille à partir de l’analyse archéomagnétique de deux foyers

Une étude archéomagnétique à des fins de datation a été menée sur deux foyers en carreaux de terre cuite mis au jour sur le site de l’ancienne abbaye cistercienne de Morimond (Haute-Marne). La désaimantation thermique complète des échantillons prélevés a permis de définir pour chacun des deux foyers une direction archéomagnétique moyenne précise, acquise lors de leur dernière utilisation. Pour dater cet instant, les directions archéomagnétiques ont été comparées à une courbe des variations directionnelles du champ géomagnétique construite à partir de données obtenues en France et dans des pays voisins. Nous obtenons, à 95% de confiance, une datation comprise entre 1585 et 1615 après J.-C. pour le premier foyer et entre 1525 et 1605 après J.-C. pour le second foyer. Bien que leurs deux intervalles d'âge se recouvrent partiellement, les deux directions archéomagnétiques moyennes ne sont pas compatibles à 95% ce qui indique que les arrêts de fonctionnement des deux foyers ne sont pas contemporains. Ces résultats archéomagnétiques confirment deux phases métallurgiques observées indépendamment lors des fouilles. Ils précisent les datations issues des radiocarbones qui ne permettaient pas de discriminer chronologiquement les deux phases. Les datations envisagées se calent avant l’abandon du bâtiment suite à plusieurs saccages évoqués dans les sources écrites.This paper presents the archeomagnetic dating results obtained from two brick fireplaces excavated inside the ancient Cistercian Abbey of Morimond (Haute-Marne). Complete thermal demagnetization of the collected samples allowed us to define a precise mean archeomagnetic direction acquired during the last cooling of each of the two structures. The dating of the last use of the two fireplaces was derived from the statistical comparison between a reference geomagnetic field directional variation curve constructed using the available French data set together with other data from nearby countries and the two directions obtained in this study. The two dating results lie, with a 95% confidence level, between 1585 and 1615 AD and between 1525 and 1605 AD. Although these dates partially overlap, the two mean archeomagnetic directions are not compatible at the 95% confidence level, indicating a chronology in the abandonment of the two structures. These archeomagnetic results therefore confirm the existence of two metallurgical phases, which were independently observed during the excavations. They further refine the radiocarbon dating unable to discriminate the two phases. The two time intervals defined by archeomagnetism pre-date the abandonment of the building due to severe damages mentioned in written sources

The impact of geomagnetic spikes on the production rates of cosmogenic 14C and 10Be in the Earth's atmosphere

We seek corroborative evidence of the geomagnetic spikes detected in the Near East ca. 980 BC and 890 BC in the records of the past production rates of the cosmogenic nuclides 14C and 10Be. Our forward modeling strategy rests on global, time-dependent, geomagnetic spike field models feeding state-of-the-art models of cosmogenic nuclide production. We find that spike models with an energy budget in line with presently inferred large-scale flow at Earth's core surface fail to produce a visible imprint in the nuclide record. Spike models able to reproduce the intensity changes reported in the Near East require an unaccountably high-magnitude core flow, yet their computed impact on cosmogenic isotope production rates remains ambiguous. No simple and unequivocal agreement is obtained between the observed and modeled nuclide records at the epochs of interest. This indicates that cosmogenic nuclides cannot immediately be used to confirm the occurrence of these two geomagnetic spikes