Pipelining the Fast Multipole Method over a Runtime System

Fast Multipole Methods (FMM) are a fundamental operation for the simulation of many physical problems. The high performance design of such methods usually requires to carefully tune the algorithm for both the targeted physics and the hardware. In this paper, we propose a new approach that achieves high performance across architectures. Our method consists of expressing the FMM algorithm as a task flow and employing a state-of-the-art runtime system, StarPU, in order to process the tasks on the different processing units. We carefully design the task flow, the mathematical operators, their Central Processing Unit (CPU) and Graphics Processing Unit (GPU) implementations, as well as scheduling schemes. We compute potentials and forces of 200 million particles in 48.7 seconds on a homogeneous 160 cores SGI Altix UV 100 and of 38 million particles in 13.34 seconds on a heterogeneous 12 cores Intel Nehalem processor enhanced with 3 Nvidia M2090 Fermi GPUs.Comment: No. RR-7981 (2012

Resilience Issues for Application Workflows on Clouds

International audienceTwo areas are currently the focus of active research, namely cloud computing and high-performance computing. Their expected impact on business and scientific computing is such that most application areas are eagerly uptaking or waiting for the associated infrastructures. However, open issues still remain. Resilience and loadbalancing are examples of such areas where innovative solutions are required to face new or increasing challenges, e.g., fault-tolerance. This paper presents existing concepts and open issues related to the design, implementation and deployment of a fault-tolerant application framework on cloud computing platforms. Experiments are sketched including the support for application resilience, i.e., faulttolerance and exception-handling. They also support the transparent execution of distributed codes on remote highperformance clusters

Applications Resilience on Clouds

International audienceCloud computing infrastructures support system and network fault-tolerance. They transparently repair and prevent communication and software errors. They also allow duplication and migration of jobs and data to prevent hardware failures. However, only limited work has been done so far on application resilience, i.e., the ability to resume normal execution after errors and abnormal executions in distributed environments and clouds. This paper addresses open issues and solutions for application errors detection and management. It also overviews a testbed used to to design, deploy, execute, monitor, restart and resume distributed applications on cloud infrastructures in cases of failures

A Comparison of Big Data Frameworks on a Layered Dataflow Model

In the world of Big Data analytics, there is a series of tools aiming at simplifying programming applications to be executed on clusters. Although each tool claims to provide better programming, data and execution models, for which only informal (and often confusing) semantics is generally provided, all share a common underlying model, namely, the Dataflow model. The Dataflow model we propose shows how various tools share the same expressiveness at different levels of abstraction. The contribution of this work is twofold: first, we show that the proposed model is (at least) as general as existing batch and streaming frameworks (e.g., Spark, Flink, Storm), thus making it easier to understand high-level data-processing applications written in such frameworks. Second, we provide a layered model that can represent tools and applications following the Dataflow paradigm and we show how the analyzed tools fit in each level.Comment: 19 pages, 6 figures, 2 tables, In Proc. of the 9th Intl Symposium on High-Level Parallel Programming and Applications (HLPP), July 4-5 2016, Muenster, German

Building and Contesting post-war Housing in Dakar

After the Second World War, European welfare planning was transposed to the African colonies. With regard to housing this meant a true turning point in urban policy. For the first time the colonial state massively invested in the housing of the African urban dwellers. However, the segregationist underground and elite‐focus of the housing schemes at the same time reinforced fundamental inequities in the African city, thereby furthering colonial goals. The promotion of African emancipation was thus accompanied by a strong ‘social engineering’. Yet, Africans were no passive victims of development schemes. In this paper we will take a close look at the housing schemes of the Société Immobilière du Cap Vert (SICAP) in Dakar (Senegal) between 1951 and 1960 (independence). Notwithstanding the significant housing shortages in Dakar, archival records show that a substantial amount of the SICAP houses remained vacant after completion. Apart from too high rents, the main reason was that the SICAP-houses seemed to be designed with the average West-European middle-class family in mind. As a consequence, most houses proved too small and little adjusted to the extended African family, which is well reflected in the many alterations the SICAP houses underwent right from their completion until today. Moreover, the SICAP housing schemes, and in particular their segregationist and elitist underground, caused strong African opposition. Many Africans opposed to the more than 80.000 forced evictions, known in the colonial jargon as ‘déguerpissements’, that were caused by the implementation of the schemes. The result was a fierce battle over land between the government and the inhabitants of Dakar. In particular the Lebou-population demanded adequate compensation for its land in case of expropriation, even if they did not possess any official land title, with equal rewards for Africans and Europeans. Due various forms of active and passive protest of the inhabitants the implementation of the SICAP housing schemes regularly came to a standstill and the government often found itself in ‘a complete impasse’. The study of these different forms of agency and resistance in Dakar is important as it shows that, although colonial rule was strict and compelling, it was possible to escape from it to some degree

High performance checksum computation for fault-tolerant MPI over InfiniBand

International audienceWith the increase of the number of nodes in clusters, the probability of failures and unusual events increases. In this paper, we present checksum mechanisms to detect data corruption. We study the impact of checksums on network communication performance and we propose a mechanism to amortize their cost on InfiniBand. We have implemented our mechanisms in the NEWMADELEINE communication library. Our evaluation shows that our mechanisms to ensure message integrity do not impact noticeably the application performance, which is an improvement over the state of the art MPI implementations

Cognitive Arguments for a Fuzzy Construction Grammar

Following Desagulier (2005), I assume that it is by studying intermediate forms that we can gain a better understanding of creativity and innovation, from both a linguistic and a cognitive perspective. My case studies tend to show that form/function reshuffling is best understood as a grammatical blend, for which I offer a new definition, based on a critical examination of works by Fauconnier and Turner (1996, 1998, 2002) and Fauconnier (1997). Constructional integration networks, which are the keystone of my model, hinge on the following principle: a construction that is cognitively salient provides can serve as the basis for the structuring of speakers' mental grammars. This stable symbolic unit can thus (i) be retrieved wholly or partially to provide a template for the composition of new constructions (ii) help speakers/hearers gain access to more complex pairings