Scheduling Dynamic OpenMP Applications over Multicore Architectures

International audienceApproaching the theoretical performance of hierarchical multicore machines requires a very careful distribution of threads and data among the underlying non-uniform architecture in order to minimize cache misses and NUMA penalties. While it is acknowledged that OpenMP can enhance the quality of thread scheduling on such architectures in a portable way, by transmitting precious information about the affinities between threads and data to the underlying runtime system, most OpenMP runtime systems are actually unable to efficiently support highly irregular, massively parallel applications on NUMA machines. In this paper, we present a thread scheduling policy suited to the execution of OpenMP programs featuring irregular and massive nested parallelism over hierarchical architectures. Our policy enforces a distribution of threads that maximizes the proximity of threads belonging to the same parallel section, and uses a NUMA-aware work stealing strategy when load balancing is needed. It has been developed as a plug-in to the ForestGOMP OpenMP platform. We demonstrate the efficiency of our approach with a highly irregular recursive OpenMP program resulting from the generic parallelization of a surface reconstruction application. We achieve a speedup of 14 on a 16-core machine with no application-level optimization

Diagnóstico de una otitis media-interna mediante resonancia magnética en un conejo con síndrome vestibular periférico

Este artículo describe el caso clínico de un conejo con signos vestibulares causados por una otitis media-interna. Tras la valoración del examen realizado y los resultados de las pruebas diagnósticas se sospechó de un proceso vestibular periférico. Debido a la inespecificidad de los resultados del examen neurológico y radiológico se realizó, para diferenciar un síndrome vestibular periférico de uno central, una resonancia magnética; en ella se evidenció la bulla timpánica izquierda llena de contenido. Se emitió un diagnóstico de otitis media-interna izquierda que se resolvió quirúrgicamente mediante la técnica Zepp y trepanación de la bulla timpánica izquierda. El cultivo de la muestra obtenida de la bulla timpánica resultó un Corynebacterium spp. muy sensible a antibióticos habituales usados por los autores. Después del tratamiento quirúrgico y médico la evolución fue favorable, aunque el animal presentaba un leve ladeo de cabeza residual hacia la izquierda. Finalmente se discuten las razones por las cuales está indicado realizar una RMN en estos casos

Auto-tuned OpenCL kernel co-execution in OmpSs for heterogeneous systems

The emergence of heterogeneous systems has been very notable recently. The nodes of the most powerful computers integrate several compute accelerators, like GPUs. Profiting from such node configurations is not a trivial endeavour. OmpSs is a framework for task based parallel applications, that allows the execution of OpenCl kernels on different compute devices. However, it does not support the co-execution of a single kernel on several devices. This paper presents an extension of OmpSs that rises to this challenge, and presents Auto-Tune, a load balancing algorithm that automatically adjusts its internal parameters to suit the hardware capabilities and application behavior. The extension allows programmers to take full advantage of the computing devices with negligible impact on the code. It takes care of two main issues. First, the automatic distribution of datasets and the management of device memory address spaces. Second, the implementation of a set of load balancing algorithms to adapt to the particularities of applications and systems. Experimental results reveal that the co-execution of single kernels on all the devices in the node is beneficial in terms of performance and energy consumption, and that Auto-Tune gives the best overall results.This work has been supported by the University of Cantabria with grant CVE-2014-18166, the Generalitat de Catalunya under grant 2014-SGR-1051, the Spanish Ministry of Economy, Industry and Competitiveness under contracts TIN2016-76635-C2-2-R (AEI/FEDER, UE) and TIN2015-65316-P. The Spanish Government through the Programa Severo Ochoa (SEV-2015-0493

Puntos de servicio en aseos públicos para minimizar y equilibrar los tiempos de espera de hombres y mujeres

The article raises the issue of the queues that usually appear in the ladies toilets in contrast to the fluidity with which gentlemen can access theirs, and points that this situation is only due to bad dimensioning of the toilets and thus that the problem has an easy solution. After describing and parameterizing the queuing forming processes in ladies and gentlemen toilets, a simulation program is used to analyze in each case the influence of the number of service points in waiting times. Finally, the results obtained are used to give recommendations in order to balance the waiting times of ladies and gentlemen while keeping them below reasonable levels.Se plantea el problema de las colas que se presentan habitualmente en los aseos de señoras en contraste con la fluidez con que se accede a los de caballeros, considerando que esta situación tiene solución ya que es sólo debida al mal dimensionado de los aseos. Tras describir y parametrizar los procesos de formación de colas en los aseos de señoras y de caballeros, se utiliza un programa de simulación para analizar en cada caso la influencia del número de puntos de servicio en los tiempos de espera. Finalmente, de acuerdo con los resultados obtenidos, se realizan unas recomendaciones para equilibrar los tiempos de espera, manteniéndolos en ambos casos por debajo de unos valores razonables

Mitochondrial fragmentation in excitotoxicity requires ROCK activation

Mitochondria morphology constantly changes through fission and fusion processes that regulate mitochondrial function, and it therefore plays a prominent role in cellular homeostasis. Cell death progression is associated with mitochondrial fission. Fission is mediated by the mainly cytoplasmic Drp1, which is activated by different post-translational modifications and recruited to mitochondria to perform its function. Our research and other studies have shown that in the early moments of excitotoxic insult Drp1 must be nitrosylated to mediate mitochondrial fragmentation in neurons. Nonetheless, mitochondrial fission is a multistep process in which filamentous actin assembly/disassembly and myosin-mediated mitochondrial constriction play prominent roles. Here we establish that in addition to nitric oxide production, excitotoxicity-induced mitochondrial fragmentation also requires activation of the actomyosin regulator ROCK. Although ROCK1 has been shown to phosphorylate and activate Drp1, experiments using phosphor-mutant forms of Drp1 in primary cortical neurons indicate that in excitotoxic conditions, ROCK does not act directly on Drp1 to mediate fission, but may act on the actomyosin complex. Thus, these data indicate that a wider range of signaling pathways than those that target Drp1 are amenable to be inhibited to prevent mitochondrial fragmentation as therapeutic optio

A COMPARISON OF METHODS FOR SELECTING PREFERRED SOLUTIONS IN MULTIOBJECTIVE DECISION MAKING

ISBN : 978-94-91216-77-0In multiobjective optimization problems, the identified Pareto Frontiers and Sets often contain too many solutions, which make it difficult for the decision maker to select a preferred alternative. To facilitate the selection task, decision making support tools can be used in different instances of the multiobjective optimization search to introduce preferences on the objectives or to give a condensed representation of the solutions on the Pareto Frontier, so as to offer to the decision maker a manageable picture of the solution alternatives. This paper presents a comparison of some a priori and a posteriori decision making support methods, aimed at aiding the decision maker in the selection of the preferred solutions. The considered methods are compared with respect to their application to a case study concerning the optimization of the test intervals of the components of a safety system of a nuclear power plant. The engine for the multiobjective optimization search is based on genetic algorithms

Extended Thomas-Fermi approximation to the one-body density matrix

The one-body density matrix is derived within the Extended Thomas-Fermi approximation. This has been done starting from the Wigner-Kirkwood distribution function for a non-local single-particle potential. The links between this new approach to the density matrix with former ones available in the literature are widely discussed. The semiclassical Hartree-Fock energy at Extended Thomas-Fermi level is also obtained in the case of a non-local one-body Hamiltonian. Numerical applications are performed using the Gogny and Brink-Boeker effective interactions. The semiclassical binding energies and root mean square radii are compared with the fully quantal ones and with those obtained using the Strutinsky averaged method.Comment: 27 pages, LateX, and 2 PostScript figures, (submitted to Nucl. Phys. A

Mfn2 downregulation in excitotoxicity causes mitochondrial dysfunction and delayed neuronal death.

Mitochondrial fusion and fission is a dynamic process critical for the maintenance of mitochondrial function and cell viability. During excitotoxicity neuronal mitochondria are fragmented, but the mechanism underlying this process is poorly understood. Here, we show that Mfn2 is the only member of the mitochondrial fusion/fission machinery whose expression is reduced in in vitro and in vivo models of excitotoxicity. Whereas in cortical primary cultures, Drp1 recruitment to mitochondria plays a primordial role in mitochondrial fragmentation in an early phase that can be reversed once the insult has ceased, Mfn2 downregulation intervenes in a delayed mitochondrial fragmentation phase that progresses even when the insult has ceased. Downregulation of Mfn2 causes mitochondrial dysfunction, altered calcium homeostasis, and enhanced Bax translocation to mitochondria, resulting in delayed neuronal death. We found that transcription factor MEF2 regulates basal Mfn2 expression in neurons and that excitotoxicity-dependent degradation of MEF2 causes Mfn2 downregulation. Thus, Mfn2 reduction is a late event in excitotoxicity and its targeting may help to reduce excitotoxic damage and increase the currently short therapeutic window in stroke