Symmetric L-graphs

In this paper we characterize symmetric L-graphs, which are either Kronecker products of two cycles or Gaussian graphs. Vertex symmetric networks have the property that the communication load is uniformly distributed on all the vertices so that there is no point of congestion. A stronger notion of symmetry, edge symmetry, requires that every edge in the graph looks the same. Such property ensures that the communication load is uniformly distributed over all the communication links, so that there is no congestion at any link.Peer Reviewe

Muerte de Simón Bolívar en Santa Marta

En el siglo XXI se continúan esclareciendo e investigando, científicamente y técnicamente, varios sucesos por definir, y demostrar cuáles fueron las verdaderas causas de la muerte del Libertador Simón Bolívar. Si nos apegamos a los boletines de su médico, Alejandro Próspero Révérend, murió de tuberculosis, y no de otras tantas enfermedades que le achacaron sus detractores

Muerte de Simón Bolívar en Santa Marta

En el siglo XXI se continúan esclareciendo e investigando, científicamente y técnicamente, varios sucesos por definir, y demostrar cuáles fueron las verdaderas causas de la muerte del Libertador Simón Bolívar. Si nos apegamos a los boletines de su médico, Alejandro Próspero Révérend, murió de tuberculosis, y no de otras tantas enfermedades que le achacaron sus detractores

S-SMART++: A Low-Latency NoC Leveraging Speculative Bypass Requests

Many-core processors demand scalable, efficient and low latency NoCs. Bypass routers are an affordable solution to attain low latency in relatively simple topologies like the mesh. SMART improves on traditional bypass routers implementing multi-hop bypass which reduces the importance of the distance between pairs of nodes. Nevertheless, the conservative buffer reallocation policy of SMART requires a large number of Virtual Channels (VCs) to offer high performance, penalizing its implementation cost. Besides, SMART zero-load latency values highly depend on HPC Max HPCMax, the maximum number of hops that can be jumped per cycle. In this article, we present Speculative-SMART++ (S-SMART++), with two mechanisms that significantly improve multi-hop bypass. First, zero-load latency is reduced by speculatively setting consecutive multi-hops. Second, the inefficient buffer reallocation policy of SMART is reduced by combining multi-packet buffers, Non-Empty Buffer Bypass and per-packet allocation. These proposals are evaluated using functional simulation, with synthetic and real loads, and synthesis tools. S-SMART++ does not need VCs to obtain the performance of SMART with 8 VCs, reducing notably logic resources and dynamic power. Additionally, S-SMART++ reduces the base-latency of SMART by at least 29.2 percent, even when using the biggest HPC Max HPCMax possibleThis work was supported by the Spanish Ministry of Science, Innovation and Universities, FPI grant BES2017-079971, the Spanish Ministry of Science, Innovation and Universities under contracts TIN2016-76635-C2-2-R (AEI/FEDER, UE) and TIC PID2019-105660RB-C22, and the European HiPEAC Network of Excellence. The Mont-Blanc project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 671697

Factores clave en la creación y desarrollo de cooperativas. Estudio empírico aplicado a la Comunidad Valenciana

Las empresas cooperativas y de la Economía Social juegan un papel clave en la crisis económica: por una parte porque son empresas más resistentes a la destrucción de empleo y por otra porque su número aumenta durante las fases recesivas. Por este motivo, puede resultar relevante determinar cuáles son los factores que influyen en la creación de este tipo de organizaciones y garantizan su supervivencia a largo plazo. Para ello, en el trabajo se realiza un estudio empírico aplicado a una muestra de cooperativas creadas en la Comunidad Valenciana entre los años 2008 y 2011 (cuatro primeros años de la crisis) con el fin de determinar dichos factores clave a través del uso de la técnica del Perfil estratégico. Los resultados demuestran que este tipo de organizaciones tienen carencias significativas en lo que se refiere a sus habilidades para la capacidad de gestión y de adaptación a los cambios del entorno, en especial en la obtención de financiación y en la profesionalización de su gestión. Por otra parte, sus principales fortalezas son la satisfacción y fidelización de los clientes, la protección del medio ambiente, la mejora de la calidad, la participación de los trabajadores y el clima laboral. Por el contrario, sus principales debilidades son el bajo poder de negociación con sus proveedores, la innovación de los procesos productivos, los niveles de endeudamiento y los costes financieros. Son, por tanto, las áreas de finanzas y de aprovisionamiento las más débiles en las cooperativas, mientras que sus fortalezas residen en sus recursos humanos y en el marketing

Low Complexity Maximum-Likelihood Detector for DSTTD Architecture Based on the QRD-M Algorithm

This paper presents a new decoder algorithm for the double space-time transmit diversity (DSTTD) system. The decoder is based on the QRD-M algorithm, which performs a breadth-first search of possible solutions tree. The search is simplified by skipping unlikely candididates, and it is stopped when no promising candidates are left. Furthermore, the search is divided into three concurrent iterations, making possible a fast, parallel implementation either in hardware or software. After presenting an analysis of the capacity and diversity of DSTTD, we present performance results showing that the proposed decoder is capable of achieving near maximum likelihood performance. We also show that the proposed algorithm exhibits lower computational complexity than other existing maximum likelihood detectors

Design and experimental validation of a software-defined radio access network testbed with slicing support

Network slicing is a fundamental feature of 5G systems to partition a single network into a number of segregated logical networks, each optimized for a particular type of service or dedicated to a particular customer or application. The realization of network slicing is particularly challenging in the Radio Access Network (RAN) part, where multiple slices can be multiplexed over the same radio channel and Radio Resource Management (RRM) functions shall be used to split the cell radio resources and achieve the expected behaviour per slice. In this context, this paper describes the key design and implementation aspects of a Software-Defined RAN (SD-RAN) experimental testbed with slicing support. The testbed has been designed consistently with the slicing capabilities and related management framework established by 3GPP in Release 15. The testbed is used to demonstrate the provisioning of RAN slices (e.g., preparation, commissioning, and activation phases) and the operation of the implemented RRM functionality for slice-aware admission control and scheduling.Peer ReviewedPostprint (published version

On random wiring in practicable folded clos networks for modern datacenters

Big scale, high performance and fault-tolerance, low-cost and graceful expandability are pursued features in current datacenter networks (DCN). Although there have been many proposals for DCNs, most modern installations are equipped with classical folded Clos networks. Recently, regular random topologies, as the Jellyfish, have been proposed for DCNs. However, their completely unstructured nature entails serious design problems. In this paper we propose Random Folded Clos (RFC) and Hydra networks in which the interconnection between certain switches levels is made randomly. Both RFCs and Hydras preserve important properties of Clos networks that provide a straightforward deadlock-free multi-path routing. The proposed networks leverage randomness to be gracefully expandable, thereby allowing for fine grain upgrading. RFCs and Hydras are compared in the paper, in topological and cost terms, against fat-trees, orthogonal fat-trees and random regular networks. Also, experiments are carried out to simulate their performance under synthetic traffic patterns emulating common loads present in warehouse scale computers. These theoretical and empirical studies reveal the interest of these topologies, concluding that Hydra constitutes a practicable alternative to current datacenter networks since it appropriately balance all the main design requirements. Moreover, Hydras perform better than the fat-trees, their natural competitor, being able to connect the same or more computing nodes with significant lower cost and latency while exhibiting comparable throughput. © 1990-2012 IEEE

Assessing the Effect of the Economy for the Common Good System on Business Performance

Extant literature has pointed to organizational hybridity to lever sustainable business transformation. Moreover, some authors hold that there is a possible trade-off between sustainability and performance. However, there is still little empirical evidence on the impact that such sustainability- driven hybridization systems have on performance. Thus, the present study's main goal is to fill this gap by providing empirical evidence on the impact of the implementation of the Economy for the Common Good, as a sustainability-driven organizational system, on business performance. To do so, the authors relied on a sample of 206 businesses from five European countries. Then, the authors followed a quantitative research approach based on a hierarchical regression analysis that allowed them to test for linear, curvilinear, and moderating effects. The authors found a positive relationship between the implementation of a sustainability-driven hybridization system and firm performance. Besides, they identified some curvilinear effects pointing to the existence of a 'too much of a good thing' effect, along with some moderating effects derived from organizational size

Polarized routing for large interconnection networks

Supercomputers and datacenters comprise hundreds of thousands of servers. Different network topologies have been proposed to attain such a high scalability, from flattened Butterfly and Dragonfly to the most disruptive Jellyfish, which is based on a random graph. The routing problem on such networks remains a challenge that can be tackled either as a topology-aware solution or with an agnostic approach. The case of random networks is a very special one since no a priori topological clues can be exploited. In this article, we introduce the polarized routing algorithm, an adaptive nonminimal hop-by-hop mechanism that can be used in most of topologies, including Jellyfish. Polarized routing follows two design criteria: a source-destination symmetry in the routes and avoiding backtracking. Experimental evaluation proves that polarized routing not only outperforms other routings in random graphs but also attains the best performance provided by ad hoc solutions for specific outstanding low-diameter interconnection networks.This work has been supported by the Spanish Ministry of Science and Innovation under contracts PID2019-105660RB-C22 and FJCI-2017-31643. Simulations were performed in the Altamira supercomputer, a node of the Spanish Super-computing Network