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Vargas R.,Barcelona Supercomputing Center | Vargas R.,Technical University of Catalonia | Quinones E.,Barcelona Supercomputing Center | Marongiu A.,ETH Zurich
Proceedings -Design, Automation and Test in Europe, DATE | Year: 2015

Next-generation many-core embedded platforms have the chance of intercepting a converging need for high performance and predictability. Programming methodologies for such platforms will have to promote predictability as a first-class design constraint, along with features for massive parallelism exploitation. OpenMP, increasingly adopted in the embedded systems domain, has recently evolved to deal with the programmability of heterogeneous many-cores, with mature support for fine-grained task parallelism. While tasking is potentially very convenient for coding real-time applications modeled as periodic task graphs, OpenMP adopts an execution model completely agnostic to any timing requirement that the target application may have. In this position paper we reason about the suitability of the current OpenMP v4 specification and execution model to provide timing guarantees in many-cores. © 2015 EDAA.


Antonopoulos A.,University of Aegean | Renzo M.,University of LAquila | Renzo M.,University Paris - Sud | Verikoukis C.,Technical University of Catalonia | Verikoukis C.,University of Barcelona
IEEE Wireless Communications | Year: 2013

The emergence of heterogeneous networks (HetNets) as an enabling paradigm for ubiquitous wireless communication has further reinforced the concept of medium range cooperation among the end users. This trend, along with the need for bidirectional communication, has triggered the design of new Network Coding (NC)-aided Medium Access Control (MAC) protocols that benefit both the throughput and the energy efficiency in the system. However, the vast majority of MAC protocols are usually designed and analyzed under simplified channel models, ignoring the severe effect of realistic physical (PHY) layer conditions on the wireless communication. In this article, we focus on the impact of correlated long-term slow fading (shadowing) on the performance of distributed wireless systems. As a case study, we discuss in detail the performance of a cooperative NC-aided Automatic Repeat reQuest (ARQ) MAC protocol under correlated shadowing conditions. Our results reveal interesting trade-offs between throughput and energy efficiency, highlighting the importance of considering the slow fading effect in the design of cooperative MAC protocols. © 2013 IEEE.


Lopez-Almansa F.,University of Barcelona | Roca P.,University of Barcelona | Sarrablo V.,International University of Catalonia | Cahis X.,University of Girona | Canet J.M.,Technical University of Catalonia
ACI Structural Journal | Year: 2010

This paper describes structural tests of thin vaults made of reinforced brick masonry. The experiments consist of concentrated loading tests of 14 full-scale laboratory vaults. These vaults are designed to include common situations such as short- to midspan length, low-mid-high rise, rigid-flexible-sliding supports, instantaneous-sustained loading, low-high strength mortar, point-line loading, central-eccentric loading, point-line supports, hinged-clamped supports, symmetric-asymmetric shape, double layer versus single layer reinforcement, and uniaxial-biaxial bending, among others. The tests mainly aim to obtain the collapse loads and to characterize the pre- arid post-peak response. The results show satisfactory structural performance, both in terms of ductility and strength. Moreover, it is possible to predict the structural response with numerical models developed specifically for this purpose. Flat specimens were also tested to determine the punching shear strength of the vaults. This work is part of a larger research project aimed at promoting innovative semi-prefabrication techniques for reinforced brick masonry vaulted light roofs. Copyright © 2010, American Concrete Institute. All rights reserved.


Martin-Vide J.-P.,University of Barcelona | Roca M.,Technical University of Catalonia | Alvarado-Ancieta C.A.,Technical University of Delft
Proceedings of the Institution of Civil Engineers: Water Management | Year: 2010

This paper presents laboratory tests using riprap as a countermeasure for river bend scouring. The bank is a vertical wall in a sharp bend. The riprap is a horizontal apron extended at the toe of this wall. The aims of the tests are to describe the behaviour of riprap in sharp bend flow and to examine how the main flow characteristics are affected by the riprap behaviour. The experimental results show that flexible riprap is able to adapt to bed deformation in river bends by tilting, spreading and paving a transverse slope which ensures that the bank remains protected. Even a blanket located at the initial bed elevation provides efficient protection if it is thick enough. The tests also show that the mainstream velocity and shear stress above the riprap increase after riprap adaptation.


Awan A.J.,KTH Royal Institute of Technology | Brorsson M.,KTH Royal Institute of Technology | Vlassov V.,KTH Royal Institute of Technology | Ayguade E.,Technical University of Catalonia
Proceedings - 2015 IEEE 5th International Conference on Big Data and Cloud Computing, BDCloud 2015 | Year: 2015

In last decade, data analytics have rapidly progressed from traditional disk-based processing to modern in-memory processing. However, little effort has been devoted at enhancing performance at micro-architecture level. This paper characterizes the performance of in-memory data analytics using Apache Spark framework. We use a single node NUMA machine and identify the bottlenecks hampering the scalability of workloads. We also quantify the inefficiencies at micro-architecture level for various data analysis workloads. Through empirical evaluation, we show that spark workloads do not scale linearly beyond twelve threads, due to work time inflation and thread level load imbalance. Further, at the micro-architecture level, we observe memory bound latency to be the major cause of work time inflation. © 2015 IEEE.

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