PerfBound: Conserving Energy with Bounded Overheads in On/Off-Based HPC Interconnects

Energy and power are key challenges in high-performance computing. System energy efficiency must be significantly improved, and this requires greater efficiency in all subcomponents. An important target of optimization is the interconnect, since network links are always on, consuming power even during idle periods. A large number of HPC machines have a primary interconnect based on Ethernet (about 40 percent of TOP500 machines), which, since 2010, has included support for saving power via Energy Efficient Ethernet (EEE). Nevertheless, it is unlikely that HPC interconnects would use these energy saving modes unless the performance overhead is known and small. This paper presents PerfBound, a self-contained technique to manage on/off-based networks such as EEE, minimizing interconnect link energy consumption subject to a bound on the performance degradation. PerfBound does not require changes to the applications and it uses only local information already available at switches and NICs without introducing additional communication messages, and is also compatible with multi-hop networks. PerfBound is evaluated using traces from a production supercomputer. For twelve out of fourteen applications, PerfBound has high energy savings, up to 70 percent for only 1 percent performance degradation. This paper also presents DynamicFastwake, which extends PerfBound to exploit multiple low-power states. DynamicFastwake achieves an energy-delay product 10 percent lower than the original PerfBound techniqueThis research was supported by European Union’s 7th Framework Programme [FP7/2007-2013] under the Mont-Blanc-3 (FP7-ICT-671697) and EUROSERVER (FP7-ICT-610456) projects, the Ministry of Economy and Competitiveness of Spain (TIN2012-34557 and TIN2015-65316), Generalitat de Catalunya (FI-AGAUR 2012 FI B 00644, 2014-SGR-1051 and 2014-SGR-1272), the European Union’s Horizon2020 research and innovation programme under the HiPEAC-3 Network of Excellence (ICT-287759), and the Severo Ochoa Program (SEV-2011-00067) of the Spanish Government.Peer ReviewedPostprint (author's final draft

The environment and human health: An agenda for research

The Working Paper Environment and Human Health gives a comprehensive review of the related literature in order to aid understanding of the (missing) link between the environment and health. Given the exhaustive literature on the subject the paper focuses on the water]related and land]related diseases namely in the fast growing and poor countries. By assessing the terrain of research on the subject, the paper aims to look beyond the causal linkage between environment and health and instead emphasis the underlying question about how environmental factors, along with man]made changes, influence human health. Specifically, the review examines the ability of the literature to define the incidence of environmentally]related diseases as well as their distribution across social and geographical scales, understands the role of diverse factors influencing these diseases and the adaptive capacity of societies in managing these illnesses or disorders. The paper draws on a wide range of sources from a variety of disciplines to unpack the linkage between the environment and health, and identifies issues, themes and questions raised by the literature. The review reveals limited understanding of the complex relationship between the environment and health. Although these researches provide grounds for a curative approach and in recent years have called for a preventive approach, they still retain a esimplistic high school modelf of examining the linear cause]effect relationship. This nevertheless fails to take on the growing risks posed by climate change and globalisation, as well as the dynamics of pathogens (and vectors) and of society affecting human health. These risks characterise complexity, uncertainty, conflicts and change. Given this characterisation of risks, the review calls for a modern approach to foresee and control the future consequences of human actions in order to live and adapt to the risks. This requires a comprehensive understanding of risk (from water pollutants) by identifying the pathways of risk assessment, understanding the impacts of pollutants and identifying a diverse set of strategies adopted by the individuals, organisations and agencies involved in bringing change to existing institutions and bio]physical resources

Origins of the midlatitude Pacific decadal variability

Analysis of multiple climate simulations shows much of the midlatitude Pacific decadal variability to be composed of two simultaneously occurring elements: One is a stochastically driven, passive ocean response to the atmosphere while the other is oscillatory and represents a coupled mode of the ocean‐atmosphere system. ENSO processes are not required to explain the origins of the decadal variability. The stochastic variability is driven by random variations in wind stress and heat flux associated with internal atmospheric variability but amplified by a factor of 2 by interactions with the ocean. We also found a coupled mode of the ocean‐atmosphere system, characterized by a significant power spectral peak near 1 cycle/20 years in the region of the midlatitude North Pacific and Kuroshio Extension. Ocean dynamics appear to play a critical role in this coupled air/sea mode

High-resolution tropical channel model simulations of tropical cyclone climatology and intraseasonal-to-interannual variability

We tailored a tropical channel configuration of the Weather Research and Forecasting (WRF) Model to study tropical cyclone (TC) activity and associated climate variabilities. This tropical channel model (TCM) covers from 308S to 508N at 27-km horizontal resolution, with physics parameterizations carefully selected to achieve more realistic simulations of TCs and large-scale climate mean states. We performed 15-member ensembles of retrospective simulations from 1982 to 2016 hurricane seasons. A thorough comparison with observations demonstrates that the TCM yields significant skills in simulating TC activity climatology and variabilities in each basin, as well as TC physical structures. The correlation of the ensemble averaged accumulated cyclone energy (ACE) with observations in the western North Pacific (WNP), eastern North Pacific (ENP), and North Atlantic (NAT) is 0.80, 0.64, and 0.61, respectively, but is insignificant in the north Indian Ocean (NIO). Moreover, the TCM-simulated modulations of El Niño–Southern Oscillation (ENSO) and the Madden–Julian oscillation (MJO) on the large-scale environment and TC genesis also agree well with observations. To examine the TCM’s potential for seasonal TC prediction, the model is used to forecast the 2017 and 2018 hurricane seasons, using bias-corrected sea surface temperatures (SSTs) from the CFSv2 seasonal prediction results. The TCM accurately predicts the hyperactive 2017 NAT hurricane season and near-normal WNP and ENP hurricane seasons when initialized in May. In addition, the TCM accurately predicts TC activity in the NAT and WNP during the 2018 season, but underpredicts ENP TC activity, in association with a poor ENSO forecast

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Sea urchin diversity and its resources from the Gulf of Mannar

Gulf of Mannar is the richest marine biodiversity hotspot along the Southeast coast of India, encompassing the territorial waters from Dhanushkodi in the north to Kanyakumari in the south. It has a chain of 21 islands, located 2 to 10 km from the mainland along the 140 km stretch between Thoothukudi and Rameswaram. The area of Gulf of Mannar under the Indian EEZ is about 15,000 km2 where commercial fishing takes place only in about 5,500 km2 and that too only up to a depth of 50m. This marine ecosystem holds nearly 117 species of corals, 441 species of fin-fishes, 12 species of sea grasses, 147 species of seaweeds, 641 species of crustaceans, 731 molluscan species (Kumaraguru, 2006). There are around 950 species of sea urchin in class Echinoidea which comes under two subclasses found around the world’s oceans

Multi-Walled Carbon Nanotubes Percolation Network Enhanced the Performance of Negative Electrode for Lead-Acid Battery

The discharge performance of lead-acid battery is improved by adding multi-walled carbon nanotubes (MWCNTs) as an alternate conductive additive in Negative Active Mass (NAM).We report thatMWCNTs added to the negative electrode, exhibits high capacity, excellent cycling performances at 10-h rate, high rate partial state of charge (HRPSoC) cycling and various rates of discharge. It significantly reduces the irreversible lead sulfate on the NAM, increases the active material utilization and improves the electrode performance. The improvement of capacity and cyclic performance of the cell is attributed to the nanoscale dimension of the MWCNTs as additive. Subsequent characterization using high resolution transmission electron microscopy and scanning electron microscopy were carried out to understand the influence of MWCNTs on the negative electrode of lead-acid battery