Performance Models for Data Transfers: A Case Study with Molecular Chemistry Kernels

With increasing complexity of hardwares, systems with different memory nodes are ubiquitous in High Performance Computing (HPC). It is paramount to develop strategies to overlap the data transfers between memory nodes with computations in order to exploit the full potential of these systems. In this article, we consider the problem of deciding the order of data transfers between two memory nodes for a set of independent tasks with the objective to minimize the makespan. We prove that with limited memory capacity, obtaining the optimal order of data transfers is a NP-complete problem. We propose several heuristics for this problem and provide details about their favorable situations. We present an analysis of our heuristics on traces, obtained by running 2 molecular chemistry kernels, namely, Hartree-Fock (HF) and Coupled Cluster Single Double (CCSD) on 10 nodes of an HPC system. Our results show that some of our heuristics achieve significant overlap for moderate memory capacities and are very close to the lower bound of makespan

Optimizing egalitarian performance in the side-effects model of colocation for data center resource management

In data centers, up to dozens of tasks are colocated on a single physical machine. Machines are used more efficiently, but tasks' performance deteriorates, as colocated tasks compete for shared resources. As tasks are heterogeneous, the resulting performance dependencies are complex. In our previous work [18] we proposed a new combinatorial optimization model that uses two parameters of a task - its size and its type - to characterize how a task influences the performance of other tasks allocated to the same machine. In this paper, we study the egalitarian optimization goal: maximizing the worst-off performance. This problem generalizes the classic makespan minimization on multiple processors (P||Cmax). We prove that polynomially-solvable variants of multiprocessor scheduling are NP-hard and hard to approximate when the number of types is not constant. For a constant number of types, we propose a PTAS, a fast approximation algorithm, and a series of heuristics. We simulate the algorithms on instances derived from a trace of one of Google clusters. Algorithms aware of jobs' types lead to better performance compared with algorithms solving P||Cmax. The notion of type enables us to model degeneration of performance caused by using standard combinatorial optimization methods. Types add a layer of additional complexity. However, our results - approximation algorithms and good average-case performance - show that types can be handled efficiently.Comment: Author's version of a paper published in Euro-Par 2017 Proceedings, extends the published paper with addtional results and proof

Saltmarshes, ecosystem services, and an evolving policy landscape: A case study of Wales, UK

Coastal areas are facing increasing pressures, resulting in unprecedented levels of change that require an adaptive and flexible governance system. Through its devolved powers, governance in Wales has undergone significant change, with new legislation providing ‘world-leading’ and ‘innovative’ approaches to a range of social, economic and environmental challenges. This provides an opportunity to examine the extent to which ecosystem services have been translated into national policy, providing a useful case study for global coastal governance. This paper reviews five recent Welsh acts, focusing specifically on the case study system of saltmarshes and their ecosystem services, benefits and processes. A number of themes are identified, highlighting opportunities and challenges for global coastal governance. One key observation found that the language used within these 5 Acts is more clearly linked to ecosystem benefits, rather than language traditionally associated with ecosystem services. This evaluation of these Acts highlighted a limited inclusion of ecosystem services – perhaps, if ecosystem services are to be the lynchpin of coastal governance, a more explicit consideration of the concept is required at the highest of policy scales. Finally, recommendations are presented calling for greater inclusion of ecosystem services within high-level policy, and for an integrated and adaptive approach to coastal governance. In addition, it should be noted that although the study is based in a Welsh context, the outcomes are framed within a global scale, providing transferable insights. This paper contributes to the ongoing dialogue surrounding the concept of ecosystem services and its application within coastal governance

Validation of Additive Manufacturing Process Trough Build Simulation

Producing parts trough Additive Manufacturing (AM) processes enables tremendous freedom in creating components with free-form and intricate features that would be impossible to manufacture through conventional methods. This freedom however does not come without its limits. Thus, when designing for AM (DfAM) one should consider, amongst which but not exclusively, variable wall thickness, deep channels, overhanging features, supports (position and support removal), lattices, as well as avoiding component distortion. Meanwhile the physics commanding these changes are hard to predict particularly in the micro-scale. To eliminate or minimize such problems solutions like build simulation have started to be looked at as a replacement for unwanted destructive tests. Finally, the materials used play a big role linking design and thermal stresses to feature behaviour. In this work a set of features was chosen to validate and conduct a sensitivity test on MS Simufact simulation software, so that future work in this area can be continued. The set of features chosen, were the diameters and roundness of three concentric rings. All the various inputs were analysed throughout this work and explained. Two materials were considered in the experiment, alloy Inconel 625 for the build powder with a stainless-steel build plate base. From the assumptions taken and software functions the first and main input to be studied was the voxel size. A relation between the simulated feature and the optimal voxel size is what is intended to be achieved. Simultaneously via Design of Experiments (DOE), other parameters were studied to assess their overall effect on result. The Simulation run results were compared with actual measured parts via a 3D optical measuring system

Continental-scale patterns of pathogen prevalence: a case study on the corncrake

Pathogen infections can represent a substantial threat to wild populations, especially those already limited in size. To determine how much variation in the pathogens observed among fragmented populations is caused by ecological factors, one needs to examine systems where host genetic diversity is consistent among the populations, thus controlling for any potentially confounding genetic effects. Here, we report geographic variation in haemosporidian infection among European populations of corncrake. This species now occurs in fragmented populations, but there is little genetic structure and equally high levels of genetic diversity among these populations. We observed a longitudinal gradient of prevalence from western to Eastern Europe negatively correlated with national agricultural yield, but positively correlated with corncrake census population sizes when only the most widespread lineage is considered. This likely reveals a possible impact of local agriculture intensity, which reduced host population densities in Western Europe and, potentially, insect vector abundance, thus reducing the transmission of pathogens. We conclude that in the corncrake system, where metapopulation dynamics resulted in variations in local census population sizes, but not in the genetic impoverishment of these populations, anthropogenic activity has led to a reduction in host populations and pathogen prevalence

Ecosystem services: A bridge or barrier for UK marine stakeholders?

Ecosystem services conceptualises the multiple interactions between ecosystems and the people and communities benefitting from their direct or indirect use, aiming to provide stakeholders and scientists with a common language. While some users appear to have adopted this language and terminology, there are concerns that the complexities associated with the concept make it inaccessible and, rather than providing stakeholders with a tool to explain complex relationships, the language and terminology itself may disengage. Through surveying UK-based coastal and marine stakeholders (n = 158), this study examines stakeholders’ perceptions of the concept of ecosystem services and its role and usefulness within the marine and coastal science-policy-practice interface. Overall, stakeholders provided favourable opinions, with findings similar across respondents with the exception of industry; which used it less, was less confident with it and believed it to be less important. The results provide an evidenced argument for the benefits of the ecosystem services approach, including communication, supporting management and linking environment to humans. The analysis also details the required advancements to ensure effective future use, including improved terminology, pluralistic valuation and shared learning. Finally, the paper highlights challenges and benefits relating to the term, creating links to ongoing discussions about effective scientific communication for marine and coastal management

Genetic parameters of the twisted legs syndrome in broiler chickens

International audienc

Physical activity accrued whilst golf caddying

Golf caddies are involved in golf at all levels of the game; however, little research has considered the physical activity (PA) accrued working in this profession. Importantly, the PA from playing golf can improve aspects of health; therefore, caddying may provide a PA that elicits similar benefits. This study, therefore, assessed the PA accrued whilst golf caddying. Eleven male caddies wore a PA monitor for 7-days and recorded time spent caddying while walking the 18-hole course at Carnoustie Golf Links, Scotland. Per day, caddies spent 224 minutes (58%) of their time caddying in light-intensity PA and 115 minutes (30%) of their time caddying in moderate-to-vigorous PA, accumulating 15480±4089 steps. Caddying accumulates enough moderate-to-vigorous PA across a week to exceed current PA guidelines, and the step count accrued is classified as highly active. Caddying can provide PA that has the potential to provide health benefits

Physical activity accrued whilst golf caddying

Golf caddies are involved in golf at all levels of the game; however, little research has considered the physical activity (PA) accrued working in this profession. Importantly, the PA from playing golf can improve aspects of health; therefore, caddying may provide a PA that elicits similar benefits. This study, therefore, assessed the PA accrued whilst golf caddying. Eleven male caddies wore a PA monitor for 7-days and recorded time spent caddying while walking the 18-hole course at Carnoustie Golf Links, Scotland. Per day, caddies spent 224 minutes (58%) of their time caddying in light-intensity PA and 115 minutes (30%) of their time caddying in moderate-to-vigorous PA, accumulating 15480±4089 steps. Caddying accumulates enough moderate-to-vigorous PA across a week to exceed current PA guidelines, and the step count accrued is classified as highly active. Caddying can provide PA that has the potential to provide health benefits