SPH-EXA: Enhancing the Scalability of SPH codes Via an Exascale-Ready SPH Mini-App

Numerical simulations of fluids in astrophysics and computational fluid dynamics (CFD) are among the most computationally-demanding calculations, in terms of sustained floating-point operations per second, or FLOP/s. It is expected that these numerical simulations will significantly benefit from the future Exascale computing infrastructures, that will perform 10^18 FLOP/s. The performance of the SPH codes is, in general, adversely impacted by several factors, such as multiple time-stepping, long-range interactions, and/or boundary conditions. In this work an extensive study of three SPH implementations SPHYNX, ChaNGa, and XXX is performed, to gain insights and to expose any limitations and characteristics of the codes. These codes are the starting point of an interdisciplinary co-design project, SPH-EXA, for the development of an Exascale-ready SPH mini-app. We implemented a rotating square patch as a joint test simulation for the three SPH codes and analyzed their performance on a modern HPC system, Piz Daint. The performance profiling and scalability analysis conducted on the three parent codes allowed to expose their performance issues, such as load imbalance, both in MPI and OpenMP. Two-level load balancing has been successfully applied to SPHYNX to overcome its load imbalance. The performance analysis shapes and drives the design of the SPH-EXA mini-app towards the use of efficient parallelization methods, fault-tolerance mechanisms, and load balancing approaches.Comment: arXiv admin note: substantial text overlap with arXiv:1809.0801

Towards a Mini-App for Smoothed Particle Hydrodynamics at Exascale

The smoothed particle hydrodynamics (SPH) technique is a purely Lagrangian method, used in numerical simulations of fluids in astrophysics and computational fluid dynamics, among many other fields. SPH simulations with detailed physics represent computationally-demanding calculations. The parallelization of SPH codes is not trivial due to the absence of a structured grid. Additionally, the performance of the SPH codes can be, in general, adversely impacted by several factors, such as multiple time-stepping, long-range interactions, and/or boundary conditions. This work presents insights into the current performance and functionalities of three SPH codes: SPHYNX, ChaNGa, and SPH-flow. These codes are the starting point of an interdisciplinary co-design project, SPH-EXA, for the development of an Exascale-ready SPH mini-app. To gain such insights, a rotating square patch test was implemented as a common test simulation for the three SPH codes and analyzed on two modern HPC systems. Furthermore, to stress the differences with the codes stemming from the astrophysics community (SPHYNX and ChaNGa), an additional test case, the Evrard collapse, has also been carried out. This work extrapolates the common basic SPH features in the three codes for the purpose of consolidating them into a pure-SPH, Exascale-ready, optimized, mini-app. Moreover, the outcome of this serves as direct feedback to the parent codes, to improve their performance and overall scalability.Comment: 18 pages, 4 figures, 5 tables, 2018 IEEE International Conference on Cluster Computing proceedings for WRAp1

A Study of the Methods Used by a Selected Group of Directors of Nursing Service in the Planning of Rotation and Assignments for Staff Nurses

The problem was to study the methods used by a selected group of directors of nursing service when planning rotation and assignments for their staff nurse group. The data were gathered by means of a questionnaire, so constructed that it was possible to (l) identify present day methods of rotation and assignment; (2) determine problems encountered in the process, and (3) elicit from the participants their recommendations for alleviating these problems. The increasing emphasis on personnel administration as a valuable tool of management prompted the desire to explore this area. The analysis of the data indicated that the majority of directors of nursing service participating in this study encountered problems when planning staff nurse rotation and assignments. Problems were more pronounced in rotation practices rather than assignment practices. Turnover and job dissatisfaction was ascribed to rotation more frequently than to assignment. Some of the participants seemed to believe problems in this area were inevitable. Recommendations offered by the directors of nursing service for alleviating the problems included good human relations, active staff education, sound personnel policies, attractive remuneration for evening and night duty, group planning for policy making and problem solving and an understanding of the individual personal preferences and domestic responsibilities of the nurse. Because of the present impetus toward meeting the individual\u27s social, psychological and emotional needs, it is apparent that there is a need for further study in this area. Where the nurse works and when she works will have much to do with her gaining satisfaction from her work situation. Soliciting the head nurse’s opinion concerning present day assignment and rotation practices is recommended in order to gain further insight into this problem. Also, a survey of the staff nurse\u27s reaction to this aspect of nursing service administration should prove Worthwhile

Note Illustrative della Carta geologica d'Italia alla scala 1:50.000, F. 269 Fano

<p>Note illustrative redatte per il Foglio geologico n. 269 Fano della Carta Geologica d'Italia alla scala 1:50.000. 76 pp.</p&gt

Note Illustrative della Carta geologica d'Italia alla scala 1:50.000, F. 292 Jesi

<p>Note illustrative redatte per il Foglio geologico n. 292 Jesi della Carta Geologica d'Italia alla scala 1:50.000. 122 pp.</p&gt

A four-surface schematic eye of macaque monkey obtained by an optical method

AbstractSchematic eyes for four Macaca fascicularis monkeys were constructed from measurements of the positions and curvatures of the anterior and posterior surfaces of the cornea and lens. All of these measurements were obtained from Scheimpflug photography through the use of a ray-tracing analysis. Some of these measurements were also checked (and confirmed) by keratometry and ultrasound. Gaussian lens equations were applied to the measured dimensions of each individual eye in order to construct schematic eyes. The mean total power predicted by the schematic eyes agreed closely with independent measurements based on retinoscopy and ultrasound results, 74.2 ± 1.3 (SEM) vs 74.7 ± 0.3 (SEM) diopters. The predicted magnification of 202 μm/deg in one eye was confirmed by direct measurement of 205 μm/deg for a foveal laser lesion. The mean foveal retinal magnification calculated for our eight schematic eyes was 211 ± (SEM) μm/deg, slightly less than the value obtained by application of the method of Rolls and Cowey [Experimental Brain Research, 10, 298–310 (1970)] to our eight eyes but just 4% more than the value obtained by application of the method of Perry and Cowey [Vision Research, 12, 1795–1810 (1985)]