Astrophysical code migration into Exascale Era

The ExaNeSt and EuroExa H2020 EU-funded projects aim to design and develop an exascale ready computing platform prototype based on low-energy-consumption ARM64 cores and FPGA accelerators. We participate in the application-driven design of the hardware solutions and prototype validation. To carry on this work we are using, among others, Hy-Nbody, a state-of-the-art direct N-body code. Core algorithms of Hy-Nbody have been improved in such a way to increasingly fit them to the exascale target platform. Waiting for the ExaNest prototype release, we are performing tests and code tuning operations on an ARM64 SoC facility: a SLURM managed HPC cluster based on 64-bit ARMv8 Cortex-A72/Cortex-A53 core design and powered by a Mali-T864 embedded GPU. In parallel, we are porting a kernel of Hy-Nbody on FPGA aiming to test and compare the performance-per-watt of our algorithms on different platforms. In this paper we describe how we re-engineered the application and we show first results on ARM SoC.Comment: 4 pages, 1 figure, 1 table; proceedings of ADASS XXVIII, accepted by ASP Conference Serie

ASSESSING THE NEED FOR ACCURATE FLOOD DAMAGE PREDICTION BASED ON FUTURE CHANGES IN PEAK FLOW OF RIVERINE SYSTEMS: IS THERE MORE UNCERTAINTY IN THE HYDROLOGY OR THE DEGREE OF DAMAGE?

In most riverine systems, the impact of future climate change on flooding remains uncertain. However, the majority of studies that evaluate future flood risk focus on discharge alone, with little assessment of the degree to which damages (the actual impact due to floods) relates to discharge. This study assesses flood-frequency, stage-discharge, and stage-damage relationships to evaluate how uncertainty in future hydroclimatological drivers of flooding may translate into uncertainty in future damages within a flood plain. The areas of interest for this study were the Onondaga Creek, Syracuse, NY and Susquehanna River, Binghamton, NY watersheds. The results of this study were that flood damages were found to be highly sensitive to the uncertainty in the hydrology of both study areas. In the Onondaga Creek watershed, damage sensitivity was amplified 3.0 times, while in the Susquehanna River basin the amplification was 3.1 to 3.6 times the uncertainty in the hydrology. The uncertainty findings indicated that hydrology plays a large role in flood damage estimations for both watersheds. Each watershed displayed the same response to different future climate change scenarios whereby future flood risk increased as a result of an increase in the magnitude of precipitation events and either remained the same or declined minimally for decreased snowmelt events. The methodology and findings of this study can aid policy and decision makers, flood risk managers, and research scientists in more accurately predicting flood risk areas and potential damages from different flood events by emphasizing a focus on more accurate hydrologic prediction and the incorporation of uncertainty analysis to better predict flood risk and allocate resources for communities in flood prone areas

An Analysis of U.S. and World Carbon Dioxide Emissions from the Consumption of Coal for Energy from 1980 to 2012

The purpose of this research is to examine the impact of carbon dioxide (CO2) emissions from U.S. coal consumption for energy on total global anthropogenic CO2 emissions from coal from 1980 to 2012. This study investigated whether the U.S. to world proportion of CO2 emissions from coal have been greater than expected when compared to global CO2 emissions on a per person basis over this time period. Data was obtained from the U.S. Energy Information Administration (U.S. E.I.A.), U.S. Census Bureau, IHS Global Insight, Inc., and Population Reference Bureau for U.S. and global coal consumption, CO2 emissions from coal, and population. This data was used to create percentages for each year of the study, which were then graphed and analyzed. The results of the study found that the U.S. has emitted more CO2 than expected for a country of its population and that U.S. CO2 emissions from coal have been decreasing with no influence on the recent increasing trend of global CO2 emissions. The driving force behind the recent increases was China. A secondary study involved analyzing the negative correlation between CO2 emissions from U.S. coal and natural gas consumption from 1980 to 2012. Data from the U.S. E.I.A. for coal and natural gas consumption was tested using graphical analysis and Pearson’s correlation coefficient tests. The results were that there was no significant negative correlation of CO2 emissions between coal and natural gas consumption. The findings of the study confirmed the first research question of the U.S. having a disproportionate influence on global CO2 emissions from coal, while rejecting the secondary question of the negative relationship between CO2 emissions from coal and natural gas consumption in the U.S

Simulating realistic disk galaxies with a novel sub-resolution ISM model

We present results of cosmological simulations of disk galaxies carried out with the GADGET-3 TreePM+SPH code, where star formation and stellar feedback are described using our MUlti Phase Particle Integrator (MUPPI) model. This description is based on simple multi-phase model of the interstellar medium at unresolved scales, where mass and energy flows among the components are explicitly followed by solving a system of ordinary differential equations. Thermal energy from SNe is injected into the local hot phase, so as to avoid that it is promptly radiated away. A kinetic feedback prescription generates the massive outflows needed to avoid the over-production of stars. We use two sets of zoomed-in initial conditions of isolated cosmological halos with masses (2-3) * 10^{12} Msun, both available at several resolution levels. In all cases we obtain spiral galaxies with small bulge-over-total stellar mass ratios (B/T \approx 0.2), extended stellar and gas disks, flat rotation curves and realistic values of stellar masses. Gas profiles are relatively flat, molecular gas is found to dominate at the centre of galaxies, with star formation rates following the observed Schmidt-Kennicutt relation. Stars kinematically belonging to the bulge form early, while disk stars show a clear inside-out formation pattern and mostly form after redshift z=2. However, the baryon conversion efficiencies in our simulations differ from the relation given by Moster et al. (2010) at a 3 sigma level, thus indicating that our stellar disks are still too massive for the Dark Matter halo in which they reside. Results are found to be remarkably stable against resolution. This further demonstrates the feasibility of carrying out simulations producing a realistic population of galaxies within representative cosmological volumes, at a relatively modest resolution.Comment: 19 pages, 21 figures, MNRAS accepte