An analysis of the feasibility and benefits of GPU/multicore acceleration of the Weather Research and Forecasting model

There is a growing need for ever more accurate climate and weather simulations to be delivered in shorter timescales, in particular, to guard against severe weather events such as hurricanes and heavy rainfall. Due to climate change, the severity and frequency of such events – and thus the economic impact – are set to rise dramatically. Hardware acceleration using graphics processing units (GPUs) or Field-Programmable Gate Arrays (FPGAs) could potentially result in much reduced run times or higher accuracy simulations. In this paper, we present the results of a study of the Weather Research and Forecasting (WRF) model undertaken in order to assess if GPU and multicore acceleration of this type of numerical weather prediction (NWP) code is both feasible and worthwhile. The focus of this paper is on acceleration of code running on a single compute node through offloading of parts of the code to an accelerator such as a GPU. The governing equations set of the WRF model is based on the compressible, non-hydrostatic atmospheric motion with multi-physics processes. We put this work into context by discussing its more general applicability to multi-physics fluid dynamics codes: in many fluid dynamics codes, the numerical schemes of the advection terms are based on finite differences between neighboring cells, similar to the WRF code. For fluid systems including multi-physics processes, there are many calls to these advection routines. This class of numerical codes will benefit from hardware acceleration. We studied the performance of the original code of the WRF model and proposed a simple model for comparing multicore CPU and GPU performance. Based on the results of extensive profiling of representative WRF runs, we focused on the acceleration of the scalar advection module. We discuss the implementation of this module as a data-parallel kernel in both OpenCL and OpenMP. We show that our data-parallel kernel version of the scalar advection module runs up to seven times faster on the GPU compared with the original code on the CPU. However, as the data transfer cost between GPU and CPU is very high (as shown by our analysis), there is only a small speed-up (two times) for the fully integrated code. We show that it would be possible to offset the data transfer cost through GPU acceleration of a larger portion of the dynamics code. In order to carry out this research, we also developed an extensible software system for integrating OpenCL code into large Fortran code bases such as WRF. This is one of the main contributions of our work. We discuss the system to show how it allows the replacement of the sections of the original codebase with their OpenCL counterparts with minimal changes – literally only a few lines – to the original code. Our final assessment is that, even with the current system architectures, accelerating WRF – and hence also other, similar types of multi-physics fluid dynamics codes – with a factor of up to five times is definitely an achievable goal. Accelerating multi-physics fluid dynamics codes including NWP codes is vital for its application to weather forecasting, environmental pollution warning, and emergency response to the dispersion of hazardous materials. Implementing hardware acceleration capability for fluid dynamics and NWP codes is a prerequisite for up-to-date and future computer architectures

車椅子用レインコートの素材の違いが降水時の衣服内気候に及ぼす影響

The effects of two kinds of raincoat with different materials on physiological parameters and clothing microclimate inside raincoat under simulated rain conditions were studied at ambient temperature of 30℃ and a relative humidity of 80％ in five female participants, aged 19.6±0.5yrs. One kind of raincoat was made of nylon with coating and calendar finishing （A） and the other of the fabric laminated with nylon, polyurethane and knitted nylon with moisture permeable properties （B）. After they took a rest for 15min, water was sprinkled at the rate of 5mm/h for 20min, followed by 15min recovery. The main results are summarized as follows: （1）Skin temperatures on the chest and back were lower under sprinkling in B than in A. （2） Clothing microclimate absolute humidities on the back were significantly lower in B than in A. （3） Comfort sensation was better in B than in A. The raincoat B made the chest and back skin temperatures and microclimate absolute humidities inside the raincoat lower. The present findings suggest that the raincoat materials are of importance in improving the comfort sensation by reduction of microclimate humidity and trunk skin temperatures

Charge order with unusual star-of-David lattice in monolayer NbTe2

Interplay between fermiology and electron correlation is crucial for realizing exotic quantum phases. Transition-metal dichalcogenide (TMD) 1T-TaS2 has sparked a tremendous attention owing to its unique Mott-insulating phase coexisting with the charge-density wave (CDW). However, how the fermiology and electron correlation are associated with such properties has yet to be claried. Here we demonstrate that monolayer 1T-NbTe2 is a new class of two-dimensional TMD which has the star-of-David lattice similarly to bulk TaS2 and isostructural monolayer NbSe2, but exhibits a metallic ground state with an unusual lattice periodicity root19xroot19 characterized by the sparsely occupied star-of-David lattice. By using angle-resolved photoemission and scanning-tunneling spectroscopies in combination with first-principles band-structure calculations, we found that the hidden Fermi-surface nesting and associated CDW formation are a primary cause to realize this unique correlated metallic state with no signature of Mott gap. The present result points to a vital role of underlying fermiology to characterize the Mott phase of TMDs.Comment: To be published in Physical Review

Surface-termination-dependent electronic states in kagome superconductors AV3Sb5 (A = K, Rb, Cs) studied by micro-ARPES

Recently discovered kagome superconductors AV3Sb5 (A = K, Rb, Cs) exhibit exotic bulk and surface physical properties such as charge-density wave (CDW) and chirality, whereas their origins remain unresolved. By using micro-focused angle-resolved photoemission spectroscopy, we discovered that AV3Sb5 commonly exhibits two distinct polar surfaces depending on the termination; electron- and hole-doped ones for the A- and Sb-termination, respectively. We observed that the kagome-derived band shows a clear splitting in the A-terminated surface while it is absent in the Sb-terminated counterpart, indicative of the polarity-dependent CDW at the surface. Close comparison of the band-dependent splitting reveals that the three-dimensional CDW structure of the K-terminated surface is different from that of the Rb- or Cs-terminated surface, suggesting the diversity of the CDW ground state. These results provide important insight into the origin of CDW in kagome superconductors AV3Sb5.Comment: 10 pages, 8 figure