Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Abe, Takato*; Sato, Takuto; Boku, Taisuke*; Fujita, Norihisa*; Kusaka, Hiroyuki*
Joho Shori Gakkai Kenkyu Hokoku, p.1 - 11, 2025/05
no abstracts in English
Kusaka, Hiroyuki*; Ikeda, Ryosaku*; Sato, Takuto; Iizuka, Satoru*; Boku, Taisuke*
Journal of Advances in Modeling Earth Systems (Internet), 16(10), p.e2024MS004367_1 - e2024MS004367_38, 2024/10
Times Cited Count：10 Percentile：85.04(Meteorology & Atmospheric Sciences)To bridge the gaps between meteorological large-eddy simulation (LES) models and computational fluid dynamics (CFD) models for microscale urban climate simulations, the present study has developed a meteorological LES model for urban areas. This model simulates urban climates across both mesoscale (city scale) and microscale (city-block scale). The paper offers an overview of this LES model, which distinguishes itself from standard numerical weather prediction models by resolving buildings and trees at the microscale simulations. It also differs from standard CFD models by accounting for atmospheric stratification and physical processes. Noteworthy features of this model include: (a) the calculation of long- and short-wave radiations in three dimensions, incorporating multiple reflections within urban canopy layers using the radiosity method, and accounting for building and tree shadows in the simulations; (b) the provision of various heat stress indices (Universal Thermal Climate Index, Wet Bulb Globe Temperature, MRT, THI); (c) the assessment of the efficacy of heat stress mitigation measures such as dry-mist spraying, roadside trees, cool pavements, and green/cool roofs strategies; (d) the capability to run on supercomputers, with the code parallelized in a three-dimensional manner, and the model can also run on a graphics processing unit cluster. Following the introduction of this model, the study confirms its basic performance through various numerical experiments, including simulations of thermals in the convective boundary layer, coherent structure of turbulence over urban canopy, and thermal environment and heat stress indices in urban districts. The model developed in this study is intended to serve as a community tool for addressing both fundamental and applied studies in urban climatology.
Fujita, Norihisa*; Nuga, Hideo*; Boku, Taisuke*; Idomura, Yasuhiro
Proceedings of 2014 IEEE 28th International Parallel & Distributed Processing Symposium Workshops (Internet), p.1266 - 1274, 2014/12
Times Cited Count：1 Percentile：27.93(Computer Science, Theory & Methods)GT5D is a nuclear fusion simulation program which aims to analyze the turbulence phenomena in tokamak plasma. In this research, we optimize it for GPU clusters with multiple GPUs on a node. Based on the profile result of GT5D on a CPU node, we decide to offload the whole of the time development part of the program to GPUs except MPI communication. Four NVIDIA M2090 GPUs get 3.35 times faster performance in maximum in function level evaluation, and 1.91 times faster performance in total than two Intel Xeon E5-2670 (SandyBridge) CPU with 8 cores. It includes 63% performance gain with overlapping the communication between MPI processes with GPU calculation.
Fujita, Norihisa*; Nuga, Hideo*; Boku, Taisuke*; Idomura, Yasuhiro
Proceedings of 19th IEEE International Conference on Parallel and Distributed Systems (ICPDCS 2013) (USB Flash Drive), 2 Pages, 2013/12
Fujita, Norihisa*; Nuga, Hideo*; Idomura, Yasuhiro; Boku, Taisuke*
no journal, ,
In this work, a fusion plasma simulation code GT5D is ported on massively parallel GPU clusters, and its computational performance is evaluated. On the HA-PACS system at Univ. Tsukuba, which has found GPUs per node, major kernels are ported on the GPU memory, and communication between GPUs are overlapped with computations. Although processing performances of the major kernels are improved by 2.3 times on average, an improvement of the total code performance is still limited to 1.3 times, because 70% of kernels are ported at the present. However, the total code performance is slightly improved to 1.85 times by applying the communication overlap technique.
Fujita, Norihisa*; Nuga, Hideo*; Boku, Taisuke*; Idomura, Yasuhiro
no journal, ,
A fusion plasma turbulence simulation code GT5D is optimized for GPU cluster systems with multiple GPUs on a single node. All the calculation loops are ported on GPUs, and communication overlap techniques are applied for main MPI communications. On the HA-PACS system, GPU-CPU computation is faster than CPU-only computation by 2.03 times.
