SESSION: Gordon Bell Earth Simulator
CHAIR:
TIME: Thursday 11/21 10:30-Noon
ROOM: 307-308

1. pap273
TITLE: 16.4 Tflops Direct Numerical Simulation of Turbulence by Fourier Spectral Method on the Earth Simulator
AUTHORS: Mitsuo Yokokawa (Japan Atomic Energy Research Institute)
Ken'ichi Itakura (Japan Marine Science and Technology Center)
Atsuya Uno (Japan Marine Science and Technology Center)
Takashi Ishihara (Nagoya University)
Yukio Kaneda (Nagoya University)

ABSTRACT:
High resolution direct numerical simulations (DNS) of incompressible turbulence with the number of grid points up to 4096^3 have been performed on the Earth Simulator (ES). The DNS are based on the Fourier spectral method, so that the equation representing the mass conservation is accurately solved. In such DNS based on spectral method, most computation time is consumed by three-dimensional (3D) Fast Fourier Transform (FFT), which requires huge global data transfer and has been the major stumbling block for achieving high performance computing. By implementing new methods to efficiently perform the 3D-FFT on the ES, we have achieved high performance DNS with 16.4 Tflops on 2048^3 grid points. The DNS yields energy spectrum exhibiting a wide inertial subrange, in contrast to existing DNS's with lower resolutions, and therefore provides valuable data for the study of universal features of turbulence at large Reynolds number.

2. pap147
TITLE: 14.9 TFLOPS Three-dimensional Fluid Simulation for Fusion Science with HPF on the Earth Simulator
AUTHORS: Hitoshi Sakagami (Himeji Institute of Technology)
Hitoshi Murai (Japan Marine Science and Technology Center)
Yoshiki Seo (NEC Corporation)
Mitsuo Yokokawa (Japan Atomic Energy Research Institute)

ABSTRACT:
We succeeded in getting 14.9 TFLOPS performance when running a plasma simulation code IMPACT-3D parallelized with High Performance Fortran on 512 nodes of the Earth Simulator. The theoretical peak performance of the 512 nodes is 32 TFLOPS, which means 45% of the peak performance was obtained with HPF. IMPACT-3D is an implosion analysis code using TVD scheme, which performs three-dimensional compressible and inviscid Eulerian fluid computation with the explicit 5-point stencil scheme for spatial differentiation and the fractional time step for time integration. The mesh size is 2048x2048x4096, and the third dimension was distributed for the parallelization. The HPF system used in the evaluation is HPF/ES, developed for the Earth Simulator by enhancing NEC HPF/SX V2 mainly in communication scalability. Shift communications were manually tuned to get best performance by using HPF/JA extensions, which was designed to give the users more control over sophisticated parallelization and communication optimizations.

3. pap331
TITLE: A 26.58 Tflops Global Atmospheric Simulation with the Spectral Transform Method on the Earth Simulator
AUTHORS: Satoru Shingu (Earth Simulator Center, Japan Marine Science and Technology Center)
Hiroshi Takahara (NEC Corporation)
Hiromitsu Fuchigami (NEC Informatec Systems, Ltd.)
Masayuki Yamada (NEC Informatec Systems, Ltd.)
Yoshinori Tsuda (Earth Simulator Center)
Wataru Ohfuchi (Earth Simulator Center)
Yuji Sasaki (NEC Informatec Systems, Ltd.)
Kazuo Kobayashi (NEC Informatec Systems, Ltd.)
Takashi Hagiwara (NEC Corporation)
Shin-ichi Habata (NEC Corporation)
Mitsuo Yokokawa (National Institute of Advanced Industrial Science and Technology)
Hiroyuki Itoh (National Space Development Agency of Japan)
Kiyoshi Otsuka (Earth Simulator Center)

ABSTRACT:
A spectral atmospheric general circulation model called AFES (AGCM for Earth Simulator) was developed and optimized for the architecture of the Earth Simulator (ES). The ES is a massively parallel vector supercomputer that consists of 640 processor nodes interconnected by a single stage crossbar network with its total peak performance of 40.96 Tflops. The sustained performance of 26.58 Tflops was achieved for a high resolution simulation (T1279L96) with AFES by utilizing the full 640-node configuration of the ES. The resulting computing efficiency is 64.9% of the peak performance, well surpassing that of conventional weather/climate applications having just 25-50% efficiency even on vector parallel computers. This remarkable performance proves the effectiveness of the ES as a viable means for practical applications.