Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 20
  • 1

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Acceleration of fusion plasma turbulence simulations using the mixed-precision communication-avoiding Krylov method

Idomura, Yasuhiro; Ina, Takuya*; Ali, Y.*; Imamura, Toshiyuki*

Proceedings of International Conference for High Performance Computing, Networking, Storage, and Analysis (SC 2020) (Internet), p.1318 - 1330, 2020/11

The multi-scale full-$$f$$ simulation of the next generation experimental fusion reactor ITER based on a five dimensional (5D) gyrokinetic model is one of the most computationally demanding problems in fusion science. In this work, a Gyrokinetic Toroidal 5D Eulerian code (GT5D) is accelerated by a new mixed-precision communication-avoiding (CA) Krylov method. The bottleneck of global collective communication on accelerated computing platforms is resolved using a CA Krylov method. In addition, a new FP16 preconditioner, which is designed using the new support for FP16 SIMD operations on A64FX, reduces both the number of iterations (halo data communication) and the computational cost. The performance of the proposed method for ITER size simulations with 0.1 trillion grids on 1,440 CPUs/GPUs on Fugaku and Summit shows 2.8x and 1.9x speedups respectively from the conventional non-CA Krylov method, and excellent strong scaling is obtained up to 5,760 CPUs/GPUs.

Journal Articles

Sorption behavior of selenide on montmorillonite

Sugiura, Yuki; Tomura, Tsutomu*; Ishidera, Takamitsu; Doi, Reisuke; Francisco, P. C. M.; Shiwaku, Hideaki; Kobayashi, Toru; Matsumura, Daiju; Takahashi, Yoshio*; Tachi, Yukio

Journal of Radioanalytical and Nuclear Chemistry, 324(2), p.615 - 622, 2020/05

 Times Cited Count:1 Percentile:0.01(Chemistry, Analytical)

Journal Articles

Electronic structure of Li$$^{+}$$@C$$_{60}$$; Photoelectron spectroscopy of the Li$$^{+}$$@C$$_{60}$$[PF$$_{6}$$$$^{-}$$] salt and STM of the single Li$$^{+}$$@C$$_{60}$$ molecules on Cu(111)

Yamada, Yoichi*; Kuklin, A. V.*; Sato, Sho*; Esaka, Fumitaka; Sumi, Naoya*; Zhang, C.*; Sasaki, Masahiro*; Kwon, E.*; Kasama, Yasuhiko*; Avramov, P. V.*; et al.

Carbon, 133, p.23 - 30, 2018/07

 Times Cited Count:8 Percentile:47.45(Chemistry, Physical)

We report first STM observation of the Li$$^{+}$$ ion endohedral C$$_{60}$$, which is of a new class of endohedral fullerenes, prepared by means of evaporation of high-purity Li$$^{+}$$@C$$_{60}$$[PF$$_{6}$$$$^{-}$$] salt in ultra-high vacuum. Prior to the STM measurements, the electronic structure of Li$$^{+}$$@C$$_{60}$$ in the Li$$^{+}$$@C$$_{60}$$[PF$$_{6}$$$$^{-}$$] salt was also precisely determined. In the salt, it is shown that Li and PF$$_{6}$$ have nearly single positive and negative charge, respectively, and the C$$_{60}$$ cage is nearly neutral, suggesting that Li$$^{+}$$@C$$_{60}$$ in the salt retains its original electronic state.

Journal Articles

Incident angle dependence of MCD at the Dy $$M$$$$_{5}$$-edge of perpendicular magnetic Dy$$_{x}$$Co$$_{100-x}$$ films

Agui, Akane; Mizumaki, Masaichiro*; Asahi, Toru*; Sayama, Junichi*; Matsumoto, Koji*; Morikawa, Tsuyoshi*; Matsushita, Tomohiro*; Osaka, Tetsuya*; Miura, Yoshimasa*

Journal of Alloys and Compounds, 408-412, p.741 - 745, 2006/02

 Times Cited Count:7 Percentile:49.06(Chemistry, Physical)

no abstracts in English

Journal Articles

Resonant O K$$alpha$$ emission spectroscopy of layered manganate La$$_{1.2}$$Sr$$_{1.8}$$Mn$$_{2}$$O$$_{7}$$

Agui, Akane; K$"a$$"a$mbre, T.*; S${aa}$the, C.*; Nordgren, J.*; Usuda, Manabu; Saito, Tomohiko*; Moritomo, Yutaka*

Journal of Electron Spectroscopy and Related Phenomena, 144-147, p.589 - 592, 2005/06

 Times Cited Count:1 Percentile:6.02(Spectroscopy)

Current research in the perovskite and layered perovskite-type manganese oxides has expanded to include the study of electronic and magnetic properties such as the colossal magnetoresistance (CMR), orbital ordering and charge ordering. The O K$$alpha$$ soft X-ray emission and absorption spectra (XES and XAS) of La$$_{1.2}$$Sr$$_{1.8}$$Mn$$_{2}$$O$$_{7}$$ were measured at selected excitation energies in order to investigate the electronic structure. The measurements were carried out by using a soft X-ray emission spectrometer at beamline BW3 at HASYLAB, Germany. The dependence of O K$$alpha$$ XES on excitation-energy was observed. It is attributed the different site of oxygen ions.

Journal Articles

Investigation of perpendicular magnetic films by means of soft X-ray spectroscopy; [Co/Pd]$$_{n}$$ multilayered films and RE-TM amorphous films

Agui, Akane; Mizumaki, Masaichiro*

Shingaku Giho, 104(409), p.7 - 10, 2004/11

no abstracts in English

Journal Articles

XAS and XPS combined analysis using high-resolution and high-flux soft X-ray from synchrotron radiation

Matsubayashi, Nobuyuki*; Tanaka, Tomoaki*; Imamura, Motoyasu*; Shimada, Hiromichi*; Saito, Takeru

Analytical Sciences (CD-ROM), 17(Suppl.), p.119 - 121, 2002/03

no abstracts in English

Journal Articles

First-principles calculations of Magnetic Circular Dichroism spectra of nonmagnetic elements in ferromagnetic ordered alloys

Yamaguchi, Masatake; Asano, S.*

Nihon Oyo Jiki Gakkai-Shi, 25(4-Part2), p.659 - 662, 2001/04

no abstracts in English

Journal Articles

Time resolved measurement of laser-ablated particles by LAPXAS

Miyashita, Atsumi; Yoda, Osamu; *

Hyomen Kagaku, 20(3), p.180 - 185, 1999/00

no abstracts in English

Oral presentation

Computational challenges towards strong scaling gyrokinetic Eulerian codes at Exa-scale

Idomura, Yasuhiro

no journal, , 

To study fusion plasma turbulence, the Gyrokinetic Toroidal 5D full-f Eulerian code GT5D has been developed. On the K-computer, inter-node parallelization techniques such as multi-dimensional/-layer domain decomposition and communication-computation overlap were developed, and strong scaling of GT5D was improved up to 73,728 nodes. However, extensions of GT5D towards burning plasmas including kinetic electrons and multi-species ions require greater computing power. Under the post-K project, we have developed computing techniques for the next generation platforms such as GPUs and MICs. In this talk, we discuss computational challenges related to complicated intra-node memory hierarchy on many core processors and relatively limited inter-node communication performance compared with accelerated computation.

Oral presentation

Development of Exa-scale computing techniques in gyrokinetic toroidal 5D full-f Eulerian code GT5D

Idomura, Yasuhiro

no journal, , 

We discuss Exa-scale computing techniques for the gyrokinetic toroidal 5D full-f Eulerian code GT5D, which have been developed under the Post-K project. Towards burning plasma simulations in ITER, we have extended physics models including kinetic electrons and multi-species ions. To compute the burning plasma model at the ITER scale, we need Exa-scale computing. To this end, techniques for utilizing many core processors with low power consumption and avoiding communication bottlenecks, which are revealed by accelerated computation. In this talk, we explain many core optimization techniques, communication overlap techniques, and communication-avoiding algorithms, which have been developed to resolve the above issues, and show their performance evaluations on the latest many core platforms such as the Plasma Simulator.

Oral presentation

Acceleration of fusion plasma turbulence simulations on many core platforms

Idomura, Yasuhiro

no journal, , 

We discuss Exa-scale computing techniques, which are developed under the Post-K project. Since fusion plasma simulations require first principles based computation of a convection-diffusion simulation in five dimensional phase space, Exa-scale computation is needed for analyzing the next generation experimental reactor ITER. To this end, techniques for utilizing many core processors with low power consumption and avoiding communication bottlenecks, which are revealed by accelerated computation. In this talk, we explain many core optimization techniques, communication-computation overlap techniques, and communication-avoiding algorithms, which have been developed to resolve the above issues, and show their performance evaluations on the latest many core platforms.

Oral presentation

Current status of sub-project D "Core design of fusion reactor"

Idomura, Yasuhiro

no journal, , 

In this talk, we review the current status of the sub-project D "Core design of fusion reactor" in the Priority Issue on Post-K computer (Accelerated Development of Innovative Clean Energy Systems). In the project, an interdisciplinary research team consisting of experts on applied mathematics, computer science, plasma theory, and plasma experiment has addressed (1) development of exascale computing technologies, (2) extension of physics models for burning plasmas, and (3) V&V of developed codes against large scale experiments such as JT-60 and LHD. Outcomes from the first two years of the project are presented focusing on computing techniques and physics models for analyzing multi time scale phenomena such as transient responses of plasma turbulence against auxiliary heating and intermittent bursts of energetic particles driven modes, and future issues in the latter half of the project.

Oral presentation

Development of exascale fusion plasma turbulence simulations for post-K

Idomura, Yasuhiro; Ina, Takuya*; Obrejan, K.; Asahi, Yuichi*; Matsuoka, Seikichi*; Imamura, Toshiyuki*

no journal, , 

Under the post-K project, we have developed computing techniques of the Gyrokinetic Toroidal 5D full-f Eulerian code GT5D towards the next generation computing platforms based on many core processors. We discuss computational challenges related to complicated intra-processor memory hierarchy and limited inter-node communication performance compared with accelerated computation. The former issue is addressed by optimizing data access patterns of a stencil kernel on each many core architecture, and high performance gains are obtained. The latter issue is resolved by using advanced communication avoiding Krylov methods, which enables an order of magnitude reduction of collective communications and improves arithmetic intensity of main computing kernels. By applying these novel computing techniques, the performance of GT5D is dramatically improved on the latest many core platforms, and excellent strong scaling up to the full system size of the Oakforest-PACS (8,192 KNLs) is achieved.

Oral presentation

Computational nuclear engineering at JAEA and Post-K project

Idomura, Yasuhiro

no journal, , 

In this overview talk, first, we review computational nuclear engineering research activities at JAEA, which cover a wide spectrum of computing needs including various CFD codes on thermal hydraulics and environmental dynamics, radiation transport codes, quantum simulations on material science, and the latest machine learning applications. Second, we talk about the development of exascale nuclear CFD simulations on state-of-the-art accelerated computing platforms. Third, we present exascale plasma codes and new data science approaches developed under the post-K project. Finally, we discuss the state of the CEA-JAEA collaboration on computational nuclear engineering.

Oral presentation

Status of GT5D

Idomura, Yasuhiro

no journal, , 

Under the Post-K project, a Gyrokinetic Toroidal 5D full-f Eulerian code GT5D has been developed towards exascale burning plasma simulations on the Post-K machine. In this talk, we review the present status on new computational techniques on GT5D. The main computing part of GT5D is given by Krylov based sparse matrix solvers for a semi-implicit time integration. We have ported computing kernels of these solvers on a prototype machine of FUGAKU and on V100 GPU, and confirmed that almost ideal performance gains are achieved on these state-of-the-art many core and GPU architectures.

Oral presentation

Optimization of fusion plasma turbulence code GT5D on FUGAKU and SUMMIT

Idomura, Yasuhiro; Ali, Y.*; Ina, Takuya*; Imamura, Toshiyuki*

no journal, , 

Implicit finite difference solvers based on Krylov subspace methods occupy dominant computing costs in the Gyrokinetic Toroidal 5D full-f Eulerian code GT5D. Under the post-K project, advanced communication avoiding (CA) Krylov subspace methods have been developed for exascale computing platforms, which have limited inter-node communication performance compared with accelerated computation. In this work, we develop a new mixed precision CA-GMRES solver using a FP16 preconditioner, which dramatically reduces the number of iterations, and thus, halo data communications. We port the new solver on FUGAKU and Summit, and compare its performance against conventional solvers on existing muti/many-core processors.

Oral presentation

Development of exascale full-f gyrokinetic simulation on Summit and FUGAKU

Idomura, Yasuhiro

no journal, , 

The Gyrokinetic Toroidal 5D full-f Eulerian code GT5D is based on a semi-implicit finite difference scheme, in which a stiff linear 4D convection operator is subject to implicit time integration, and the implicit finite difference solver for fast kinetic electrons occupies more than 80% of the total computing cost. The implicit solver was originally developed using a Krylov subspace method, in which global collective communications and halo data communications were becoming bottlenecks on the latest accelerator based platforms. To resolve this issue, the convergence property is improved by using a new FP16 preconditioner, and an order of magnitude reduction of the number of iterations and thus, communications was achieved. A communication-avoiding (CA) solver based on the FP16 preconditioner was developed by utilizing the new support for FP16 SIMD operations on FUGAKU, and was ported also on Summit. The new CA solver showed significant speedups both on FUGAKU and SUMMIT, and its performance portability was demonstrated.

Oral presentation

Development of exascale CFD simulation technologies

Idomura, Yasuhiro

no journal, , 

The multi-phase multi-component thermal hydraulics code JUPITER, the urban wind analysis code CityLBM, and the in-situ visualization software In-Situ PBVR were ported and optimized on Fugaku, and their performances were evaluated. The performance of JUPITER, which is implemented in C, was compared against Oakforest-PACS, and a reasonable speedup due to the improved hardware was confirmed. In addition, the performance was further improved by using FP16 SIMD operations on A64FX. On the other hand, Fujitsu C compiler had many optimization issues on CityLBM, which is implemented in C++, and its performance was two orders of magnitudes slower than Tsubame, when the same number of computing nodes are used. Finally, we constructed an in-situ visualization environment on Fugaku using In-Situ PBVR, which was released as an open source software.

20 (Records 1-20 displayed on this page)
  • 1