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RIKEN Center for Computational Science Large-Scale Parallel Numerical Computing Technology Research Team

Team Leader: Toshiyuki Imamura (Ph.D.)

Research Summary

Toshiyuki  Imamura(Ph.D.)

The Large-scale Parallel Numerical Computing Technology Research Team conducts research and development of a large scale, highly parallel and high-performance numerical software library for the supercomputer Fugaku. Simulation programs require various numerical algorithms for the solution of linear systems, eigenvalue problems, fast Fourier transforms, and non-linear equations. In order to take advantage of the full potential of Fugaku, we must select algorithms and develop a numerical software library based on the concepts of high parallelism, high performance, high precision, resiliency, and scalability. We achieve this through close collaboration among computational science (simulation), computer science (hardware and software) and numerical mathematics. Our goal is to establish a fundamental technique to develop numerical software libraries, called KMATHLIB, for next generation supercomputer systems based on strong cooperation within R-CCS.

Main Research Fields

  • Mathematical & Physical Sciences


  • Parallel Algorithms
  • High Performance Computing
  • Numerical Linear Algebra
  • Mixed-precision Numerical Computing
  • Minimal Precision Computing

Selected Publications

  • 1. Shuhei Kudo, Yusaku Yamamoto, Toshiyuki Imamura,
    "Error Analysis of the Cholesky QR-Based Block Orthogonalization Process for the One-Sided Block Jacobi SVD Algorithm,"
    COMPUTING AND INFORMATICS, Vol. 39(6), 1203–1228, 2021.
  • 2. Hisashi Yashiro, Koji Terasaki, Yuta Kawai, Shuhei Kudo, Takemasa Miyoshi, Toshiyuki Imamura, Kazuo Minami, Hikaru Inoue, Tatsuo Nishiki, Takayuki Saji, Masaki Satoh, and Hirofumi Tomita. 2020.:
    "A 1024-member ensemble data assimilation with 3.5-km mesh global weather simulations."
    "In Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis (SC '20). IEEE Press, Article 1, 1–10.
  • 3. Daichi Mukunoki, Katsuhisa Ozaki, Takeshi Ogita, Toshiyuki Imamura:
    "DGEMM using Tensor Cores, and Its Accurate and Reproducible Versions,
    ISC High Performance 2020, Lecture Notes in Computer Science, Vol. 12151, pp. 230-248, Jun. 2020.
  • 4. Toshiyuki Imamura, Takeshi Fukaya, Yusuke Hirota, Susumu Yamada and Masahiko Machida.:
    "CAHTR: Communication-Avoiding Householder TRidiagonalization"
    Proc. ParCo2015, Advances in Parallel Computing, Vol. 27: Parallel Computing: On the Road to Exascale, pp. 381-390, 2016.
  • 5. Yusuke,Hirota.,and Toshiyuki Imamura.:
    "Divide-and-Conquer Method for Banded Generalized Eigenvalue Problems"
    Journal of Information Processing Computing System, Vol.52,Nov,20,2015.
  • 6. Takeshi,Fukaya., and Toshiyuki,Imamura.:
    "Performance evaluation of the EigenExa eigensolver on Oakleaf-FX: tridiagonalization versus pentadiagonalization"
    Parallel and Distributed Processing Symposium Workshop (IPDPSW), 2015 IEEE International, pp. 960-969, May 25 2015.
  • 7. T,Imamura.:
    "The EigenExa Library - High Performance & Scalable Direct Eigensolver for Large-Scale Computational Science"
    International Supercomputing Conference (ISC14), Leipzig, June (2014). (invited talk)
  • 8. Y,Idomura., M,Nakata., S,Yamada., M,Machida., T,Imamura., T,Watanabe., M,Nunami., H,Inoue., S,Tsutsumi., I,Miyoshi., and N,Shida.:
    "Communication-overlap techniques for improved strong scaling of gyrokinetic Eulerian code beyond 100k cores on the K-computer"
    International Journal of High Performance Computing Applications, 28(1) 73-86 (2014), SAGE publications,
    doi: 10.1177/1094342013490973.

Related Links

Lab Members

Principal investigator

Toshiyuki Imamura
Team Leader

Core members

Atsushi Suzuki
Senior Scientist
Kengo Nakajima
Senior Scientist
Daichi Mukunoki
Research Scientist
Daisuke Takahashi
Senior Visiting Scientist
Mitsuo Yokokawa
Senior Visiting Scientist


Position Deadline
Seeking Research Scientist or Postdoctoral Researcher (R-CCS2320) Open until filled

Contact Information

7-1-26, Minatojima-minami-machi, Chuo-ku,
650-0047, Japan
Email: imamura.toshiyuki [at] riken.jp