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R-CCS Cafe

R-CCS Cafe (formerly AICS Cafe) is a place where the researchers in R-CCS can frankly discuss about their researches beyond their own disciplinary wall in order to collaborate with each other. We plan to have it twice a month regularly. We welcome all people including the promotion office and administration division of K computer in R-CCS .

  • Purpose : In order to promote the research collaboration beyond each of existing research disciplines, this seminar provides the discussion field for exchanging information, understanding neighboring researchers, and collaboration between each other.
  • Place: Lecture Hall (6th floor) at R-CCS
  • Language : presentation in Japanese or English, the slide in English
  • Etc.: Please give your presentations clearly to researchers in other fields. Please do not hesitate to ask a question to the speakers.

The 151st R-CCS Cafe
Date and Time: Thu. Oct. 25, 2018, 15:30 - 16:30
Place: Lecture Hall (6th floor) at R-CCS

Title: Variational and Adiabatically Navigated Quantum Eigensolver
Speaker: Shunji Matsuura(1QBit)

Presentation Language: Japanese
Presentation Material: English

Abstract:

最近の量子コンピューター技術の発展により、近い将来量子コンピューターを用いてどのような計算が可能になるかという研究が活発に行われるようになってきました。現在の量子コンピューターに共通する問題点は実質的なコヒーレンス時間が短い事、そして誤り訂正を行うことができないことです。このため、短時間で計算を終わらせるためのアルゴリズムの開発が非常に重要になってきます。その一つとして注目を集めているのが、量子、古典両方のコンピューターを用いたハイブリッド型のアルゴリズムです。 今回の講演では前半に量子計算に関する現状のレビューを行い、後半で断熱量子計算におけるハイブリッドアルゴリズム(VanQver: Variational and Adiabatically Navigated Quantum Eigensolver)の紹介を行います。特に量子化学への応用に関しての計算結果について説明する予定です。

The 150th R-CCS Cafe-part I
Date and Time: Fri. Oct. 19, 2018, 13:30 - 14:30
Place: Lecture Hall (6th floor) at R-CCS

Title: The Long and Winding Road to Exascale
Speaker: Henry Tufo (Univ. of Colorado at Boulder)

Presentation Language: English
Presentation Material: English

Abstract:

We present a brief history of high-performance computing (HPC) through the lens of the tera-, peta-, and pre-exascale milestones. Key challenges and (potential) solutions are discussed and trends identified. An overview of the current HPC landscape is provided and, when coupled with technology roadmaps and evolving workloads, several possible avenues to practical exascale computing are identified. But many challenges remain and we discuss them in the context of several real world examples.

The 150th R-CCS Cafe-part Ⅱ
Date and Time: Fri. Oct. 19, 2018, 14:30 - 15:00
Place: Lecture Hall (6th floor) at R-CCS

Title: The Evaluation of the Chebyshev smoother and the MSDO-CG of enlarged Krylov subspace method
Speaker: Ryo Yoda (Kogakuin University)

Presentation Language: English
Presentation Material: English

Abstract:

The first topic is the Chebyshev smoother utilized in the multigrid method. The Chebyshev smoother is derived from the Chebyshev polynomials. This smoother is the nonstationary method, unlike Jacobi and Gauss-Seidel method. It has as high parallelism as Jacobi method and has high convergence like Gauss-Seidel method. We made use of the Jacobi, Gauss-Seidel, or Chebyshev iteration as the smoother of the multigrid method, and compared the number of iterations of the multigrid preconditioned conjugate gradient method and the improvement of the eigenvalue distribution. The second topic is the enlarged Krylov subspace method. The enlarged Krylov subspace method divides the solution vector and the search direction set into spatially distinct sets. It enlarges DOF of the search direction space compared to the Krylov subspace method. On the other hand, Multiple Search Direction Conjugate Gradient method (MSD-CG), which is one of the conventional versions of the enlarged Krylov subspace CG method, does not satisfy A-orthogonality in the search direction vectors. The Multiple Search Direction Conjugate Gradient method with Orthogonalization (MSDO-CG) is adapted to A-orthogonalization processes to guarantee faster convergence. We implemented MSDO-CG, and evaluated the convergence behavior.

The 150th R-CCS Cafe-part Ⅲ
Date and Time: Fri. Oct. 19, 2018, 15:30 - 16:30
Place: Lecture Hall (6th floor) at R-CCS

Title: 職域救命説明会
Speaker: Ryoko Kawamura (Health Care Center)

Presentation Language: Japanese
Presentation Material: Japanese

Abstract:

R-CCSでは、年間多くのセミナーが各チーム主催で開催されます。また『京』コンピューターの見学のために年間約1万人の外来者が来場しています。もし、主催するセミナーで心肺停止の方が発生した場合はどのように対応しますか?救急通報を行ってから、8分間何も行わなかった場合は救命の可能性は10%を切ってしまいます。救命の説明と昨年度神戸市市民救命講習を受講された方によるデモンストレーションでR-CCSにおける救命の手順を知るきっかけとしてください。また、今回救急時に使用するために購入したフルフラットになる車いすの取扱い説明も行います。

The 149th R-CCS Cafe-part I
Date and Time: Wed. Oct. 10, 2018, 13:45 - 14:25
Place: Lecture Hall (6th floor) at R-CCS

Title: Filter consists of a few resolvents to solve symmetric definite generalized eigenproblems
Speaker: Hiroshi Murakami (Tokyo Metropolitan University)

Presentation Language: English
Presentation Material: English

Abstract:

By using a filter, those eigenpairs of a symmetric definite generalized eigenproblem "A v = lambda Bv" are solved whose eigenvalues are in a specified real interval "[a,b]". In present study, the filter we use is a polynomial of the real part of a linear combination of a few resolvents. Applications of a few resolvents are given by solving corresponding systems of linear equations. We are to solve these systems of linear equations by some matrix decomposition methods. Since we use a few resolvents, the number of matrix decompositions required is also a few (2 to 4).

The 149th R-CCS Cafe-part II
Date and Time: Wed. Oct. 10, 2018, 14:30 - 15:10
Place: Lecture Hall (6th floor) at R-CCS

Title: 1. The BEAST eigensolver and 2. Recent developments and results for the BEAST eigensolver
Speaker: Martin Galgon (University of Wuppertal), Sarah Huber (University of Wuppertal)

Presentation Language: English
Presentation Material: English

Abstract:

1. We will introduce the BEAST eigensolver, which incorporates both polynomial and contour integral type filter diagonalization schemes for the solution of large sparse eigenproblems. The solver incorporates multiple levels of parallelism as well as a variety of algorithmic advances for fast, accurate, and robust solution. The underlying filter diagonalization schemes and the resulting solver will be introduced here.
2. In this talk we will discuss some of the latest advances of the BEAST eigensolver, including the availability of mixed precision calculations for reduced calculation time while maintaining accuracy. We also show results from recent tests showing the scalability of BEAST to very large problem sizes and numbers of cores.

The 149th R-CCS Cafe-part III
Date and Time: Wed. Oct. 10, 2018, 15:50 - 16:20
Place: Lecture Hall (6th floor) at R-CCS

Title: High-performance implementation of the Jacobi based eigen- and singular value decomposition methods
Speaker: Shuhei Kudo (Large-scale Parallel Numerical Computing Technology Research Team)

Presentation Language: English
Presentation Material: English

Abstract:

In this talk, we explain our progress in developing high-performance implementations of the Jacobi method. The Jacobi method is an old algorithm to compute eigen- and singular value decompositions. Although its large computational cost, it has advantages against the conventional method on recent supercomputers when it is used with the blocking and the parallelizing techniques which improve the arithmetic intensity and reduce the communication cost. Our optimized implementations of the Jacobi method show high strong scalability on recent supercomputers with more than ten thousand nodes and outperform the conventional method.

The 149th R-CCS Cafe-part IV
Date and Time: Wed. Oct. 10, 2018, 16:25 - 16:55
Place: Lecture Hall (6th floor) at R-CCS

Title: Numerical evaluation of preconditioned CG method with higher precision
Speaker: Satoshi Kawai (HPC Usability Research Team)

Presentation Language: English
Presentation Material: English

Abstract:

Solving large-scale systems of linear equations which has sparse coefficient matrices derived from generalized eigenvalue problems are challenging for iterative solvers. Although the coefficient matrices have ill-conditioned, eigenvalue solvers require higher accuracy of approximate solutions. In this study, we evaluate an effect of a higher precision of a Krylov subspace method with a parallel ILU preconditioner. The ILU preconditioner with regularizations and multi-coloring parallelism showed higher robustness and good performance. To achieve higher accuracy and convergence, we applied quad precision to an IC-COCG method. In this talk, we will have a discussion about the accuracy, convergence ratio and computational time among single, double and quad precisions of the IC-COCG method with well and ill-conditioned problems.

The 148th R-CCS Cafe-part Ⅰ
Date and Time: Fri. Oct. 5, 2018, 13:00 – 14:00
Place: Lecture Hall (6th floor) at R-CCS

Title: Toward a Science of HPC software (and hardware)
Speaker: Junichiro Makino (Team Leader, Particle Simulator Research Team)

Presentation Language: English
Presentation Material: English

Abstract:

In the last three decades, it has been becoming more and more difficult to achieve high, or even modest efficiency on advanced HPC systems. As everybody here in R-CCS knows, the development of highly efficient and highly scalable software for modern HPC systems like K or Post-K requires multi-year effort of a team of exceptionally good researchers. Of course, many other HPC systems are even harder to use. Our particle simulator research team has been working on a new approach to solve this problem through the use of framework. Our FDPS framework allows the users to write their programs in the way very close to the way they would write them for a single-processor machine, and run them on large-scale parallel systems with very high efficiency. The guiding principle for the design of FDPS is to minimize inter-node communication and main memory access per timestep, without increasing the floating-point operations too much. I will discuss current state of FDPS and also our framework for stencil calculation, Formura. If time allows, I'll discuss how hardware design should be changed to achieve better efficiency, not just that relative to peak but the power efficiency which is far more important.

The 148th R-CCS Cafe-part Ⅱ
Date and Time: Fri. Oct. 5, 2018, 14:15 – 15:15
Place: Lecture Hall (6th floor) at R-CCS

Title: An Overview of Post-K Hardware and System Software
Speaker: Yutaka Ishikawa (Project Leader, Flagship 2020 Project)

Presentation Language: English
Presentation Material: English

Abstract:

RIKEN R-CCS and Fujitsu are developing Post-K, successor of K computer, that will be available for early access program in Q2 of 2020 and will begin general operation in 2021. Fujitsu recently announced the specification of CPU, named A64FX, and its interconect, TofuD, for Post-K. A64FX is the first implementation of Arm 64bit HPC architecture (Scalable Vector Extension) and TofuD is an enhanced version of Tofu used in K computer. The system software developed in the post K supercomputer includes a novel operating system for general-purpose manycore architectures, low-level communication and MPI libraries, and file I/O middleware. In this presentation, after inroducing an overview of Post-K hardware and system software, future research directions will be addressed.