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AICS Cafe

AICS Cafe is a place where the researchers in AICS 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 AICS.

  • 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: Workshop room (6th floor) at AICS
  • Lang : 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 115th AICS Cafe
Date and Time: Wed. July 12, 2017, 15:30-16:30
Place: Workshop room (6th floor) at AICS

Title: Development of FDPS (Framework for Developing Particle Simulators) on Sunway Taihulight
Speaker: Daisuke Namekata (Particle Simulator Research Team)

Presentation Language: English
Presentation Material: English

    Abstract: Detail

FDPS is a library for massively parallel particle simulations, which has been developed by our team. The current released version of FDPS can generate a parallel code that scales up to the K computer (Iwasawa et al. 2015, PASJ, 68, 54). However, it is not clear that FDPS generate a scalable code in the next generation of supercomputers. In order to identify potential problems of FDPS and to improve FDPS more, we need to analyze FDPS in a system larger than the K computer. In late January, we started the development of FDPS on Sunway Taihulight, which is the most powerful supercomputer in the world (as of Nov. 2016, 125.4 PFlops). In this talk, I'd like to introduce the current status of this project.

The 114th AICS Cafe
Date and Time: Wed. June 21, 2017, 15:30-16:30
Place: Workshop room (6th floor) at AICS

Title: Optimization of communications on Large scale parallel computers
Speaker: Yoshiyuki Morie (System Software Research Team)

Presentation Language: Japanese
Presentation Material: English

    Abstract: Detail

In the recently, the scale of supercomputer has been increasing remarkably. This trend will have been going from now. On the other hand, in network, multiple communication devices are installed and fat-tree, mesh/torus as network topology are adopted. There are several problems to be solved for adopting these. One is the efficient utilization of multiple communication devices. Another one is shortening communication delay by reducing the number of hops or contentions on a such network topology. We will introduce the optimization of communication for these problems.

The 113th AICS Cafe
Date and Time: Wed. June 7, 2017, 15:30-16:30
Place: Workshop room (6th floor) at AICS

Title: Study of Mercury's magnetosphere based on the MHD simulation and trajectory tracings
Speaker: Manabu Yagi (Programming Environment Research Team)

Presentation Language: Japanese
Presentation Material: English

    Abstract: Detail

Interaction between solar wind(supersonic plasma flow from the Sun) and intrinsic magnetic field of planets such as Earth forms plasma circulation system called "magnetosphere". A great number of studies have been done for the Earth magnetosphere using spacecraft observations, numerical simulations, and modelings. On the other hands, comparative studies of planetary magnetosphere such as Mercury or Jupiter are also important from a perspective of universal plasma physics. In this study, we try to discover the dynamics of Mercury's magnetosphere using magnetohydrodynamics(MHD) simulation, and trajectory tracings of test particles.

The 112th AICS Cafe
Date and Time: Wed. May 24, 2017, 15:30-16:30
Place: Workshop room (6th floor) at AICS

Title: Contribution of computational science for reducing the damage of flood disaster and activities among citizens, authorities and academia
Speaker: Satoru Oishi (Unit Leader for Computational Disaster Mitigation and Reduction Research Unit)

Presentation Language: Japanese
Presentation Material: Japanese

    Abstract: Detail

After flood disaster happened in Kinugawa river basin in 2015, citizens in Mukogawa river basin warried about torrential rain in the basin and they wanted to know what kind of damage they would suffer when it should be similar rain. The presentation explains the result of simulation with several introductions including Japanese river improvement plan and implementation, newer trial of computation science for dam utilization and contribution of science and technology to evacuation activity of citizens.

The 111th AICS Cafe
Date and Time: Wed. May 10, 2017, 15:30-16:30
Place: Workshop room (6th floor) at AICS

Title: BCS states and the Quantum Chemistry
Speaker: Wataru Uemura (Computational Molecular Science Research Team)

Presentation Language: Japanese
Presentation Material: English

    Abstract: Detail

In Quantum Chemistry, usually we use the molecular orbitals to discretize the physical space. In that case, the dimension of the Hilbert space would increase combinatorially with the system size. To solve this problem, there are suggested variety of Quantum Chemistry algorithms so far. We are inventing new formalism that would use several BCS-like states to describe the molecular systems. With usage of explicit mathematical operations, we can describe the Quantum state effectively. We will introduce the recent developments with a comparison towards the already established algorithms.

The 110th AICS Cafe
Date and Time: Wed. Apr. 5, 2017, 15:30-16:30
Place: Workshop room (6th floor) at AICS

Title: How to raise our own worth: A theory from Adlerian psychology
Speaker: Sachiyo Ikeda (Research support devision, Helth center)

Presentation Language: Japanese
Presentation Material: Japanese

    Abstract: Detail

I have low self-esteem. Actually the results of tests for measuring self-esteem show that my self-esteem is low level. In such circumstances, I have been interested in raising my self-esteem. On one occasion, I met with an Adlerian psychological literature named “The Courage of Being Disliked”, and I found three important keywords many times: proprioception, contributions of others and trusting of others, in it. Adler said that the contribution of others is an essential part in raising one’s worth. What is the “contribution of others”? I would like to introduce the Adlerian psychology and discuss the issue with computational scientists.

The 109th AICS Cafe
Date and Time: Wed. Mar. 22, 2017, 15:30-16:30
Place: Workshop room (6th floor) at AICS

Title: Fixed-mesh method for solid/structure simulation: past, present and future
Speaker: Koji Nishiguchi (Complex Phenomena Unified Simulation Research Team)

Presentation Language: English
Presentation Material: English

    Abstract: Detail

For the last several decades, Lagrangian finite element methods, which use deformed-mesh, have been the de facto standard for solid/structure simulations. This method can track the surface of solid with high accuracy and compute constitutive relation of solid with ease, since a geometric domain of the solid is spatially discretized using unstructured mesh which conforms to the deforming solid.
On the other hand, an Eulerian finite element method for solid/structure mechanics was proposed in the early 1990s. This method uses spatially fixed mesh and thus allows solid material to flow through the mesh. In this context, compared to Lagrangian finite element methods (Deformed-mesh methods), Eulerian finite element methods (Fixed-mesh methods) are attractive for computing large deformation problems, computing fracture problems, and generating computational mesh easily.
Utilizing the above advantages, Eulerian finite element methods have been applied for bullet impact analysis, solid-fluid interaction analysis, soft adhesive analysis, and soft resin analysis. However, the computational challenges have been their expensive computational cost, the diffusion of the solution due to the advection, and the modeling of contact interfaces. In my presentation, I will explain the past, present and future studies of fixed-mesh methods for solid/structure mechanics.

The 108th AICS Cafe
Date and Time: Wed. Mar. 15, 2017, 15:30-16:30
Place: Workshop room (6th floor) at AICS

Title: Parallel Image Compositing on Massively Parallel Rendering Environments
Speaker: Jorji Nonaka (Advanced Visualization Research Team)

Presentation Language: Japanese
Presentation Material: English

    Abstract: Detail

Sort-last visualization approach has become the defacto standard for massively parallel rendering environments. In this approach, the entire set of the images generated by the rendering nodes needs to be combined into a single final image, and for this purpose, parallel image compositing algorithms which try to minimize the idle time of the nodes have been widely used. As the number of nodes increases, the parallel rendering processes can have their workload reduced. However, for the parallel image compositing process, the workload increases proportionally with the increase in the number of rendering nodes, which is similar to the weak scaling case. In this talk, I will present the parallel image compositing library, named 234Compositor, primarily developed for the HIVE visualization application which works on the K computer massively parallel environment.

The 107th AICS Cafe
Date and Time: Wed. Feb. 15, 2017, 15:30-16:30
Place: Workshop room (6th floor) at AICS

Title: How accurate are the weather forecast simulations? Let’s check it!
Speaker: Taeka Awazu (Data Assimilation Research Team)

Presentation Language: Japanese
Presentation Material: English

    Abstract: Detail

How should the rain forecast simulations be evaluated when we compare the simulations with the observation data? Is it possible to evaluate the simulations comprehensively by the shape and location of rainfall areas? The commonly used verification methods for the rain forecast have difficulties to evaluate the shape and location error of the rainfall areas. If the forecast has location errors even though the shape of rainfall areas is predicted perfectly, these methods evaluate the forecast lower. This evaluation does not match with our intuition.
Therefore, we propose a new verification method for the rain forecast using the shape and location of the rainfall areas. In this method, to mimic the human recognition, the close rainfall areas are combined, and the features of shape and location of the rainfall areas in the combined areas are computed. The proposed method can evaluate the shape and location error that cannot be evaluated by the frequently used methods. Additionally, by using the visualization with colors, this method can verify the rain forecast intuitively.

The 106th AICS Cafe
Date and Time: Wed. Feb. 8, 2017, 15:30-16:30
Place: Workshop room (6th floor) at AICS

Title: Fast Evaluation of Two-Electron Integrals using Pseudospectral Methods
Speaker: Keisuke Sawada (Computational Molecular Science Research Tea)

Presentation Language: Japanese
Presentation Material: English

    Abstract: Detail

A fast estimation of two-electron repulsive integrals (ERIs) is an important and imperative subject in any ab-initio quantum chemical calculations. Since the computational cost of the ERIs formally increases as N4, where N is the number of basis functions, we often suffer from much time-consuming estimations in large molecular systems.
In order to address the tough problem, several methodologies have been developed to date. Among them, the pseudospectral (PS) method is a strong candidate for a quick and efficient evaluation of the ERIs. In the PS method, one analytical integral is replaced by a numerical summation consisting of discrete grid points and the computational cost is reduced from O(N4) to O(MN2), where M is the number of grid points.
In this study, we implement the PS method into our NTChem program and investigate the performances of this method using the MPI/OpenMP hybrid parallelized code. In large molecular system which includes more than 8,000 basis sets, we find that the PS method shows a good scaling with respect to used CPU cores and becomes much faster than the analytic integral methods.