Project/Area Number  07304025 
Research Category 
GrantinAid for Scientific Research (A)

Section  総合 
Research Field 
Astronomy

Research Institution  Niigata University 
Principal Investigator 
TOMISAKA Kohji Faculty of Education, Niigata University, Associate Professor, 教育学部, 助教授 (70183879)

CoInvestigator(Kenkyūbuntansha) 
YOSHIDA Tatsuo Faculty of Science, Ibaragi University, Asscociate Professor, 理学部, 助教授 (60241741)
GOUDA Naoteru School of Science, Osaka University, Asscociate Professor, 理学部, 助教授 (50202073)
MATSUMOTO Ryoji Faculty of Science, Chiba University, Asscociate Professor, 理学部, 助教授 (00209660)
HANAWA Tomoyuki School of Science, Nagoya University, Asscociate Professor, 理学部, 助教授 (50172953)
NOGUCHI Masafumi School of Science, Tohoku University, Asscociate Professor, 理学部, 助教授 (20241515)

Project Fiscal Year 
1995 – 1996

Project Status 
Completed(Fiscal Year 1996)

Budget Amount *help 
¥6,100,000 (Direct Cost : ¥6,100,000)
Fiscal Year 1996 : ¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 1995 : ¥3,800,000 (Direct Cost : ¥3,800,000)

Keywords  Numerical Methods / Supercomputers / Parallel Computers / Adaptive Scheme / 数値計算法 / スーパーコンピュータ / 並列計算機 / 適応型計算法 
Research Abstract 
We are able to use several kinds of supercomputers in the field of astrophysics. They are vectorparallel machines, massive parallel machines, and special purpose machines. To bring their full play, we have to choose the most effective numerical method. Although the field of numerical astrophysics is wide : from the solar system to the universe, there must be a common bottleneck which should be broken to make a breakthrough. This project were planned to answer the above point. 1.The (magneto) hydrodynamics equation is one of the most important ones in the astrophysics. Equations for the unsteady hydrodynamics are hyperbolictype. In this case, it is shown that data are easily divided and allocated onto a number of processors. We are able to parallelize the code and achive high performance. 2.On the other hand, the ellipticaltype equation, such as the Poisson equation, which is also one of the most important ones in the astrophysics, is poorly parallelized. This is mainly due to the fact that it is difficult to parallelize the preconditioning of the coefficient matrix. 3.As a Poisson solver, we have found that "multigrid iteration method" is fast compared to the ordinary solvers which were poorly parallelized. We have measured the CPU time necessary to solve the Poisson equation once by this method. It is only a half of the time required to solve the magnetohydrodynamics equations for one time step. 4.It is shown that the nested grid technique is very efficient for a problem with a large spatial dynamic range. It uses a number of grids ; coarser grids covers a whole numerical box, while finer ones cover a region which require a fine spatial resolution. 5.To proceed from the nested grid scheme to a fully adaptive one, we have to develop a method of creation/destruction of the grids. This requires the code to understand which part should be calculated closely.
