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Journal Articles

Thick-restart block Lanczos method for large-scale shell-model calculations

Shimizu, Noritaka*; Mizusaki, Takahiro*; Utsuno, Yutaka; Tsunoda, Yusuke*

Computer Physics Communications, 244, p.372 - 384, 2019/11

 Times Cited Count:75 Percentile:99.63(Computer Science, Interdisciplinary Applications)

no abstracts in English

Journal Articles

Numerical analytic continuation of Euclidean data

Tripolt, R.-A.*; Gubler, P.; Ulybyshev, M.*; von Smekal, L.*

Computer Physics Communications, 237, p.129 - 142, 2019/04

 Times Cited Count:39 Percentile:98.44(Computer Science, Interdisciplinary Applications)

In this work we present a direct comparison of three different numerical analytic continuation methods: the Maximum Entropy Method, the Backus-Gilbert method and the Schlessinger point or Resonances Via Pade method. First, we perform a benchmark test based on a model spectral function and study the regime of applicability of these methods depending on the number of input points and their statistical error. We then apply these methods to more realistic examples, namely to numerical data on Euclidean propagators obtained from a Functional Renormalization Group calculation, to data from a lattice Quantum Chromodynamics simulation and to data obtained from a tight-binding model for graphene in order to extract the electrical conductivity.

Journal Articles

Implementation of a gyrokinetic collision operator with an implicit time integration scheme and its computational performance

Maeyama, Shinya*; Watanabe, Tomohiko*; Idomura, Yasuhiro; Nakata, Motoki*; Nunami, Masanori*

Computer Physics Communications, 235, p.9 - 15, 2019/02

 Times Cited Count:4 Percentile:43.62(Computer Science, Interdisciplinary Applications)

We have implemented the Sugama collision operator in the gyrokinetic Vlasov simulation code, GKV, with an implicit time-integration scheme. The new method is versatile and independent of the details of the linearized collision operator, by means of an operator splitting, an implicit time integrator, and an iterative Krylov subspace solver. Numerical tests demonstrate stable computation over the time step size restricted by the collision term. An efficient implementation for parallel computation on distributed memory systems is realized by using the data transpose communication, which makes the iterative solver free from inter-node communications during iteration. Consequently, the present approach achieves enhancement of computational efficiency and reduction of computational time to solution simultaneously, and significantly accelerates the total performance of the application.

Journal Articles

CUDA programs for the GPU computing of the Swendsen-Wang multi-cluster spin flip algorithm; 2D and 3D Ising, Potts, and XY models

Komura, Yukihiro; Okabe, Yutaka*

Computer Physics Communications, 185(3), p.1038 - 1043, 2014/03

 Times Cited Count:12 Percentile:65.21(Computer Science, Interdisciplinary Applications)

We present sample CUDA programs for the GPU computing of the Swendsen-Wang multi-cluster spin flip algorithm. We deal with the classical spin models; the Ising model, the $$q$$-state Potts model, and the classical XY model. As for the lattice, both the 2D (square) lattice and the 3D (simple cubic) lattice are treated. We already reported the idea of the GPU implementation for 2D models. We here explain the details of sample programs, and discuss the performance of the present GPU implementation for the 3D Ising and XY models. We also show the calculated results of the moment ratio for these models, and discuss phase transitions.

Journal Articles

Numerical techniques for parallel dynamics in electromagnetic gyrokinetic Vlasov simulations

Maeyama, Shinya; Ishizawa, Akihiro*; Watanabe, Tomohiko*; Nakajima, Noriyoshi*; Iio, Shunji*; Tsutsui, Hiroaki*

Computer Physics Communications, 184(11), p.2462 - 2473, 2013/11

 Times Cited Count:16 Percentile:69.76(Computer Science, Interdisciplinary Applications)

Journal Articles

Efficient computation of Hamiltonian matrix elements between non-orthogonal Slater determinants

Utsuno, Yutaka; Shimizu, Noritaka*; Otsuka, Takaharu*; Abe, Takashi*

Computer Physics Communications, 184(1), p.102 - 108, 2013/01

 Times Cited Count:12 Percentile:63.41(Computer Science, Interdisciplinary Applications)

no abstracts in English

Journal Articles

Orbit-based representation of equilibrium distribution functions for low-noise initialization of kinetic simulations of toroidal plasmas

Bierwage, A.; Di Troia, C.*; Briguglio, S.*; Vlad, G.*

Computer Physics Communications, 183(5), p.1107 - 1123, 2012/05

 Times Cited Count:8 Percentile:49.13(Computer Science, Interdisciplinary Applications)

Journal Articles

Simulation technique of free-boundary equilibrium evolution in plasma ramp-up phase

Honda, Mitsuru

Computer Physics Communications, 181(9), p.1490 - 1500, 2010/09

 Times Cited Count:21 Percentile:74.62(Computer Science, Interdisciplinary Applications)

We describe a new scheme for a consistent linkage between the transport and equilibrium solvers in the integrated transport code TOPICS for a transport simulation in tokamaks during a plasma volume ramp-up phase. Although the flux conserving tokamak (FCT) equilibrium solver implemented in TOPICS is well consistent with the transport solver, it cannot evaluate a toroidal magnetic flux associated with an evolving equilibrium by itself. The evolution of the equilibrium is then modelled with a combination of the determination of the toroidal magnetic flux by the iterative solution of the Grad-Shafranov equation and the FCT scheme. The new scheme developed is applied to a predictive simulation with the volume expansion in JT-60U.

Journal Articles

Benchmark test of drift-kinetic and gyrokinetic codes through neoclassical transport simulations

Satake, Shinsuke*; Idomura, Yasuhiro; Sugama, Hideo*; Watanabe, Tomohiko*

Computer Physics Communications, 181(6), p.1069 - 1076, 2010/06

 Times Cited Count:29 Percentile:81.16(Computer Science, Interdisciplinary Applications)

Two simulation codes that solve the drift-kinetic or gyrokinetic equation in toroidal plasmas are benchmarked by comparing the simulation results of neoclassical transport. In a tokamak configuration, neoclassical radial heat flux and the force balance relation, which relates the parallel mean flow with radial electric field and temperature gradient, are compared between these two codes, and their results are also compared with the local neoclassical transport theory. It is found that the simulation results of the two codes coincide very well in a wide rage of plasma collisionality parameter $$nu^* = 0.01 sim 10$$ and also agree with the theoretical estimations. The time evolution of radial electric field and particle flux, and the radial profile of the geodesic acoustic mode frequency also coincide very well.

Journal Articles

MINERVA; Ideal MHD stability code for toroidally rotating tokamak plasmas

Aiba, Nobuyuki; Tokuda, Shinji; Furukawa, Masaru*; Snyder, P. B.*; Chu, M. S.*

Computer Physics Communications, 180(8), p.1282 - 1304, 2009/08

 Times Cited Count:26 Percentile:79.18(Computer Science, Interdisciplinary Applications)

A new linear MHD stability code MINERVA is developed for investigating a toroidal rotation effect on the stability of ideal MHD modes in tokamak plasmas. This code solves the Frieman-Rotenberg equation as not only the generalized eigenvalue problem but also the initial value problem. The parallel computing method used in this code realizes the stability analysis of both long and short wavelength MHD modes in short time. The results of some benchmarking tests show the validity of this MINERVA code. The numerical study with MINERVA about the toroidal rotation effect on the edge MHD stability shows that the rotational shear destabilizes the long/intermediate wavelength modes but stabilizes the short wavelength edge localized MHD modes, though the rotation frequency destabilizes both the long and the short wavelength MHD modes.

Journal Articles

Conservative global gyrokinetic toroidal full-$$f$$ five-dimensional Vlasov simulation

Idomura, Yasuhiro; Ida, Masato; Kano, Takuma; Aiba, Nobuyuki; Tokuda, Shinji

Computer Physics Communications, 179(6), p.391 - 403, 2008/09

 Times Cited Count:73 Percentile:95.42(Computer Science, Interdisciplinary Applications)

A new conservative global gyrokinetic toroidal full-$$f$$ five-dimensional Vlasov simulation (GT5D) is developed using a novel non-dissipative conservative finite difference scheme. The scheme guarantees numerical stability by satisfying relevant first principles in the modern gyrokinetic theory, and enables robust and accurate simulations of tokamak micro-turbulence. GT5D is verified through comparisons of zonal flow damping tests, linear analyses of ion temperature gradient driven (ITG) modes, and nonlinear ITG turbulence simulations against a global gyrokinetic toroidal $$delta f$$ particle code. In the comparison, global solutions of the ITG turbulence are identified quantitatively by using two gyrokinetic codes based on particle and mesh approaches.

Journal Articles

Linear comparison of gyrokinetic codes with trapped electrons

Rewoldt, G.*; Lin, Z.*; Idomura, Yasuhiro

Computer Physics Communications, 177(10), p.775 - 780, 2007/11

 Times Cited Count:35 Percentile:82.5(Computer Science, Interdisciplinary Applications)

Three codes that solve the gyrokinetic equation in toroidal geometry are compared in the linear limit for the growth rates and real frequencies of the ion temperature gradient (ITG) mode and the trapped electron mode (TEM). The three codes are the gyrokinetic toroidal code (GTC) and GT3D, both of which are radially-global particle-in-cell initial value codes, and FULL, which is a radially-local continuum eigenvalue code. With the same standard input parameters on a reference magnetic surface, the three codes give good agreement for the linear eigenfrequencies, both without (i.e., with adiabatic electron response) and with trapped electrons, as the perpendicular wavenumber and the ion temperature gradient input parameters are varied.

Journal Articles

A Global collisionless PIC code in magnetic coordinates

Jolliet, S.*; Bottino, A.*; Angelino, P.*; Hatzky, R.*; Tran, T. M.*; McMillan, B. F.*; Sauter, O.*; Appert, K.*; Idomura, Yasuhiro; Villard, L.*

Computer Physics Communications, 177(5), p.409 - 425, 2007/09

 Times Cited Count:164 Percentile:98.53(Computer Science, Interdisciplinary Applications)

A global plasma turbulence simulation code, ORB5, is presented. A particular feature is the use of straight-field-line magnetic coordinates and a field-aligned Fourier filtering technique that dramatically improves the performance of the code in terms of both the numerical noise reduction and the maximum time step allowed. Another feature is the capability to treat arbitrary axisymmetric ideal MHD equilibrium configurations. The code is validated against an analytical theory of zonal flows and against other codes for a selection of linear and nonlinear tests.

Journal Articles

Extension of the Newcomb equation into the vacuum for the stability analysis of tokamak edge plasmas

Aiba, Nobuyuki; Tokuda, Shinji; Ishizawa, Tomoko*; Okamoto, Masao*

Computer Physics Communications, 175(4), p.269 - 289, 2006/08

 Times Cited Count:40 Percentile:83.68(Computer Science, Interdisciplinary Applications)

The formulation for solving numerically the two-dimensional Newcomb equation has been extended to calculate the vacuum energy integral by using a vector potential method. According to this extention, a stability code MARG2D has been adapted, and coded for parallel computing in order to reduce substantially the CPU time. The MARG2D code enables a fast stability analysis of ideal external MHD modes from low to high toroidal mode numbers on the basis of the single physical model, and then the code works as a powerful tool in an integrated simulation where it is combined with transport codes, and also in the analysis of tokamak edge plasma experiments.

Journal Articles

Accurate basis set by the CIP method for the solutions of the schr$"o$dinger equation

Utsumi, Takayuki*; Yabe, Takashi*; Koga, J. K.; Aoki, Takayuki*; Sekine, Masatoshi*

Computer Physics Communications, 157(2), p.121 - 138, 2004/02

 Times Cited Count:13 Percentile:52.51(Computer Science, Interdisciplinary Applications)

no abstracts in English

Journal Articles

Accurate numerical method for the solutions of the Schr$"o$dinger equation and the radial integrals based on the CIP method

Utsumi, Takayuki*; Koga, J. K.

Computer Physics Communications, 148(3), p.267 - 280, 2002/11

 Times Cited Count:5 Percentile:28.83(Computer Science, Interdisciplinary Applications)

no abstracts in English

Journal Articles

New numerical method for the solutions of the MCDF equations based on the CIP method

Utsumi, Takayuki*; Koga, J. K.

Computer Physics Communications, 148(3), p.281 - 290, 2002/11

 Times Cited Count:1 Percentile:7.33(Computer Science, Interdisciplinary Applications)

no abstracts in English

Journal Articles

Two-Dimensional Fluid Simulation of Glow Discharge Plasma Reactors for Immobilization of Krypton

Hayashi, Shinichiro; ; *; *; *

Computer Physics Communications, 125, p.60 - 74, 2000/00

 Times Cited Count:7 Percentile:36.87(Computer Science, Interdisciplinary Applications)


Journal Articles

A Numerical method for solving the one-dimensional Vlasov-Poisson equation in phase space

*; Kunugi, Tomoaki; Koga, J. K.

Computer Physics Communications, 108(2-3), p.159 - 179, 1998/00

 Times Cited Count:14 Percentile:63.69(Computer Science, Interdisciplinary Applications)

no abstracts in English

Journal Articles

Stability and accuracy of the cubic interpolated propagation scheme

*; Kunugi, Tomoaki; Aoki, Takayuki*

Computer Physics Communications, 101(1-2), p.9 - 20, 1997/00

 Times Cited Count:52 Percentile:90.48(Computer Science, Interdisciplinary Applications)

no abstracts in English

22 (Records 1-20 displayed on this page)