Search

Your search keyword '"Grandgirard, Virginie"' showing total 81 results
Start Over Author "Grandgirard, Virginie" Language english
81 results on '"Grandgirard, Virginie"'

6. Building and Auto-Tuning Computing Kernels: Experimenting with Boast and Starpu in the Gysela Code★

Author

Bigot Julien, Grandgirard Virginie, Latu Guillaume, Mehaut Jean-Francois, Millani Luís Felipe, Passeron Chantal, Masnada Steven Quinito, Richard Jérôme, and Videau Brice

Subjects
Applied mathematics. Quantitative methods, T57-57.97, Mathematics, QA1-939
Abstract

Modeling turbulent transport is a major goal in order to predict confinement performance in a tokamak plasma. The gyrokinetic framework considers a computational domain in five dimensions to look at kinetic issues in a plasma; this leads to huge computational needs. Therefore, optimization of the code is an especially important aspect, especially since coprocessors and complex manycore architectures are foreseen as building blocks for Exascale systems. This project aims to evaluate the applicability of two auto-tuning approaches with the BOAST and StarPU tools on the GYSELA code in order to circumvent performance portability issues. A specific computation intensive kernel is considered in order to evaluate the benefit of these methods. StarPU enables to match the performance and even sometimes outperform the hand-optimized version of the code while leaving scheduling choices to an automated process. BOAST on the other hand reveals to be well suited to get a gain in terms of execution time on four architectures. Speedups in-between 1.9 and 5.7 are obtained on a cornerstone computation intensive kernel.

Published
2018
Full Text
View/download PDF

7. Targeting Realistic Geometry in Tokamak Code Gysela★

Author

Bouzat Nicolas, Bressan Camilla, Grandgirard Virginie, Latu Guillaume, and Mehrenberger Michel

Subjects
Applied mathematics. Quantitative methods, T57-57.97, Mathematics, QA1-939
Abstract

In magnetically confined plasmas used in Tokamak, turbulence is respon-sible for specific transport that limits the performance of this kind of reactors. Gyroki-netic simulations are able to capture ion and electron turbulence that give rise to heat losses, but require also state-of-the-art HPC techniques to handle computation costs. Such simulations are a major tool to establish good operating regime in Tokamak such as ITER, which is currently being built. Some of the key issues to address more re- alistic gyrokinetic simulations are: efficient and robust numerical schemes, accurate geometric description, good parallelization algorithms. The framework of this work is the Semi-Lagrangian setting for solving the gyrokinetic Vlasov equation and the Gy-sela code. In this paper, a new variant for the interpolation method is proposed that can handle the mesh singularity in the poloidal plane at r = 0 (polar system is used for the moment in Gysela). A non-uniform meshing of the poloidal plane is proposed instead of uniform one in order to save memory and computations. The interpolation method, the gyroaverage operator, and the Poisson solver are revised in order to cope with non-uniform meshes. A mapping that establish a bijection from polar coordinates to more realistic plasma shape is used to improve realism. Convergence studies are provided to establish the validity and robustness of our new approach.

Published
2018
Full Text
View/download PDF

8. Kinetic plasma-sheath self-organization

Author

Munschy, Yann, Bourne, Emily, Dif-Pradalier, Guilhem, Donnel, Peter, Ghendrih, Philippe, Grandgirard, Virginie, Sarazin, Yanick, Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), and European Project: 824158,H2020-EU.1.4. - EXCELLENT SCIENCE - Research Infrastructures ,EoCoE-II(2019)

Subjects
Kinetic, [PHYS]Physics [physics], Sheath, simulation, Plasma physics, Plasma wall interaction
Abstract

The interaction between a plasma and a solid surface is studied in a (1D-1V) kinetic framework using a localized particle and convective energy source. Matching the quasineutral plasma region and sheath horizon is addressed in the fluid framework with a zero heat flux closure. It highlights non-polytropic nature of the physics of parallel transport. Shortfalls of this approach compared to a reference kinetic simulation, highlighting the importance of the heat flux, leads to addressing the sound velocity, non-collisional closure and higher moment closure. No gain in the predictive capability is obtained. The kinetic constraint at the sheath horizon is discussed and modified to account for conditions that are actually met in simulations, namely quasineutrality with a small but finite charge density. Analyzing the distribution functions shows that collisional transfer is mandatory to achieve steady-state self-organization on the open field lines.

Published
2023

9. Optimization of the Gyroaverage operator based on Hermite interpolation

Author

Rozar Fabien, Steiner Christophe, Latu Guillaume, Mehrenberger Michel, Grandgirard Virginie, Bigot Julien, Cartier-Michaud Thomas, and Roman Jean

Subjects
Applied mathematics. Quantitative methods, T57-57.97, Mathematics, QA1-939
Abstract

Gyrokinetic modeling is appropriate for describing Tokamak plasma turbulence, and the gyroaverage operator is a cornerstone of this approach. In a gyrokinetic code, the gyroaveraging scheme needs to be accurate enough to avoid spoiling the data but also requires a low computation cost because it is applied often on the main unknown, the 5D guiding-center distribution function, and on the 3D electric potentials. In the present paper, we improve a gyroaverage scheme based on Hermite interpolation used in the Gysela code. This initial implementation represents a too large fraction of the total execution time. The gyroaverage operator has been reformulated and is now expressed as a matrix-vector product and a cache-friendly algorithm has been setup. Different techniques have been investigated to quicken the computations by more than a factor two. Description of the algorithms is given, together with an analysis of the achieved performance.

Published
2016
Full Text
View/download PDF

10. Evaluating Kernels on Xeon Phi to accelerate Gysela application

Author

Latu Guillaume, Haefele Matthieu, Bigot Julien, Grandgirard Virginie, Cartier-Michaud Thomas, and Rozar Fabien

Subjects
Applied mathematics. Quantitative methods, T57-57.97, Mathematics, QA1-939
Abstract

This work describes the challenges presented by porting parts of the Gysela code to the Intel Xeon Phi coprocessor, as well as techniques used for optimization, vectorization and tuning that can be applied to other applications. We evaluate the performance of some generic micro-benchmark on Phi versus Intel Sandy Bridge. Several interpolation kernels useful for the Gysela application are analyzed and the performances are shown. Some memory-bound and compute-bound kernels are accelerated by a factor 2 on the Phi device compared to Sandy architecture. Nevertheless, it is hard, if not impossible, to reach a large fraction of the peak performance on the Phi device, especially for real-life applications as Gysela. A collateral benefit of this optimization and tuning work is that the execution time of Gysela (using 4D advections) has decreased on a standard architecture such as Intel Sandy Bridge.

Published
2016
Full Text
View/download PDF

11. An approach to increase reliability of HPC simulation, application to the Gysela5D code

Author

Bigot Julien, Latu Guillaume, Cartier-Michaud Thomas, Grandgirard Virginie, Passeron Chantal, and Rozar Fabien

Subjects
Applied mathematics. Quantitative methods, T57-57.97, Mathematics, QA1-939
Abstract

Reproducibility of results is a strong requirement in most fields of research for experimental results to be called science. For results obtained through simulation software using high performance computing (HPC) this translates as code quality requirements. While there are many works focusing on software quality, these typically do not take the specificities of HPC scientific simulation softwareinto account. This paper presents an approach to introduce quality procedures in HPC scientific simulation softwarewhile remaining the less invasive as possible so as to ease its adoption. The approach relies on quality procedures including human code review and automated testing and offers a dedicated procedure to help correct defects found this way. These procedures are integrated in a development work-flow designed to improve the traceability of defects. By implementing this approach for the development of the Gysela code, we show that it is indeed viable and that the return on investment is positive. We also identify multiple reusable elements developed for this experiment that should reduce the cost of adopting the approach for other codes as well as some aspects that can still be improved to ensure a widespread propagation of the approach in the community.

Published
2016
Full Text
View/download PDF

12. Collisions in magnetised plasmas

Author

Ghendrih Philippe, Cartier-Michaud Thomas, Dif-Pradalier Guilhem, Esteve Damien, Garbet Xavier, Grandgirard Virginie, Latu Guillaume, Norscini Claudia, and Sarazin Yanick

Subjects
Applied mathematics. Quantitative methods, T57-57.97, Mathematics, QA1-939
Abstract

Approximations for closing the kinetic equation for the one particle distribution function are calculated by using propagators. These provide the formal structure of the collision term in the Landau approximation. The method allows one to investigate the effect of inhomogeneities at the Debye scale and to analyse magnetised collisions, when the Larmor radius is smaller than the Debye length. This method also allows one developing a simple renormalisation scheme to derive the Lenard-Balescu collision operator.

Published
2015
Full Text
View/download PDF

13. Role of avalanche transport in competing drift wave and interchange turbulence

Author

Ghendrih, Philippe, Dif-Pradalier, Guilhem, Panico, Olivier, Sarazin, Yanick, Bufferand, Hugo, Ciraolo, Guido, Donnel, Peter, Fedorczak, Nicolas, Garbet, Xavier, Grandgirard, Virginie, Hennequin, Pascale, Serre, Eric, Tamain, Patrick, Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), École polytechnique (X), Centre National de la Recherche Scientifique (CNRS), and Aix Marseille Université (AMU)

Subjects
History, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], Computer Science Applications, Education
Abstract

We complete the 2D 2-fields turbulence model previously used with an interchange-like instability by slightly modifying the parallel loss terms to drive drift wave instabilities. We show that the instability driven by temperature fluctuations of the sheath losses is identical to that of the drift wave turbulence. The linear analysis is performed and used to select control parameters that yield identical maximum growth rates for the interchange alone and drift wave alone instability. Combining the two instabilities doubles the maximum growth rate. The non-linear simulations are used to analyse the SOL width. The simulations allow one to identify a low field side SOL region where interchange and drift wave are unstable and a high field side SOL region where only the drift wave is unstable. The SOL profiles appear exponential in the region close to the source but depart from a simple exponential fall-off in the far SOL. The low field side SOL width is found to be larger in the interchange alone case, slightly smaller when both instabilities are present and finally narrower when only the drift waves. For the high field side SOL, without interchange, the drift wave SOL width is observed to be identical to that on the low field side and larger than that when both instabilities at play. The Sherwood dimensionless parameter, ratio of convective particle flux divided by the diffusive particle flux, is used to compare the efficiency of turbulent transport. The profiles of the Sherwood parameter for time and flux surface averaged transport indicate that turbulent transport is dominant close to the separatrix but is less effective towards the far SOL. The Sherwood parameter evolution, determined with the flux-surface averaged transport, indicates that outward avalanche transport with corrugations governs the case with interchange only. When combining the two instabilities, outward avalanche transport is less pronounced and inward avalanche transport is observed, reducing the overall turbulent transport efficiency. The avalanche transport with drift waves only compared to interchange only is found to be inhibited.

Published
2022

14. Unraveling the competition/synergy between turbulence and 3D magnetic perturbations

Author

Varennes, Robin, Garbet, Xavier, Bourne, Emilie, Vermare, L., Sarazin, Yanick, Dif-Pradalier, Guilhem, Grandgirard, Virginie, Ghendrih, Philippe, Donnel, Peter, Peret, Mathieu, Obrejan, Kevin, Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire de Physique des Plasmas (LPP), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and icard, valerie

Subjects
[NLIN] Nonlinear Sciences [physics], [NLIN]Nonlinear Sciences [physics]
Abstract

International audience

Published
2022

15. New advances to prepare GYSELA-X code for exascale global gyrokinetic plasma turbulence simulations: porting on GPU and ARM architectures

Author

Grandgirard, Virginie, Obrejan, Kevin, Midou, Dorian, Asahi, Y, Bernard, P-E, Bigot, J, Bourne, E, Dechard, J, Dif- Pradalier, G, Donnel, P, Garbet, X, Gueroudji, A, Hager, G, Murai, H, Ould-Ruis, Yacine, Padioleau, T, Nguyen, L, Peybernes, M, Sarazin, Y, Sato, M, Tsuji, M, Vezolle, P, Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Japan Atomic Energy Agency, Hewlett Packard Enterprise (Hewlett Packard) (HPE), Maison de la Simulation (MDLS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut National de Recherche en Informatique et en Automatique (Inria)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), AS+ Groupe EOLEN, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), RIKEN Center for Computational Science [Kobe] (RIKEN CCS), RIKEN - Institute of Physical and Chemical Research [Japon] (RIKEN), Data Aware Large Scale Computing (DATAMOVE ), Inria Grenoble - Rhône-Alpes, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Laboratoire d'Informatique de Grenoble (LIG), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Ecole Polytechnique Fédérale de Lausanne (EPFL), the Association for Computing Machinery (ACM), and the Swiss National Supercomputing Centre (CSCS)

Subjects
[NLIN]Nonlinear Sciences [physics]
Abstract

International audience

Published
2022

16. Simulation Verification with PoPe

Author

Ghendrih, Philippe, Cartier-Michaud, Thomas, Grandgirard, Virginie, Serre, Eric, Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire de Mécanique, Modélisation et Procédés Propres (M2P2), Aix Marseille Université (AMU)-École Centrale de Marseille (ECM)-Centre National de la Recherche Scientifique (CNRS), and Aix Marseille Université (AMU)

Subjects
[PHYS.PHYS.PHYS-COMP-PH]Physics [physics]/Physics [physics]/Computational Physics [physics.comp-ph], [PHYS.PHYS.PHYS-FLU-DYN]Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn], [PHYS.PHYS.PHYS-CLASS-PH]Physics [physics]/Physics [physics]/Classical Physics [physics.class-ph], [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [PHYS.COND.CM-SM]Physics [physics]/Condensed Matter [cond-mat]/Statistical Mechanics [cond-mat.stat-mech]
Abstract

We present the theoretical background of the PoPe and iPoPe verification scheme. The verification that is performed uses the output of actual simulations of production runs. With a small computing overhead it is possible to check that the problem that is solved numerically is consistent with the equations that are to be addressed. In fact, one shows that the numerical error determined by both procedures can be split into a part proportional to the existing operators of the equations, thus modifying their control parameters, completed by a residual error orthogonal to these operators. The accuracy of the numerical solution can be tested on the error as well as on the modification of the control parameters. To illustrate the method, the evolution equation of a simple mechanical system with two conjugate degrees of freedom is used as simulation test bed. Importantly, although dissipative, the trajectory equations evolve towards a chaotic attractor, a strange attractor, characterised by a positive Lyapunov exponent and therefore sensitivity to initial conditions. It is shown that the chaotic state cannot be verified with the standard Method of Manufactured Solution. We present different facets of the PoPe verification method applied to this test case. We show that the evaluation of the accuracy is case dependent for two reasons. First, the error that is generated depends on the values of the control parameter and not only on the numerical scheme. Second, the target accuracy will depend on the problem one wants to address. In a case characterised by bifurcations between different states, the accuracy is determined by the level of detail of the bifurcation phenomena one wants to achieve. A unique verification index is proposed to characterise the accuracy, and consequently the verification, of any given simulation in the production runs. This PoPe index then gives a level of confidence of each simulation. A PoPe index of zero characterises a situation with 100% error level. One finds that although the accuracy is poor the robust features of the solution can still be recovered. The maximum PoPe index is determined by machine precision, typically in the range of 12 to 14. As an illustration this PoPe index is used to choose between a high order integration scheme and a reduced order integration scheme that is less precise but requires less operations. For the chosen example the PoPe index indicates that the high order scheme leads to a reduction of computer resources up to a factor 4 at given accuracy.

Published
2022

21. Performance portable implementation of a kinetic plasma simulation mini-app

Author

Asahi, Yuuichi, Latu, Guillaume, Grandgirard, Virginie, and Bigot, Julien

Abstract

Performance portability is considered to be an inevitable requirement in the exascale era. We explore a performance portable approach for fusion plasma turbulence simulation code employing kinetic model, namely the GYSELA code. For this purpose, we extract the key features of GYSELA such as the high dimensionality and the semi- Lagrangian scheme, and encapsulate them into a mini-application which solves the similar but a simplied Vlasov-Poisson system. We implement the mini-app with a mixed OpenACC/OpenMP and Kokkos implementation, where we suppress unnecessary duplications of code lines. For a reference case with the problem size of 1284, the Skylake (Kokkos), Nvidia Tesla P100 (OpenACC), and P100 (Kokkos) versions achieve an acceleration of 1.45, 12.95, and 17.83, respectively, with respect to the baseline OpenMP version on Intel Skylake. In addition to the performance portability, we discuss the code readability and productivity of each implementation. Based on our experience, Kokkos can oer a readable and productive code at the cost of initial porting eorts, which would be enormous for a large scale simulation code like GYSELA., SC19

Published
2019

22. How to prepare the GYSELA-X code to future exascale edge-core simulations

Author

Grandgirard, Virginie, Asahi, Y, Bigot, J, Bourne, E, Dif-Pradalier, Guilhem, Donnel, P, Garbet, X, Ghendrih, Ph., Güçlü, Yaman, Kormann, K, Midou, D, Munschy, Y, Obrejan, K, Passeron, Ch, Varennes, R, Sarazin, Y, Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Japan Atomic Energy Agency, Maison de la Simulation (MDLS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut National de Recherche en Informatique et en Automatique (Inria)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Ecole Polytechnique Fédérale de Lausanne (EPFL), Max-Planck-Institut für Plasmaphysik [Garching] (IPP), Association for Computing Machinery (ACM), and the Swiss National Supercomputing Centre (CSCS)

Subjects
[PHYS]Physics [physics], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2021

23. Model order reduction approach to one-dimensional collisionless closure problem

Author

Gillot, Camille, Dif-Pradalier, Guilhem, Garbet, Xavier, Ghendrih, Philippe, Grandgirard, Virginie, Sarazin, Yanick, CEA Cadarache, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), and Sarazin, Yanick

Subjects
[PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], [PHYS.PHYS.PHYS-PLASM-PH] Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph]
Published
2021

24. Key role of phase dynamics & diamagnetic drive on Reynolds stress in fusion plasma turbulence

Author

Sarazin, Y., Dif-Pradalier, Guilhem, Ghendrih, Ph., Garbet, X., Berger, A., Bigué, R., Bourne, Emilie, Grandgirard, Virginie, Obrejan, Kevin, Varennes, R., Vermare, L., icard, valerie, Implementation of activities described in the Roadmap to Fusion during Horizon 2020 through a Joint programme of the members of the EUROfusion consortium - EUROfusion - - H20202014-01-01 - 2018-12-31 - 633053 - VALID, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Laboratoire de Physique des Plasmas (LPP), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and European Project: 633053,H2020,EURATOM-Adhoc-2014-20,EUROfusion(2014)

Subjects
[PHYS]Physics [physics], [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], [PHYS.PHYS.PHYS-PLASM-PH] Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], ComputingMilieux_MISCELLANEOUS, [PHYS] Physics [physics]
Abstract

International audience

Published
2021

25. Formation of the radial electric field profile in WEST tokamak

Author

Vermare, Laure, Dif-Pradalier, Guilhem, Hennequin, Pascale, Gunn, James, Garbet, Xavier, Artaud, Jean-Francois, Gurcan, Ozgur, Bourdelle, Clarisse, Clairet, Frédéric, Fedorczak, Nicolas, Honoré, Cyrille, Morales, Jorge, Sarazin, Yanick, Grandgirard, Virginie, Varennes, Robin, Vezinet, Didier, Peret, Mathieu, Dumont, Rémi, Goniche, Marc, Maget, Patrick, icard, valerie, Implementation of activities described in the Roadmap to Fusion during Horizon 2020 through a Joint programme of the members of the EUROfusion consortium - EUROfusion - - H20202014-01-01 - 2018-12-31 - 633053 - VALID, Laboratoire de Physique des Plasmas (LPP), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), The WEST Team, and European Project: 633053,H2020,EURATOM-Adhoc-2014-20,EUROfusion(2014)

Subjects
[PHYS]Physics [physics], [PHYS] Physics [physics]
Abstract

International audience; The shear of the radial electric field at the edge is widely accepted to be responsible for turbulence reductionin edge transport barriers and thought as a key ingredient of the improved confinement of H-mode plasmas.Nevertheless, a full understanding of how its profile builds up at the edge is still lacking. It can either beformulated as the result of a competition between several mechanisms that generate and damp flows or as theresult of a non-ambipolar particle flux, which enhances radial charge separation imposing a radial electric fieldprofile. Among possible mechanisms, one can think of turbulence generated flow via Reynolds stress, ion orbitlosses, toroidal magnetic ripple and the effect of neutral friction at the edge. Based on previous results obtainedon Tore Supra, the radial profile of the perpendicular flow expected in WEST can be separated in three spatialareas. Inside ρ = 0.8, the radial electric field is dominated by losses of thermal ions in the magnetic ripple while between 0.7 < ρ < 0.95, a competition between this latter and the generation of large scale flows byturbulence appears as a possible explanation of the measured poloidal asymmetry of the mean perpendicularvelocity. In addition, edge conditions such as contact points and parallel dynamics in the scrape-off-layer(SOL) influence the edge profiles beyond ρ = 0.9 (3). This contribution presents unexpected differences in theradial electric field profile observed in WEST between Lower Single Null (LSN) and Upper Single Null (USN)configurations and a study of the competition between specific mechanisms playing a role in the formationof this profile.

Published
2021

26. Overlapping communications in gyrokinetic codes on accelerator-based platforms

Author

Asahi, Yuuichi, Latu, Guillaume, Bigot, Julien, Maeyama, Shinya, Grandgirard, Virginie, Idomura, Yasuhiro, and Yuuichi, Asahi

Abstract

Communication and computation overlapping techniques have been introduced in the five‐dimensional gyrokinetic codes GYSELA and GKV. In order to anticipate some of the exa‐scale requirements, these codes were ported to the modern accelerators, Xeon Phi KNL and Tesla P 100 GPU. On accelerators, a serial version of GYSELA on KNL and GKV on GPU are respectively 1.3× and 7.4× faster than those on a single Skylake processor (a single socket). For the scalability, we have measured GYSELA performance on Xeon Phi KNL from 16 to 512 KNLs (1024 to 32k cores) and GKV performance on Tesla P 100 GPU from 32 to 256 GPUs. In their parallel versions, transpose communication in semi‐Lagrangian solver in GYSELA or Convolution kernel in GKV turned out to be a main bottleneck. This indicates that in the exa‐scale, the network constraints would be critical. In order to mitigate the communication costs, the pipeline and task‐based overlapping techniques have been implemented in these codes. The GYSELA 2D advection solver has achieved a 33% to 92% speed up, and the GKV 2D convolution kernel has achieved a factor of 2 speed up with pipelining. The task‐based approach gives 11% to 82% performance gain in the derivative computation of the electrostatic potential in GYSELA. We have shown that the pipeline‐based approach is applicable with the presence of symmetry, while the task‐based approach can be applicable to more general situations.

Published
2019

27. Accelerating a kinetic plasma simulation mini-app keeping performance portability

Author

Asahi, Yuuichi, Latu, Guillaume, Grandgirard, Virginie, and Bigot, Julien

Abstract

プラズマ乱流の運動論モデルは、4次元以上の高次元性と各次元の低い解像度に特徴付けられる。これらのコードを、性能可搬性を維持しつつ、GPUによって加速するため、OpenACCとKokkosなどのフレームワークを用いて実装を行った。性能可搬性は、Nvidia P100、Nvidia V100、Marvell Thunder X2、Intel Xeon Goldなど最新のCPU、GPU上で検証した。発表では、OpenACCとKokkosの利点、欠点を性能、可搬性、抽象化などの観点から論じる。, 5th US-Japan JIFT Exascale Computing Collaboration

Published
2019

28. Turbulence/Neoclassical interaction through poloidal convective cells

Author

Asahi, Yuuichi, Grandgirard, Virginie, Idomura, Yasuhiro, Latu, Guillaume, Sarazin, Yanick, Guilhem, Dif-Pradalier, Garbet, Xavier, and Donnel, Peter

Abstract

乱流が非線型結合によって駆動するconvective cellモードに対し数値フィルタを適用する場合としない場合の比較を通じ、その輸送への影響評価を行う。フィルタの有無で乱流スペクトルなどに大きな変化は見られなかったが、フィルタはconvective cellモードを介して間接的に分布関数へ作用し、その分布関数の応答によって新古典熱輸送が変化する場合があることを明らかにした。, 10th Festival de Théorie

Published
2019

29. Compressing the time series of five dimensional distribution function data from gyrokinetic simulation using principal component analysis

Author

Asahi, Yuuichi, Fujii, Keisuke, Manuel Heim, Dennis, Maeyama, Shinya, Garbet, Xavier, Grandgirard, Virginie, Sarazin, Yanick, Guilhem, Dif-Pradalier, Idomura, Yasuhiro, Yagi, Masatoshi, Yuuichi, Asahi, Yasuhiro, Idomura, and Masatoshi, Yagi

Abstract

Phase space structures are extracted from the time series of five dimensional distribution function data computed by the flux-driven full-f gyrokinetic code GT5D. Principal component analysis (PCA) is applied to reduce the dimensionality and the size of the data. Phase space bases in ðu; vk;wÞ and the corresponding spatial coefficients (poloidal cross section) are constructed by PCA, where u; vk, and w, respectively, mean the toroidal angle, the parallel velocity, and the perpendicular velocity. It is shown that 83% of the variance of the original five dimensional distribution function can be expressed with 64 principal components, i.e., the compression of the degrees of freedom from 1:3 1012 to 1:4 109. One of the important findings—resulting from the detailed analysis of the contribution of each principal component to the energy flux—deals with avalanche events, which are found to be mostly driven by coherent structures in the phase space, indicating the key role of resonant particles. Another advantage of the proposed analysis is the decoupling of 6D (1D time and 5D phase space) data into the combinations of 3D data which are visible to the human eye.

Published
2021

30. The GYSELA project: A semi-Lagrangian code addressing gyrokinetic full-f global simulations of flux driven tokamak plasmas

Author

Grandgirard, Virginie, Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Université de Strasbourg, IRMA, Eric Serre(eric.serre@l3m.univ-mrs.fr), and Grandgirard, Virginie

Subjects
gyrokinetic global full-f flux-driven simulations, méthode semi-Lagrangienne, plasma turbulence, calcul haute performance, semi-Lagrangian method, [PHYS.MPHY]Physics [physics]/Mathematical Physics [math-ph], high-performance computing, turbulence plasma, [PHYS.MPHY] Physics [physics]/Mathematical Physics [math-ph], simulations gyrocinétiques globales full-f forcées par le flux
Published
2016

31. A multi-species collisional operator for full-F global gyrokinetics codes : Numerical aspects and validation with the GYSELA code

Author

Donnel, Peter, Garbet, Xavier, Sarazin, Yanick, Grandgirard, Virginie, Asahi, Yuuichi, Bouzat, Nicolas, Caschera, Elisabetta, Dif-Pradalier, Guilhem, Ehrlacher, Charles, Ghendrih, Philippe, Latu, Guillaume, Passeron, Chantal, Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), TOkamaks and NUmerical Simulations (TONUS), Institut de Recherche Mathématique Avancée (IRMA), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Inria Nancy - Grand Est, and Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)

Subjects
[PHYS.PHYS.PHYS-COMP-PH]Physics [physics]/Physics [physics]/Computational Physics [physics.comp-ph], multispecies, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], H-theorem, neoclassic, collision
Abstract

A linearized multi-species collision operator valid for arbitrary masses and charges has been developed and implemented in the gyrokinetic code GYSELA [9]. This operator has all the required properties : it conserves particles, total momentum and energy, fulfills the Boltzmann H theorem and recovers neoclassical results. This operator takes into account both pitch angle scattering and energy diffusion while operting in the v , µ phase space. Derivatives with respect to the magnetic moment are treated using a projection on a set of orthogonal polynomials. The numerical aspects of the implementation are detailed and a set of physical benchmarks allows a verification of the properties of the operator.

Published
2018

32. Synergy of turbulent and neoclassical transport through poloidal convective cells

Author

Asahi, Yuuichi, Grandgirard, Virginie, Sarazin, Yanick, Donnel, Peter, Garbet, Xavier, Idomura, Yasuhiro, Guilhem, Dif-Pradalier, and Latu, Guillaume

Subjects
Physics::Fluid Dynamics
Abstract

The role of poloidal convective cells—i.e. low frequency axisymmetric modes of the electric potential—on transport processes is studied with the full-F gyrokinetic code GYSELA. In order to understand the impact of convective cells, we apply a numerical filter to convective cells and compare the simulation results with and without the filter. The energy flux driven by the magnetic drifts (due to the curvature of the magnetic field lines and to the gradient of the magnetic field intensity ∇B) Q_i^D turns out to be reduced by a factor of about 2 once the numerical filter is applied. A careful analysis reveals that the frequency spectrum of the convective cells is well-correlated with that of the turbulent Reynolds stress tensor, giving credit to their turbulence driven origin. The impact of convective cells on Q_i^D can be interpreted as a synergy between turbulence and neoclassical dynamics.

Published
2019

33. Synergetic effects of collisions, turbulence and sawtooth crashes on impurity transport

Author

Garbet, Xavier, Ahn, Jae-H, Breton, S, Donnel, P, Esteve, D, Guirlet, R, Lütjens, H, Nicolas, T, Sarazin, Yanick, Bourdelle, C, Février, O, Dif-Pradalier, Guilhem, Ghendrih, Philippe, Grandgirard, Virginie, Latu, Guillaume, Luciani, J.F., Maget, P, Marx, A, Smolyakov, A, Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Centre de Physique Théorique [Palaiseau] (CPHT), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Nastional Institute for Fusion Science (NIFS), NIFS, University of Saskatchewan [Saskatoon] (U of S), Garbet, Xavier, and École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS)

Subjects
fusion, Magnetized plasmas, Physics::Plasma Physics, MHD, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], [PHYS.PHYS.PHYS-PLASM-PH] Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], turbulence, tokamaks
Abstract

This paper investigates the interplay of neoclassical, turbulent and MHD processes, which are simultaneously at play when contributing to impurity transport. It is shown that these contributions are not additive, as assumed sometimes. The interaction between turbulence and neoclassical effects leads to less effective thermal screening, i.e. lowers the outward flux due to temperature gradient. This behavior is attributed to poloidal asymmetries of the flow driven by turbulence. Moreover sawtooth crashes play an important role to determine fluxes across the q = 1 surface. It is found that the density profile of a heavy impurity differs significantly in sawtoothing plasmas from the one predicted by neoclassical theory when neglecting MHD events. Sawtooth crashes impede impurity accumulation, but also weaken the impurity outflux due to the temperature gradient when the latter is dominant.

Published
2016

34. Targeting Realistic Geometry in Tokamak Code Gysela.

Author

Grigori, L., Japhet, C., Moireau, P., Bouzat, Nicolas, Bressan, Camilla, Grandgirard, Virginie, Latu, Guillaume, and Mehrenberger, Michel

Subjects
TOKAMAKS, TURBULENCE, HEAT losses, POISSON processes
Abstract

In magnetically confined plasmas used in Tokamak, turbulence is respon-sible for specific transport that limits the performance of this kind of reactors. Gyroki-netic simulations are able to capture ion and electron turbulence that give rise to heat losses, but require also state-of-the-art HPC techniques to handle computation costs. Such simulations are a major tool to establish good operating regime in Tokamak such as ITER, which is currently being built. Some of the key issues to address more re- alistic gyrokinetic simulations are: efficient and robust numerical schemes, accurate geometric description, good parallelization algorithms. The framework of this work is the Semi-Lagrangian setting for solving the gyrokinetic Vlasov equation and the Gy-sela code. In this paper, a new variant for the interpolation method is proposed that can handle the mesh singularity in the poloidal plane at r = 0 (polar system is used for the moment in Gysela). A non-uniform meshing of the poloidal plane is proposed instead of uniform one in order to save memory and computations. The interpolation method, the gyroaverage operator, and the Poisson solver are revised in order to cope with non-uniform meshes. A mapping that establish a bijection from polar coordinates to more realistic plasma shape is used to improve realism. Convergence studies are provided to establish the validity and robustness of our new approach. [ABSTRACT FROM AUTHOR]

Published
2018
Full Text
View/download PDF

35. Building and Auto-Tuning Computing Kernels: Experimenting with Boast and Starpu in the Gysela Code.

Author

Grigori, L., Japhet, C., Moireau, P., Bigot, Julien, Grandgirard, Virginie, Latu, Guillaume, Mehaut, Jean-Francois, Millani, Luís Felipe, Passeron, Chantal, Masnada, Steven Quinito, Richard, Jérôme, and Videau, Brice

Subjects
SELF-tuning controllers, KERNEL functions, TURBULENCE, AUTOMATION, MATHEMATICAL optimization
Abstract

Modeling turbulent transport is a major goal in order to predict confinement performance in a tokamak plasma. The gyrokinetic framework considers a computational domain in five dimensions to look at kinetic issues in a plasma; this leads to huge computational needs. Therefore, optimization of the code is an especially important aspect, especially since coprocessors and complex manycore architectures are foreseen as building blocks for Exascale systems. This project aims to evaluate the applicability of two auto-tuning approaches with the BOAST and StarPU tools on the GYSELA code in order to circumvent performance portability issues. A specific computation intensive kernel is considered in order to evaluate the benefit of these methods. StarPU enables to match the performance and even sometimes outperform the hand-optimized version of the code while leaving scheduling choices to an automated process. BOAST on the other hand reveals to be well suited to get a gain in terms of execution time on four architectures. Speedups in-between 1.9 and 5.7 are obtained on a cornerstone computation intensive kernel. [ABSTRACT FROM AUTHOR]

Published
2018
Full Text
View/download PDF

36. Comprehensive comparisons of geodesic acoustic mode characteristics and dynamics between Tore Supra experiments and gyrokinetic simulations

Author

Storelli, A., Vermare, Laure, Hennequin, Pascale, Gürcan, Özgür, Dif-Pradalier, Guilhem, Sarazin, Y., Garbet, X., Görler, T., Singh, Rameswar, Morel, Pierre, Grandgirard, Virginie, Ghendrih, Philippe, Tore Supra, Team, Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
Statistics::Applications, Physics::Plasma Physics, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], Statistics::Computation
Abstract

International audience; In a dedicated collisionality scan in Tore Supra, the geodesic acoustic mode (GAM) is detected and identified with the Doppler backscattering technique. Observations are compared to the results of a simulation with the gyrokinetic code GYSELA. We found that the GAM frequency in experiments is lower than predicted by simulation and theory. Moreover, the disagreement is higher in the low collisionality scenario. Bursts of non harmonic GAM oscillations have been characterized with filtering techniques, such as the Hilbert-Huang transform. When comparing this dynamical behaviour between experiments and simulation, the probability density function of GAM amplitude and the burst autocorrelation time are found to be remarkably similar. In the simulation, where the radial profile of GAM frequency is continuous, we observed a phenomenon of radial phase mixing of the GAM oscillations, which could influence the burst autocorrelation time.

Published
2015
Full Text
View/download PDF

37. Toward memory scalability of GYSELA code for extreme scale computers

Author

Rozar, Fabien, Latu, Guillaume, Roman, Jean, Grandgirard, Virginie, Maison de la Simulation (MDLS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut National de Recherche en Informatique et en Automatique (Inria)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), High-End Parallel Algorithms for Challenging Numerical Simulations (HiePACS), Laboratoire Bordelais de Recherche en Informatique (LaBRI), Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Centre National de la Recherche Scientifique (CNRS)-Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Électronique, Informatique et Radiocommunications de Bordeaux (ENSEIRB)-Inria Bordeaux - Sud-Ouest

Subjects
KEY WORDS: Memory scalability, Extreme scale, CONCURRENCY AND COMPUTATION: PRACTICE AND EXPERIENCE, Concurrency Computat: Pract Exper 0000, 00:1–15, Plasma Physics, Gyrokinetics, memory footprint, memory scalability, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC]
Abstract

International audience; Gyrokinetic simulations lead to huge computational needs. Up to now, the Semi-Lagrangian code GYSELA performed large simulations using up to 65k cores. To understand more accurately the nature of plasma turbulence, finer resolutions are necessary, which make GYSELA a good candidate to exploit the computational power of future extreme scale machines. Among the Exascale challenges, the less memory per core is one of the most critical issues. This paper deals with memory management in order to reduce the memory peak and presents a general method to understand the memory behavior of an application when dealing with very large meshes. This enables us to extrapolate the behavior of GYSELA for expected capabilities of extreme scale machines.

Published
2014
Full Text
View/download PDF

38. Hydraulic preferences of shrimps and fishes in tropical insular rivers

Author

Grandgirard, Virginie, Monti, Dominique, Valade, P., Lamouroux, N., Mallet, J.P., Grondin, H., Milieux aquatiques, écologie et pollutions (UR MALY), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Dynamique des écosystèmes Caraïbe et biologie des espèces associées (DYNECAR EA 926), Université des Antilles et de la Guyane (UAG), aucun, Organisme Consultant en Environnement Aquatique, and A.R.D.A

Subjects
ZONE TROPICALE, MICROHABITAT, [SDE]Environmental Sciences, HYDRAULIQUE, ANTILLES, ILE DE LA REUNION
Abstract

Hydraulic habitat models based on the preferences of species for the hydraulic characteristics of their microhabitats are frequently used to evaluate the impact on the habitat of a change in river flow regime. Their application in a tropical insular environment is still limited as little is known about the hydraulic preferences of species. Hydraulic preference models have been developed for 15 taxa (diadromous shrimps and fishes) sampled in 52 rivers in the Caribbean (the French West Indies) and the Indian Ocean (the Reunion island). Five datasets were used and group 8353 samples collected by electrofishing during 320 surveys (reach date) performed between 1999 and 2011. Generalized additive models were used to link variations of taxa density within surveys to the hydraulic characteristics of the microhabitat (velocity, depth and substrate). Hydraulic preferences within each region (Caribbean and Indian Ocean) are significant for most of the taxa and vary little between rivers and surveys. The hydraulic variables explain up to 18.1% (univariate models) and 30.0% (multivariate models) of the deviance of densities within survey. Of the taxa selected, Atya scabra, Macrobrachium heterochirus, Xiphocaris elongata and the Sicydiinae are the most demanding.

Published
2014
Full Text
View/download PDF

39. Non regression testing for the JOREK code

Author

Latu, Guillaume, Becoulet, Marina, Dif-Pradalier, Guilhem, Grandgirard, Virginie, Hoelzl, Matthias, Huysmans, G., Lacoste, Xavier, Nardon, Eric, Orain, Francois, Passeron, Chantal, Ramet, Pierre, and Ratnani, Ahmed

Subjects
FOS: Computer and information sciences, Mathematics - Analysis of PDEs, Computer Science - Distributed, Parallel, and Cluster Computing, FOS: Mathematics, Distributed, Parallel, and Cluster Computing (cs.DC), Analysis of PDEs (math.AP)
Abstract

Non Regression Testing (NRT) aims to check if software modifications result in undesired behaviour. Suppose the behaviour of the application previously known, this kind of test makes it possible to identify an eventual regression, a bug. Improving and tuning a parallel code can be a time-consuming and difficult task, especially whenever people from different scientific fields interact closely. The JOREK code aims at investing Magnetohydrodynamic (MHD) instabilities in a Tokamak plasma. This paper describes the NRT procedure that has been tuned for this simulation code. Automation of the NRT is one keypoint to keeping the code healthy in a source code repository., No. RR-8134 (2012)

Published
2012

40. Berk-Breizman and diocotron instability testcases

Author

Mehrenberger, Michel, Crouseilles, Nicolas, Grandgirard, Virginie, Hirstoaga, Sever Adrian, Madaule, Eric, Pétri, Jérôme, Sonnendrücker, Eric, Scientific computation and visualization ( CALVI ), Institut de Recherche Mathématique Avancée ( IRMA ), Université de Strasbourg ( UNISTRA ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Strasbourg ( UNISTRA ) -Centre National de la Recherche Scientifique ( CNRS ) -Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection ( LSIIT ), Centre National de la Recherche Scientifique ( CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Inria Nancy - Grand Est, Institut National de Recherche en Informatique et en Automatique ( Inria ) -Institut National de Recherche en Informatique et en Automatique ( Inria ) -Institut Élie Cartan de Lorraine ( IECL ), Université de Lorraine ( UL ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Lorraine ( UL ) -Centre National de la Recherche Scientifique ( CNRS ), Université de Strasbourg ( UNISTRA ) -Centre National de la Recherche Scientifique ( CNRS ), Invariant Preserving SOlvers ( IPSO ), Institut de Recherche Mathématique de Rennes ( IRMAR ), Université de Rennes 1 ( UR1 ), Université de Rennes ( UNIV-RENNES ) -Université de Rennes ( UNIV-RENNES ) -AGROCAMPUS OUEST-École normale supérieure - Rennes ( ENS Rennes ) -Institut National de Recherche en Informatique et en Automatique ( Inria ) -Institut National des Sciences Appliquées ( INSA ) -Université de Rennes 2 ( UR2 ), Université de Rennes ( UNIV-RENNES ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Rennes 1 ( UR1 ), Université de Rennes ( UNIV-RENNES ) -Centre National de la Recherche Scientifique ( CNRS ) -Inria Rennes – Bretagne Atlantique, Institut National de Recherche en Informatique et en Automatique ( Inria ), Université de Rennes ( UNIV-RENNES ) -Centre National de la Recherche Scientifique ( CNRS ), Institut de Recherche sur la Fusion par confinement Magnétique ( IRFM ), Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ), Institut Jean Lamour ( IJL ), Université de Lorraine ( UL ) -Centre National de la Recherche Scientifique ( CNRS ), Observatoire astronomique de Strasbourg ( OAS ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique ( CNRS ), Max-Planck-Institut für Plasmaphysik [Garching] ( IPP ), Mehrenberger, Michel, Scientific computation and visualization (CALVI), Institut de Recherche Mathématique Avancée (IRMA), Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Inria Nancy - Grand Est, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institut Élie Cartan de Lorraine (IECL), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), Invariant Preserving SOlvers (IPSO), Institut de Recherche Mathématique de Rennes (IRMAR), AGROCAMPUS OUEST, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-École normale supérieure - Rennes (ENS Rennes)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-AGROCAMPUS OUEST, Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Inria Rennes – Bretagne Atlantique, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA), Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut Jean Lamour (IJL), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Observatoire astronomique de Strasbourg (OAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Plasmaphysik [Garching] (IPP), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École normale supérieure - Rennes (ENS Rennes)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-INSTITUT AGRO Agrocampus Ouest, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Inria Rennes – Bretagne Atlantique, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-AGROCAMPUS OUEST-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-École normale supérieure - Rennes (ENS Rennes)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Inria Rennes – Bretagne Atlantique, Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[ MATH ] Mathematics [math], [MATH] Mathematics [math], [MATH]Mathematics [math]
Abstract

International audience; Berk-Breizman and diocotron testcases are proposed.

Published
2012

41. Accuracy of unperturbed motion of particles in a gyrokinetic semi-Lagrangian code

Author

Latu, Guillaume, Grandgirard, Virginie, Abiteboul, Jérémie, Bergot, Morgane, Crouseilles, Nicolas, Garbet, Xavier, Ghendrih, Philippe, Mehrenberger, Michel, Sarazin, Yanick, Sellama, Hocine, Sonnendrücker, Eric, Zarzoso, David, Scientific computation and visualization ( CALVI ), Institut de Recherche Mathématique Avancée ( IRMA ), Université de Strasbourg ( UNISTRA ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Strasbourg ( UNISTRA ) -Centre National de la Recherche Scientifique ( CNRS ) -Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection ( LSIIT ), Centre National de la Recherche Scientifique ( CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Inria Nancy - Grand Est, Institut National de Recherche en Informatique et en Automatique ( Inria ) -Institut National de Recherche en Informatique et en Automatique ( Inria ) -Institut Élie Cartan de Lorraine ( IECL ), Université de Lorraine ( UL ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Lorraine ( UL ) -Centre National de la Recherche Scientifique ( CNRS ), Institut de Recherche sur la Fusion par confinement Magnétique ( IRFM ), Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ), Institut de Recherche Mathématique de Rennes ( IRMAR ), Université de Rennes 1 ( UR1 ), Université de Rennes ( UNIV-RENNES ) -Université de Rennes ( UNIV-RENNES ) -AGROCAMPUS OUEST-École normale supérieure - Rennes ( ENS Rennes ) -Institut National de Recherche en Informatique et en Automatique ( Inria ) -Institut National des Sciences Appliquées ( INSA ) -Université de Rennes 2 ( UR2 ), Université de Rennes ( UNIV-RENNES ) -Centre National de la Recherche Scientifique ( CNRS ), Invariant Preserving SOlvers ( IPSO ), Université de Rennes ( UNIV-RENNES ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Rennes 1 ( UR1 ), Université de Rennes ( UNIV-RENNES ) -Centre National de la Recherche Scientifique ( CNRS ) -Inria Rennes – Bretagne Atlantique, Institut National de Recherche en Informatique et en Automatique ( Inria ), Université de Strasbourg ( UNISTRA ) -Centre National de la Recherche Scientifique ( CNRS ), INRIA, ANR-BLANC-SIMI-9-GYSPI,GYPSI,Simulation GYrocinétique haute Performance Pour ITER ( 2010 ), Scientific computation and visualization (CALVI), Institut de Recherche Mathématique Avancée (IRMA), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Inria Nancy - Grand Est, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institut Élie Cartan de Lorraine (IECL), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut de Recherche Mathématique de Rennes (IRMAR), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École normale supérieure - Rennes (ENS Rennes)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-INSTITUT AGRO Agrocampus Ouest, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Invariant Preserving SOlvers (IPSO), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Inria Rennes – Bretagne Atlantique, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), ANR-10-BLAN-0941,GYPSI,Simulation GYrocinétique haute Performance Pour ITER(2010), AGROCAMPUS OUEST, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-École normale supérieure - Rennes (ENS Rennes)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-AGROCAMPUS OUEST, and Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Inria Rennes – Bretagne Atlantique

Subjects
gyrokinetic, FSL, [ INFO.INFO-DC ] Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], [ MATH.MATH-AP ] Mathematics [math]/Analysis of PDEs [math.AP], [MATH.MATH-AP]Mathematics [math]/Analysis of PDEs [math.AP], [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], conservation laws
Abstract

Inaccurate description of the equilibrium can yield to spurious effects in gyrokinetic turbulence simulations. Also, the Vlasov solver and time integration schemes impact the conservation of physical quantities, especially in long-term simulations. Equilibrium and Vlasov solver have to be tuned in order to preserve constant states (equilibrium) and to provide good conservation property along time (mass to begin with). Several illustrative simple test cases are given to show typical spurious effects that one can observes for poor settings. We explain why Forward Semi-Lagrangian scheme bring us some benefits. Some toroidal and cylindrical GYSELA runs are shown that use FSL.; Une description imparfaite de l'équilibre peut conduire à des artéfacts numériques dans des simulations turbulentes gyrocinétiques. Aussi, le solveur de Vlasov and le schéma d'intégration en temps ont un impact fort sur la conservation de quantités physiques, notamment lorsque les simulations sont en temps long. L'équilibre et le solveur Vlasov doivent être finement choisis et paramétrés pour conserver les états constants (équilibre) et pour autoriser de bonnes propriétés de conservation en temps (en commençant par la conservation de la masse). Plusieurs cas tests illustratifs sont donnés pour montrer les problèmes numériques typiques que l'on peut observer si les choix pris ne sont pas adéquats. Nous expliquons pourquoi le schéma FSL (Forward Semi-Lagrangian) apporte une réponse à certains problèmes. Des simulations en configuration cylindrique et torique de GYSELA sont présentées qui utilisent FSL.

Published
2012

42. Conservative Semi-Lagrangian solvers on mapped meshes

Author

Mehrenberger, Michel, Bergot, Morgane, Grandgirard, Virginie, Latu, Guillaume, Sellama, Hocine, Sonnendrücker, Eric, Scientific computation and visualization (CALVI), Institut de Recherche Mathématique Avancée (IRMA), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Inria Nancy - Grand Est, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institut Élie Cartan de Lorraine (IECL), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), ANR-10-BLAN-0941,GYPSI,Simulation GYrocinétique haute Performance Pour ITER(2010), Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), and Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)

Subjects
[MATH.MATH-AP]Mathematics [math]/Analysis of PDEs [math.AP], [MATH.MATH-NA]Mathematics [math]/Numerical Analysis [math.NA]
Abstract

International audience; We are interested in the numerical solution of the collisionless kinetic or gyrokinetic equations of Vlasov type needed for example for many problems in plasma physics. Different numerical methods are classically used, the most used is the Particle In Cell method, but Eulerian and Semi- Lagrangian (SL) methods that use a grid of phase space are also very interesting for some applications. Rather than using a uniform mesh of phase space which is mostly done, the structure of the solution, as a large variation of the gradients on different parts of phase space or a strong anisotropy of the solution, can sometimes be such that it is more interesting to use a more complex mesh. This is the case in particular for gyrokinetic simulations for magnetic fusion applications. We develop here a generalization of the Semi-Lagrangian method on mapped meshes. Classical Backward Semi-Lagrangian methods (BSL), Conservative Semi-Lagrangian methods based on one-dimensional splitting or Forward Semi- Lagrangian methods (FSL) have to be revisited in this case of mapped meshes. A first use of the classical advective BSL method on a mapped mesh has been described in 1. We consider here the problematic of conserving exactly some equilibrium of the distribution function, by using an adapted mapped mesh, which fits on the isolines of the Hamiltonian. This could be useful in particular for Tokamak simulations where instabilities around some equilibrium are investigated. We also consider the problem of mass conservation. In the cartesian framework, the FSL method automatically conserves the mass, as the advective and conservative form are shown to be equivalent. This does not remain true in the general curvilinear case. Numerical results are given on some gyrokinetic simulations performed with the GYSELA code and show the benefit of using a mass conservative scheme like the conservative version of the FSL scheme.

Published
2012
Full Text
View/download PDF

43. Scaling GYSELA code beyond 32K-cores on Blue Gene/Q

Author

Bigot, Julien, Grandgirard, Virginie, Latu, Guillaume, Passeron, Chantal, Rozar, Fabien, Thomine, Olivier, Maison de la Simulation (MDLS), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Recherche en Informatique et en Automatique (Inria)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), European Project, and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut National de Recherche en Informatique et en Automatique (Inria)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[INFO.INFO-PF]Computer Science [cs]/Performance [cs.PF], [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], ACM: J.: Computer Applications/J.2: PHYSICAL SCIENCES AND ENGINEERING/J.2.8: Physics, ACM: D.: Software/D.1: PROGRAMMING TECHNIQUES/D.1.3: Concurrent Programming/D.1.3.1: Parallel programming, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC], ACM: B.: Hardware/B.8: PERFORMANCE AND RELIABILITY/B.8.2: Performance Analysis and Design Aids
Abstract

International audience; Gyrokinetic simulations lead to huge computational needs. Up to now, the semi- Lagrangian code Gysela performed large simulations using a few thousands cores (8k cores typically). Simulation with finer resolutions and with kinetic electrons are expected to increase those needs by a huge factor, providing a good example of applications requiring Exascale machines. This paper presents our work to improve Gysela in order to target an architecture that presents one possible way towards Exascale: the Blue Gene/Q. After analyzing the limitations of the code on this architecture, we have implemented three kinds of improvement: computational performance improvements, memory consumption improvements and disk i/o improvements. As a result, we show that the code now scales beyond 32k cores with much improved performances. This will make it possible to target the most powerful machines available and thus handle much larger physical cases.; Les simulations gyrocinétiques ont des coûts en calcul extrêmement importants. Jusqu'à maitenant, le code semi-Lagrangien Gysela réalisait de grandes simulations en employant quelques milliers de cœurs (8k cœurs typiquement). Il est prévu que des simulations à grain plus fin et incluant les électrons cinétiques augmentent ces besoins d'un facteur important, fournissant un exemple d'application nécessitant des machines Exascale. Ce papier présente notre travail pour améliorer Gysela afin de viser une architecture qui offre une direction possible vers l'Exascale : la Blue Gene/Q. Après avoir analysé les limitations du code sur cette architecture, nous avons mis en œuvre trois types d'améliorations : des améliorations de performances de calcul, des améliorations de consomation mémoire et des améliorations d'E/S disque. Nous montrons que suite à ces travaux, le code monte en charge au delà de 32k cœurs avec des performances bien améliorées. Il devient ainsi possible de viser les machines les plus performantes disponibles et de gérer des cas physiques nettement plus grands.

Published
2012
Full Text
View/download PDF

44. Innovative zinc based mixed oxide sorbent regenerable at low temperature for syngas desulfurization

Author

Grandgirard, Virginie, Baudot, A., Bazer-Bachi, Delphine, Chiche, D., Geantet, C., RAFFINAGE (RAFFINAGE), Institut de recherches sur la catalyse et l'environnement de Lyon (IRCELYON), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), and IRCELYON, ProductionsScientifiques

Subjects
[CHIM.CATA] Chemical Sciences/Catalysis, [SDE.ES] Environmental Sciences/Environmental and Society, [CHIM.CATA]Chemical Sciences/Catalysis, [SDE.ES]Environmental Sciences/Environmental and Society
Abstract

RAFFINAGE+CGE

Published
2012

45. Some numerical aspects of the conservative PSM scheme in a 4D drift-kinetic code

Author

Braeunig , Jean-Philippe, Crouseilles , Nicolas, Grandgirard , Virginie, Latu , Guillaume, Mehrenberger , Michel, Sonnendrücker , Eric, DAM Île-de-France ( DAM/DIF ), Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ), Invariant Preserving SOlvers ( IPSO ), Institut de Recherche Mathématique de Rennes ( IRMAR ), Université de Rennes 1 ( UR1 ), Université de Rennes ( UNIV-RENNES ) -Université de Rennes ( UNIV-RENNES ) -AGROCAMPUS OUEST-École normale supérieure - Rennes ( ENS Rennes ) -Institut National de Recherche en Informatique et en Automatique ( Inria ) -Institut National des Sciences Appliquées ( INSA ) -Université de Rennes 2 ( UR2 ), Université de Rennes ( UNIV-RENNES ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Rennes 1 ( UR1 ), Université de Rennes ( UNIV-RENNES ) -Centre National de la Recherche Scientifique ( CNRS ) -Inria Rennes – Bretagne Atlantique, Institut National de Recherche en Informatique et en Automatique ( Inria ), Université de Rennes ( UNIV-RENNES ) -Centre National de la Recherche Scientifique ( CNRS ), Institut de Recherche sur la Fusion par confinement Magnétique ( IRFM ), Scientific computation and visualization ( CALVI ), Institut de Recherche Mathématique Avancée ( IRMA ), Université de Strasbourg ( UNISTRA ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Strasbourg ( UNISTRA ) -Centre National de la Recherche Scientifique ( CNRS ) -Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection ( LSIIT ), Centre National de la Recherche Scientifique ( CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Inria Nancy - Grand Est, Institut National de Recherche en Informatique et en Automatique ( Inria ) -Institut National de Recherche en Informatique et en Automatique ( Inria ) -Institut Élie Cartan de Lorraine ( IECL ), Université de Lorraine ( UL ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Lorraine ( UL ) -Centre National de la Recherche Scientifique ( CNRS ), Université de Strasbourg ( UNISTRA ) -Centre National de la Recherche Scientifique ( CNRS ), CALVI, IPSO, DAM Île-de-France (DAM/DIF), Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Invariant Preserving SOlvers (IPSO), Institut de Recherche Mathématique de Rennes (IRMAR), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École normale supérieure - Rennes (ENS Rennes)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-INSTITUT AGRO Agrocampus Ouest, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Inria Rennes – Bretagne Atlantique, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Scientific computation and visualization (CALVI), Institut de Recherche Mathématique Avancée (IRMA), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Inria Nancy - Grand Est, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institut Élie Cartan de Lorraine (IECL), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), AGROCAMPUS OUEST, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-École normale supérieure - Rennes (ENS Rennes)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-AGROCAMPUS OUEST, Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Inria Rennes – Bretagne Atlantique, and Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)

Subjects
conservative scheme, maximum principle, Physics::Plasma Physics, 2010 MSC 65M08, 76M12, 76N99, numerical simulation, plasma turbulence, FOS: Mathematics, Computer Science - Numerical Analysis, Numerical Analysis (math.NA), Mathematics - Numerical Analysis, [ MATH.MATH-NA ] Mathematics [math]/Numerical Analysis [math.NA], [MATH.MATH-NA]Mathematics [math]/Numerical Analysis [math.NA]
Abstract

The purpose of this work is simulation of magnetised plasmas in the ITER project framework. In this context, kinetic Vlasov-Poisson like models are used to simulate core turbulence in the tokamak in a toroidal geometry. This leads to heavy simulations because a 6D dimensional problem has to be solved, even if reduced to a 5D in so called gyrokinetic models. Accurate schemes, parallel algorithms need to be designed to bear these simulations. This paper describes the numerical studies to improve robustness of the conservative PSM scheme in the context of its development in the GYSELA code. In this paper, we only consider the 4D drift-kinetic model which is the backbone of the 5D gyrokinetic models and relevant to build a robust and accurate numerical method.

Published
2011

46. Scalable Quasineutral solver for gyrokinetic simulation

Author

Latu, Guillaume, Grandgirard, Virginie, Crouseilles, Nicolas, Dif-Pradalier, Guilhem, Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Scientific computation and visualization (CALVI), Institut de Recherche Mathématique Avancée (IRMA), Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Inria Nancy - Grand Est, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institut Élie Cartan de Lorraine (IECL), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), University of California [San Diego] (UC San Diego), University of California, INRIA, Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), and University of California (UC)

Subjects
[MATH.MATH-MP]Mathematics [math]/Mathematical Physics [math-ph], Gyrokinetics, [PHYS.MPHY]Physics [physics]/Mathematical Physics [math-ph], MPI, OpenMP, Quasineutrality solver, [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC]
Abstract

Modeling turbulent transport is a major goal in order to predict confinement issues in a tokamak plasma. The gyrokinetic framework considers a computational domain in five dimensions to look at kinetic issues in a plasma. Gyrokinetic simulations lead to huge computational needs. Up to now, the gyrokinetic code GYSELA performed large simulations using a few thousands of cores. The work proposed here improves GYSELA onto two points: memory scalability and execution time. The new solution allows the GYSELA code to scale well up to 64k cores.; La modélisation du transport turbulent est un point clef pour prédire les propriétés de confinement d'un plasma de fusion. La théorie gyrocinétique propose une description à 5 dimensions permettant de calculer et comprendre les effets cinétiques dans un plasma. Les simulations gyrocinétiques conduisent à des coûts en calcul réellement prohibitifs. Jusqu'à maintenant, le code gyrocinétique GYSELA réalisait de grosses simulations en utilisant quelques milliers de coeurs de calcul. Le travail proposé ici améliore GYSELA sur deux aspects: l'extensibilité mémoire et le temps d'exécution. La nouvelle solution permet au code GYSELA d'être opérationnel et scalable jusque 64k coeurs au moins.

Published
2011

47. Parallel bottleneck in the Quasineutrality solver embedded in GYSELA

Author

Latu, Guillaume, Crouseilles, Nicolas, Grandgirard, Virginie, Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), Centre National de la Recherche Scientifique (CNRS), Institut de Recherche Mathématique Avancée (IRMA), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Scientific computation and visualization (CALVI), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Inria Nancy - Grand Est, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institut Élie Cartan de Lorraine (IECL), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), INRIA, Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), and Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT)

Subjects
[MATH.MATH-MP]Mathematics [math]/Mathematical Physics [math-ph], [PHYS.MPHY]Physics [physics]/Mathematical Physics [math-ph], [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC]
Abstract

This report shows some performance results of the Quasineutraliy Poisson solver used in the GYSELA code. The numerical schemes of this Poisson solver is explained, and the computation and communication steps on a parallel machine are described. Benchmarks shows several time measurement from 32 cores to 4096 cores. Present bottlenecks and problems of the parallel algorithm are discussed. Some possible solutions are foreseen.; Ce rapport présente des prises de performances du solveur Poisson Quasi-neutre utilisé dans le code GYSELA. Le schéma numérique de ce solveur Poisson est décrit, ainsi que les différentes étapes de calculs et de communication sur machine parallèle. Une série de benchmarks on été effectués de 32 à 4096 coeurs, cela donne un aperçu des performances de ce solveur parallèle. Les goulots d'étranglement et les limitations de l'algorithme parallèle utilisé sont explicités. Enfin, des solutions possibles sont envisagées.

Published
2011

48. Some parallel algorithms for the Quasineutrality solver of GYSELA

Author

Latu, Guillaume, Grandgirard, Virginie, Crouseilles, Nicolas, Belaouar, Radoin, Sonnendrücker, Eric, Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), Centre National de la Recherche Scientifique (CNRS), Institut de Recherche Mathématique Avancée (IRMA), Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), Scientific computation and visualization (CALVI), Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Inria Nancy - Grand Est, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institut Élie Cartan de Lorraine (IECL), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), INRIA, Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), and Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT)

Subjects
[MATH.MATH-MP]Mathematics [math]/Mathematical Physics [math-ph], [PHYS.MPHY]Physics [physics]/Mathematical Physics [math-ph], [INFO.INFO-DC]Computer Science [cs]/Distributed, Parallel, and Cluster Computing [cs.DC]
Abstract

The very first parallelizations of the quasineutrality Poisson solver used in the GYSELA code are presented here. We investigate some numerical schemes. For each considered scheme, we propose an algorithmic decomposition in term of parallel computations and inter-processor communications. A set of benchmarks on a parallel machine has permitted to evaluate the performance of the different versions of the Quasineutrality solver.; Les toutes premières parallelisations du solveur Poisson quasi-neutre utilisées dans le code GYSELA sont présentées ici. Les schémas numériques qui ont été envisagés pour ce solveur Poisson sont décrits. Pour chaque schéma, nous proposons une décomposition en terme d'étapes de calculs et de communications inter-processeurs. Des benchmarks sur machine parallèle ont permis d'évaluer les performances de ces différentes versions du solveur Poisson quasi-neutre.

Published
2011

49. Test of some numerical limiters for the conservative PSM scheme for 4D Drift-Kinetic simulations

Author

Guterl, Jerome, Braeunig, Jean-Philippe, Crouseilles, Nicolas, Grandgirard, Virginie, Latu, Guillaume, Mehrenberger, Michel, Sonnendrücker, Eric, Institut de Recherche Mathématique Avancée (IRMA), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), DAM Île-de-France (DAM/DIF), Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Scientific computation and visualization (CALVI), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Inria Nancy - Grand Est, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Institut Élie Cartan de Lorraine (IECL), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de recheche conventionné MESO (LRC MESO), École normale supérieure - Cachan (ENS Cachan)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), INRIA, Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), and Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT)

Subjects
conservative scheme, [MATH.MATH-MP]Mathematics [math]/Mathematical Physics [math-ph], numerical simulation, ITER, plasma turbulence, [INFO.INFO-NA]Computer Science [cs]/Numerical Analysis [cs.NA]
Abstract

The purpose of this work is simulation of magnetised plasmas in the ITER project framework. In this context, Vlasov-Poisson like models are used to simulate core turbulence in the tokamak in a toroidal geometry. This leads to heavy simulation because a 6D dimensional problem has to be solved, 3D in space and 3D in velocity. The model is reduced to a 5D gyrokinetic model, taking advantage of the particular motion of particles due to the presence of a strong magnetic field. However, accurate schemes, parallel algorithms need to be designed to bear these simulations. This paper describes a Hermite formulation of the conservative PSM scheme which is very generic and allows to implement different semi-Lagrangian schemes. We also test and propose numerical limiters which should improve the robustness of the simulations by diminishing spurious oscillations. We only consider here the 4D drift-kinetic model which is the backbone of the 5D gyrokinetic models and relevant to build a robust and accurate numerical method.; Ce travail concerne la simulation de plasmas magnétisés dans le cadre du projet ITER. Pour cette application, des modèles de type Vlasov-Poisson sont utilisés pour simuler la turbulence à coeur dans un tokamak, en géométrie toroidale. Ces études mènent à résoudre des problèmes dans un espace à 6 dimensions, 3D en espace 3D en vitesse, qui sont très lourds à simuler en terme de ressources informatiques. Le modèle est réduit à un modèle gyrocinétique 5D en exploitant les caractéristiques de ce plasma, dont le mouvement des particules est fortement influencé par la présence d'un champ magnétique intense. Cependant, il est nécessaire de mettre au point des schémas précis et des algorithmes parallèles pour mener ces simulations. Ce rapport décrit une formulation de type Hermite du schéma conservatif PSM qui est très générique et qui permet d'implémenter différent schémas semi-Lagrangiens. Nous testons et proposons également des limiteurs numériques de pente qui doivent accroître la robustesse des simulations en réduisant les oscillations d'origine numérique. Dans ce travail, nous l'utilisons pour résoudre le modèle drift-kinetic 4D, qui est le squelette du modèle gyrocinétique 5D. Ce modèle 4D est suffisamment pertinent pour la conception d'une méthode numérique robuste et précise pour le modèle 5D.

Published
2010

50. Nonlocal dynamics of Turbulence, Transport and Zonal Flows in Tokamak Plasmas

Author

Dif-Pradalier, Guilhem, Ku, S, Diamond, P.H, Chang, C.S., Sarazin, Yanick, Grandgirard, Virginie, Abiteboul, J, Allfrey, S., Garbet, Xavier, Ghendrih, Philippe, Latu, Guillaume, Strugarek, A., Center for Astrophysics and Space Sciences [La Jolla] (CASS), University of California [San Diego] (UC San Diego), University of California-University of California, Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Courant Institute of Mathematical Sciences [New York] (CIMS), New York University [New York] (NYU), NYU System (NYU)-NYU System (NYU), Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), and University of California (UC)-University of California (UC)

Subjects
Physics::Fluid Dynamics, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], [NLIN]Nonlinear Sciences [physics]
Abstract

THC/P4-06; International audience; The understanding of plasma turbulent transport in tokamaks used to rely on a local process, in the sense that locally excited fluctuations exhibit short radial correlation lengths only, ultimately leading to diffusive transport. We find here that the intrinsic nature of turbulent heat transport in tokamaks is nonlocal. This nonlocality is thoroughly defined and quantified. In the same vein, it is also found that the global structure of turbulence and transport results from a synergy between edge-driven inward propagation of turbulence intensity with outward heat transport. This synergy results in inward-outward pulse scattering leading to spontaneous production of strong internal shear layers in which the turbulent transport is almost suppressed over several radial correlation lengths. These two examples represent different sides of the same coin: the turbulence-generated self-organised processes which occur at mesoscales are central to our understanding of transport processes as they govern shear generation and flow pattern formation.

Published
2010

Catalog

Books, media, physical & digital resources
See catalog results