# Laurent PlagneTriScale innov · www.triscale-innov.com

Laurent Plagne

PhD

## About

37

Publications

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339

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Introduction

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January 2001 - September 2017

January 2001 - October 2017

## Publications

Publications (37)

This paper presents an efficient parallel method for the deterministic solution of the 3D stationary Boltzmann transport equation applied to diffusive problems such as nuclear core criticality computations. Based on standard MultiGroup-Sn-DD discretization schemes, our approach combines a highly efficient nested parallelization strategy with the PD...

This paper presents an efficient parallel method for the deterministic solution of the 3D stationary Boltzmann transport equation applied to diffusive problems such as nuclear core criticality computations. Based on standard MultiGroup-Sn-DD discretization schemes, our approach combines a highly efficient nested parallelization strategy with the PD...

This paper presents an efficient parallel method for the deterministic solution of the 3D stationary Boltzmann transport equation applied to diffusive problems such as nuclear core criticality computations. Based on standard MultiGroup-Sn-DD discretization schemes, our approach combines a highly efficient nested parallelization strategy with the Pi...

This paper presents Legolas++ arrays, a C++ multi-dimensional array library. Parameterized type of Legolas++ arrays enable data layout adaptation for specific Single Instruction Multiple Data (SIMD) core architectures. The mapping of complex array-based kernels to regular collections of data is efficiently vectorized. In addition, Legolas++ arrays...

EDF has been developping a new calculation chain, ANDROMÈDE, to replace the current one, CASSIOPEE. This work has been underway for more than 10 years now, and among the different components, there is the neutronic core code COCAGNE, which is the subject of this paper. COCAGNE has state-of-the-art fux solvers, an efficient microscopic (isotopic) de...

Ecole IN2P3 d’informatique 2016 - Parallélisme sur matériel hétérogène

This paper describes the design and the performance of DOMINO, a 3D Cartesian SN solver that implements two nested levels of parallelism (multicore + SIMD) on shared memory computation nodes. DOMINO is written in C++, a multi-paradigm programming language that enables the use of powerful andgeneric parallel programming tools such as Intel TBB and E...

High-fidelity nuclear power plant core simulations require solving the Boltzmann transport equation. In discrete ordinates methods, the most computationally demanding oper-ation of this equation is the sweep operation. Considering the evolution of computer architectures, we propose in this paper, as a first step toward heterogeneous distributed arc...

This paper describes the design and the performance of DOMINO, a 3D Cartesian SN solver that implements two nested levels of parallelism (multicore+SIMD) on shared memory computation nodes. DOMINO is written in C++, a multi-paradigm programming language that enables the use of powerful and generic parallel programming tools such as Intel TBB and Ei...

The past few years have been marked by a noticeable increase in the interest in 3D whole-core heterogeneous deterministic neutron transport solvers for reference calculations. Due to the extremely large problem sizes tackled by such solvers, they need to use adapted numerical methods and need to be efficiently implemented to take advantage of the f...

As part of its activity, EDF R&D is developing a new nuclear core simulation code named COCAGNE. This code relies on DIABOLO, a Simplified PN (SPN) method to compute the neutron flux inside the core for eigenvalue calculations. In order to assess the accuracy of SPN calculations, we have developed DOMINO, a new 3D Cartesian SN solver. The parallel...

As part of its activity, EDF R&D is developing a new nuclear core simulation code named COCAGNE.
This code relies on DIABOLO, a Simplified PN (SP N ) method to compute the neutron flux inside the core
for keff eigenvalue problems. In order to complete complex simulations involving a large number of suc-
cessive eigenvalue calculations within accept...

When dealing with nuclear reactor calculation schemes, the need for three dimensional (3D) transport-based reference solutions is essential for both validation and optimization purposes. Considering a benchmark problem, this work investigates the potential of discrete ordinates (Sn) transport methods applied to 3D pressurized water reactor (PWR) fu...

This paper presents two parallel Simplified PN (SPN) solver implementations for both multi-core Central Processing Units (CPU) and Graphics Processing Units (GPU). For a nuclear operator such as Électricité de France (EDF), the time required to carry out nuclear reactor core simulations is rather critical when dealing with production constraints. T...

This article introduces MTPS, a C++ template library dedicated at vectorizing algorithms for different target architectures. Algorithms written with MTPS benefit from optimized memory access patterns and show performances close to hardware limits, both on multicore CPU and on GPU.

Highly structured sparse matrices arise frequently from numerical discretizations of partial differential equations. Legolas++ is a C++ generic library designed for describing and manipulating such multi-level blocked matrices with the corresponding blocked vectors and algorithms. Legolas++ allows a very detailed description of the linear systems t...

This paper presents the design of an efficient multi-target (CPU+GPU) implementation for the Parallel_for skeleton. Emerging massively parallel architectures promise very high performances for a low cost. However, these architectures change faster than ever. Thus, optimization of codes be-comes a very complex and time consumming task. We have ident...

This paper describes a short and simple way of improving the performance of vector operations (e.g. X = aY +bZ +..) applied to large vectors. In a previous paper [1] we described how to take advantage of high performance vector copy op-eration provided by the ATLAS library [2] in the context of C++ Expression Template (ET) mechanism. Here we presen...

This paper presents a successful parallel implementation on Graphics Processing Units (GPUs) for the Simplified PN (SPN) calculations in the 3D case. For a nuclear operator such as EDF, the time required to compute nuclear reactor core simulations is rather critical. The SPN method provides a convenient trade-off between accuracy and numerical comp...

This paper presents the Benchmark Template Library in C++, in short BTL++, which is a flexible framework to assess the run time of user defined computational kernels. When the same kernel is implemented
in several different ways, the collected performance data can be used to automatically construct an interface library that
dispatches a function ca...

This paper describes a short and simple way of improving the performance of vector operations (e.g. X = aY + bZ + ..) applied to large vectors. The principle is to take advantage of high performance vector copy operation provided by the ATLAS library [1] used as a ker-nel for a C++ Expression Template (ET) mechanism. The proposed ET implementation...

The aim of this paper is to describe the parallel implementation of the Tensorial Basis Spline Collocation Method for solving Poisson's equation. The TBSCM Poisson solver has been developed mainly in High Performance Fortran(HPF) [For97]. Some small parts, which were inefficiently compiled by the pghpf2.3 HPF compiler, have been written with the Me...

This paper discusses the implementation of neutron transport codes via generic programming techniques. Two different Boltzmann equation approximations have been implemented, namely the Sn and SPn methods. This implementation experiment shows that generic programming allows to improve maintainability and readability of source codes with no performan...

The electron-ion collision frequency in a strong laser field is calculated in the framework of the quantum Vlasov theory in first-order Born approximation. Using a Wigner representation of the density matrix, the collision frequency can be expressed in terms of the Lindhard dielectric function and a close correspondence between classical and quantu...

Classical predictions of field ionization of hydrogen and of Coulomb scattering in strong laser fields are compared with corresponding
exact numerical solutions of the time-dependent Schrödinger equation. In the quasi-static approximation, ionization rates
are significantly lower than the quasi-classical tunneling rates in the regime of above-barri...

Both quantal and semiclassical mean-field theories based on the density-functional theory have recently been applied to describe the dynamical evolution of electrons during and after the collision between highly charged ions and metallic clusters. We here compare and assess both methods. The quantal calculation solves the time-dependent Kohn-Sham e...

This paper aims to describe the tensorial basis spline collocation method applied to Poisson's equation. In the case of a localized 3D charge distribution in vacuum, this direct method based on a tensorial decomposition of the differential operator is shown to be competitive with both iterative BSCM and FFT-based methods. We emphasize the O(h4) and...

Potential scattering in strong laser fields is treated non-perturhatively in the framework of the time-dependent Schrödinger equation (TDSE) by a finite-difference alternating-direction implicit method (ADI). The numerical method accounts for the specific initial and boundary conditions of scattering problems with an incoming plane wave. Energy spe...

We describe the dynamics of electrons during and after the collision at large impact parameters between a highly charged ion and a cluster of from a few ten up to several hundred alkali-metal atoms. The theoretical model gives the time evolution of the electronic one-body phase-space density as the solution of the self-consistent Vlasov equation. I...

Metallic clusters of between ten and a few thousand atoms offer the possibility to study the combined dynamics of electrons and ions in conditions that differ dramatically from those prevailing in bulk metal. During the last decade, clusters of simple metal atoms, such as sodium, have been the subject of both experimental and theoretical focus; qui...

The aim of this work is to study theoretically the non-linear response of the valence electrons in a sodium cluster during a collision with an ion. We use a semi-classical approximation, which replaces the wave function with N quantum particles representing the phase-space density of valence electrons. The evolution of this density is determined by...

Collisions of ions with metal clusters offer the possibility to study the onset and development of Coulomb instabilities in an as yet unexplored regime. Soft peripheral collisions with highly charged ions (Ar8+ or Xe25+ for example) allow to resonantly strip a few hundred atom sodium cluster of a number of delocalized weakly bound electrons without...

We discuss the Coulomb fragmentation of highly charged metal clusters. The analogy with a classical conducting liquid drop is assessed from molecular dynamics calculations. Experimentally, the highly charged metal clusters are formed in collisions with highly charged ions (Xe20+, Ar11+, Ar8+, Ar3+, and O5+) at low velocity. We show new experimental...