In a recent publication (Eghtesad et al., 2018), we have reported a message passing interface (MPI)-based domain decomposition parallel implementation of an elasto-viscoplastic fast Fourier ...transform-based (EVPFFT) micromechanical solver to facilitate computationally efficient crystal plasticity modeling of polycrystalline materials. In this paper, we present major extensions to the previously reported implementation to take advantage of graphics processing units (GPUs), which can perform floating point arithmetic operations much faster than traditional central processing units (CPUs). In particular, the applications are developed to utilize a single GPU and multiple GPUs from one computer as well as a large number of GPUs across nodes of a supercomputer. To this end, the implementation combines the OpenACC programming model for GPU acceleration with MPI for distributed computing. Moreover, the FFT calculations are performed using the efficient Compute Unified Device Architecture (CUDA) FFT library, called CUFFT. Finally, to maintain performance portability, OpenACC-CUDA interoperability for data transfers between CPU and GPUs is used. The overall implementations are termed ACC-EVPCUFFT for single GPU and MPI-ACC-EVPCUFFT for multiple GPUs. To facilitate performance evaluation studies of the developed computational framework, deformation of a single phase copper is simulated, while to further demonstrate utility of the implementation for resolving fine microstructures, deformation of a dual-phase steel DP590 is simulated. The implementations and results are presented and discussed in this paper.
•A Multi-GPU implementation of EVPFFT model is developed by coupling MPI and OpenACC.•OpenACC-CUDA interoperability is used to facilitate CUDA implementation within OpenACC.•Compute unified device architecture FFT library is used to accelerate FFT calculations.•P100 GPU outperforms 64 Intel Xeon 2695 v4 processes for an RVE size of 1283 or greater.•The GPU implementation facilitates massive crystal plasticity simulations using EVPFFT.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Proton mirror modes are large amplitude nonpropagating structures frequently observed in the magnetosheath. It has been suggested that electron temperature anisotropy can enhance the proton mirror ...instability growth rate while leaving the proton cyclotron instability largely unaffected, therefore causing the proton mirror instability to dominate the proton cyclotron instability in Earth's magnetosheath. Here we use particle‐in‐cell simulations to investigate the electron temperature anisotropy effects on proton mirror instability evolution. Contrary to the hypothesis, electron temperature anisotropy leads to excitement of the electron whistler instability. Our results show that the electron whistler instability grows much faster than the proton mirror instability and quickly consumes the electron‐free energy so that there is no electron temperature anisotropy left to significantly impact the evolution of the proton mirror instability.
Key Points
Temperature anisotropy instabilities in space plasma
Effects of proton to electron mass ratio in particle‐in‐cell simulations of the proton mirror instability
Effects of electron temperature anisotropy on the growth and saturation of proton cyclotron and proton mirror instabilities
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Abstract Energy dissipation in collisionless plasmas is one of the most outstanding open questions in plasma physics. Magnetic reconnection and turbulence are two phenomena that can produce the ...conditions for energy dissipation. These two phenomena are closely related to each other in a wide range of plasmas. Turbulent fluctuations can emerge in critical regions of reconnection events, and magnetic reconnection can occur as a product of the turbulent cascade. In this study, we perform 2D particle-in-cell simulations of a reconnecting Harris current sheet in the presence of turbulent fluctuations to explore the effect of turbulence on the reconnection process in collisionless nonrelativistic pair plasmas. We find that the presence of a turbulent field can affect the onset and evolution of magnetic reconnection. Moreover, we observe the existence of a scale-dependent amplitude of magnetic field fluctuations above which these fluctuations are able to disrupt the growing of magnetic islands. These fluctuations provide thermal energy to the particles within the current sheet and preferential perpendicular thermal energy to the background population.
We present ADIOS 2, the latest version of the Adaptable Input Output (I/O) System. ADIOS 2 addresses scientific data management needs ranging from scalable I/O in supercomputers, to data analysis in ...personal computer and cloud systems. Version 2 introduces a unified application programming interface (API) that enables seamless data movement through files, wide-area-networks, and direct memory access, as well as high-level APIs for data analysis. The internal architecture provides a set of reusable and extendable components for managing data presentation and transport mechanisms for new applications. ADIOS 2 bindings are available in C++11, C, Fortran, Python, and Matlab and are currently used across different scientific communities. ADIOS 2 provides a communal framework to tackle data management challenges as we approach the exascale era of supercomputing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We present the Exascale Framework for High Fidelity coupled Simulations (EFFIS), a workflow and code coupling framework developed as part of the Whole Device Modeling Application (WDMApp) in the ...Exascale Computing Project. EFFIS consists of a library, command line utilities, and a collection of run-time daemons. Together, these software products enable users to easily compose and execute workflows that include: strong or weak coupling, in situ (or offline) analysis/visualization/monitoring, command-and-control actions, remote dashboard integration, and more. We describe WDMApp physics coupling cases and computer science requirements that motivate the design of the EFFIS framework. Furthermore, we explain the essential enabling technology that EFFIS leverages: ADIOS for performant data movement, PerfStubs/TAU for performance monitoring, and an advanced COUPLER for transforming coupling data from its native format to the representation needed by another application. Finally, we demonstrate EFFIS using coupled multi-simulation WDMApp workflows and exemplify how the framework supports the project’s needs. We show that EFFIS and its associated services for data movement, visualization, and performance collection does not introduce appreciable overhead to the WDMApp workflow and that the resource-dominant application’s idle time while waiting for data is minimal.
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The inclusion of kinetic effects into fluid models has been a long standing problem in magnetic reconnection and plasma physics. Generally, the pressure tensor is reduced to a scalar which is an ...approximation used to aid in the modelling of large scale global systems such as the Earth's magnetosphere. This unfortunately omits important kinetic physics which have been shown to play a crucial role in collisionless regimes. The multi-fluid ten-moment model, however, retains the full symmetric pressure tensor. The ten-moment model is constructed by taking moments of the Vlasov equation up to second order, and includes the scalar density, the vector bulk-flow and the symmetric pressure tensor for a total of ten separate components. Use of the multi-fluid ten-moment model requires a closure which truncates the cascading system of equations. Here we look to leverage data-driven methodologies to seek a closure which may improve the physical fidelity of the ten-moment multi-fluid model in collisionless regimes. Specifically, we use the sparse identification of nonlinear dynamics (SINDy) method for symbolic equation discovery to seek the truncating closure from fully kinetic particle-in-cell simulation data, which inherently retains the relevant kinetic physics. We verify our method by reproducing the ten-moment model from the particle-in-cell (PIC) data and use the method to generate a closure truncating the ten-moment model which is analysed through the nonlinear phase of reconnection.
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•Models at grain-level, microstructural cell-level, and component-level are linked into a multi-level modeling framework.•The widely-used elasto-visco-plastic fast Fourier transform ...model is implemented in Abaqus standard.•Constitutive response at each integration point is that of the elasto-visco-plastic microstructural cell, which evolves with strain.•The implementation is a high-performance parallel computing with CPUs at the mesh-level and GPUs at the microstructure-level.•Several benchmark and application case studies are used to illustrate potential and versatility of the multi-level approach.
This paper presents an implementation of the elasto-visco-plastic fast Fourier transform (EVPFFT) crystal plasticity model in the implicit finite element (FE) method of Abaqus standard through a user material (UMAT) subroutine to provide a constitutive relationship between stress and strain at FE integration points. To facilitate the implicit coupling ensuring fast convergence rates, an analytical Jacobian is derived. The constitutive response at every integration point is obtained by the full-field homogenization over an explicit microstructural cell. The implementation is a parallel computing approach involving multi-core central processing units (CPUs) and graphics processing units (GPUs) for computationally efficient simulations of large plastic deformation of metallic components with arbitrary geometry and loading boundary conditions. To this end, the EVPFFT solver takes advantages of GPU acceleration utilizing Nvidia’s high performance computing software development kit (SDK) compiler and compute unified device architecture (CUDA) FFT libraries, while the FE solver leverages the message passing interface (MPI) for parallelism across CPUs. The high-performance hybrid CPU-GPU multi-level framework is referred to as FE-GPU-EVPCUFFT. Simulations of simple compression of Cu and large strain cyclic reversals of dual phase (DP) 590 have been used to benchmark the accuracy of the implementation in predicting the mechanical response and texture evolution. Subsequently, two applications are presented to illustrate the potential and utility of the multi-level simulation strategy: 4-point bending of textured Zr bars, in which the model captures the shape variations as a consequence of texture with respect to the bending plane and another bending of DP1180, in which the model reveals details of spatial micromechanical fields.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We studied the role of electron physics in 3‐D two‐fluid 10‐moment simulation of Ganymede's magnetosphere. The model captures nonideal physics like the Hall effect, electron inertia, and anisotropic, ...nongyrotropic pressure effects. A series of analyses were carried out: (1) The resulting magnetic field topology and electron and ion convection patterns were investigated. The magnetic fields were shown to agree reasonably well with in situ measurements by the Galileo satellite. (2) The physics of collisionless magnetic reconnection were carefully examined in terms of the current sheet formation and decomposition of generalized Ohm's law. The importance of pressure anisotropy and nongyrotropy in supporting the reconnection electric field is confirmed. (3) We compared surface “brightness” morphology, represented by surface electron and ion pressure contours, with oxygen emission observed by the Hubble Space Telescope. The correlation between the observed emission morphology and spatial variability in electron/ion pressure was demonstrated. Potential extension to multi‐ion species in the context of Ganymede and other magnetospheric systems is also discussed.
Plain Language Summary
Jupiter's moon, Ganymede, is revealed by many space missions to have a dipole magnetic field, much like the Earth's. Unlike the Earth's strong dipole field, however, Ganymede is much smaller in size and its dipole field is also much weaker. Consequently, a great portion of energetic particles, accelerated in a process called “magnetic reconnection” near Ganymede, are able to travel at high speed and impact the moon's surface, exciting a bright aurora, in the polar regions. During this process, high‐energy electrons are supposed to play an important role, but their detailed dynamics have been rarely studied. We performed computational modeling of Ganymede, for the first time, revealing how electrons are accelerated near the moon and impact the polar regions of the moon. They turn out to be quite important in transporting the Jovian energy and materials to near Ganymede and might have a substantial influence on the strength and location of the bright aurora. The lessons we learned here can also help us to understand the space weather near the Earth, which is greatly controlled by the same magnetic reconnection process and where electron physics can also be critical.
Key Points
Nongyrotropic electron pressure tensor effects are important in Ganymede's collisionless magnetic reconnection
Electrons and ions form highly asymmetric and distinct drift patterns in the magnetosphere
Some key features of the observed oxygen emission morphologies are reproduced by the model
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