DISPATCH: A Numerical Simulation Framework for the Exa-scale Era. I. Fundamentals

We introduce a high-performance simulation framework that permits the semi-independent, task-based solution of sets of partial differential equations, typically manifesting as updates to a collection of `patches' in space-time. A hybrid MPI/OpenMP execution model is adopted, where work tasks are controlled by a rank-local `dispatcher' which selects, from a set of tasks generally much larger than the number of physical cores (or hardware threads), tasks that are ready for updating. The definition of a task can vary, for example, with some solving the equations of ideal magnetohydrodynamics (MHD), others non-ideal MHD, radiative transfer, or particle motion, and yet others applying particle-in-cell (PIC) methods. Tasks do not have to be grid-based, while tasks that are, may use either Cartesian or orthogonal curvilinear meshes. Patches may be stationary or moving. Mesh refinement can be static or dynamic. A feature of decisive importance for the overall performance of the framework is that time steps are determined and applied locally; this allows potentially large reductions in the total number of updates required in cases when the signal speed varies greatly across the computational domain, and therefore a corresponding reduction in computing time. Another feature is a load balancing algorithm that operates `locally' and aims to simultaneously minimise load and communication imbalance. The framework generally relies on already existing solvers, whose performance is augmented when run under the framework, due to more efficient cache usage, vectorisation, local time-stepping, plus near-linear and, in principle, unlimited OpenMP and MPI scaling.Comment: 17 pages, 8 figures. Accepted by MNRA

HPCCP/CAS Workshop Proceedings 1998

This publication is a collection of extended abstracts of presentations given at the HPCCP/CAS (High Performance Computing and Communications Program/Computational Aerosciences Project) Workshop held on August 24-26, 1998, at NASA Ames Research Center, Moffett Field, California. The objective of the Workshop was to bring together the aerospace high performance computing community, consisting of airframe and propulsion companies, independent software vendors, university researchers, and government scientists and engineers. The Workshop was sponsored by the HPCCP Office at NASA Ames Research Center. The Workshop consisted of over 40 presentations, including an overview of NASA's High Performance Computing and Communications Program and the Computational Aerosciences Project; ten sessions of papers representative of the high performance computing research conducted within the Program by the aerospace industry, academia, NASA, and other government laboratories; two panel sessions; and a special presentation by Mr. James Bailey

Advanced software techniques for data management systems. Volume 1: Study of software aspects of the phase B space shuttle avionics system

An overview of the executive system design task is presented. The flight software executive system, software verification, phase B baseline avionics system review, higher order languages and compilers, and computer hardware features are also discussed

The 21st Aerospace Mechanisms Symposium

During the symposium technical topics addressed included deployable structures, electromagnetic devices, tribology, actuators, latching devices, positioning mechanisms, robotic manipulators, and automated mechanisms synthesis. A summary of the 20th Aerospace Mechanisms Symposium panel discussions is included as an appendix. However, panel discussions on robotics for space and large space structures which were held are not presented herein

Proceedings, MSVSCC 2018

Proceedings of the 12th Annual Modeling, Simulation & Visualization Student Capstone Conference held on April 19, 2018 at VMASC in Suffolk, Virginia. 155 pp

Research & Technology Report Goddard Space Flight Center

The main theme of this edition of the annual Research and Technology Report is Mission Operations and Data Systems. Shifting from centralized to distributed mission operations, and from human interactive operations to highly automated operations is reported. The following aspects are addressed: Mission planning and operations; TDRSS, Positioning Systems, and orbit determination; hardware and software associated with Ground System and Networks; data processing and analysis; and World Wide Web. Flight projects are described along with the achievements in space sciences and earth sciences. Spacecraft subsystems, cryogenic developments, and new tools and capabilities are also discussed

Research and Technology Report. Goddard Space Flight Center

This issue of Goddard Space Flight Center's annual report highlights the importance of mission operations and data systems covering mission planning and operations; TDRSS, positioning systems, and orbit determination; ground system and networks, hardware and software; data processing and analysis; and World Wide Web use. The report also includes flight projects, space sciences, Earth system science, and engineering and materials

MIST: a portable and efficient toolkit for molecular dynamics integration algorithm development

The main contribution of this thesis is MIST, the Molecular Integration Simula- tion Toolkit, a lightweight and efficient software library written in C++ which provides an abstract interface to common Molecular Dynamics codes, enabling rapid and portable development of new integration schemes for Molecular Dynamics. The initial release provides plug-in interfaces to NAMD-Lite, GROMACS, Amber and LAMMPS and includes several standard integration schemes, a constraint solver, temperature control using Langevin Dynamics, temperature and pressure control using Nosé-Hoover chains, and five advanced sampling schemes. I describe the architecture, functionality and internal details of the library and the C and Fortran APIs which can be used to interface additional MD codes to MIST. As an example to future developers, each of the existing plug-ins and the integrators that are included with MIST are described. Brief instructions for compilation and use of the library are also given as a reference to users. The library is designed to be expressive, portable and performant, and I show via a range of test systems that MIST introduces negligible overheads for serial, parallel, and GPU-accelerated cases, except for Amber where the native integrators run directly on the GPU itself, but only run on the CPU in MIST. The capabilities of MIST for production-quality simulations are demonstrated through the use of a simulated tempering simulation to study the free energy landscape of Alanine-12 in both vacuum and detailed solvent conditions. I also present the evaluation and application of force-field and ab initio Molecular Dynamics to study the structural properties and behaviour of olivine melts. Three existing classical potentials for fayalite are tested and found to give lattice parameters and Radial Distribution Functions in good agreement with experimental data. For forsterite, lattice parameters at ambient pressure and temperature are slightly over-predicted by simulation (similar to other reported results in the literature). Likewise, higher-than expected thermal expansion coefficients and heat capacities are obtained from both ab initio and classical methods. The structure of both the crystal and melt are found to be in good agreement with experimental data. Several methodological improvements which could improve the accuracy of melting point determination and the thermal expansion coefficients are discussed