Improved Multi-GPU parallelization of a Lagrangian Transport Model

This report highlights our work on improving GPU parallelization by supporting compute nodes with multiple GPUs. However, since the default support for multi-GPUs in OpenACC is limited[6], the current implementation allows each MPI process to access only a single GPU. Thus, the only way to take full advantage of multi-GPU nodes in the current version is to launch multiple processes, which increases resource contention. We investigated the benefits of having only one process offload to all available GPU devices.Comment: Technical Repor

PARALLEL COMPUTATIONS WITH LARGE-SCALE AIR\ud POLLUTION MODELS

Large-scale mathematical models are very powerful tools in the efforts to provide more\ud information and more detailed information about the pollution levels, especially about pollution\ud levels which exceed certain critical values.. However, the model used must satisfy at\ud least two conditions: (i) it must be verified that the model results are reliable and (ii) it\ud should be possible to carry out different study by using the model. It is clear that comprehensive\ud studies about relationships between different input parameters and the model results\ud can only be carried out (a) if the numerical methods used in the model are sufficiently\ud fast and (b) if the code runs efficiently on the available high-speed computers.\ud Some results obtained recently by a new unified version of the Danish Eulerian Model will\ud be presented in this paper

Simulating Radiating and Magnetized Flows in Multi-Dimensions with ZEUS-MP

This paper describes ZEUS-MP, a multi-physics, massively parallel, message- passing implementation of the ZEUS code. ZEUS-MP differs significantly from the ZEUS-2D code, the ZEUS-3D code, and an early "version 1" of ZEUS-MP distributed publicly in 1999. ZEUS-MP offers an MHD algorithm better suited for multidimensional flows than the ZEUS-2D module by virtue of modifications to the Method of Characteristics scheme first suggested by Hawley and Stone (1995), and is shown to compare quite favorably to the TVD scheme described by Ryu et. al (1998). ZEUS-MP is the first publicly-available ZEUS code to allow the advection of multiple chemical (or nuclear) species. Radiation hydrodynamic simulations are enabled via an implicit flux-limited radiation diffusion (FLD) module. The hydrodynamic, MHD, and FLD modules may be used in one, two, or three space dimensions. Self gravity may be included either through the assumption of a GM/r potential or a solution of Poisson's equation using one of three linear solver packages (conjugate-gradient, multigrid, and FFT) provided for that purpose. Point-mass potentials are also supported. Because ZEUS-MP is designed for simulations on parallel computing platforms, considerable attention is paid to the parallel performance characteristics of each module. Strong-scaling tests involving pure hydrodynamics (with and without self-gravity), MHD, and RHD are performed in which large problems (256^3 zones) are distributed among as many as 1024 processors of an IBM SP3. Parallel efficiency is a strong function of the amount of communication required between processors in a given algorithm, but all modules are shown to scale well on up to 1024 processors for the chosen fixed problem size.Comment: Accepted for publication in the ApJ Supplement. 42 pages with 29 inlined figures; uses emulateapj.sty. Discussions in sections 2 - 4 improved per referee comments; several figures modified to illustrate grid resolution. ZEUS-MP source code and documentation available from the Laboratory for Computational Astrophysics at http://lca.ucsd.edu/codes/currentcodes/zeusmp2

Multilayered Heterogeneous Parallelism Applied to Atmospheric Constituent Transport Simulation

Heterogeneous multicore chipsets with many levels of parallelism are becoming increasingly common in high-performance computing systems. Effective use of parallelism in these new chipsets constitutes the challenge facing a new generation of large scale scientific computing applications. This study examines methods for improving the performance of two-dimensional and three-dimensional atmospheric constituent transport simulation on the Cell Broadband Engine Architecture (CBEA). A function offloading approach is used in a 2D transport module, and a vector stream processing approach is used in a 3D transport module. Two methods for transferring incontiguous data between main memory and accelerator local storage are compared. By leveraging the heterogeneous parallelism of the CBEA, the 3D transport module achieves performance comparable to two nodes of an IBM BlueGene/P, or eight Intel Xeon cores, on a single PowerXCell 8i chip. Module performance on two CBEA systems, an IBM BlueGene/P, and an eight-core shared-memory Intel Xeon workstation are given

High-Performance Computing and Four-Dimensional Data Assimilation: The Impact on Future and Current Problems

This is the final technical report for the project entitled: "High-Performance Computing and Four-Dimensional Data Assimilation: The Impact on Future and Current Problems", funded at NPAC by the DAO at NASA/GSFC. First, the motivation for the project is given in the introductory section, followed by the executive summary of major accomplishments and the list of project-related publications. Detailed analysis and description of research results is given in subsequent chapters and in the Appendix

Parallel Computations with Large-scale Air Pollution Models

Large-scale mathematical models are very powerful tools in the efforts to provide more information and more detailed information about the pollution levels, especially about pollution levels which exceed certain critical values.. However, the model used must satisfy at least two conditions: (i) it must be verified that the model results are reliable and (ii) it should be possible to carry out different study by using the model. It is clear that comprehensive studies about relationships between different input parameters and the model results can only be carried out (a) if the numerical methods used in the model are sufficiently fast and (b) if the code runs efficiently on the available high-speed computers. Some results obtained recently by a new unified version of the Danish Eulerian Model will be presented in this paper.Великомасштабні математичні моделі – дуже потужний інструмент для одержання більш детальної інформації щодо рівнів забруднень. Проте використовувана модель повинна задовольнити принаймні двом умовам: (i) результати моделювання повинні бути надійними і (ii) повинна існувати можливість уточнення і вивчення різноманітних характеристик моделей. Всебічне вивчення відношень між різноманітними параметрами входу і результатами моделювання може бути виконане, якщо (a) чисельні методи, використовувані в моделі, достатньо швидкі та (b) програмне забезпечення на доступних швидкодіючих комп'ютерах достатньо ефективне. Подані результати рівнобіжної реалізації моделювання забруднення атмосфери, отримані в новій об'єднаній версії датської Ейлерової моделі.Крупномасштабные математические модели – очень мощный инструмент для получения более детальной информации относительно уровней загрязнений. Однако модель должна удовлетво- рить по крайней мере двум условиям: (i) результаты моделирования должны быть надежными и (ii) должна существовать возможность уточнения и изучения характеристик модели. Всестороннее изучение отношений между различными параметрами входа и результатами моделирования может быть выполнено, если (a) численные методы, используемые в модели, достаточно быстры и (b) программное обеспечение на доступных быстродействующих компь- ютерах достаточно эффективно. Представлены результаты параллельной реализации моделирования загрязнения атмосферы, полученные в новой объединенной версии датской Эйлеровой модели

Parallelization and visual analysis of multidimensional fields: Application to ozone production, destruction, and transport in three dimensions

Atmospheric modeling is a grand challenge problem for several reasons, including its inordinate computational requirements and its generation of large amounts of data concurrent with its use of very large data sets derived from measurement instruments like satellites. In addition, atmospheric models are typically run several times, on new data sets or to reprocess existing data sets, to investigate or reinvestigate specific chemical or physical processes occurring in the earth's atmosphere, to understand model fidelity with respect to observational data, or simply to experiment with specific model parameters or components