Petaflops Geospace Simulations

近年来，人们共同努力开发地球总循环模型。S磁层呢？太阳与太阳风和地球的相互作用？美国的高层大气一直是空间科学界关注的焦点。朝着这个目标已经取得了很大的进展，但是很明显，计算需求非常大。该项目将开发一个具有千万亿次运算能力的OpenGGCM（开放地球空间环流模型）版本，这是一个地球？磁层、电离层和热层。OpenGGCM在计算上具有挑战性的部分是MHD磁层核心代码，在目前的代码中，该代码的分辨率不足，并且缺乏一些必要的物理来模拟磁层-太阳风相互作用的一些关键方面。千万亿次的OpenGGCM将通过包含针对新硬件（如IBM Cell宽带引擎（CBE））的优化代码来克服这些限制。该项目还将开发一个代码库，可以智能地减少和压缩模拟的数据输出。这种I/O减少对于千兆级模拟是必要的，因为I/O带宽和容量跟不上CPU性能。压缩技术将使用小波压缩在输出数据写入存储之前减少输出数据。这将有助于从模拟中提取最优数量的信息。该项目为下一代地球空间模拟奠定了基础，有望研究空间物理的最基本问题。这将是第一次真正的多尺度模拟，涵盖了从全球磁层尺度到流体近似失效的最小尺度的所有尺度。模型分辨率的提高将大大减少数值效应，使研究湍流等耗散敏感现象及其影响成为可能。I/O减少算法的发展引入了一种新的方法来缓解千兆级系统固有的I/O瓶颈。在此项目期间开发的所有代码都将公开提供。具体来说，支持千兆级的P-OpenGGCM将在社区协调建模中心（CCMC）提供按需运行，并且开发用于利用CBE架构和执行I/O压缩的库将公开提供。OpenGGCM不仅是一个研究工具，也是空间天气预测的候选模型，因此具有重大社会影响的潜力。该项目对模型的改进将大大提高其在这方面的价值。压缩库将是通用工具，可用于任何千万亿次模拟，使用三维直线网格上的时间序列数据。

In recent years a concerted effort to develop General Circulation Models of Earth?s magnetosphere and it?s interaction with the solar wind and Earth?s upper atmosphere has been a major focus of the space sciences community. Much progress has been made toward this goal, but it has become clear that the computational requirements are very large. This project will develop a petaflop-capable version of the OpenGGCM (Open Geospace General Circulation Model), which is a coupled community model of the Earth?s magnetosphere, ionosphere, and thermosphere. The computationally challenging part of the OpenGGCM is the MHD magnetosphere core code which, in the current code, is under-resolved and lacks some of the necessary physics to model some of the key aspects of the magnetosphere - solar wind interaction. The petaflop OpenGGCM will overcome these limitations by including optimized code for new hardware, such as the IBM Cell Broadband Engine (CBE). The project will also develop a code library that intelligently reduces and compresses the data output from the simulation. Such I/O reduction becomes necessary for petascale simulations because I/O bandwidth and capacity does not keep pace with CPU performance. The compression technique will use wavelet compression to reduce output data before they are written to storage. This will facilitate the extraction of the optimal amount of information from the simulation. This project lays the groundwork for the next generation of geospace simulations, which promise to allow the study of the most fundamental problems of space physics. These will be the first true multiscale simulations that encompass all scales from the global scale of the magnetosphere down to the smallest scales at which the fluid approximation breaks down. The increased model resolution will dramatically reduce numerical effects and will make it possible to study dissipation sensitive phenomena such as turbulence and its effects. The development of I/O reduction algorithms introduces a new approach to mitigate the I/O bottlenecks inherent to petascale systems. All code developed during this project will be publicly available. Specifically, the petascale enabled P-OpenGGCM will be made available at the Community Coordinated Modeling Center (CCMC) for runs on demand, and the libraries developed to exploit the CBE architecture and to perform I/O compression will be made publicly available. The OpenGGCM is not just a research tool but also a candidate model for Space Weather prediction, and thus has the potential for a significant societal impact. The model improvements from this project will enhance its value in this capacity significantly. The compression libraries will be generic tools that can be utilized by any petascale simulation using time series data on three-dimensional rectilinear grids.