Collaborative Research: SI2-SSE: A Petascale Numerical Library for Multiscale Phenomena Simulations

多尺度现象对理论、模拟和实验都是一个巨大的挑战。很难理解最高和最低级别的现象，以及介于两者之间的所有现象。这一挑战出现在不同的领域。理解宇宙学结构的形成是宇宙学中长期存在的问题之一。在这一过程的计算机模拟中，挑战是在保留基本物理原理的同时提高网格分辨率。在酶的全原子分子动力学模拟中，挑战是模拟具有大量原子的系统，同时解决远程相互作用并具有足够高的吞吐量。这样的模拟对于理解重要的生物过程和最终设计新药至关重要。多尺度现象的另一个主要例子是湍流，这是一个丰富而复杂的主题，与当今的许多主要技术问题非常相关，包括气候、能源以及石油和生物危害的管理。了解湍流流动对于设计新型运输车辆、提高燃烧过程的效率和管理其环境污染是至关重要的。在这里，模拟在历史上一直是有限的，由于极高的计算成本，即使使用今天研究人员可用的高端计算系统，模拟仍然是有限的。降低这一成本，并有效地利用计算资源，往往需要专业的专业知识，以及大量的开发时间和成本，许多研究小组负担不起。该项目将开发一套强大的关键软件组件，以提供执行多尺度现象模拟的工具。该套件将采用最先进的技术来降低通信成本，通信成本已成为总模拟成本的最重要贡献因素，特别是在更大的规模上。它将提供一组灵活的功能，使其可以在跨学科的大量代码中使用。特别是，除了广泛使用的通信例程(转置、光晕交换)外，该库还将包括用户友好的界面，用于傅立叶变换、三维光谱和紧致微分。这种对可伸缩性能和丰富功能的强调相结合，使该套件在目前存在的其他库中是独一无二的。考虑到模拟多尺度现象的非同寻常的挑战，这个库将提供一条通向亿级的现实道路。该套件将在开放源码许可下提供。将通过项目网站、邮寄名单、用户调查和专题介绍进行用户外联。

Multiscale phenomena are a grand challenge for theory, simulations and experiments. It is difficult to understand phenomena at both highest and lowest scales, as well as all those in between. This challenge shows up in diverse fields. One of the long-standing problems in cosmology is understanding cosmological structure formation. In computer simulations of this process the challenge is increasing grid resolution while retaining the essential physics. In all-atom molecular dynamics simulations of enzymes the challenge is simulating systems with a large number of atoms while resolving long-range interactions and having sufficiently high throughput. Such simulations are critical in understanding important biological processes and eventually designing new drugs. Another prime example of multiscale phenomena is turbulent flows, a rich and complex subject of great relevance to many of the main technological issues of the day, including climate, energy, and the management of oil and biohazards. Understanding turbulent flows is critical for design of new transportation vehicles, improving efficiency of combustion processes and managing their environment pollution. Here simulations have been historically limited, and remain so, due to extremely high computational cost, even using the high-end computational systems available to researchers today. Reducing this cost, and efficiently using the computational resources, often requires specialized expertise, as well as significant development time and cost many research groups cannot afford. This project will develop a powerful suite of critical software components to provide tools for performing simulations of multiscale phenomena. The suite will implement state-of-the-art techniques for reducing communication cost, which has become the most important contributing factor to the total simulation cost, especially at larger scales. It will provide a flexible set of features that will make it usable in a great number of codes across the disciplines. In particular, the library will include user-friendly interfaces for Fourier transforms, spectral and compact differentiation in three dimensions, in addition to widely used communication routines (transposes, halo exchanges). This combination of emphasis on scalable performance and richness of features makes this suite unique among other libraries in existence today. Given the extraordinary challenge of simulations of multiscale phenomena, this library will provide a realistic path towards the Exascale. The suite will be available under an open source license. User outreach will be undertaken through the project website, mailing list, user surveys and presentations.