SI2-SSE: Petascale Enzo: Software Infrastructure Development and Community Engagement

该项目的目的是开发一个天体物理学和宇宙学软件应用程序“Enzo-P”，建立在高度可扩展的并行自适应网格细化（AMR）软件框架“Cello”上，该框架正在同时开发。Enzo-P应用程序将能够运行极端尺度的数值模拟，以研究恒星形成、分子云湍流、星际介质动力学、星系形成、星系间介质、第一批恒星和星系的形成、星系团和宇宙再电离等前沿问题。这个新软件将使当前庞大而多样化的Enzo用户/开发人员社区能够充分利用当前和未来的高性能计算机（HPC）系统。Cello AMR框架可以独立于Enzo-P使用，从而使其他不同科学领域的研究人员能够开发能够在“千兆级及以上”HPC平台上运行的AMR应用程序。Cello使用的新方法是使用charm++并行编程系统实现“八叉树森林”AMR方案。基于八树的AMR已被证明是最高可伸缩性的AMR方法之一，可以扩展到超过200K的CPU内核。面向对象的并行编程语言Charm++支持数据驱动的异步执行，具有固有的延迟容忍性，并自动将计算与通信重叠，并为开发Exascale应用程序提供支持，包括内存中的分布式检查点和复杂的动态负载平衡方案。Enzo- p的开发将由充满活力的Enzo开放开发社区指导，他们将把Enzo的自重力、宇宙学、化学和冷却、MHD和辐射流体动力学能力迁移到Cello可扩展的AMR框架中。

The purpose of this project is to develop an astrophysics and cosmology software application "Enzo-P", built on the highly scalable parallel adaptive mesh refinement (AMR) software framework "Cello" that is being developed concurrently. The Enzo-P application will be capable of running extreme scale numerical simulations to investigate frontier questions in star formation, molecular cloud turbulence, interstellar medium dynamics, galaxy formation, intergalctic medium, formation of the first stars and galaxies, galaxy clusters, and cosmic reionization. This new software will empower the current large and diverse Enzo user/developer community to take full advantage of current and future high performance computer (HPC) systems. The Cello AMR framework can be used independently of Enzo-P, thus enabling researchers in other diverse scientific fields to develop AMR applications capable of running on "Petascale-and-beyond" HPC platforms. The novel approach used for Cello is to implement a "forest-of-octree" AMR scheme using the Charm++ parallel programming system. Octree-based AMR has been shown to be among the highest scaling AMR approaches, with demonstrated scaling to over 200K CPU cores. The Charm++ object-oriented parallel programming language supports data-driven asynchronous execution, is inherently latency-tolerant and automatically overlaps computation with communication, and provides support for developing Exascale applications, including in-memory distributed checkpointing and sophisticated dynamic load balancing schemes. Enzo-P development will be directed by the vibrant Enzo open development community, who will migrate Enzo's self-gravity, cosmology, chemistry and cooling, MHD, and radiation hydrodynamics capabilities to use the Cello scalable AMR framework.