XPS: FULL: FP: Tools and Algorithms for Resilient, Power-efficient ExaScale Computing Using the GNU-CAF Compiler

具有技术意义和深刻科学兴趣的各种问题需要使用具有最高并行水平的并行计算机。因此，科学界普遍认为，这项研究需要在Exascale计算机上进行，即计算机的计算能力比今天的计算机大一千倍。但是，扩大规模的技术努力也带来了一些随之而来的问题，例如能够重用现有代码，并使普通开发人员能够编写可扩展的软件，这些软件在功耗方面也是有效的，并且是容错的。这个项目通过提供一个开源（GNU许可），免费的FORTRAN编译器来满足这些需求，该编译器可以使现有的代码为Exascale做好准备，并且允许程序员只需要熟悉FORTRAN（并且有很多）来开发可扩展的，节能的和容错的代码，而不必学习过多的新编程技能。该项目还将为首席研究员编写的科学计算教科书以及团队中其他2名研究人员编写的高性能计算教科书做出贡献。项目网站已经存在，将向公众免费传播这些知识。这个网站每年的点击量已经超过5万次。该提案将取得以下变革性进展：1）开发一个成熟的，开源的，Exascale就绪的GNU编译器，实现Fortran 2008标准的新颖并行功能。这些Fortran特性以CoarrayFortran（CAF）的名称命名。最近的工作表明，CAF是竞争力或优于最近的MPI-3标准，同时允许最终用户表达Petascale级并行更简单。未来的体系结构应该使单边CAF风格的消息传递与其他消息传递风格相比功耗更低。2）Exascale计算机将需要支持核心之间的十亿路并发，结果是节点可能会经常失败。必须在编译器技术和最终用户应用程序中建立故障恢复能力。将在GNU编译器中实现故障恢复能力的早期实现，并将用于探索这些功能如何在一大类计算流体动力学（CFD）算法中工作。3）Exascale应用程序也将不得不非常节省地使用功率。这只能通过决定何时将资源集中在通信上，何时将资源集中在计算上来实现。需要新的算法，将相对适度的通信量与大量的计算量穿插在一起。此外，专家级算法开发人员应该能够通过编译器指令将这些不同的资源需求传达给运行时系统。拟议的工作将开发一类高精度CFD算法，可以通过GNU编译器中的编译器扩展将其资源需求传达给运行时系统。

Various problems of technological significance as well as of deep scientific interest require the use of parallel computers with the highest levels of parallelism. Thus, it is well-recognized in the scientific community that this research needs to be performed on Exascale computers, i.e. computers that have a thousand-fold greater computing power than computers today. But the technological endeavour of scaling-up comes with several attendant problems, such as being able to reuse existing code and giving the ability to ordinary developers to write scalable software that is also efficient with respect to power consumption, and is fault tolerant. This project addresses these needs by providing a open-source (GNU licensed), free, FORTRAN compiler that can make existing code Exascale ready, and which allows a programmer who only needs to be familiar with FORTRAN (and there are many of those) to develop scalable, power-efficient and fault-tolerant code, without having to learn an inordinate amount of new programming skills. The project will also contribute to a textbook on scientific computation that is being written by the Principal Investigator, as well as to a textbook on high performance computing that is being written by 2 other researchers on the team. The project website already exists that will freely distribute such knowledge to the public. This website already gets more than 50,000 hits per year. The proposal will make the following transformative advances:1) Develop a full-fledged, open-source, Exascale-Ready GNU compiler that implements novel parallel features of the Fortran 2008 standard. These Fortran features go under the name of Coarray Fortran (CAF). Recent work has shown that CAF is either competitive or outperforms the recent MPI-3 standard while allowing the end-user to express Petascale-class parallelism much more simply. Future architectures should make the one-sided CAF-style messaging much less power-hungry compared to alternative styles of messaging.2) Exascale computers will need to support billion-way concurrency among cores, with the result that nodes might fail quite frequently. Resiliency to failure will have to be built into the compiler technologies and end-user application. An early implementation of failure-resiliency within the GNU compiler will be made and it will be used to explore how those features work within a large class of Computational Fluid Dynamics (CFD) algorithms.3) Exascale applications will also have to use power very parsimoniously. This can only be done by deciding when to focus resources on communication and when to focus them on computation. New algorithms are needed that intersperse relatively modest amounts of communication with large amounts of computation. Furthermore, the expert-level algorithm developer should be able to communicate these different resource needs to the run-time system via compiler directives. The proposed work will develop a class of high-accuracy CFD algorithms that can communicate their resource needs to the run-time system via compiler extensions in the GNU compiler.