Collaborative Research: EAGER: Real-time Strategies and Synchronized Time Distribution Mechanisms for Enhanced Exascale Performance-Portability and Predictability

几十年来，整个科学和工程领域的进步都是由高性能计算(HPC)推动的，随着计算能力的不断创新，发现的速度也在加快。但随着半导体技术现在面临基本的物理限制，即使大规模系统正在达到仓库规模，新的方法也变得对实现计算资源的有效利用至关重要。特别是，考虑到规模的这种差异，高性能计算系统必然变得更加分布式和异步(从系统时钟是异步的意义上讲)，导致越来越多的可变和不可预测的执行。虽然这些影响被认为是高性能混凝土性能的关键障碍，但其机制尚未完全了解。然而，已知的是，许多HPC基础设施的任务是处理因异步、可变性和不可预测性而导致的低效，从而导致深度和复杂的硬件/软件支持堆栈。项目团队的假设是，虽然每个堆栈元素提供了一个局部解决方案，但它也可能加剧全球问题：这种复杂性导致了更多的可变性，而不是更少，并使确定其原因变得更加困难。该项目探讨了通过移除和简化支持层来扭转日益复杂的趋势的可能性。然而，这一策略的可实现收益仍然有限，而根本原因--执行异步--仍然没有得到解决。这种方法首先利用最近开发的技术，使时钟即使在行星范围内分布时也能保持极高的精度。这种准确的分布式时钟用于支持良性循环，其中同步建立基线可预测性，进而减少变异性，并且在周期的每个阶段能够降低支持堆栈的复杂性。这种方法的一个好处是，各个步骤在很大程度上都很简单，可以直接应用于现有的软件系统。这个为期一年的项目旨在获得关于同步性和可预测性对提高HPC计算效率从而改善大规模程序执行的重要性的早期发现和实际演示。共进行了五项工作。首先是通过扩展现有的HPC网络基础设施来演示精确时钟分配的可行性。第二个是演示同步在建立良性循环方面的应用，以简化软件/系统支持堆栈。第三是设计使用所提出的方法对系统进行建模、测量和验证的机制。第四个是调查在不同的应用程序类别中应用基于同步的良性循环的相对好处。第五个是通过一个涉及生产应用的案例研究来证明所提出的方法的总体效果。总体而言，该项目致力于确定通过准确的时钟增加的同步是否能够在计算资源的使用效率方面显著改进HPC计算。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Advances throughout science and engineering have for several decades been driven by High Performance Computing (HPC), with the pace of discovery accelerating in concert with continued innovation in computing capabilities. But as semiconductor technology now faces fundamental physical limits, even while large-scale systems are reaching warehouse scales, new approaches are becoming essential to achieving efficient use of computing resources. In particular, given this divergence of scales, HPC systems have necessarily become more distributed and asynchronous (in the sense that system clocks are asynchronous), resulting in increasingly variable and unpredictable execution. While these effects are recognized as critical hindrances to HPC performance, the mechanisms are not yet fully understood. What is known, however, is that much HPC infrastructure is tasked with dealing with inefficiency derived from asynchrony, variability, and unpredictability, leading to a deep and complex hardware/software support stack. The project team's hypothesis is that while each stack element provides a local solution, it may also exacerbate the global problem: that complexity has resulted in more variability, not less, and made determining its causes more difficult. This project explores the possibility of reversing the trend of ever-increasing complexity by removing and simplifying support layers. This strategy’s achievable gains remain limited, however, while the underlying cause, execution asynchrony, remains unaddressed. The approach begins by leveraging recently developed technology that enables clocks to remain extremely accurate even when distributed on a planetary scale. Such accurate, distributed clocks serve to underpin a virtuous cycle where synchrony establishes baseline predictability, which, in turn, reduces variability, and at each stage of the cycle enables reduction in the complexity of the support stack. A benefit of this approach is that the individual steps are largely simple and can be applied directly to existing software systems. This one-year project aims to obtain early findings and practical demonstrations for the importance of synchrony and predictability to increase HPC compute efficiency and thereby improve large-scale program execution. Five tasks are conducted. The first is to demonstrate the feasibility of accurate clock distribution by augmenting existing HPC network infrastructure. The second is to demonstrate the application of synchrony in the establishing a virtuous cycle enabling simplifications to the software/system support stack. The third is to devise mechanisms to model, measure, and validate systems using the proposed methods. The fourth is to investigate the relative benefits of applying the synchrony-based virtuous cycle with respect to various application classes. The fifth is to demonstrate the overall efficacy of the proposed approach through a case study involving a production application. Overall, the project works to determine whether added synchronization through accurate clocks enables significant improvements to HPC computations in terms of how efficiently they use computational resources.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.