CAREER: Programming the Existing and Emerging Memory Systems for Extreme-scale Parallel Performance

高性能计算(HPC)专注于使用数值模型来模拟复杂的科学和工程现象，如星系、天气和气候、分子相互作用、电网和飞行中的飞机。在接下来的十年中，我们的目标是建立能够极高性能(每秒1exaflop(1018)次运算)和处理1018艾字节(1018)数据的HPC并行系统。然而，实现极致性能的最大挑战之一是所谓的硬件内存墙，这是关于CPU执行的计算速度和从内存系统向CPU提供数据的速度之间日益扩大的差距(大约慢100倍)。现代HPC系统的低性能效率(平均60%，可能低至5%)体现了内存墙的影响，因为大量的计算周期被浪费在等待输入数据的到达上。创建有效的软件解决方案，以实现硬件的计算潜力，提高现有和未来计算系统的效率和可用性，变得非常关键。这样的解决方案将使使用并行计算机解决科学和工程问题的广泛学科显著受益，并加快科学发现和问题解决，以提高社会生活质量。这个职业项目开发了创新的软件技术，以解决现有和新兴存储系统的编程和性能挑战：1)用于编程、编译和执行并行应用程序的可移植抽象机模型，2)用于数据映射、移动和一致性的新编程接口和模型，以及3)机器感知编译和数据感知调度技术，以实现隐藏数据移动延迟的异步任务流执行模型。它通过开发以内存为中心的编程范例来解决内存墙挑战，以帮助实现并行应用程序的极端规模性能，并将对可编程性的损害降至最低。在教育方面，该项目涉及从高中开始的高性能计算和计算机科学领域的更广泛的社区。

High performance computing (HPC) focuses on using numerical model to simulate complex science and engineering phenomena, such as galaxies, weather and climate, molecular interactions, electric power grids, and aircraft in flight. Over the next decade the goal is to build HPC parallel system capable of extreme-scale performance (one exaflop (1018)operations per second) and processing exabyte (1018) of data. However, one of the biggest challenges of achieving extreme-scale performance is what is known as the hardware memory wall, which is about the growing gap between the speed of computation performed by CPU and the speed of supplying data to the CPU from memory systems (about x100 time slower). The low performance efficiency of modern HPC system (average 60% and could be as low as 5%) manifests the memory wall impact since a huge amount of computation cycles are wasted for waiting for the arrival of input data. It becomes very critical to create effective software solutions for achieving the computation potential of hardware and for improving the efficiency and usability of the existing and future computing system. Such solutions will significantly benefit a broad range of disciplines that use parallel computers to solve scientific and engineering problems, and accelerate scientific discovery and problem solving to improve quality of life of the society. This CAREER project develops innovative software techniques to address the programming and performance challenges of the existing and emerging memory systems: 1) a portable abstract machine model for programming, compiling and executing parallel applications, 2) new programming interface and model for data mapping, movement, and consistency, and 3) machine-aware compilation and data-aware scheduling techniques to realize an asynchronous task flow execution model to hide the latency of data movement. It addresses the memory wall challenge by developing a memory-centric programming paradigm for helping achieve extreme-scale performance of parallel applications with minimum impairment to programmability. For education, the project involves a broader community starting from high school in the area of HPC and computer science.