SHF:Large:Collaborative Research:Unified Runtime for Supporting Hybrid Programming Models on Heterogeneous Architecture

大多数传统的高端计算(HEC)应用程序和当前的千万亿级应用程序都是使用消息传递接口(MPI)编程模型编写的。其中一些应用程序在MPI+OpenMP模式下运行。然而，对于表现出不规则和动态通信模式的应用程序来说，使用MPI或MPI+OpenMP并保持性能是非常困难的。分区GlobalAddress Space(PGAS)编程模型为这些应用程序提供了一种表达并行性的灵活方式。加速器引入了其他编程模型：CUDA、OpenCL或Openacc。因此，新兴的异构体系结构需要支持多种混合编程模型：MPI+OpenMP、MPI+PGAS和MPI+PGAS+OpenMP，并带有用于多级别并行的扩展API。不幸的是，对于当前和下一代HEC系统上的一系列应用程序，没有一个统一的运行时可以为所有这些混合编程模型提供最佳的性能和可伸缩性。这就带来了一个广泛的挑战：“能否为混合编程模型设计一个统一的运行时，提供比其各部分之和更大的好处？”俄亥俄州立大学(OSU)和俄亥俄超级计算机中心(OSC)的计算机科学家，以及来自加州大学圣地亚哥分校(UCSD)的德克萨斯高级计算中心(TACC)和圣地亚哥超级计算机中心(SDSC)的计算科学家，提出了一个协同和综合的研究计划，以创新的解决方案来应对上述广泛的挑战。研究人员将具体解决以下挑战：1)对于千万亿级应用程序集使用混合编程模型的要求和限制是什么？2)统一运行时需要什么特性和机制？3)如何设计和实现统一运行时和编程模型API的相关扩展？4)如何设计候选千万亿级应用程序以利用建议的统一运行时？以及5)建议的方法可以获得哪些好处(在性能、可伸缩性和生产率方面)？这项研究将由一组来自NSF计算科学研究人员的应用程序驱动，这些研究人员在OSC、SDSC和OSU的Ranger和其他系统上进行大规模模拟。建议的设计将被集成到开源的MVAPICH2库中。在TACC、SDSC和OSC建立的全国性培训和推广计划将用于传播这项研究的结果。

Most of the traditional High-End Computing (HEC) applications andcurrent petascale applications are written using the Message PassingInterface (MPI) programming model. Some of these applications are runin MPI+OpenMP mode. However, it can be very difficult to use MPI orMPI+OpenMP and maintain performance for applications which demonstrateirregular and dynamic communication patterns. The Partitioned GlobalAddress Space (PGAS) programming model presents a flexible way forthese applications to express parallelism. Accelerators introduceadditional programming models: CUDA, OpenCL or OpenACC. Thus, theemerging heterogeneous architectures require support for varioushybrid programming models: MPI+OpenMP, MPI+PGAS, and MPI+PGAS+OpenMPwith extended APIs for multiple levels of parallelism. Unfortunately,there is no unified runtime which delivers the best performance andscalability for all of these hybrid programming models for a range ofapplications on current and next-generation HEC systems. This leadsto the following broad challenge: "Can a unified runtime for hybridprogramming model be designed which can provide benefits that aregreater than the sum of its parts?"A synergistic and comprehensive research plan, involving computerscientists from The Ohio State University (OSU) and Ohio SupercomputerCenter (OSC) and computational scientists from the Texas AdvancedComputing Center (TACC) and San Diego Supercomputer Center (SDSC),University of California San Diego (UCSD), is proposed to address theabove broad challenge with innovative solutions. The investigatorswill specifically address the following challenges: 1) What are therequirements and limitations of using hybrid programming models for aset of petascale applications? 2) What features and mechanisms areneeded in a unified runtime? 3) How can the unified runtime andassociated extension to programming model APIs be designed andimplemented? 4) How can candidate petascale applications beredesigned to take advantage of proposed unified runtime? and 5) Whatkind of benefits (in terms of performance, scalability andproductivity) can be achieved by the proposed approach? The researchwill be driven by a set of applications from established NSFcomputational science researchers running large scale simulations onRanger and other systems at OSC, SDSC and OSU. The proposed designswill be integrated into the open-source MVAPICH2 library. Theestablished national-scale training and outreach programs at TACC,SDSC and OSC will be used to disseminate the results of this research.