D7.3: Inventory of Exascale Tools and Techniques
Creators: name: Donnell, Nicola Mc
Publisher: name: Zenodo
Year: 2016
Subjects: Deliverable
HPC
Research infrastructure
GPGPU
Centres of Excellence
Exascale
MPI
OpenMP

description: The objective of the Partnership for Advanced Computing in Europe Fourth Implementation Phase project (PRACE-4IP) Work Package 7 (WP7) ‘Application Enabling and Support’ is to provide enabling support for High Performance Computing (HPC) applications codes, to ensure that these applications can effectively exploit multi-petaflop systems and future PRACE Exascale systems. Task 7.2, within WP7, ‘Preparing for Future PRACE Exascale Systems’ aims to investigate the various programming tools, languages, libraries and algorithms needed for future Exascale systems through an analysis and exploitation phase. The purpose of the analysis phase is to understand the needs of the HPC community and in doing so to develop links with the recently established Applications Centres of Excellence (CoEs) and build on existing links with European Exascale projects. A questionnaire was designed, which was circulated to through a Point of Contact (PoC) for each CoE. The analysed findings are the subject of this document. It is organised in two main sections, Section 2 :‘Review across questionnaires’, and Section 3 :‘Review across CoEs’.<br> The participating CoEs are: BioExcel, Centre of Excellence for Biomolecular Research; CoeGSS, Center of Excellence for Global Systems Science; E-CAM, An e-Infrastructure for software training and consultancy in simulation and modelling; EoCoE, Energy oriented Centre of Excellence for computer applications; ESiWACE, Excellence in Simulation of Weather and Climate in Europe; MaX Materials, Design@eXascale; NoMaD, The Novel Materials Discovery Laboratory; and POP, Performance Optimisation and Productivity. In Section 2, we summarise our findings separately by topic: programming interfaces and standards, debuggers and profilers, scalable libraries and algorithms and I/O management techniques, European Exascale projects, and general questions, where we focus on the most salient points to consider for the subsequent exploitation phase of Task 7.2a.<br> <em>Programming interfaces and standards</em><br> All the CoEs are using MPI (Message Passing Interface) and OpenMP (Open Multi-Processing), and all are using, or have an interest in, one or more of the GPU (Graphics Processing Unit) programming interfaces.<br> <em>Debuggers and Profilers</em><br> A wide variety of tools are used, 17 in total, and the regularity with which they are used varies greatly across the centres. However, all centres still use manual or console based debugging and profiling to a high degree. Scalasca, a tool for analysing the runtime behaviour and performance of parallel programs, is also used by all centres, though with less regularity. Most tools were seen as being easy to use with the exception of Extrae/Paraver, trace performance analyzer tools, and Intel VTune, a performance insight tool.<br> <em>Scalable Libraries and Algorithms</em><br> One library that has been identified as being commonly exploited by several CoEs is the FFTW library, a well-known FFT (Fast Fourier Transform) library. It is clear that classical HPC library domains (dense and sparse linear algebra, FFTs) remain important for a significant number of CoEs.<br> <em>I/O Management Techniques</em><br> For the CoEs focused on materials science, such as MaX, E-CAM and BioEXCEL, Input/Output (I/O) is not typically found to be a major performance bottleneck on current petascale systems. Several CoEs have highlighted the desire for a common standard that would allow for the exchange of data between different materials science codes within the CoE and have identified HDF5, a data model, library and file format for storing and managing data, as a possible candidate due to its popularity. I/O Management is deemed to be the key to success to those CoEs with a Big Data (data sets that are so large or complex that traditional data processing applications are inadequate) focus.<br> <em>European Exascale Projects</em><br> Many of the CoEs are aware of, or have partners contributing to, the larger European Exascale projects (CRESTA, DEEP/DEEP-er, Mont Blanc/Mont Blanc 2), but there are fewer connections to the smaller projects (NUMEXAS, EXA2CT, EPiGRAM). Only E-CAM has no connections to any Exascale projects.<br> <em>General Questions</em><br> The most requested system performance characteristics are floating-point performance, high speed memory, and low latency networking. There is a strong interest in accelerator technology. The main areas of interest for PRACE interactions are computer expertise, training and documentation; there is a smaller need for domain expertise and general assistance.<br> The notable findings of Section 3 are outlined below. BioExcel may require from PRACE general assistance in performing large-scale benchmarks as well as expertise in the area of development, porting and tuning of codes for some specific platforms and temporally and spatially align their training events. PRACE is expected to support CoeGSS in terms of general assistance, training, online documentation, domain related expertise, and code development/porting/tuning. The exploitation of HPC systems at the E-CAM CoE will focus mainly on developing testing and benchmarking materials science codes, modules and workflows on supercomputers/HPC clusters, and their exploitation of accelerator hardware. EoCoE supports a large number of application codes, 23 in total. Several of the application codes considered are concerned with the solution of large sparse linear systems at some point. The sparse linear solver used for achieving this task greatly influences the overall scalability of the applications. ESiWACE signalled a strong need for general assistance and computer expertise in code development, porting and tuning, and a moderate need for training. There is not much experience in Xeon Phi (Intel’s many core platform) and GPU profiling within ESiWACE yet, which could be an excellent opportunity for assistance from the side of PRACE-4IP Work Package7 (WP7). Due to the diversity of the actions planned within the MaX CoE, there where will be requirements in general processing, the exploitation of accelerator hardware, storage and I/O solutions as well as HPC software and tools stacks. NoMaD was unable to complete many questions as they are still at an early stage in defining their requirements. This highlights the need to re-engage with the CoE periodically to reassess the HPC requirements. POP needs fast, but short duration access to PRACE resources for approximately 10% of their 150 selected codes. POP is also interested in the questionnaire responses from the other CoEs to the ‘Debuggers and Profilers’ section. In conclusion, it should be emphasised that all of the exploitation work proposed to be carried out during the next phase of Task 7.2a will continue to be informed and inspired by the on-going research across the various European and US (United States of America) exascale projects. Furthermore, the requirements of the CoEs’ are expected to change over their lifetime and as such communication between PRACE and the CoEs should be maintained, as we face into the exascale frontier.