SC16 Salt Lake City, UT

OpenACC API User Experience, Vendor Reaction, Relevance, and Roadmap

Authors: Mr. Duncan Poole (NVIDIA Corporation)

BP Abstract: Since SC11, the OpenACC BOF brings together the user and developer communities to gather valuable feedback on the specification and discuss newer features as required by the scientific community code owners. Up for discussion are the OpenACC extensions used on the Sunway TaihuLight supercomputer. Also, AMD, Intel and NVIDIA released accelerators using high bandwidth memory, which present optimization opportunities for the OpenACC roadmap. OpenACC adoption is driven by the member-users. This BOF allows users to discuss new experiences, and scaling developer engagement like Hackathons, to improve the use of directives in new and legacy code.

Long Description: OpenACC, a highly user-driven standard, offers a directive-based programming model for the scientific community code owners to port their code to massively parallel platforms. This BoF will invite users from different scientific domains to share their programming experiences of migrating legacy code such as ACME-CAM, NekCEM, S3D, MRI reconstruction to TITAN and other supercomputers. The talks will focus on how OpenACC can interact with MPI in the ‘X’ + MPI model. Such code migrations have directly impacted real-world scenario such as accelerating large scale simulations to improve carbon sequestration techniques or to ensure the safety and reliability of nation’s nuclear deterrent. The BoF attendees will learn about a newer OpenACC implementation that maps CAM code on world’s #1 supercomputer Sunway Taihulight’s ShenWei processors. Researchers working on Sunway will share their path forward on developing and using the OpenACC model for their supercomputer. This BoF has been and will continue to serve as a forum gathering feedback from users on creating newer language extensions along with identifying challenges and opportunities that the standard should address. Critical topics of discussions will include how to tackle memory management (HBM, HMC, unified memory) at the programming model level; how to do work where the data resides or how to move computation closer to data. The BoF will discuss OpenACC’s support for varied architectures including upcoming DOE CORAL systems. The model currently supports IBM’s Power processors, hybrid Power CPUs with NVIDIA’s Tesla GPUs; this marks OpenACC’s support for OpenPOWER. Attendees will learn from technical experts, the best programming practices to achieve performance portable solutions on targets ranging from X86, GPUs, ARM, Power Processors, FPGA and Co-Processors. Attendees will also gain insight into the OpenACC’s availability in GCC (7.1 release expected). The BoF will highlight Hackathons led by the standard committee in 2016 at Germany, USA and Switzerland. ~ 25 teams including NASA, NCI, BNL, Naval Research Laboratory, KTH and Universities migrated their legacy codes to TITAN and other supercomputers using OpenACC directives. Two of the most critical and tangible outcomes have been: (a) Creation of a professional HPC workforce and (b) Improvement of compilers’ quality. At past OpenACC BoF(s), we have discussed specification releases, users' success stories, demonstrated performance results, and most importantly received user feedback from application developers that ported astrophysics, seismic and weather codes to accelerators. Such feedback have been instrumental in guiding the direction of the standard. We also observed that open source compilers enabled the community to do research, recognize applications needs and build tools eco-systems. Similarly, this year too, we will create survey reports from attendees identifying specific programming challenges from application scientists, discrepancies across compilers, and new features and improvements. All of these feed back to the standard committee as we believe this information helps us create a better and more pertinent standard. Lastly, a “Best Paper Award” winner from WACCPD Workshop@SC16 will be identified and presented with a Pascal card. We request that this BoF be not scheduled during Top 500 BoF as it may affect attendance.

Conference Presentation: pdf

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