Birds of a Feather

OpenACC Users Forum

Authors: Jeff Larkin (Nvidia Corporation), Sunita Chandrasekaran (University of Delaware), Barbara Chapman (Hewlett Packard Enterprise (HPE)), Jack Wells (NVIDIA Corporation)

Abstract: OpenACC organization helps researchers and developers advance science by expanding their parallel computing skills and supporting a directive-based, high-level parallel programming model on CPUs, GPUs, and more. OpenACC supports over 25 global hackathons annually and facilitated the acceleration of over 200 applications on multiple platforms (e.g., Frontier, Perlmutter, JUWELS, Summit, and Piz Daint). This BoF serves as a forum for OpenACC users, implementers, and the organization officers to openly discuss the status of OpenACC and its community. Presentations will be given by OpenACC officers, compiler implementers, and invited users, followed by an open mic discussion with the audience.

Long Description: The OpenACC organization represents a vibrant community of public and private institutions spanning academia, supercomputing and research center, national laboratories and industries who place priority on accelerated, high-performance computing. Integral to the organization's activities is the stewardship of a well-established directive-based programming model, OpenACC, designed to provide an easy on-ramp to parallel computing on CPUs, GPUs and other devices. This programming model has been created with regular feedback from this diverse community of users, while keeping usability and productive performance in mind.

The model targets x86, Arm, and OpenPOWER CPUs, NVIDIA and AMD GPUs, the PEZY-SC manycore processor, and FPGAs. Current discussions include: (i) Overcoming technical challenges to support and migrate HPC apps to the next generation of HPC platforms such as Arm, (ii) Progress of open-source implementations (i.e., GCC and LLVM) and vendor-supported implementations (i.e., HPE and NVIDIA) of the OpenACC specification, especially in light of AMD-systems like Frontier coming online, (iii) Collaborating with ISO language standards to support parallelization natively without directives.

With over 200 applications choosing OpenACC, its ever-growing user community enjoys more time available for science and less time spent on programming. OpenACC fosters a cross-platform API complementary to, and interoperable with, OpenMP, MPI, CUDA, and OpenCL. Applications ported to GPUs using OpenACC include Quantum Espresso, NWChem, Nek5000/NekCEM, CASTRO, Gaussian, ANSYS, ICON, and VASP, among other top HPC applications. Over time, the organization’s membership is increasingly placing emphasis on achieving high performance and effective portability through the ISO standard languages with the OpenACC specification maintaining currency with the ISO language parallel standards.

This interactive BoF will bring together the user and developer communities to discuss successes, challenges, and brainstorm new feature requests, clarifications of definitions and implementations of existing features, and ideas for future direction. The direction of the standard is heavily driven by OpenACC users/application developers. Feedback includes new feature requests or clarifications to existing ones. Current activities include clarifications for existing features, new Fortran API routines, and extensions to support lambdas and other C++ features. Recent C++ work is in part driven by feedback from C++ abstraction library developers. An updated version of the specification with revised definitions for some of the current features and how OpenACC plans to address different memory models, will be released during the SC time frame.

Additionally, the topic of Hackathons has always kindled a vibrant conversation among BOF attendees who are either seeking help to accelerate their codes or are interested in either hosting similar hackathons or sending teams to such events in order to increase accelerated computing proficiency, increase compute resource utilization, and augment more traditional training and education modalities. Since SC14, over 550 mini-apps and applications spanning astrophysics, climate modeling, nuclear physics and quantum chemistry have been ported to large scale machines via hackathons held around the globe. Hackathons represent a global network (Asian, Europe, North and South America) of parallel computing expert advocates and motivated teams for focused, advanced training and hand-on experience guided by expert mentors. https://openhackathons.org https://www.openacc.org



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