Implementing the OpenACC Data Model

TitleImplementing the OpenACC Data Model
Publication TypeConference Paper
Year of Publication2017
AuthorsWolfe, Michael, Lee Seyong, Kim Jungwon, Tian Xiaonan, Xu Rengan, Chandrasekaran Sunita, and Chapman Barbara
Conference NameThe Seventh International Workshop on Accelerators and Hybrid Exascale Systems (AsHES) in conjunction with IPDPS17
Conference LocationLake Buena Vista, FL, USA
ISBN Number978-1-5386-3408-0

Programming accelerators today usually requires managing separate virtual and physical memories, such as allocating space in and copying data between host and device memories. The OpenACC API provides data directives and clauses to control this behavior where it is required. This paper describes how the data model is supported in current OpenACC implementations, ranging from research compilers (OpenUH and OpenARC) to a commercial compiler (the PGI OpenACC compiler). This includes implementation of the data directives and clauses, testing whether the data is already present on the device, OpenCL support, managing asynchronous data transfers and memory allocations, handling aliased data, reusing device memory, managing partially present data, and support for shared memory between host and device. Lastly, it also discusses on-going work to manage large, complex dynamic data structures.