Performance Portability and OpenACC
D. Miles, David Norton, Michael J. Wolfe · 2014
Performance portability means a single program gives good performance across a variety of systems, without modifying the program. OpenACC is designed to offer performance portability across CPUs with SIMD extensions and accelerators based on GPU or many-core architectures. Using a sequence of examples, we explore the aspects of performance portability that are well-addressed by OpenACC itself and those that require underlying compiler optimization techniques. We introduce the concepts of forward and backward performance portability, where the former means legacy codes optimized for SIMD-capable CPUs can be compiled for optimal execution on accelerators and the latter means the opposite. The goal of an OpenACC compiler should be to provide both, and we uncover some interesting opportunities as we explore the concept of backward performance portability.