Open ACC Programs Examined: A Performance Analysis Approach

The Open ACC standard has been developed to simplify parallel programming of heterogeneous systems. Based on a set of high-level compiler directives it allows application developers to offload code regions from a host CPU to an accelerator without the need for low-level programming with CUDA or Open CL. Details are implicit in the programming model and managed by Open ACC API-enabled compilers and runtimes. However, it is still possible for the application developer to explicitly specify several performance-related details for the execution. To tune an Open ACC program and efficiently utilize available hardware resources, sophisticated performance analysis tools are required. In this paper we present a framework for detailed analysis of Open ACC applications. We describe new analysis capabilities introduced with an Open ACC tools interface and depict the integration of performance analysis for low-level programming models. As proof of concept we implemented the concept into the measurement infrastructure Score-P and the trace browser Vampir. This provides the program developer with a clearer understanding of the dynamic runtime behavior of the application and for systematic identification of potential bottlenecks.