DG-kernel: A Climate Benchmark on Accelerated and Conventional Architectures

While the emergence of many-core technology from Intel and Vida has illustrated great potential, capitalizing on this potential presents considerable challenges for large scientific applications. In particular we focus on the domain of climate modeling. Climate models typically have very large code bases with over one million lines of code which makes support of multiple version of the code infeasible. Climate models are computationally very expensive which places a premium on model performance. Furthermore because of the large user base of these applications, there is a need to support a wide range of computational platforms. These three characteristics of climate modeling make it a particularly challenging application domain for which to apply accelerator technology. We describe the work to optimize and analyze a kernel benchmark developed at the National Center for Atmospheric Research on Intel Xeon Phi, Intel Sandy Bridge, and Vida GPU. The DG-kernel is a gradient calculation from the discontinuous Galerkin version of the High Order Methods Model Environment. We explored several different programming paradigms, including Fortran with both OpenACC and OpenMP, F2C-ACC, and Cuda C/Fortran. We analyze low-level hardware characteristics and their impact on the performance of the DG-kernel.