accULL: An OpenACC Implementation with CUDA and OpenCL Support

The irruption in the HPC scene of hardware accelerators, like GPUs, has made available unprecedented performance to developers. However, even expert developers may not be ready to exploit the new complex processor hierarchies. We need to find a way to leverage the programming effort in these devices at programming language level, otherwise, developers will spend most of their time focusing on device-specific code instead of implementing algorithmic enhancements. The recent advent of the OpenACC standard for heterogeneous computing represents an effort in this direction. This initiative, combined with future releases of the OpenMP standard, will converge into a fully heterogeneous framework that will cope the programming requirements of future computer architectures. In this work we present accULL, a novel implementation of the OpenACC standard, based on the combination of a source to source compiler and a runtime library. To our knowledge, our approach is the first providing support for both OpenCL and CUDA platforms under this new standard.