A solution to generate code for CUDA and OpenCL with C++:

Generating OpenCL/CUDA source code from C++ expressions in VexCL

by Denis Demidov

From the talk description:

VexCL is an opensource C++ vector expression template library for OpenCL/CUDA. It has been created for ease of GPGPU development with C++ and provides convenient and intuitive notation for linear algebra operations, vector arithmetic and various parallel primitives.