I don't think we should be looking at either CUDA or OpenCL directly.
We should be looking for a generic library that can target either and
is well maintained and actively developed. Any GPU code we write
ourselves would rapidly be overtaken by changes in the hardware and
innovations in parallel algorithms. If we find a library that provides
a sorting api and adapt our code to use it then we'll get the benefits
of any new hardware feature as the library adds support for them.
