FAH Support for ATI GPUs

We have been working to improve our support for AMD/ATI GPUs. AMD/ATI originally supported the Brook language for GPU programming, but has since moved to OpenCL, dropping support for Brook. This means that in order for FAH to support ATI GPUs, we have had to rewrite our ATI GPU core in OpenCL. This has been a huge undertaking, but is coming to fruition (check out http://simtk.org/home/openmm for details and a change log with progress updates). Due to ATI's decision to drop Brook in lieu of OpenCL, new FAH ATI GPU core development can only be done in OpenCL and thus can only run on GPUs which ATI supports with OpenCL. 

We want to give ATI donors a heads up that ATI does not support all of its GPUs with OpenCL (the series 3xxx are not supported and the series 4xxx does not have sufficient OpenCL support for efficient FAH calculations). For the short term, we will support both the older (Brook coded) ATI core 11, and the newer (OpenCL coded) ATI core 16, but we cannot support the Brook-based core for much longer. We plan to support ATI core 11 until September 1, 2011 (hopefully longer, but we want to get this on donors' radars). Closing support for a given platform is never a popular decision, but in this case, we have no choice due to the lack of vendor support of that platform.

The good news is that ATI's support for OpenCL is very strong and we're excited about our new ATI openCL core (core 16), which is undergoing testing right now. ATI core 16 will be publicly released after the v7 client is released, as the core needs the new client.