Cool, but we weren't talking about compute. We know OpenCL can seek compute cores across different vendor GPUs. This part of the discussion segued from gaming and OpenGL API support for mixed GPUs on OSX.
As far as I know, OpenGL can be used for offscreen drawing and computing as well:
https://developer.apple.com/library...gGuide/opengl_offscreen/opengl_offscreen.html
However, I guess not many apps take advantage of this, especially in multiple GPU environment. I see that Metal will eventually replace both OpenCL and OpenGL. Core Animation and Core Graphics are built on top of Metal according to the WWDC 2015 slides. We just have to wait for the first games…