I'm looking to do some programming on the GPU but don't need any sort of 3D or high level graphics capability. Essentially all I need to do is call functions that loop through thousands of iterations very quickly. I started looking into OpenCL but it seems that support for that is much, much lower that OpenGL as I can use OpenGL ES even on mobile and WebGL on web. Web isn't that big of an importance to me at this point, but is there a viable alternative that has the wide support that OpenGL has but more used for calculation? I want something that will be able to run on as many computers and devices out there.
EDIT: I'm also looking for the best support of various graphics cards from AMD, Nvidia, etc.