In OpenCL platform model, there are terms like OpenCL Device, Compute Unit and Processing Element. For CPU the a Compute Unit is a CPU Hyper Thread and for HD Graphics Compute Unit is mapping to Execute Unit. So to what does Processing Element is mapping on CPU and HD Graphics? And on what does an OpenCL thread (work item) run on CPU and GPU?
An OpenCL workgroup executes on a single compute unit. On HD graphics a workgroup is executed on multiple EU threads. So you can safely assume PEs map to the SIMD channels.