I am new to openCL and trying to learn the basics. I have a doubt that if i specify the size of work-group and NDRange in a way so that the total number of work-items excede the processing elements in a device , whether it is possible to execute those work-items in parallel and if yes how it is implemented.

I will also be grateful if someone can explain how the abstract model of openCL is mapped to hardware model with some example.