A model for parallel programming is an abstraction in addition its machine architecture is independent. A model is able to be implemented on different hardware and memory architectures. There are numerous parallel programming models such as Threads model, Shared Memory model, Message Passing model, Hybrid model and Data Parallel model etc.
As these models are hardware independent they can (theoretically) be applied on some different underlying types of hardware. The decision about which model to employ in an application is frequently a combination of some factors comprising available resources as well as nature of application. There is no universally best implementation of a model although there are certainly a number of implementations of a model better than others.