An apparatus for performing data processing in a single program multiple data fashion on a target data set is provided, having execution circuitry configured to execute multiple threads, thread schedule configuration storage configured to store information defining a plurality of thread schedule configurations, and thread scheduling circuitry configured to cause the execution circuitry to execute the multiple threads in a selected order defined by a selected thread schedule configuration. A method of operating the apparatus, as well as a method of compiling a source program for the apparatus are also provided.