An Extended PRAM-NUMA Model of Computation for TCF Programming

The Parallel Random Access Machine - Non Uniform Memory Access (PRAM-NUMA) model of computation can be used to implement efficient emulated shared memory (ESM) computers for general purpose parallel applications and yet support sequential and NUMA legacy code and avoid loss of performance in applications with low parallelism. While programming of these computers is provably easy, there is still room for improvement since they make implementing time-shared multitasking expensive, sometimes replicate much of the execution unnecessarily, and force a programmer to use looping and conditional control primitives in the case the application parallelism does not match the hardware parallelism. Thick Control Flow (TCF) is a parallel programming model that does not provide a fixed number of threads like PRAM-NUMA but a number of control flows that have certain thickness that can vary according to needs of the application catching the best parts of the dynamicism and generality of the original unbounded PRAM model and simplicity of the Single Instruction Stream Multiple Data Streams (SIMD) model. In this paper we study implementing the TCF model on a top of the PRAM-NUMA model and propose an extended PRAM-NUMA model that makes this straight-forward. Architectural implementation and programming of the extended model are discussed with short examples.