Models of Computation — Enabling Exascale

A model of computation provides a set of governing principles and a discipline determining the objects, their interrelationships, parallel flow control, and distribution. In so doing it provides a conceptual framework for the co-design and operation for all layers of the software and hardware architecture system stack from programming model through system software to processor core instruction set and structures. As enabling technologies advance changing capabilities, balance, and design challenges, the response has been a phase change in how HPC systems are realized reflected by the development and adoption of new models of computation to best fit the emerging underlying technology conditions. This has occurred at least through five technology epochs in the past and the field is entering a sixth such with the heterogeneous multicore Petaflops decade. A brief presentation of the nature and characteristics of models of computation is offered here to contribute to the current community discussions on how to proceed towards the realization of the promise of practical Exascale computing by the end of the next decade.